We investigate why hydrodynamical numerical simulations have difficulties (Weinmann et al. 2011) in reproducing the Main Sequence (MS) of star-forming galaxies, i.e. the fact that galaxies forming stars lie on a tight power law sequence in the stellar mass (M*), star formation rate (SFR) plane (Schreiber et al. 2015). Instead of trying to improve the agreement of simulations with the observations by modifying the subgrid recipes of baryons, we take here a step back to check whether the accretion onto dark matter halos is consistent with the existence of the main sequence of star forming galaxies.

Gamma-ray bursts are the most luminous objects known: they outshine their host galaxies making them ideal candidates for probing large-scale structure. Earlier it has been found that the angular distribution of different groups of GRBs (long, intermediate and short) show deviation from the full randomness at different levels (e.g. Vavrek et al. (2008)).

In the current sample there are more than 361 GRBs with position and redshift: the large scale homogeneous and isotropic distribution were checked with nearest-neighbour tests and with the two-point correlation function.

We studied the space distribution of the starburst galaxies from Millennium XXL database at z = 0.82. We examined the starburst distribution in the classical Millennium I (De Lucia et al. (2006)) using a semi-analytical model for the genesis of the galaxies. We simulated a starburst galaxies sample with Markov Chain Monte Carlo method. The connection between the large scale structures homogenous and starburst groups distribution (Kofman and Shandarin 1998), Suhhonenko et al. (2011), Liivamägi et al. (2012), Park et al. (2012), Horvath et al. (2014), Horvath et al. (2015)) on a defined scale were checked too.

We investigate the alignment effect of red-sequence dwarf galaxies using a sample of 121 low-redshift galaxy clusters and cluster galaxies selected from the HST Frontier Fields.

Recent studies of Population III (Pop III) star formation suggest that the primordial star-forming clouds can fragment to form binary or multiple stellar systems inside dark matter minihalos. Here, we briefly present the chemical enrichment of the Pop III binary scenarios.

An important effort has been recently made to detect spectroscopically galaxies at z ~ 6 and higher where the cosmic reionization is thought to occur. The drop of the fraction of Lyman Alpha Emitters (LAEs) at z>6 is currently interpreted as an effect of the increasing neutral hydrogen density.

We present preliminary results from the latest VLT/FORS2 programs, combined with ESO archival data, to perform a large census of z ~ 6 galaxies. We derive their physical properties as stellar mass and dust attenuation with an SED fitting tool including nebular emission which is of primeval importance because IRAC channels are strongly contaminated by emission lines at those redshifts. We take a special care to derive with precision the redshift of non LAEs to perform a comparison of their properties with the LAE population and derive as accurately as possible the fraction of LAEs. In particular, we compare the UV beta slope with the Lyα equivalent width which are known to correlate at lower redshift.

We also report the detection of few peculiar z ~ 6 galaxies with extremely blue UV β slope (~−3), which can be a signature of unusual stellar populations (e.g., very hot and massive stars).

We present the results of a multi-wavelength photometric study of the high redshift supercluster RCS2319+00. RCS2319+00 is a high-redshift (z ~ 0.9) supercluster comprising three spectroscopically confrmed cluster cores discovered in the Red Sequence Cluster Survey (RCS) (Gladders & Yee 2005). Core proximities and merger rates estimate coalescence into a 1015M⊙ cluster by z ~ 0.5 (Gilbank et al. 2008). Spectroscopic studies of the system have revealed over 300 supercluster members located in the cores and several infalling groups (Faloon et al. 2013). RCS2319 presents a diverse range of dynamical systems and densities making it an ideal laboratory in which to study the effects of environment on galaxy properties.

Imaging in optical and near infrared (griz' from MegaCam, JKs from WIRCam, both at CFHT), as well as 3.6 μm and 4.5μm from IRAC have enabled the assembly of a large photometric catalogue. Coupled with an extensive spectroscopic survey (Faloon et al. 2013) providing nearly 2400 redshifts across the field, photometric redshifts were determined using the template fitting code EAZY (Brammer et al. 2008). Nearly 80 000 photometric redshifts were measured providing a sample of nearly 3000 cluster members.

