Division J - Poster Abstracts


Testing Star Formation Laws Using ALMA On A High-Redshift Lensed Galaxy

Sharda, Piyush

Using high-resolution (sub-kpc scale) submm data obtained from ALMA, we analyze the dust spectral energy distribution (SED) and kinematics of CO (5-4) in a molecular cloud in SDP.81, a high-redshift lensed galaxy at z~3. We fit the SED by a modified blackbody (MBB) function and subsequently obtain the bestfit temperature and emissivity as 39.5 K and 2.5, respectively. Integrating the bestfit MBB (to estimate far infrared luminosity) and using the Kennicutt luminosity-SFR relation, we calculate the observed SFR surface density (?_SFR) in this clump to be 357+135-85 MT per year per kpc².We use a new gradient subtraction algorithm to find the turbulent velocity dispersion in the plane of sky. By evaluating the gas surface density, free fall time and turbulent Mach number, our calculations reveal that the role of turbulence is vital to explaining the observed SFR in this clump. Using the measured ?_SFR and gas properties, we test three popular star formation relations on this extreme starburst clump: the Kennicutt-Schmidt relation, the Krumholz-Dekel-McKee relation and the Salim-Federrath-Kewley relation. While the gas surface density based Kennicutt Schmidt (KS) relation predicts a ?_SFR = 52±17 MT per year per kpc², the single-freefall time based Krumholz, Dekel and McKee (KDM) relation predicts ?_SFR = 106±37 MT per year per kpc². On the contrary, the multi-freefall (turbulence) based Salim, Federrath and Kewley (SFK) relation estimates the ?_SFR = 491+139-194 MT per year per kpc².  Although the SFK relation overestimates the SFR in this clump (possibly due to the negligence of magnetic fields), it provides the best prediction of the SFR in this clump. We also compare the star formation and gas properties of our high-redshift molecular clump to local star-forming regions and find that the SFK relation provides good estimates of ?_SFR in both local and high-redshift clouds.

Gauss' Law for Gravity with Cylindrical Distribution of Gravitational Field Flux to Interpret Flat Rotation Curve and Baryonic Tully-Fisher Relation of Disk Galaxies

Wang, Te Chun

This report proposes an interpretation, by considering an integral Gauss’s law of gravity with anisotropic gravitational flux distribution, for the flat rotation curve as well as Baryonic Tully-Fisher relation of disk galaxies.It is pointed out that a flux distribution of cylindrical symmetry on the side wall of outer part of a disk galaxy may convert the inverse square radius dependence of the Newtonian gravitational field into a direct inverse dependence and the flat rotation curve can directly be derived under the circular motion approximation.It is also shown that the Baryonic Tully-Fisher relation can be proved valid if we assume the gravitational field flux distribution switches from spherical symmetry to cylindrical symmetry at a critical field strength near 10^(-10) m/s^2.Related consequences and implications of this an-isotropic gravitational field picture are discussed.

Strong limit on delta alpha/alpha from analysis QSO spectra

Thong, Le

We use the observed spectra from the white dwarf star G191-B2B to constrain the space-time variation of the fine-structure constant. The analysis was combined with laboratory and astronomical lines in [Ni V] to find delta alpha/alpha = (-0.003+- 0.072) x 10-6 . This result represents the most stringent limit on delta alpha/ alpha compared with the results using the same data published in the literature.

Cosmological simulations in Fourier space

Tugay, Anatoliy

We propose a new method of simulation of large-scale structure of the Universe. We use hydrodynamical equations of dust (dark) matter in own Newtonian gravitational field. Instead of N-body simulation we use Fourier harmonics for density contrast and potential of irrotational velocity field. We consider periodic structure of plane waves in 100 Mpc cube. We obtained equations for harmonics in 3D case and prepared a code for simulation. In this work we described the regimes of runaway, when quasinonlinear approach becomes irrelevant. Further development will allow to test Wick theorem for average values and to constrain the methods of perturbation theory in cosmology. Simulated matter distribution will be compared with observational data such as power spectrum of QSO Ly-alpha forest and correlation functions of galaxies.

Low Luminosity AGNs in the Local Universe

ikiz, tuba

Galaxies are known to contain black holes (e.g.Ferrarese & Merritt 2000), whose mass correlates with the mass of their bulge. A fraction of them also has an Active Galactic Nucleus (AGN), showing excess emission thought to be due to accretion of mass by the supermassive black hole at the center of the galaxy. It is thought that AGNs play a very important role during the formation of galaxies by creating large outflows that stop star formation in the galaxy (e.g. Kormendy & Ho 2013). The aim is to detect the fraction of Low Luminosity Active Galactic Nucleus (LLAGN) in the nearby Universe. At present, they are typically found using optical spectroscopy (e.g.Kauffmann, Heckman et al. 2003), who discuss the influence of the AGN on the host galaxy and vice versa. However, optical spectra are seriously affected by extinction in these generally very dusty objects, and therefore can only give us partial information about the AGN. I used a newly-found method, and apply it to the S4G(The Spitzer Survey of Stellar Structure in Galaxies) sample, a large, complete, sample of nearby galaxies, which I am studying in detail with a large collaboration, to detect the fraction of low luminosity AGNs, and to better understand the relation between AGNs and their host galaxy which is thought to be crucial for their formation. I will present the results of our study based on AGN fractions in nearby universe.

An HST and VLA view of the physics that drive the emerging ionizing flux (LyC) in the local dwarf galaxy Tololo 1247-232

Puschnig, Johannes

The driving mechanism of the reionization of the Universe is yet not well constrained, but low- and intermediate mass galaxies are widely discussed as source of ionizing photons, i.e. Lyman Continuum (LyC). However, proof of emerging LyC emission is an ongoing observational challenge at all redshifts. Using highly resolved photometry and far-UV spectroscopy obtained with the Hubble Space Telescope (HST) as well as interferometric observations performed with the Karl G. Jansky Very Large Array (VLA), we have studied the ionized and neutral gas content in the local dwarf galaxy Tololo 1247-232. My talk is based on Puschnig et al. (2017), describing physical mechanisms that drive the LyC escape in Tololo 1247-232, which is to date one of the very few known/confirmed LyC emitters in the Universe._x000D_ Using HST's Cosmic Origins Spectrograph (COS), in combination with an improved data reduction routine, we have directly measured the amount of LyC emerging from the galaxy, finding an escape fraction of 1.5+/-0.5 percent only, i.e. the lowest LyC escape fraction reported for the galaxy so far. We further use far-UV absorption line analysis to probe the neutral and ionized gas, e.g. the covering fraction of the neutral medium could be constrained. We show that the LyC photons emerge from density bounded regions and finally escape through a clumpy medium. However, from Lyman Alpha line analysis, we also conclude that an additional diffuse interclump medium must be present that prevents Lyman Alpha to be seen at systemic velocity. The LyC escpae is further supported by our VLA 21cm observations, from which a very low gas fraction of less than 20 percent could be derived.

Dark Matter and Dark Energy as Remnants of Visible matter in Cosmological Models

Morcos, Abd El Fady

The accelerated expansion of our universe needs consistent theoretical models to explain the origin of this acceleration. The cosmological equations describing the formation of large-scale structures in a homogeneous and isotropic universe are systems of ordinary differential equations. The formations of large-scale structures depend on the cosmological model and the framework of the theory in which the model has been formed. It is assumed, in this work, that the remnants after the formation of large-scale structures (visible universe) represent the dark matter and dark energy. Different cosmological models have been used as Saez and de Juan model, The self-consistent model, and the standard model. It is found that the description of dark matter and dark energies as remnants of visible matter depends on a parameter which depends on the model itself.

Observations of the Starburst Galaxy M82 with SOFIA/FIFI-LS

Latzko, Serina T.

The active galaxy M82 at 3.7 Mpc is one of the closest laboratories to study massive starburst phenomena in detail. Radio observations revealed two Ultra Luminous X-Ray Sources (ULXs) near its center. Optical and near-infrared (NIR) observations focused on super star clusters in the core of M82 while the cool and warm molecular interstellar medium (ISM) was investigated using Infrared Space Observatory (ISO) observations in the mid-infrared (MIR) and far-infrared (FIR). We present new [CII] 157µm observations on the galactic wind emerging perpendicular to the disk of M82 at high velocities obtained with FIFI-LS onboard SOFIA using its spectral mapping capability. Our data also extend the investigation on the processes prevailing in the core of M82 by using spectral lines that were previously inaccessible, e.g., [OIII] 52µm, in particular at high angular resolution of about 6 arcsec. 

GRB X-ray light curve types, and the nature of dark energy.

Leaman, Jesse

Following an analysis of 775 (739 long, 36 short) Gamma-ray bursts (GRB) from 2005 to 2017 it was found that GRB types should be based on the x-ray light curve (LC) shape, the number of breaks in the LC, and the LC slope (steep or shallow) between breaks. The 36 SGRBs fall into one of 7 types, likely the merger of a certain combination of compact objects, neutron stars and black holes. The 739 LGRBs fall into one of four optical afterglow (OA) families: Supernova (5 types), Kilonova (32 types), Forward shock (15 types), and Dark (13 types). Most GRB types, Kilonova and Supernova, arise from different inclination angles, and gas and dust distributions, around collapsing massive stars. Other types, especially those with little or no OA, and occurring near the center of galaxies, might represent the annihilation of matter and antimatter (AM). The later may be evidence of the release of dark energy (DE), and the creation of dark matter (DM). The first black holes (BHs) twisted space-time (ST) into strings a plank length (lp) in radius, with vast tensile strength. Over the eons, BHs merged within their potential wells, lp-strings became entangled, and BHs grew to massive sizes at the center of their own galaxies. The lp-strings connecting BHs in separate potential wells, stretch as the universe expands, until they tear, and ST unravels, reducing the mass/size of the BHs.When the AM emerges from the event horizon, a GRB is accompanied by an X-ray flare, and a stream of neutrinos. Information about the original entanglement determines the vector and mass of the expelled AM. Conservation of momentum requires the galaxy to experience an acceleration in the opposite direction, resulting in the accelerated expansion of the universe observed today. Evidence that this conversion of stored DE has been ongoing for billions of years, can be found in the DM distributions around, and between, clusters of galaxies. 