To investigate effects of global environment, analysis was done utilizing a friend-of-friends group finding algorithm identifying several large and small infalling groups along with the three cluster cores. The cores are found to be dominated by massive, red galaxies and the field galaxies are populated by low mass, blue galaxies, as is the case in the local universe. Interestingly, the large groups exhibit intermediate properties between field and core populations, suggesting possible pre-processing as they are being accreted into the core halos.

Relative fifth-nearest neighbour overdensity, log(1+δ5), is used as a proxy for local environment to investigate environmental dependence on galaxy colour. While there is an overall dependence of colour on local density, when controlled for stellar mass the dependence largely disappears. Indeed, galaxy mass is the dominant factor in determining colour, with local density a secondary effect only noticeable in lower mass galaxies at the 3 σ level for both colour and red fraction.

RCS2319+00 presents a rare opportunity to probe many different densities and environments all located within the same object. We're able to investigate how galaxy evolution is affected by the environment, from field galaxies to infalling to groups to dense cluster cores, as well as the different density regions within each environment.

The Near Infrared Imager and Slitless Spectrograph (NIRISS) aboard the James Webb Space Telescope (JWST) will offer wide-field slitless spectroscopy (WFSS) with a resolving power R = 150 at wavelengths from 0.8 to 2.25 microns. In this band, NIRISS will be sensitive to Lyman α emission lines and continuum breaks in the spectra of galaxies with redshifts 6 < z < 17, allowing it to probe the first stars and ionizing sources in the early universe. NIRISS observations of the high-redshift universe will provide a wealth of information on foreground objects, creating a unique library of optical emission-line spectra from the faintest galaxies at lower redshifts. To explore its ability to identify and characterize galaxies at all redshifts, we have modeled a NIRISS observation of a massive strong-lensing galaxy cluster and analyzed the synthetic images using standard software tools. Our simulations demonstrate that WFSS with NIRISS will provide a powerful tool for the exploration of galaxies near and far.

We present preliminary results from MUSE on the Lyα luminosity function in the Hubble Deep Field South (HDFS). Using a large homogeneous sample of LAEs selected through blind spectroscopy, we utilise the unprecedented detection power of MUSE to study the progenitors of L* galaxies back to when the Universe was just ~2 Gyr old. We present these results in the context of the current literature, and highlight the importance of the forthcoming Hubble Ultra Deep Field (HUDF) study with MUSE, which will increase the size of our sample by a factor of ~ 10.

We present a measurement of the spatial clustering of massive compact galaxies at 1 ≤ z ≤ 3 in CANDELS/3D-HST. We obtain the correlation length and characteristic DM halo masses for compact quiescent galaxies (cQGs) at z ~ 1.5 and compact starforming galaxies (cSFGs) at z ~ 2.5. By comparison with extended starforming galaxies (eSFGs), our result indicates that eSFGs are less possible to be the progenitors of cQGs at lower redshift. Our results indicates that cQGs at z ~ 1.5 could be the progenitors of local luminous ETGs and the descendants of cSFGs and SMGs at z > 2.

Supermassive black hole accretion and feedback play central role in the evolution of galaxies, groups, and clusters. I review how AGN feedback is tightly coupled with the formation of multiphase gas and the newly probed chaotic cold accretion (CCA). In a turbulent and heated atmosphere, cold clouds and kpc-scale filaments condense out of the plasma via thermal instability and rain toward the black hole. In the nucleus, the recurrent chaotic collisions between the cold clouds, filaments, and central torus promote angular momentum cancellation or mixing, boosting the accretion rate up to 100 times the Bondi rate. The rapid variability triggers powerful AGN outflows, which quench the cooling flow and star formation without destroying the cool core. The AGN heating stifles the formation of multiphase gas and accretion, the feedback subsides and the hot halo is allowed to cool again, restarting a new cycle. Ultimately, CCA creates a symbiotic link between the black hole and the whole host via a tight self-regulated feedback which preserves the gaseous halo in global thermal equilibrium throughout cosmic time.

The extraordinary sensitivity and spatial resolution of the future extremely large telescopes will allow us to extensively characterize the photometrical and structural properties of high redshift galaxies in spite of their very small size. With such future facilities it will be possible to derive both accurate photometry and detailed morphology of very distant galaxies that are mandatory to tackle fundamental problems on the processes of galaxy formation and evolution.

The extensive ground-based spectroscopy campaign from the VIMOS Ultra-Deep Survey (VUDS), and the deep multi-wavelength photometry in three very well observed extragalactic fields (ECDFS, COSMOS, VVDS), allow us to investigate physical properties of a large sample (~4000 galaxies) of spectroscopically confirmed faint (iAB ≲ 25 mag) SFGs, with and without Lyα in emission, at z ~ 2–6. The fraction of Lyα emitters (LAEs; equivalent width (EW) ≥ 20Å) increases from ~10% at z ~ 2 to ~40% at z ~ 5–6, which is consistent with previous studies that employ higher Lyα EW cut. This increase in the LAE fraction could be, in part, due to a decrease in the dust content of galaxies as redshift increases. When we compare best-fit SED estimated stellar parameters for LAEs and non-LAEs, we find that Es(B-V) is smaller for LAEs at all redshifts and the difference in the median Es(B-V) between LAEs and non-LAEs increases as redshift increases, from 0.05 at z ~ 2 to 0.1 at z ~ 3.5 to 0.2 at z ~ 5. For the luminosities probed here (~L*), we find that star formation rates (SFRs) and stellar masses of galaxies, with and without Lyα in emission, show small differences such that, LAEs have lower SFRs and stellar masses compared to non-LAEs. This result could be a direct consequence of the sample selection. Our sample of LAEs are selected based on their continuum magnitudes and they probe higher continuum luminosities compared to narrow-band/emission line selected LAEs. Based on our results, it is important to note that all LAEs are not universally similar and their properties are strongly dependent on the sample selection, and/or continuum luminosities.

One major deficiency of state-of-the-art galaxy formation models consists in their inability of capturing the observed galaxy downsizing trend significantly over-estimating the number density of low-mass galaxies, in particular at high redshifts. Employing an enhanced galaxy formation model with a full chemical enrichment scheme (DeLucia et al., 2014), we present an improved model for stellar feedback (based on parametrizations from cosmological zoom simulations), in which strong gas outflows occur due to bursty star formation at high z, while star formation is mainly “quiescent” not causing any significant outflows anymore at low z. Due to the stronger gas outflows at high z, early star formation is strongly delayed towards later times. This helps to sufficiently detach the evolution of galaxy growth from the hiearchical dark matter assembly resulting in a fairly good agreement with the evolution of the observed stellar mass function (SMF, see Fig. 1). With our new feedback scheme, we can also successfully reproduce many other observational constraints, such as the metallicity content, the cold gas fractions or the quiescent galaxy fractions at both low and high redshifts. The resulting new-generation galaxy catalogues (Hirschmann et al., in prep) based on that model are expected to significantly contribute to the interpretation of current and up-coming large-scale surveys (HST, JWST, Euclid). This will, in turn, provide a rapid verification and refinement of our modeling.