The formation of supermassive binary black holes in galaxy mergers

Ho, Yu-Heng

Using N-body simulations, we've investigated the formation of supermassive binary black holes(BBH) under different impact parameters, i.e. BBHs with different initial angular momentum, we've traced the individual supermassive black hole(SMBH) at an initial distance of 300 kpc, to the stage when the BBH becomes hard, the time scale of different stages has been estimated, and the relation between the orbital evolution and the properties of the stellar cores are discussed, also, the transfer of the angular momentum between the galaxy and the BBH is studied, we find that certain merger geometries of the galaxies do affect the lifetime of the BBH significantly, the duration time of the individual SMBH from entering the core of the merged galaxy towards forming a hard binary can be as long as 1.5 Gyr. Furthermore, in traditional loss-cone theory, triaxial systems are generally believed to be efficient towards removing the angular momentum of the BBH so that the binary can be driven into coalescence at the hardening phase, we find that this might not be the case for the early stage of the binary formation while dynamical friction still plays the dominant role of subtracting the BBH orbital energy. We conclude that the geometry of the merger as well as the structure of the galactic angular momentum also plays an important role of determining the lifetime of the BBH, the situation might be more complicated if, for example, multiple mergers or larger mass ratio between the SMBHs are considered.

Coma cluster: A sharp view using upgraded GMRT

Lal, Dharam

We have used upgraded GMRT, an SKA pathfinder instrument as a testbed to demonstrate the capabilities of wide field, wide band imaging of Coma cluster of galaxies at 1050-1450 MHz and at 250-500 MHz bands. These images detected more than 100 radio sources and here we summarise their radio properties in a statistical sense. We also present spatially resolved radio morphologies and spectral structures, and the effect of intra-cluster medium for several radio galaxies using upgraded GMRT and Chandra. We discuss the importance of multi-wavelength imaging, and the improvements that will be possible due to upgraded GMRT and the role of low-frequency instruments.

Why is the observed distribution of Quasars on the celestial sphere highly anisotropic?

McGruder, Charles

Standard cosmological theory assumes that the matter in the universe is distributed homogenously. Is this assumption correct? Homogeneity implies isotropy. But, it is known that the observed distribution of quasars is highly anisotropic. We show that if we employ supergalactic coordinates and consider only those quasars that have been observed from outer space, then the distribution of quasars as a function of supergalactic latitude is nearly isotropic.

A wide and deep survey for low-luminosity quasars at z~5 with Subaru Hyper Suprime-Cam

Niida, Mana

Observational surveys for protoclusters in the high-redshift Universe are crucial to understand the formation and evolution of clusters of galaxies. Quasars have been sometimes used to discover protoclusters at high redshift. Quasars in protoclusters are interesting also to study the triggering mechanism of the mass accretion onto supermassive black holes and possible effects of the quasar activity to the evolution of protoclusters. Therefore quasar surveys at high redshift over a wide luminosity range are required. However there are only small number of low-luminosity quasars at z>5 identified so far, due to insufficient area and sensitivity in past surveys. We are searching for low-luminosity quasars at z~5 by using wide and deep optical imaging survey data obtained through the Subaru strategic program (SSP) with Hyper Suprime-Cam (HSC). This survey covers a wide survey area (~82 deg^2) and has deep sensitivity, which is ~3 mag deeper than SDSS, enough to observe faint quasars at z~5. We selected photometric candidates of low-luminosity quasars at z~5 by adopting the so-called Lyman-break method. Consequently, we obtained a large sample of quasar candidates at z~5 (224 objects) with a luminosity range of -27.4<m_1450<-22.4. we="" derived="" the="" quasar="" luminosity="" function="" (qlf)="" at="" z~5,="" taking="" into="" account="" of="" survey="" and="" contamination="" galactic="" stars="" galaxies.="" as="" a="" result,="" faint="" end="" slope="" our="" qlf="" is="" flatter="" than="" that="" previous="" studies="" (giallongo="" et="" al.="" 2015).="" trend="" consistent="" with="" z~4="" using="" hsc="" data="" (akiyama="" 2018).="" in="" this="" presentation,="" would="" like="" to="" discuss="" also="" redshift="" evolution="" number="" density.<="" p="">

Discovery of a LAE overdensity in a concentrated region of damped Ly-alpha systems

Ogura, Kazuyuki

To investigate the early phase of the galaxy evolution, we focus on two populations of gas-rich young systems, damped Lya systems (DLAs) and Lya emitters (LAEs). The DLA is a class of quasar absorptionline systems with NHI>1020.3 cm-2 and is a key population to understand the galaxy evolution in the following respects: (1) DLAs provide a powerful tool to investigate the nature of the cold gas at high redshift since they trace the intervening gas that can be detected as a strong Lya absorption line on quasar spectra regardless of the luminosity of their stellar component, and (2) it is known that DLAs dominate the neutral-gas content in a wide redshift range and they are thought to be gas reservoirs for the star-formation. Another important population of young galaxies is the LAE. Typical mass and age of LAEs are 108-109 Msun and order of 100 Myr, respectively. Although most of the galaxy counterparts of DLA at z>2 that have been identified to date show the Lya emission, the relation between those two population is still unclear.We focus on concentrated regions of DLAs to investigate the physical relationship between DLAs and LAEs. Here we define the concentrated region of DLAs as a region where three or more DLAs distribute within a (50 Mpc)3 cubic box. We conducted narrow-band imaging observations of LAEs in the J1230+34 field, where four DLAs present, with Subaru/Suprime-Cam. In the entire target field of ~50 Mpc scale, we have found no difference between the obtained Lya luminosity function and those in blank fields at similar redshift. The frequency distribution of Lya rest-frame EW is also not different from those in blank fields and a overdensity region at similar redshift. On the other hand, in the small scale of ~10 Mpc, we have found a possible overdensity of LAEs around a DLA with highest NHI (logNHI=21.08 cm-2) in the J1230+34 field. This may correspond to a possible discovery of a gas-rich protocluster traced by DLAs for the first time.

A joint image-visibility study of the Sunyaev-Zeldovich effect at high resolution

Di Mascolo, Luca

The Sunyaev-Zeldovich effect (SZE) represents an ideal tool for studying the formation of galaxy clusters. First of all, it is indeed well-known that, due to the redshift-independence of the SZE surface brightness, it can provide an exceptional view on large-scale structures at high redshifts. Second, the SZE signal is sensitive to different thermodynamic properties of the hot electrons within clusters than X-ray emissions. A comparison of SZE and X-ray observations can thus provide a wealth of information on the dynamical and thermal state of the intracluster medium. This is the result of the numerous merger events and accretions of substructure a galaxy cluster has undergone during its growth, and its study can give an insight into the cluster formation history.Nevertheless, such investigation requires a combination of high-resolution, high-sensitivity data and accurate modeling of galaxy cluster morphology. To date, ALMA is the only instrument capable of providing measurements of the SZE signal with an angular resolution of ~5 arcsec. However, imaging of interferometric data may be strongly biased by the specific choice of the deconvolution technique. Moreover, the determination of a transfer function (instrument response) for accounting for large-scale filtering and missing flux is a non-trivial task. In order to avoid such issues, it is then more advisable to work directly in visibility space. On the other hand, bolometric data can complement interferometric measurements by adding information on the large-scale properties of galaxy clusters.For these reasons, we developed a joint image-visibility MCMC modeling pipeline for the determination of 2D parametric models of cluster SZE signal. As a test case, we applied this tool to the well-known galaxy cluster RX J1347.5-1145. I will discuss the recent results from the joint analysis of Planck, BOLOCAM, MUSTANG-2, ACA and ALMA data.

Orbital Dynamics in Galaxy Clusters

Lotz, Marcel

The effect of galactic orbits on a galaxy's internal evolution within a galaxy cluster environment has been the focus of heated debate in recent years. To disentangle this relationship, we investigate the velocity anisotropy, phase space and the orbital evolution of cluster satellites. Through the use of the hydrodynamic cosmological Magneticum Pathfinder simulations, we evaluate the orbits of subhalos associated with clusters above a mass threshold of 1014 Msol from redshift z = 2 to z = 0.2. Through the inspection of different cluster masses and redshifts, we are able to achieve a diverse statistically relevant sample of subhalos inside clusters, which we further split into quiescent and star forming subhalos. This split allows us to observe the internal subhalo evolution and study its dependence on the velocity anisotropy parameter and the radial distance. To evaluate the validity of the simulation-based findings, we compare, where possible, with observations. We find that independent of mass and redshift, the star forming subhalo population experiences a continuous decrease in star formation at radii above the virial radius. More importantly, after crossing below the virial radius the vast majority of star forming subhalos are quenched through ram-pressure stripping during their first passage.

Star formation rate calibrations: the effect of the upper mass limit of the IMF

Obi, Ikechukwu

We construct a large library of star-burst models for a large range of physical parameters using our spectrophotometric code GRASIL. The adopted Simple Stellar Populations (SSP) are computed at various metallicities and upper mass limits of the Initial Mass Function (IMF), using PARSEC (PAdova TRieste Stellar Evolution Code) evolutionary tracks. We derive analytic relations that provide the star formation rates (SFR) of star forming galaxies from their UV to radio continuum  and main recombination lines luminosities, by explicitly accounting for different IMF upper mass limit and metallicites. The relations are particularly useful for young star forming systems not strongly attenuated by dust, with a FIR luminosity that is only a fraction of the bolometric one. We discuss possible diagnostics for the IMF upper mass limits.

Sloshing in its cD halo: MUSE kinematics of the central galaxy NGC 3311 in the Hydra I cluster

Arnaboldi, Magda

We aim to identify the main structural components of the Hydra I cD galaxy NGC 3311 to investigate the connection between the central galaxy and the surrounding stellar halo. We produce maps of the line-of-sight velocity distribution (LOSVD) moments from a mosaic of MUSE pointings covering NGC 3311 out to 25 kpc. Combining deep photometric and spectroscopic data, we model the LOSVD maps using a finite mixture distribution, including four non-concentric components that are nearly isothermal spheroids, with different line-of-sight systemic velocities V, velocity dispersions σ, and small (constant) values of the higher order Gauss-Hermite moments h3 and h4._x000D_ The kinemetry analysis indicates that NGC 3311 is classified as a slow rotator, although the galaxy shows a line-of-sight velocity gradient along the photometric major axis. The comparison of the correlations between h3 and h4 with V/σ with simulated galaxies indicates that NGC 3311 assembled mainly through dry mergers. The σ profile rises to ≃ 400 km s-1 at 20 kpc, a significant fraction (0.55) of the Hydra I cluster velocity dispersion, indicating that stars there were stripped from progenitors orbiting in the cluster core. The finite mixture distribution modeling supports three inner components related to the central galaxy and a fourth component with large effective radius (51 kpc) and velocity dispersion (327 km s-1) consistent with a cD envelope. We find that the cD envelope is offset from the center of NGC 3311 both spatially (8.6 kpc) and in velocity (ΔV = 204 km s-1), but coincides with the cluster core X-ray isophotes and the mean velocity of core galaxies. Also, the envelope contributes to the broad wings of the LOSVD measured by large h4 values within 10 kpc. We conclude that the cD envelope of NGC 3311 is dynamically associated with the cluster core, which in Hydra I is in addition displaced from the cluster center, presumably due to a recent subcluster merger.

Mapping the Galaxy Distribution in and around Galaxy Clusters

Hwang, Ho Seong

Measurement of the mass distribution in galaxy clusters is an important test of structure formation models. Among many ways to map the matter distribution in clusters, three methods including galaxy redshift, weak lensing and X-ray surveys have been widely used. The three methods are complementary, and the combination of them is helpful for better understanding the assembly history of the cluster and understanding the systematics of each method. We present the results from extensive redshift surveys of nearby clusters focusing on the comparisons of galaxy distributions with the matter distributions from weak-lensing and/or X-ray surveys.

A Comparison of Galaxy Spiral Arm Pitch Angle Measurements Using Manual and Automated Techniques

Treuthardt, Patrick

The established relationship between galaxy spiral arm pitch angle (PA) and supermassive black hole (SMBH) mass provides a powerful and time-efficient means of estimating the mass of the black hole found in the nucleus of most galaxies. A single, uncalibrated, broadband image with sufficient contrast provides the data necessary to determine SMBH mass via the PA-SMBH relationship and predict which galaxies might harbor intermediate mass black holes (MBH < 105 M?). In order to better understand the accuracy of different methods used in measuring spiral arm PA in galaxies, we tested four different PA measurement techniques including SpArcFiRe, the Ringermacher & Mead (RM) formula, standard input P2DFFT, and P2DFFT with input from visually traced arms. The tests were conducted on images of simple, artificially generated logarithmic spiral arm galaxies (toy models) of various pitch angles, numbers of arms, and arm widths. We further tested three of the techniques (sans RM) on a set of 9 real spiral galaxy images of various morphologies ranging from non-barred to strongly barred and from early- to late-type. We find that our tracing method in combination with P2DFFT generates the most accurate results with the toy models. For the set of real galaxies, SpArcFiRe and P2DFFT with traced arm input produced consistent results. Improvements to standard input P2DFFT are also explored.

Searching for extended circumgalactic halos around galaxies

Azanha, Luiz

A full understanding of the galactic halo physical properties is an important missing piece in the picture of galaxy formation and evolution. The circumgalactic halo of a galaxy is important given that it may represent the reservoir of gas for future star formation. Radio observations of spiral galaxies using the 21cm-line of hydrogen show that galaxies have typically extended disks of neutral hydrogen which show a sharp edge. Beyond this point the galaxy may be dominated by ionized gas. This ionization may be caused either by the ultraviolet radiation from the galaxy itself or by ultraviolet background radiation. Detecting a hydrogen ionized halo gives us information about the total baryonic mass in galaxies and also about galaxy evolution. This detection is also a valuable as an indirect probe of the UVB radiation, which carries information about the cumulative history of star formation and AGN activity. This project is part of S-PLUS, a photometric survey of the southern hemisphere, which uses 12 bands, 5 SDSS broad and 7 narrow bands, designed to study stars and nearby galaxies. One of the filters covers Ha, which is the emission line related to recombination in ionized hydrogen. We will stack images of nearby galaxies using this sample, separating by morphology and stellar masses. A careful continuum subtraction will be necessary, using one or more broad band images. We expect to detect Ha emission from the halo, which is a direct detection of an ionized hydrogen gas. We will present our partial results.

Radial population gradients in cD galaxies

Pérez-Hernández, Ernesto

 cD galaxies have two components, one has a light profile similar to the de Vaucouleurs law(n=4) while there is also a component from an extended luminous envelope. D and cD galaxies are usually brightest cluster members (BCM) and, while there are many ways of forming the extended luminous envelope, it is not clear why not all BCMs have one.We present a study of optical long-slit spectroscopy of 14 cD galaxies with 4 runs using the Boller & Chivens spectrograph at the 2.1 m San Pedro Mártir telescope and data for A2162 using the OSIRIS spectrograph at the 10.4 m GTC telescope respectively, to find gradients in age and metallicity, plus 2 runs of photometry with the 2.1m telescope looking for radial color gradients. Preliminary results of radial variations of spectral indices for 7 cD galaxies show mostly flat age gradients, in agreement with the photometry, while others present flat age and metallicity variations which appear as radial color gradients in the photometry. Preliminary results for A2162 from GTC include the measurement of spectral index variations between the center and radius 50”(~31.51 kpc), this could be due the existence of metallicity and/or age variations.

The spectral energy distributions of quasars

Brown, Michael

We present spectral energy distributions of quasars spanning from 0.1 to 35 microns, which can be used for photometric redshifts, k-corrections and modelling object selection. AGN photometric redshifts will be critical for key science with square kilometre array pathfinders and LOFAR, as many of the sources detected by these wide-field surveys won’t have spectroscopic redshifts. Our templates incorporate (but are not limited to) photometry and spectroscopy from FUSE, IUE, Hubble, SDSS, PanSTARRS, Skyampper, IRTF, GNIRS, XShooter, Akari, Spitzer and WISE. Our templates have higher spectral resolution and include spectral features that are often absent from quasar templates from the prior literature. We illustrate the utility of these templates by using them to generate photometric redshifts for AGNs in the Bootes field.

Systematic study of Quasar Radiative Feedback in High-z Universe

Uchiyama, Hisakazu

High-z luminous quasars are thought to appear through a major merger of gas-rich galaxies.  It is, hence, speculated that they preferentially reside in galaxy overdense regions, where galaxy merger frequently happens. On the other hand, there could be an important feedback process from quasar to galaxies, photoevapolation, which could be effective in protocluster regions around quasars, especially for low-luminosity galaxies.  Low luminous galaxies are closely bound up with the surrounding inter-galactic medium. The photoionization heating by strong ultra-violet (UV) background from quasar evaporates the collapsed gas in the halo and in hibits gas cooling. We have carried out deep and wide field imagings with Suprime-Cam targeting for 11 quasar fields in order to systematically study the photoionization effect for low luminous galaxies at z~2-3. The quasars are selected to have various properties, such as radio-quiet/loud, less/more massive black hole mass, and bright/faint in order to examine a variation of the ionization effects. We selected Lyman alpha emitters (LAEs) in each quasar fields to obtain 1297 LAEs in total. The vicinity of quasars was defined by the region where the local UV radiation is expected to be enhanced compared with the UV background. We found that LAEs with high rest-equivalent width of Lyman alpha emission, EW0 ? 150A or faint UV luminosity,  MUV ? -17.0, are averagely segregated in the vicinity of the quasars. The value of EW0 or MUV corresponds to the notably smaller halo mass Mh ~  109 - 1010M?. The LAEs with such halo mass are expected to be subjected from quasar  photoevaporation in a hydrodynamical simulation. The feedback seems to be less effective in Hyper luminous or dusty quasar fields, implying that the quasars are thought to be in the early stage of quasar active phase. In addition, it is found that the quasar pair tend to reside in the LAE overdense regions.

Foreground Subtraction in redshifted 21cm Observations - Simulations and Observations

Datta, Abhirup

Observations of HI 21 cm transition line is an important and promising probe into the cosmic Dark Ages and Epoch of Reionization. Detection of this redshifted 21 cm signal is one of the key science goal for several upcoming and future low frequency radio telescopes like Hydrogen Epoch of Reionization Array (HERA), Square Kilometer Array (SKA) and Dark Ages Radio Explorer (DARE). One of the major challenges for the detection of this signal is the accuracy of the foreground source removal. At these frequencies the signal is largely dominated by bright foregrounds which are four to five orders of magnitude stronger than the redshifted signal.In addition, the ground based experiment are affected by the human generated RFI , like the FM band, and Earth’s ionosphere.The diffuse galactic synchrotron emission is expected to be the most dominant foreground. Several novel techniques have been explored already to remove bright foregrounds from both interferometric as well as total power experiments. Also, several telescopes have been used to characterise the foregrounds both in the northern and southern hemispheres. Here, we present results from both simulations with novel techniques as well as real observations with the SKA pathfinder for India, the uGMRT. In this presentation, we discuss results from a) Observations with the uGMRT in order to constrain nature of the foreground sources near the redshifted 21cm signal from Epoch of Reionization, and b) application of Artificial Neural Network to detect the faint 21cm global signal in presence of the strong foregrounds as well as imperfect instrument.

The evolution of galaxy stellar mass functions at z = 6-9 in the Hubble Frontier Fields

Bhatawdekar, Rachana

Exploring the very first galaxies is one of the major contemporary problems in astronomy. We do not know when the first galaxies formed, nor how their formation occurred. The James Webb Space Telescope (JWST) will be launched between March and June of 2019 and will search for the First Light objects in the redshift range of z=10-15. Reaching these galaxies will be routine with JWST, however, until then, our best chance to study these systems is through deep observations of lensing clusters with the Hubble Space Telescope (HST) by using them as `Cosmic Telescopes'. Therefore, to extend its reach even farther beyond its technical capabilities before JWST is launched, the HST is observing six massive clusters of galaxies as gravitational lenses to find the faintest and earliest galaxies in the Universe, ~10-100 times fainter than any previously studied, as a part of the Hubble Frontier Fields (HFF) program. In this talk, I will present how we detect and examine the objects behind HFFs lensing cluster MACSJ0416.1-2403, Abell 2744 and their parallel fields.  We have developed a novel method to subtract the massive galaxies from these clusters, allowing for a deeper and cleaner detection of the faintest systems. We present a photometric study of distant z>5 galaxies using all 10 bands available for Frontier Fields (HST, Spitzer and K-band). From this, we have derived the first galaxy stellar mass function (GSMF) at z > 5 for Frontier Fields program. I will further discuss how these results reveal new information on the faint-end of the mass function from the faintest galaxies at high-z, unveiling the potential science that can be done with JWST data.

SCUBA-2 Observations of High-redshift Clusters/Protoclusters of Starbursting Galaxies Selected by Planck and Herschel

Cheng, Tai-An

Crossmatching between Planck and Herschel (HerMES and H-ATLAS surveys) data has revealed a number of candidate high-redshift clusters/protoclusters with starbursting galaxies. These starbursting galaxies are believed to be progenitors of quiescent and elliptical galaxies residing in cores of today's massive galaxy clusters. Hence studies of these starbursting protoclusters and their cluster galaxies are important in understanding the formation of clusters and cluster galaxies. In this talk we will present follow-up observations of 13 of our candidate starbursting protoclusters using SCUBA-2 at 850 micron on the JCMT. Combining other far-infrared instruments, such as Herschel-SPIRE, we have estimated the colours, number counts, photometric redshifts, etc., of these protocluster candidates. We found that these candidates are likely to be protoclusters of starbursting galaxies in their formation periods. Crossmatching with our multi-wavelength follow-up data also reveals their radio and optical/near-infrared properties, such as multiplicity, morphologies, and possible AGNs.