The UV escape fraction, fescUV, is a key parameter determining the apparent SED of star forming galaxies. However, it is not well known how fescUV depends on the global geometry of dust distribution, nor how it evolves with time, although several models are proposed (e.g., Calzetti (2001)). We use ~130 normal star-forming galaxies (114 at z ~ 0 from Cortese et al. (2012) and 15 at z ~ 1–3 from Magnelli et al. (2012) and Saintonge et al. (2013)), to find that the z ~ 0 galaxies show a relatively tight anti-correlation between fescUV and surface dust mass density, Σd (See Fig. 1(a)). This correlation can be reproduced by a dust geometry model that well-mixed stars and dust follow the same exponential profile (Fig. 1(b)) with an effective mass-absorption coefficient κ(1600 Å) = 7.6+5.3−3.0 × 104 cm2 g−1, similar to the Milky Way value including absorption and scatter. The z ~ 1–3 galaxies are not inconsistent with this model. Our model can be easily implemented in semi-analytic models and cosmological hydrodynamics simulations (CHSs) of galaxy formation. Initial results for Shimizu et al. (2014)'s CHSs are presented.

At local, galaxy properties are well known to be clearly different in different environments. However, it is still an open question how this environment-dependent trend has been shaped. We present the results of our investigation about the evolution of star-formation properties of galaxies over a wide redshift range, from z ~ 2 to z ~ 0.5, focusing its dependence on their stellar mass and environment (Lee et al. 2015). In the UKIDSS/UDS region, covering ~2800 square arcmin, we estimated photometric redshifts and stellar population properties, such as stellar masses and star-formation rates, using the deep optical and near-infrared data available in this field. Then, we identified galaxy cluster candidates within the given redshift range. Through the analysis and comparison of star-formation (SF) properties of galaxies in clusters and in field, we found interesting results regarding the evolution of SF properties of galaxies: (1) regardless of redshifts, stellar mass is a key parameter controlling quenching of star formation in galaxies; (2) At z < 1, environmental effects become important at quenching star formation regardless of stellar mass of galaxies; and (3) However, the result of the environmental quenching is prominent only for low mass galaxies (M* < 1010 M⊙) since the star formation in most of high mass galaxies are already quenched at z > 1.

We investigate the contribution of major mergers to star formation in spheroidal galaxies at z ~ 2. Galaxies are visually classified from a sample of massive galaxies in CANDELS. At the redshifts used, the observed morphological disturbances are due to recent major mergers as minor mergers are too faint. The percentage of blue spheroids showing morphological disturbances is 21 ± 4%, indicating that major mergers are not the dominant star formation mechanism in these galaxies. Thus, minor mergers or cold accretion are likely to be the main drivers of star formation. We investigate the U-band luminosity emission of the sample and find that only a small fraction of the cosmic L(U) is from galaxies involved in a major merger, ~30%. Using the ratio of specific star formation rate for LTGs to mergers and combining this with the results for the luminosity budget shows that only ~6% of the total L(U) emitted at z ~ 2 is due to the major merger process.

We present a model for the evolution of the galaxy ultraviolet (UV) luminosity function (LF) where star formation is linked to the assembly of dark matter halos under the assumption of a mass dependent, but redshift independent, efficiency. With a calibration at a single redshift, and no further degrees of freedom, our model captures the evolution of the UV LF over all available observations (0≲ z ≲ 10). We make predictions for reionization and future high-redshift surveys with JWST and WFIRST.

High–redshift quasars and blazars are among the most powerful sources in the Universe and among the highest luminosity sources, as in optical, so as in X–ray, UV, IR and radio range. We have created a full sample of blazars and high–redshift quasars (z≥2.15). The evolutionary relation of high–redshift quasars and blazars to high–redshift galaxies is discussed using the luminosity evolution.

Recent studies show increasing evidence for the possibility of the Initial Mass Function (IMF) of galaxies to vary as a function of numerous physical parameters. These studies mainly focus on the low redshift galaxies (at z≤0.1) and is not backed by any studies at higher redshifts. Using MOSFIRE data from KECK, we use the Hα Equivalent-Width (EW) as a proxy for the IMF to study in situ IMF of galaxies at z ~ 2. In this proceedings we focus on the underlying physics of this method and present our initial findings. More work is needed to interpret the results accurately and will be presented in our future papers.