Cosmological constraints from high-SNR weak lensing peak statistics using KiDS-450

Liu, Xiangkun

Emerged as one of the important probes in cosmological studies, weak lensing (WL) peak statistics is an efficient way to probe the nonlinear regime of the structure formation, and thus can provide important complements to the cosmic shear two-point correlation analysis. In this talk, I will report our latest cosmological results with high-SNR WL peak statistics using ~450 deg2 of imaging data from the Kilo Degree Survey (KiDS-450) . Accounting for different systematics, particularly for the boost factor and the effect of baryons on the mass-concentration relation of dark matter haloes, we derive the cosmological constraints on (Om, s8) and find a slightly flatter degeneracy direction compared with the cosmic shear analyses, which indicates that combining cosmic shear with peak statistics has the potential to break the degeneracy in Om and s8. Our results are consistent with the cosmic shear tomographic correlation analysis of the same data set and ~2s lower than the Planck 2016 results. More thorough studies on different systematic effects should be performed to understand the origin of this discrepancy.

Dust in Clusters: Separating the Contribution of Galaxies and Intracluster Media

Gutierrez, Carlos

Analyzing Herschel data for a large sample clusters of galaxies up to redshift 0.70 strong constraints ontheir mean intracluster emission of dust have been obtained; withina radius of 5 arcmin centered in each cluster, the 95% C.L. limits obtained are 86.6,48.2, and 30.9 mJy at the observed frequencies of 250, 350, and 500 micras. From theserestrictions, and assuming physical parameters typical of interstellar media in theMilky Way, we have obtained tight upper limits on the visual extinction of backgroundgalaxies due to the intracluster media (ICM): AV(95% C.L.) <~ 10^(-3) mag. Strongconstraints are also obtained for the mass of such dust; for instance, using the dataat 350 mum we establish a 95% upper limit of <10^9 Msun within a circle with aradius of 5 arcmin centered in the clusters. This corresponds to a fraction of thetotal mass of the clusters of 9.5 × 10^(-6), and indicates a deficiency in thegas-to-dust ratio in the ICM by about three orders of magnitude in relation to thevalue found in the Milky Way. Computing the total infrared luminosity of the clustersin three ranges of redshift (0.05-0.24, 0.24-0.42, and 0.42-0.71) and two ranges ofmass (<10^14 and >10^14 Msun), respectively, a strong evolution of luminosity inredshift (L ~ z^1.5) for both ranges of masses is found. The results indicate a strongdeclining in star formation rate with time in the last ~6 Gyr.

Star Formation Activity and Molecular Gas in Nearby Galaxies across Environments

Koyama, Shuhei

The fraction of passive early-type galaxies increases with local galaxy number density, while that of young, star-forming late-type galaxies decreases. These strong correlations between galaxy properties and environment suggest that there exist some mechanisms which accelerate galaxy growth and/or efficient quenching of star formation in high-density environments, so called environmental effect. However, the physical mechanisms responsible for the environmental effect are still unclear, and identifying the key mechanism is one of the most important goals of the modern extra-galactic astronomy.To reveal these mechanisms, we present the molecular gas mass fraction (f(H2) = M(H2)/M*) and star formation efficiency (SFE = SFR/M(H2)) of local galaxies on the basis of our new CO(J=1-0) observations with the Nobeyama 45m radio telescope, combined with the COLDGASS catalog, as a function of galaxy environment. As a result, we revealed that both f(H2) and SFE have strong positive correlations with the SFR offset from the star-forming main sequence (?MS), and most importantly, we find that these correlations are universal across all environments.Our results demonstrate that the average f(H2) and SFE are determined by the average ?MS of the sample, regardless their surrounding environment. Since the average ?MS strongly depends on environment, it is not surprising to see the environmental dependence of average f(H2) and SFE if the samples are selected randomly without considering their ?MS distribution. In other words, our results suggest that f(H2) and SFE do not depend on environment at fixed ?MS. Based on our observational results, we conclude that the star formation process occurring within individual galaxies is not strongly affected by their global environment, but primarily controlled by their molecular gas content. In other words, our results suggest that the role of environment is to reduce the gas reservoir in galaxies.

MOS spectroscopy of a z= 6.5 proto-cluster candidate galaxies

Calvi, Rosa

Galaxy clusters are the most massive gravitationally bound structures in the universe. They form in regions of enhanced dark matter density. The distribution of those structures at different redshifts tell us how the primordial density fluctuations evolve in a given cosmology. Hence, the detection of proto-clusters at very high-z sets important constraints on the cosmological models in use. We show the results of two runs of  multi-object spectroscopic observations of the subset of candidate LAEs sources at z=6.5 that we could fit in one OSIRIS/GTC mask: the imaging observations, including the observing strategy, the data reduction and its analysis. 

Towards the formation theory of protoclusters and superclusters of galaxies: method of random matrices

Nuritdinov, Salakhutdin

At an earlier stage of the Universe evolution the influence of effects of high non-stationarity and turbulence on a separated volume has a random character. It is interesting to find out whether the statistical effect of the randomness can bring to the formation of volume protoclusters and superclusters of galaxies or we will have an elongated formation. A computer program of this process is worked out by the method of random matrices. In the report the algorithm and preliminary results will be given.

The Star-Formation History of the Early Universe as Revealed by Blind Searches for Far-infrared Emission Lines

Hayatsu, Natsuki H.

Using blind line searches to understand the cosmic star-formation history is one of the strategies that will be pursued by next-generation millimetre/sub-millimetre single-dish telescopes which will have high sensitivity and mapping speed.  Before moving into such a new era, it is essential to develop a method to efficiently detect faint line-emitting sources whilst considering the completeness of source detection and contamination by false detections.  Furthermore, in order to propose robust strategies for blind line searching, it is necessary to know to what extent we can constrain the luminosity function using existing ALMA archival data.In this presentation, we report the current status of tests using a blind line-searching method and show preliminary results using ALMA archival data.  We discuss the detectability of line-emitting sources with various properties, e.g. peak flux, line width and spatial size, by injecting artificial sources into the ALMA data.  To be as realistic as possible, this is done in the visibility plane, and we also investigate the effect of non-Gaussian noise.  We compare the performance of the following three methods: (1) clump-finding and smoothing, (2) matched-filter analysis and (3) Bayesian analysis.We plan to apply our final results to various science cases for future observations, e.g. cross-checking the luminosity density using an intensity-mapping technique or estimating the redshift evolution of ionisation state or metallicity by combining with JWST or SPICA data. We plan to release our code as a CASA task.

The galaxy cluster of GRBH051022 at z=0.8 by Subaru HSC

Pinter, Sandor

Gamma-ray bursts (GRBs) are the most powerful explosions in the Universe. To determine whether their host galaxies (GRBH) are in special positions in their local neighborhood we performed high spatial resolution multi-wavelength Subaru Hyper Suprime-Cam observations toward GRB051022. From the deep images one can derive photometric redshifts for the nearby galaxies which can be used to indentify the galaxy cluster where the GRB occured. Than the parameters of those galaxies can be estimated using SED fitting methods to derive the position of the GRBH within the cluster as well as the difference of some physical properties compared to the cluster's average.

Additional ALMA Observations of Major Mergers Among the Host Galaxies of Fast-growing, High-redshift, Supermassive Black Holes

Nguyen, Nathen

We present new ALMA band-7 data for a sample of twelve luminous quasars at z~4.8, powered by fast-growing super massive black holes (SMBHs) with rather uniform properties: the typical accretion rates and black hole masses are L/L_edd ~ 0.7 and M_BH ~ 10^9 solar masses. Our sample of twelve sources is a follow up of six pilot observations lead by Benny Trakhtenbrot. Our sample consists of six “FIR-bright” sources, which were individually detected in previous Herschel/SPIRE observations with star formation rates of SFR > 1000 Solar masses per year, and six “FIR-faint” sources for which Herschel stacking analysis implies a typical SFR of ~400 Solar masses per year.The dusty interstellar medium in the hosts of eleven of the twelve quasars is clearly detected in the ALMA data and resolved on scales of ~2 kpc, in both continuum (rest wave length ~ 150 micrometers) and [C II] with wavelength 157.74 micrometer line emission. The continuum emission is in good agreement with the expectations from the Herschel data, confirming the intense SF activity in the Quasar hosts. We detect companion sub-millimeter galaxies (SMGs) for two sources, one faint and one bright. This is ratio (1 in 6 targets having companions) is much lower than the ratio found in our pilot sample (1 in 2). While we argue that these major mergers are important drivers for rapid early SMBH growth, the smaller percent of companions implies that other factors are leading to the rapid growth, and are in fact more common than major mergers.

Cluster star formation quenching probed by gas metallicity

Ziegler, Bodo

In Maier+16 we presented an analysis of gas metallicity (O/H abundances) in the CLASH cluster MACS0416 at z=0.4 subdividing 76 members in phase space into accreted and infalling galaxies finding a stark contrast: the fraction of metal-rich galaxies is in the inner region much higher than in the outskirts (63% to 28%). The high O/H abundances are not in line with the Fundamental Metallicity Relation and violate simple bathtub model predictions. Chemical evolution models instead demonstrate that a shut-off of (primordial) gas accretion onto the disk is required that can be achieved by strangulation mechanisms that also quench ongoing star formation. Currently, we expand this study by analysing galaxies in six LoCuSS clusters at z=0.2 revealing a "slow-then-quick" quenching process for infalling galaxies. These observational results are compared to cosmologically zoom-in simulations coupled to nebular-emission models by Hirschmann+17 to trace the impact of various star formation histories of cluster galaxies. Altogether we investigate quantitatively the physical processes of the transition of active galaxies into passive cluster members.

Evolution of N/O ratios in galaxies from cosmological chemodynamical simulations

Vincenzo, Fiorenzo

We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved galaxies. We make use of a cosmological hydrodynamical simulation including detailed chemical enrichment, which properly takes into account the variety of different stellar nucleosynthetic sources of O and N in galaxies. For the local and global measurements, the observed increasing trend of N/O at high O/H can be explained, respectively, (i) as the consequence of metallicity gradients which have settled in the galaxy interstellar medium, where the innermost galactic regions have the highest O/H abundances and the highest N/O ratios, and (ii) as the consequence of an underlying average mass-metallicity relation that galaxies obey as they evolve across cosmic epochs, where -- at any redshift -- less massive galaxies have lower average O/H and N/O ratios than the more massive ones. For both local and global relations, the predicted N/O--O/H relation is due to the mostly secondary origin of N in stars. We also predict that the O/H and N/O gradients in the galaxy interstellar medium gradually flatten as functions of redshift, with the average N/O ratios being strictly coupled with the galaxy star formation history. Because N production strongly depends on O abundances, we obtain a universal relation for the N/O--O/H abundance diagram whether we consider average abundances of many unresolved galaxies put together or many abundance measurements within a single spatially resolved galaxy.

Probing the Mass Assembly of Galaxy Systems With Weak Lensing

Zamorano Vitorelli, André

Several indicators have been proposed as proxies for early formed galaxy systems: magnitude gaps (the difference in magnitude between the central galaxy and the brightest satellite in the inner region), the physical offset between the central galaxy and the luminosity centroid, the mass-concentration relation, and the luminosity of the brightest galaxy among others. We investigate the nature of fossil systems (those with very large magnitude gaps) in particular, and the mass assembly history of galaxy systems in general, using weak lensing to characterize their mass-concentration relations and overall mass distributions, and compare it to the other indicators and their luminosity functions in data from several current (SDSS, CS82) and upcoming (Blink, JPAS) surveys, as well as their luminosity functions across several redshift slices.



Using the Hubbles law V=H*R the dark energy produce an acceleration a=R*H2. We use the approximation of the universe as a Minkowski flat spacetime and Maxwell type equations (GEM formalism) to calculate inferior bound to the gravitomagnetic acceleration that hole universe produce over one galaxy located at cosmological distance Z of the Milky Way. As result we find that gravitomagnetic acceleration a= 0.27*Z*H2 which implies, it can explain at least 27 percent of the dark energy effect.

Parameters of GRB host galaxies based on CIGALE SED fitting

Kovács, Tímea Orsolya

Gamma ray bursts (GRB) are the most luminous known events in the gamma ray sky, they are sudden flashes which are strongest in the gamma range, and can be observed up to high redshift. GRBs can be divided into four groups based on their duration: short, long, intermediate and ultralong. Long GRBs (LGRB) are emitted at the end of the lives of massive stars, during supernova explosions. Because these massive stars are very short lived, LGRBs can indicate star formation in distant galaxies.It is crucial to have observations in the far infrared to constrain the dust emission, and with that the star formation rate of these galaxies. So we determined Herschel fluxes and upper limits from Herschel intensity maps, and together with photometric data collected from the literature and databases we fitted the spectral energy distributions of these GRB hosts with CIGALE (Code Investigating GALaxy Emission), a spectral energy fitting software package developed by the Laboratoire d'Astrophysique de Marseille.CIGALE has multiple models for different physical processes in galaxies, and can handle a wide wavelength range from the UV to the radio. We determined different parameters of GRB hosts, for example the stellar mass, the dust mass, the luminosity and star formation rate. We compared the results with the main sequence of galaxies and with the results of previous articles.

The mass and light distributions in groups and superclusters of galaxies

Castejon Molina, Mirian

Through mass map reconstruction from weak gravitational lensing it is possible to recover the matter distribution of the large scale structure from measurements of galaxy shapes. This technique offers the possibility of detecting and probing mass concentrations by their gravitational effect on the rays of light coming from distant galaxies only, without relying on simplifying physical assumptions about the nature of that mass, making it a direct probe of dark matter. Those dark matter maps allow the determination of cosmological parameters and the identification of structures, such as groups, clusters and superclusters of galaxies. Mass maps are also particularly important to study the connection between dark and baryonic matter, through mass-to-luminosity ratio maps in diverse environments.The goal of this study is to investigate the relationships between peaks in mass and luminosity maps to understand the nature of substructures in superclusters of galaxies, and the mass distribution of fossil groups (those in which the central galaxy dominates the overall group luminosity).For this study we use CFHT images of five fossil galaxy groups in two bands  (g, r) and Subaru observations of two galaxy superclusters in z~0.4 from Las Campanas Distant Cluster Survey (LCDCS) in four bands (g,r,i,z), both with excellent depth and quality.

Galaxy clusters mergers, shocks and turbulence: what are the effects on galaxy evolution?

Afonso, Ana

Galaxy populations in relaxed clusters are dominated by ellipticals. However, little is known about the effect of disturbed clusters on galaxy evolution. Merging clusters represent an extremely violent environment permeated by Mpc-wide shock waves and cluster-wide turbulence. Stroe et al. (2016) completed the first narrow-band survey of Ha emitters in a sample of low-redshift clusters sampling a range of masses and relaxation states. The results have shown that relaxed environments have 25 times fewer Ha emitters when compared to merging clusters. What drives this reversal of typical environmental trends and how could shocks and turbulence trigger star formation in cluster galaxies remains unclear. Multi-object spectroscopic observations have been obtained using VLT/VIMOS and WHT/AF2 in order to efficiently follow-up star-forming galaxies and AGNs uniformly selected in relaxed and merging clusters. This allowed us to measure the precise redshift, powering source, metallicity, electron density and ionization parameters of these sources as well as to correlate the optical spectroscopic properties with the galaxy morphologies. Given the similarities between low-redshift disturbed clusters and high-redshift protoclusters, this unique study not only provides an excellent opportunity to connect observations and theory but it may also provide important clues to the evolution of galaxies at high-redshift analogs. 

Infrared photometry of GRB host galaxies with deblending algorithm

Kovács, Tímea Orsolya

Gamma ray bursts (GRB) are the most luminous events in the gamma ray sky. The longest GRB signal the death of very massive stars and are observed up to redshift 9. Many of their host galaxies have been observed spectroscopically and most of them have been observed with the X-Shooter spectrograph of VLT. Another method to calculate the parameters of galaxies is to fit their Spectral Energy distributions (SED). This method offer the best results when using Infrared data which are of paramount importance to determine host parameters, especially the star formation rate. However, the best understanding of the host parameters is obtained joining spectroscopy and SED fitting.The aim of this work is to enlarge the sample of hosts with IR detection and X-Shooter spectroscopy. Therefore, from the X-Shooter sample we chose GRB hosts with observations from the Spitzer Space Telescope, and carried out source detection and photometry on Spitzer images with the IDL code CuTEx (CUrvature Thresholding EXtractor). CuTEx was developed to perform photometry on crowded fields observed with the Herschel space telescope. The code finds sources on second derivative maps, and then fits the close sources simultaneously with 2D Gaussians.We compared fluxes of the GRB hosts obtained with multiple methods: i) with the photometry routine in CuTEx; ii) aperture photometry on images without the contaminating sources, removed using model images obtained from the parameters of the Gaussians fitted by CuTEx.When possible we compared the results with the literature. These results will be used to fit the SEDs of the host galaxies, that will be later compared with the results obtained from the analysis of X- Shooter spectra. Thanks to this work, we increased the number of hosts with IR detection and obtained more robust photometry for most of the other hosts.

On the UV compactness and morphologies of typical Lya emitters from z~ 2 to z~ 6

Afonso, Ana

Lya is, intrinsically, the strongest nebular emission line in actively star-forming galaxies (SFGs), but its resonant nature and uncertain escape fraction limit its applicability. The structure, size, and morphology may be key to understand the escape of Lya photons and the nature of Lya emitters (LAEs). In Paulino-Afonso et al. (2018) we investigate the rest-frame UV morphologies of a large sample of ~4000 LAEs from z~2 to z~6, selected in a uniform way with 16 different narrow- and medium-bands over the full COSMOS field (SC4K, Sobral et al., 2018). From the magnitudes that we measure from UV stacks, we find that these galaxies are populating the faint end of the UV luminosity function. We find also that LAEs have roughly the same morphology. The median size, ellipticities, Sérsic index, and light concentration show little to no evolution. LAEs with the highest equivalent widths are the smallest/most compact. In a scenario where galaxies with a high Lya escape fraction are more frequent in compact objects, these results are a natural consequence of the small sizes of LAEs. When compared to other SFGs, LAEs are found to be smaller at all redshifts. The difference between the two populations changing with redshift, from a factor of ~1 at z=5 to SFGs being a factor of ~2-4 larger than LAEs for z=2. This means that at the highest redshifts, where typical sizes approach those of LAEs, the fraction of galaxies showing Lya in emission should be much higher, consistent with observations. In this era of new and upcoming cutting-edge facilities, linking the theoretical perspectives and numerical simulations with the observational studies of the properties of the LAEs across the Universe seems to be a key to understand reionization and early stages of galaxy formation.

Low - frequency observations and Cosmic Ray propagation in NGC 6946

Piotrowska, Julia

Cosmic Ray electrons (CREs), which are propagating through the interstellar medium in the presence of magnetic field are traced by radio synchrotron emission. Since low radio frequency CREs can travel to more distance regions from galactic disk than at higher frequencies hence more extensive radio synchrotron halos are expected to appear at longer wavelengths. Observations of the grand-design face-on spiral galaxy NGC6946 was conducted with the LOFAR High Frequency Antennas (HBA) in order to explore CREs propagation in interarm regions and extended disk.We also study the local radio - FIR correlation between non-thermal radio emission at 150\,MHz and the far - infrared emission at 70\,$\mu$m in arm and interarm region at scales 1kpc.We compare obtained radial profile of radio emission at 150\,MHz with its counterparts at 330\,MHz and 1.4\,GHz to study scale lengths of outer disk. We determined total magnetic field by assuming equipartition between the energy density of CREs(synchrotron emission) and magnetic field. Analysis  of integrated radio emission spectra shows no significant flattening at low - frequencies due to thermal (free - free) absorption.

State of the Art Population Synthesis Models

Bruzual, Gustavo

We present state of the art population synthesis models that improve on the following aspects with respect to most available models. (a) Treatment of the UV spectral range, including new evolutionary tracks and updated treatment of the ionizing radiation emitted by the stellar population, including a new treatment of P-AGB evolution and emission spectra. (b) Improved treatment of TP-AGB stars that dominate the NIR spectral range. The number of these stars present in a stellar population has been calibrated carefully by comparison with observations of the LMC/SMC, and the spectra assigned to these stars include both the stellar emission and the emission from circumstellar dust. (c) Definition of new diagnostics to characterize the combined stellar and nebular emission and the cold ISM in galaxies. Models are available in a wide range of metallicity, from Z = 0 to Z = 0.06, and are ready to use to interpret the spectra of galaxies of any age at low and high redshift.

Galaxy Clusters and Olbers’ Paradox

Molnar, Sandor

Foreground galaxy clusters may pose a difficulty to detect protoclusters, therefore it is important to study the distribution of these clusters in the sky and estimate the confusion they may cause. We use a semi-analytic modeling based on the latest results of cosmological simulations to study the angle on the sky occupied by the gas in clusters of galaxies. We simulate images of X-ray emission and Sunyaev-Zel’dovich signal of an evolving population of clusters of galaxies and estimate their covering factor.

The impact of kinematics on the SFH of the Herschel Reference Survey (HRS)

GOMEZ LOPEZ, Jesus Alberto

The Herschel Reference Survey (HRS) is a complete K-band-selected, volume-limited sample of 323 nearby galaxies spanning a wide range in morphological type and stellar mass. Gathering and analyzing high-resolution 2D Perot-Fabry spectroscopic H-alpha data for the star forming objects of the sample is providing a complementary kinematical information to the sample. I have been actively participating in a long-term observing campaign started in December 2015 and scheduled for 3 years, at the 1.93m telescope at OHP observatory with GHASP instrument, and at the 2.1m telescope in SPM Observatory using the PUMA instrument. Combined with multifrequency data spanning the whole electromagnetic spectrum (from UV GALEX to far-IR Herschel, including HI and CO), and multizone chemo-spectrophotometric models of galaxy evolution as well as with the CIGALE SED fitting code, these data are necessary to study the role played by velocity rotation and turbulence down to kpc scales in the process of star formation occurring in normal late-type galaxies. This is being done by comparing the radial variations of the star formation activity of galaxies, corrected for dust attenuation using infrared data, and modulated by the variation of the rotational velocity, to the gas surface density of the galaxies. The multifrequency dataset in hour hands will allow us to determine in a self consistent way, and with unprecedented precision, the 2D-distribution of the different galaxy components (atomic, molecular, dust masses), the dust attenuation, the typical age and metallicity of the different stellar populations and several other properties critical for the study of the radial variation of the star formation history of these galaxies.

Color Dispersion as an Indicator of Stellar Population Complexity in Galaxies

Lee, Joon Hyeop

We investigate the properties of 32 bright (Mr = -21.3 mag) galaxies with various morphological types in two low-redshift clusters Abell 1139 and Abell 2589, using the pixel color-magnitude diagram (pCMD) analysis technique. After masking contaminants with two-step procedures in our CFHT/MegaCam observation images, we examine how the detailed properties in pCMDs depend on galaxy morphology and infrared color. The mean g - r color as a function of surface brightness (µr) in the pCMD of a galaxy shows fine performance in distinguishing between early- and late-type galaxies, but it is not perfect because of the similarity between elliptical galaxies and bulge-dominated spiral galaxies. On the other hand, the g - r color dispersion as a function of µr works better. We find that the best set of parameters for galaxy classification is the combination of the minimum color dispersion at µr = 21.2 mag/arcsec2 and the maximum color dispersion at 20.0 = µr = 21.0 mag/arcsec2: the latter reflects the complexity of stellar populations at the disk component in a typical spiral galaxy. Finally, the color dispersion measurements of an elliptical galaxy appear to be correlated with the WISE infrared color ([4.6] - [12]). This indicates that the complexity of stellar populations in an elliptical galaxy is related with its recent star formation activities. From this observational evidence, we infer that gas-rich minor mergers or gas interactions may have usually happened during the recent growth of massive elliptical galaxies.

The YSZ,Planck -YSZ,XMM scaling relation and its difference between cool-core and non-cool-core clusters

JIA, Shumei

We construct a sample of 70 clusters using data from XMM-Newton and Planck. YSZ,XMM is calculated by accurate de-projected temperature and electron number density pro?les derived from XMM-Newton. YSZ,Planck is the latest Planck data restricted to our precise X-ray size ?500. To study the cool-core in?uences on YSZ,Planck -YSZ,XMM scaling relation, we apply two criteria, limits of central cooling time and classic mass deposition rate, to distinguish cool-core clusters (CCCs) from non-cool-core clusters (NCCCs). We also use YSZ,Planck from other papers, which are derived from di?erent methods, to con?rm our results. The intercept and slope of the YSZ,Planck -YSZ,XMM scaling relation are A = -0.86±0.30, B = 0.83±0.06. The intrinsic scatter is sins = 0.14±0.03. The ratio of YSZ,Planck/YSZ,XMM is 1.03±0.05, which is perfectly agreed with unity. Discrepancies of YSZ,Planck -YSZ,XMM scaling relation between CCCs and NCCCs are found in observation. They are independent of cool core classi?cation criteria and YSZ,Planck calculation methods, although discrepancies are more signi?cant under the classi?cation criteria of classic mass deposition rate. The intrinsic scatter of CCCs (0.04) is quite small compared to that of NCCCs (0.27). The ratio of YSZ,Planck/YSZ,XMM for CCCs is 0.89±0.05, suggesting that CCCs YSZ,XMM may overestimate SZ signal. By contrast, the ratio of YSZ,Planck/YSZ,XMM for NCCCs is 1.14±0.12, which indicates that NCCCs YSZ,XMM may underestimate SZ signal.


Higuera G., Mario A.

Using techniques of integral field spectroscopy, it was made a study of the impact of AGN in its host galaxy, looking for kinematics of ionized gas of Ha, [OIII]5007 lines. There is evidence of a distortion in the velocity distribution field for objects with presence of an AGN. In order to develop the velocity field maps there was used a pipeline PIPE3D, which was elaborated by Sánchez, S.F. et al. 2016. There was found that in the central region of each working galaxy, there is evidence of higher kinematic speeds and higher dispersion speeds for the Ha and [OIII]5007 emission  lines, compared with the velocities that were observed in the control galaxies. It can confirm the activity in the nuclear region due to the presence of an AGN. It was found a disturbance in the velocity distribution field of the host galaxy, an alteration of the kinematic axis and of the velocity field distribution, which is different than expected for ideal disk galaxies. In contrast, the control galaxies showed properties of rather continuous and symmetric velocity distribution, as well as the presence of a kinematic axis. A difference in the distribution of kinematic speeds of Ha was observed in the circum-nuclear region of active galaxies. In a first approximation the object NGC 5443, presents higher kinematic speeds of Ha and [OIII]5007, in the central region compared to those that were evidenced in non-active galaxies, being very similar to the distributions found in the work galaxies NGC 5971 and NGC 2410. The object NGC 5443 does not have records in the literature as a LINER type object or as an active galaxy. It can be inferred first, that the IFS in a first approximation, is a potential tool that allows to demonstrate the presence of an AGN in places where previously such evidence could not be found; and secondly, that the maps of the ionized gas kinematics trace the possible existence of an AGN that may or may not be identified by other methods of study.

Discovery of GeV gamma-ray emission from the LMC B0443-6657 with the Fermi Large Area Telescope

Tang, Qingwen

I would like to report the discovery of gamma-ray detection from the LMC B0443-6657 using the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. LMC B0443-6657 is a flat spectrum radio source and possible to associate with a supernova remnant in the Large Magellanic Cloud (LMC N4). Employing the 8 years of the LAT observations between 0.2-100~GeV, our result reveals a significant excess (>9.4 sigma) above the background, which is based on either the 4-years LAT catalog (Acero et al. 2015 ApJS) or the best source model of 73.3 months data (Ackermann et al. 2016 A&A). The hadronic model predicts a low X-ray or TeV flux while the leptonic predicts an observable flux in these two energy bands. The follow-up observations of the LMC B0443-6657 in X-ray or TeV band would help constrain the contribution from the CR electrons and protons.

CANDELS: From Outside-in to Inside-out Quenching of Galaxies at Intermediate Redshift

Liu, Fengshan

We investigate the galaxy quenching process at intermediate redshift using a sample of $\sim4400$ galaxies with $M_{\ast} > 10^{9}M_{\odot}$ between redshift 0.5 and 1.0 in all five CANDELS fields. We divide this sample, using the integrated specific star formation rate (sSFR), into four sub-groups: star-forming galaxies (SFGs) above and below the ridge of the star-forming main sequence (SFMS), transition galaxies and quiescent galaxies.We study their $UVI$ ($U-V$ versus $V-I$) color gradients to infer their sSFR gradientsout to twice effective radii. We show that on average both star-forming and transition galaxies at all masses are not fully quenched at any radii, whereas quiescent galaxies are fully quenched at all radii. We find that at low masses ($M_{\ast} = 10^{9}-10^{10}M_{\odot}$) SFGs both above and below the SFMS ridge generally have flat sSFR profiles, whereas the transition galaxies at the same masses generally have sSFRs that are more suppressed in their outskirts. In contrast, at high masses ($M_{\ast} > 10^{10.5}M_{\odot}$), SFGs above and below the SFMS ridge and transition galaxies generally have varying degrees of more centrally-suppressed sSFRs relative to their outskirts. These findings indicate that at $z\sim~0.5-1.0$ the main galaxy quenching mode depends on its already formed stellar mass, exhibiting a transition from the outside-in at $M_{\ast} < 10^{10}M_{\odot}$ to the inside-out at $M_{\ast} > 10^{10.5}M_{\odot}$. In other words, our findings support that the internal processesdominate the quenching of massive galaxies, whereas the external processes dominate the quenching of low-mass galaxies.

Evolution of Isophote Shapes of Early-Type Galaxies In Massive Clusters from z~1

Mitsuda, Kazuma

Galaxy clusters provide unique environments for studying evolution of early-type galaxies (ETGs) because there are large number of ETGs including very massive ones such as central and cD galaxies, and galaxies evolve within the cluster once they enter into such an environment. Exploiting this advantage, we compare the isophote shape parameter a4 between z~1 and 0 as a proxy for dynamics to investigate the epoch at which the dynamical properties are established. We create cluster ETG samples with log(M*/Msun)>=10.5 with spectroscopic redshifts. We have 130 ETGs at z~1 from the Hubble Space Telescope Cluster Supernova Survey and 355 ETGs at z~0 from the Sloan Digital Sky Survey. We find similar dependence of the a4 parameter on stellar masses at z~1 and 0; the main population changes from disky to boxy at a critical mass of log(M*/Msun)~11.5 with the massive end dominated by boxy ones. The disky ETG fraction is consistent between these redshifts. Although uncertainties are large, the results suggest that the isophote shapes and probably dynamical properties of cluster ETGs are already in place at z>1 and do not significantly evolve at z<1, despite significant size evolution. The constant disky fraction implies that the processes responsible for the size evolution are not violent enough to convert the dynamical properties. The boxy shapes of massive ETGs in z~1 clusters can be originated from major mergers at z>1 when the velocity dispersion of clusters are small. We are now developing a next generation adoptive optics system for the 8-m Subaru telescope aiming to obtain spatially resolved properties of high-redshift galaxies such as stellar kinematics and stellar population which will provide new insights into evolution of galaxies and clusters at high redshifts.

The Tianlai 21cm experiment

Chen, Xuelei

The Tianlai 21cm intensity mapping experiment is located in Hongliuxia, Balikun (Barkol) county in Xinjiang, China. Currently there is a cylinder array with three cylinder reflectors, and a dish array with 16 dishes. The aim of the pathfinder is to explore the 21cm observation and data processing techniques, which if successful can map out the large scale structure with high precision and fast speed, and by using the baryon acoustic oscillation features the dark energy equation of state can be constrained.  I present the details of the experiment setup, the organization of the Tianlai international collaboration, and the progress of the Tianlai survey.

Proto-BCG candidates at z~4 by using HSC-SSP data

Ito, Kei

 Brightest Cluster Galaxy (BCG) is the brightest and the most massive galaxy in a galaxy cluster. In nearby universe, BCGs are known to have distinguished characteristics compared to other cluster galaxies and field galaxies. Theoretical research predicts that most of the stellar mass was already formed at z~3 (De Lucia and Blaizot 2007); therefore, it is a key to find the progenitor of BCGs (proto-BCGs) at high-redshift in order to understand the formation of BCGs. However, it has been difficult to systematically study the high-z BCGs due to a small size of previous protocluster sample. Here, we report our survey of proto-BCGs candidates at z~4 by using Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We are ongoing the largest survey of high-redshift protoclusters to date by using imaging data produced by HSC-SSP. We constructed g-dropout galaxies catalog and found 179 protocluster candidates at z~4 (Toshikawa et al. 2018) over 121 square degrees. This is roughly ten times larger than any previous survey, enabling us, for the first time, to also construct a large sample of proto-BCGs. After removing contaminants (e.g. foreground galaxies or stars) which dominate bright-end, we identified 58 proto-BCGs candidates by 1) selecting the brightest member galaxy in each protocluster and 2) requiring the magnitude difference between the fifth and the first in a region is greater than 1.1 mag in i-band. Interestingly, members of protoclusters with proto-BCGs are found to be redder in (i-z), indicating that the dust extinction is more severe than that in field galaxies and members of protoclusters without proto-BCGs. This suggests that proto-BCGs may trace more developed structures than those without proto-BCGs. Also, we report the result of the morphological analysis in this poster.

Photometric Properties and Spatial Distribution of RSGs of Nearby Galaxy System: Leo Triplet

Lee, Sowon

We present the near infrared JHK photometric properties and the spatial distribution of red supergiants(RSGs) of NGC 3623, NGC 3627 and NGC 3628 in the Leo Triplet system using the data obtained with 3.8m UKIRT(United Kingdom Infra-Red Telescope) at Hawaii. We checked interaction between the three galaxies by making a spatial density map of RSGs. From (J-K,K)0 Color-Magnitude Diagram which include resolved stars in three galaxy and control field with PARSEC isochrone, we figured out the RSG candidates of the Leo triplet are at 1.0 < (J-K)0 < 1.3, mK < 17.5 and separated them from background and foreground sources. Using gaussian kernel density estimation, we drew spatial density map of RSGs in the Leo triplet with an assumption that all RSGs are an identical population. The density map shows extended features of NGC 3628 to NGC 3627 along the declination direction. The asymmetries between NGC 3627 and NGC 3628 might be evidence for that the distribution of actual star components(RSGs) follows the neutral hydrogen distribution and also for interaction between two galaxies. And the extended features along the right ascension direction might be a supporting evidence for the existence of a TDG(Tidal Dwarf Galaxy). In case of NGC 3623, we could not see any sign of interaction in density map.

NIR Color–Metallicity Relations and Color Distributions of Globular Cluster system in Elliptical Galaxy NGC 4649 with Subaru/MOIRCS

Jeong, Jong-Hoon

We present Subaru Near-Infrared (NIR) photometry for the globular cluster (GC) system in NGC 4649 (M60), the giant elliptical galaxy belonging to the Virgo cluster. NIR data are obtained in Ks - band with the Subaru/MOIRCS, and HST/ACS and Gemini/GMOS optical data available in the literature are used to investigate the origin of GC color bimodality in early-type galaxies. A clear bimodal color distribution is observed in the optical colors g475 – z850 and g'– i', and this bimodality is commonly considered as evidence for the presence of two GC subpopulations with different metallicities. By contrast, the more metallicity-sensitive Opt-NIR colors such as z850 – Ks and i'– Ks show a considerably weakened or no bimodality in their distributions. Furthermore, color–color relations of the optical and Opt-NIR colors for the NGC 4649 GC system exhibit a nonlinear feature. Our results support the recent claim that the optical color bimodality observed in GC systems of early-type galaxies is caused by the nonlinear nature of their color–metallicity relations.

Stellar and AGN feedback in isolated early-type galaxies: the role in regulating star formation and ISM properties

Li, Yaping

Understanding how galaxies maintain the inefficiency of star formation with physically self-consistent models is a central problem for galaxy evolution. Although numerous theoretical models by invoking different feedback processes have been proposed in recent decades, the debate still exists. By means of high-resolution two-dimensional hydrodynamical simulations, we study the three feedback (the thermalization of winds from AGBs, red giants, planetary nebula phases, SNe feedback, and AGN feedback) effects in suppressing star formation activities on the cosmological evolution of early-type galaxies with different stellar masses. AGN feedback models are updated based on Yuan et al.'s recent work. The availability of gas sources for star formation comes exclusively from the mass losses of dying low-mass stars for most of our models. We find that SNe feedback can keep star formation at a significantly low level for low mass galaxies for a cosmological evolution time. For the high mass elliptical galaxies, AGN feedback can efficiently offset the radiative cooling and thus plays a dominate role in regulating the star formation activities. Such a suppression of star formation is extremely efficient in the inner region of the galaxies. As expected, AGB heating cannot balance the cooling losses in the whole galaxies and hence cannot account for the suppression for both cases. The hot plasma X-ray temperature $T_{\rm X}$ can be in agreement with the observed data with the inclusion of effective feedback processes. We further find that X-ray luminosity $L_{\rm X}$ for the hot gas in our effective feedback models is consistent with the observed values. These results thus suggest that we can use $T_{\rm X}$ and $L_{\rm X}$ to probe the role of different feedback processes. The inclusion of additional gas sources can make the mass scale between SNe and AGN feedback dominating in suppressing star formation decrease to an observationally inferred value of a few $10^{10}~M_{\odot}$.

Resolving the Missing AGN Problem with Radio Selection

Wilkes, Belinda

The complex nuclear structures of active galactic nuclei (AGN)lead to strong selection effects in most wavebands, including the X-ray.Highly obscured AGN are hard to find, and identify. Estimating theirnumbers, a function of luminosity and redshift, remains a major questboth for AGN science, and in understanding the level of accretionpower particularly in the early Universe.Multi-wavelength observations of the low-frequency, radio-selected 3CR luminousAGN sample (z>0.5) largely avoid selection biases, revealing the obscured AGN,and probing both their intrinsic, and orientation-dependent properties.Chandra, Spitzer, Herschel and multi-wavelength observations confirm thatthe FIR (> ~40um) does not depend on orientation and that ~half the sampleis significantly obscured with ~a quarter being Compton thick. This is alarger fraction than typically estimated for optically- or X-ray-selected,high-luminosity samples. Once the primary X-ray power-law is obscured, AGNX-ray spectra are complex, and detecting and estimating X-ray obscurationlevels becomes highly uncertain. This is particularly true for sources closeto the flux limit. The loss or miss-classification of obscured AGN in surveysalso results in large (*10-1000) uncertainties on their intrinsic luminosities.This may explain discrepant obscured fractions reported for variousoptical- and X-ray-samples, and may also affect the shape of derived luminosityfunctions. The use of independent measures of the AGN power, suchas the low-frequency radio, or [OIII] emission line luminosity, both used here, help tocounteract such problems, and so to probe the intrinsic AGN properties. Other properties which effect a radio galaxy's spectral energy distribution even when limiting the redshift range include: gravitational lensing (e.g. 3C220.3), and merger history.

A Blind Analytical CMB Foreground Removal Method: ABS

Yao, Jian

Recovering CMB temperature information out of received signal which includes complex foregrounds, calculating the power spectrum and then comparing with the related models to get cosmological parameters is a kind of basic pipeline in CMB research field. We focus on the first step which is a challenging task and present an analytical algorithm aiming at extracting CMB signal, then test it under different compositions of input signal, including dust, synchrotron, free-free and AME, which are simulated by PYSM, a python package. The power spectra recovered by our algorithm have shown a high consistency with the input values and performed well even in the extreme case. In the future, we will expand the application to CMB polarization, which contains much more information of cosmology. 

Local galactic kinematics from Gaia DR2 proper motions

Liao, Shilong

The stellar velocity field within 500pc of the solar system is investigated from the Gaia DR2 proper motions. The motion of the Sun with respect to the Local Standard of Rest is studied, the relative velocity field is modified in the frame work of the Milne-Ogorodnikov model, leading to eight parameters charcterizing the flow, including the Oort Constants. I use the data from Gaia DR2 and also the radial velocity information to determine the Oort Constants: A=14.7+-0.3km/s/kpc. B=-11.5+-0.4km/s/kpc, C=-3.5+-0.2km/s/kpc and K= -3.1+-0.5km/s/kpc. 

Application of fuzzy logic in the study of the variety of galaxies in the universe

Girola Schneider, Rafael

According to the most recent observation techniques, the great variety of galaxies existing in the near universe, shows the complexity of the physical processes responsible for their formation and evolution. The observations show the properties of galaxies that are at different distances. A model that explains the evolution of galaxies for different distances must be consistent in order to reproduce the local universe, since it represents the end point of evolution. As a continuation of the work on fuzzy logic in the context of the classification of galaxies, the theoretical and practical foundations of a method for the study of sky surveys are presented, in different wavelengths, analyzing the relationships between the properties of the stars, gas and dust that make up the galaxies at different times, using the information obtained (type, age, redshift) as validation measures for the optimal determination of stellar clusters, using fuzzy logic algorithms.

Dependence of substructure abundance of clusters on large-scale filaments

Shim, Junsup

Substructure abundance of clusters in large-scale filaments is studied to investigate the environmental dependence of halo formation by using the dark matter halos of Big Multidark-Planck simulations. The abundance of substructures with (M = 1012h-1M?) in cluster halos with (M = 1014h-1M?) are examined, as a function of the specific size of host filament defined as the spatial extent divided by the number of member clusters. The clusters in filaments with larger specific size tend to have fewer substructures or vice versa. This anti-correlation persists, even if the formation epoch of the clusters or the number of member clusters of the host filament is constrained. Assuming the filaments with the larger specific size form in higher tidal coherence regions, we claim that the stronger development of the flows perpendicular to the filament, obstructs satellites infalling and matter accreting onto the clusters. 

SAMI Galaxy Survey Data Release 2: Absorption-line Physics

van de Sande, Jesse

We present the second data release from the Sydney-AAO Multi-bundle Integral field Spectrograph (SAMI) Galaxy Survey at the Anglo-Australian Telescope. The data release will contain reduced spectral cubes for 1559 galaxies at 0.02 < z < 0.10. This release will also include stellar kinematic and stellar population value-added products derived from absorption line measurements, and all emission line value-added products from Data Release One. Our poster will highlight several galaxies from the SAMI Galaxy Survey that have interesting stellar and gas kinematics. For more information about data release 2, please see: https://protect-au.mimecast.com/s/anaNC3Q8Z2FVYo1LSgubFF?domain=sami-survey.org

The Hubble Space Telescope Frontier Fields Program

Koekemoer, Anton

[This abstract is for the Mini-symposium IV/V "Build-up of Galaxy clusters" on 27 Aug 2018]The Hubble Space Telescope Frontier Fields program is a large Director's Discretionary program of 840 orbits, to obtain ultra-deep observations of six strong lensing clusters of galaxies, together with parallel deep blank fields, making use of the strong lensing amplification by these clusters of distant background galaxies to detect the faintest galaxies currently observable in the high-redshift universe. The entire program has now completed successfully for all 6 clusters, namely Abell 2744, Abell S1063, Abell 370, MACS J0416.1-2403, MACS J0717.5+3745 and MACS J1149.5+2223,. Full sets of high-level science products have been generated for all these clusters by the team at STScI, including cumulative-depth data releases during each epoch, as well as full-depth releases after the completion of each epoch. These products include all the full-depth distortion-corrected drizzled mosaics and associated products for each cluster, which are science-ready to facilitate the construction of lensing models as well as enabling a wide range of other science projects. Many improvements beyond default calibration for ACS and WFC3/IR are implemented in these data products, including corrections for persistence, time-variable sky, and low-level dark current residuals, as well as improvements in astrometric alignment to achieve milliarcsecond-level accuracy. The full set of resulting high-level science products and mosaics are publicly delivered to the community via the Mikulski Archive for Space Telescopes (MAST) to enable the widest scientific use of these data, as well as ensuring a public legacy dataset of the highest possible quality that is of lasting value to the entire community.

Concept study of the LiteBIRD satellite for CMB B-mode polarization

Dotani, Tadayasu

LiteBIRD is a next generation scientific satellite aiming to detect the footprint of the primordial gravitational wave in a form of polarization pattern called B-mode in the Cosmic Microwave Background (CMB).  LiteBIRD is a candidate for JAXA's strategic large mission in Japan under the close collaboration with NASA, ESA, and Canada.  It is planned to be launched in the latter half of 2020s with an H3 launch vehicle.  The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of delta r < 0.001, which is enough to test representative inflationary models.  It will cover the frequency range of 34-448 GHz with two telescopes and scan the whole sky from the Sun-Earth Lagrangian point L2.  A 3-year full sky survey will achieve a sensitivity of 2.5 micro-K-arcmin with an angular resolution of 30 arcmin around 100 GHz.  We will describe the current status of the concept design of LiteBIRD with its scientific goal in the poster.

AGN torus properties investigated by the 4.7 micron CO absorption band

Baba, Shunsuke

In the active galactic nucleus (AGN) unified scheme, the central engine is supposed to be surrounded by a toroidal dusty material, so-called AGN torus, which is responsible for the obscuration of the radiation from the nucleus. The unified scheme of AGNs requires verification of the existence of AGN torus and investigation of its nature possibly linked with the surrounding environment. However, the small physical scale of the torus prevents us from direct spatially-resolved observations of it applicable for a large sample of AGNs. Instead, spectroscopy of near-infrared absorption lines can, with thermal radiation from a compact region heated by the nucleus as the background continuum, effectively resolve the foreground material and examine its physical states. On the basis of this approach, we observed the 4.7 micron CO absorption band (v=1<-0, DeltaJ=+/-1) in nearby (z<0.07) 47 infrared galaxies with the AKARI satellite. Many of the sample galaxies showed large column densities (N_H~10^23 cm-2) and high temperatures (several x 100 K) through the CO band profile. Such a large column of warm gas is difficult to be attained via UV and shock heating and probably heated by X-ray from an AGN. The distribution of the gas column density against the 14-micron luminosity used as an indicator of the AGN luminosity was qualitatively consistent with the obscured fraction determined in X-ray observations. This consistency supports the assumption that the CO absorption likely probes the region dominated by X-ray. We also found that AGN-starburst composites showed on average larger column densities than Seyfert 2s. This result suggests that the obscuration by an AGN torus is also effective in a composite and that the torus is geometrically thicker than that in a typical Seyfert. This difference may reflect the AGN-starburst connection that supernovae in a circum-nuclear disk assist the formation of a thick torus.

Evidence for the existence of abundant intracluster light ~5 billion years after the Big Bang

Ko, Jongwan

Not all stars in the universe are gravitationally bound to galaxies. Observations have clearly revealed that a significant stellar component fills the space between galaxies in nearby galaxy clusters, creating diffuse intracluster light (ICL). However, when and how these stars form are still in debate. Galaxy clusters at the epoch when mature galaxy clusters began to appear are crucial to answer these questions. We present a ICL study of MOO J1014+0038 at z=1.24, using high-quality HST/WFC3 near-IR imaging data that enables us to reach a very low surface brightness threshold (~29 mag arcsec-2) and obtain a clear two-dimensional ICL map out to ~200 kpc from the center of the cluster. We find that the ICL color is consistent with that of the bright, red cluster galaxies. However, unlike the radial color variation of galaxies, we do not detect any significant radial dependence of the ICL color. Using simple stellar population synthesis with an exponentially decaying star formation model, we estimate that the ICL stars had formed at z~2 or earlier. Despite our conservative analysis, the ICL fraction still exceeds ~10% of the total cluster light at r<200 kpc. These results strongly support that intracluster stars might have formed during a short period and early in the history of the Virgo-like massive cluster formation and might be concurrent with the formation of the brightest cluster galaxy.

Black Hole mass measurements with ALMA

Henao, Lady

We will present the results of our project to use molecular gas emission to measure or constrain the  mass of the supermassive black hole (SMBH) in a sample of nearby galaxies. Sample galaxies were selected to be those whose SMBHs are expected to have the largest angular  'sphere of influence' (SOI). We will present our high precision SMBH mass measurements in NGC 4751 and NGC 4945, and the implications of our (relatively highly resolved SOIs) results for SMBH constraints in galaxies whose SOIs are only partially resolved. 

Does A Galaxy Group Environment Affect Molecular Gas Properties in Galaxies?

Kaneko, Hiroyuki

Galaxy groups are a common environment, since about a half of nearby galaxies belong to them. Then, to understand the galaxy evolution including star formation history, it is important to investigate whether molecular gas properties in groups are similar to that in clusters. However, the limited number of CO images prohibits us to study statistical nature of molecular gas in galaxies, for example, how much it  exists or how it distributes. We, a CO Multiline Imaging of Nearby Galaxies (COMING) project team, have performed imaging observations of more than 100 nearby galaxies with 12CO(J=1-0), 13CO(J=1-0), and C18O(J=1-0) lines. With the first data, we present the result of molecular gas mass, atomic gas mass, and a molecular gas fraction. We find these three quantities are not different between isolated galaxies and galaxy groups. This implies that selective HI stripping and galaxy suffocation by shock compression, which are seen in galaxy clusters, and effective molecular gas formation under a strong galaxy interaction may not play a dominant role in galaxy groups.

Optical identifications of high-redshift galaxy clusters from Planck Sunyaev-Zeldovich survey

Burenin, Rodion

We present the results of optical identifications and spectroscopic redshifts measurements for galaxy clusters from 2-nd \emph{Planck} catalogue of Sunyaev-Zeldovich sources (\emph{PSZ2}), located at high redshifts, $z\approx0.7$--$0.9$.  We used the data of optical observations obtained with Russian-Turkish 1.5-m telescope (RTT150), Sayan observatory 1.6-m telescope, Calar Alto 3.5-m telescope and 6-m SAO RAS telescope (Bolshoi Teleskop Alt-azimutalnyi, BTA). Spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2\,G$126.57\!+\!51.61$, from the cosmological sample of \emph{PSZ2} catalogue. In central regions of two clusters, PSZ2\,G$069.39\!+\!68.05$ and PSZ2\,G$087.39\!-\!34.58$, the strong gravitationally lensed background galaxies are found, one of them at redshift $z=4.262$.  The data presented below roughly double the number of known galaxy clusters in the second \emph{Planck} catalogue of Sunyaev-Zeldovich sources at high redshifts, $z\approx0.8$.

Characterizing the effect of emission lines on photometric redshift estimation

Dobos, Laszlo

We present the results of our study on the performance and capabilities of empirical and template-based photometric redshift estimation techniques for samples containing strong emission line galaxies. In order to artificially control the photometric error and emission line contribution of our test data set, we developed a stochastic mock catalog generation algorithm. The algorithm can provide a large number of synthetic spectra and magnitudes with high signal-to-noise ratio, as well as match the physical and observational parameter distribution of any input spectroscopic galaxy sample. Instead of running the computationally expensive stellar population synthesis and nebular emission codes, our algorithm generates realistic spectra with a statistical approach, and as an alternative to attempting to constrain the priors on input model parameters, works by matching output observational parameters. Our technique can successfully reproduce the observed color indices and the BPT diagram. By using such a mock catalog, we investigated the behavior of empirical photometric redshift estimation methods in the four dimensional color index space of the SDSS u, g, r, i, z filter set. While photo-z is clearly limited by the photometric error and not the color index degeneracies, one interesting finding is that at low redshift, the presence of emission lines is responsible for resolving the degeneracies and this is one important reason why empirical methods outperform template fitting significantly. Template fitting photo-z methods should use a wide range of templates to fit the colors of low redshift emission line galaxies, or even better, use a two step photo-z estimation technique to first estimate the redshift empirically and fit the colors with templates of a constant redshift to calculate the K-correction and other parameters.

The Lyman Continuum Leakage of the dwarf galaxy Tololo 1247-232 under review

Puschnig, Johannes

The driving mechanism of the reionization of the Universe is yet not well constrained, but low- and intermediate mass galaxies are widely discussed as source of ionizing photons, i.e. Lyman Continuum (LyC). However, proof of emerging LyC emission is an ongoing observational challenge at all redshifts. Using highly resolved photometry and far-UV spectroscopy obtained with the Hubble Space Telescope (HST) as well as interferometric observations performed with the Karl G. Jansky Very Large Array (VLA), we have studied the ionized and neutral gas content in the local dwarf galaxy Tololo 1247-232. My talk is based on Puschnig et al. (2017), describing physical mechanisms that drive the LyC escape in Tololo 1247-232, which is to date one of the very few known/confirmed LyC emitters in the Universe. Using HST's Cosmic Origins Spectrograph (COS), in combination with an improved data reduction routine, we have directly measured the amount of LyC emerging from the galaxy, finding an escape fraction of 1.5+/-0.5 percent only, i.e. the lowest LyC escape fraction reported for the galaxy so far. We further use far-UV absorption line analysis to probe the neutral and ionized gas, e.g. the covering fraction of the neutral medium could be constrained. We show that the LyC photons emerge from density bounded regions and finally escape through a clumpy medium. However, from Lyman Alpha line analysis, we also conclude that an additional diffuse interclump medium must be present that prevents Lyman Alpha to be seen at systemic velocity. The LyC escpae is further supported by our VLA 21cm observations, from which a very low gas fraction of less than 20 percent could be derived.

XXX IAU General Assembly | ACV - Austria Center Vienna  | Bruno-Kreisky-Platz 1  | 1220 Vienna