Search

We review in this paper the main results recently obtained on the identification and study of very high-z galaxies using lensing clusters as natural gravitational telescopes. We present in detail our pilot survey with ISAAC/VLT, aimed at the detection of z$>7$ sources. Evolutionary synthesis models for extremely metal-poor and PopIII starbursts have been used to derive the observational properties expected for these high-$z$ galaxies, such as expected magnitudes and colors, line fluxes for the main emission lines, etc. These models have allowed to define fairly robust selection criteria to find z$\sim 7-10$ galaxies based on broad-band near-IR photometry in combination with the traditional Lyman drop-out technique. The first results issued from our photometric and spectroscopic survey are discussed, in particular the preliminary confirmation rate, and the global properties of our high-z candidates, including the latest results on the possible z=10.0 candidate A1835-1916. The search efficiency should be significantly improved by the future near-IR multi-object ground-based and space facilities. However, strong lensing clusters remain a factor of $\sim$ 5-10 more efficient than blank fields in the z $\sim$ 7-11 domain, within the FOV of a few arcminutes around the cluster core, for the typical depth required for this survey project.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html [ABSTRACT FROM PUBLISHER]

We report the results obtained from optical and near-infrared spectroscopy and also broad-band photometry of lensed low-luminosity galaxies ($1.3\leq z\leq 2.3$) located in the core of lensing clusters. The amplification factor allowed us to obtain the physical properties (SFR, abundance ratios, mass, age of the burst, dust contents, etc.) of star-forming galaxies, 1 to 2 magnitudes fainter than galaxies in a blank field, using the same indicators as in studies of low-redshift galaxies. A part of this study was concentrated on the dynamics of distant lensed galaxies using Integral Field Spectroscopy (SINFONI/VLT science verification programme). [ABSTRACT FROM PUBLISHER]

A highlight science case for the European ELT is: First light - The First Galaxies and the Ionization State of the Early Universe. It aims at understanding the formation and evolution of the first sources of light at the end of the Dark Ages and of the re-ionization of the Universe. The corresponding instrument requirements are: a few tens of integral field units with spatial sampling $\sim$20mas and individual fields of ${\sim}1''$ over a wide field of view of $5' \times 5'$ or larger. Multi-Object Adaptive Optics is required to locally provide significant image quality enhancement. Spectroscopic observations are required in the near IR domain with a spectral resolution of a few 1000. MOMFIS is a preliminary instrument concept designed for OWL around this science case. The instrument concept and preliminary design are presented. Development efforts are estimated, as well as development risks and required R&D activities. [ABSTRACT FROM PUBLISHER]

Dwarf galaxies represent the dominant population at high redshift and they most likely contributed in great part to star formation history of the Universe and cosmic reionization. The importance of dwarf galaxies at high redshift has been mostly recognized in the last decade due to large progress in observing facilities allowing deep galaxy surveys to identify low-mass galaxies. This population appear to have extreme emission lines and ionizing properties that challenge stellar population models. Star formation follows a stochastic process in these galaxies, which has important implication on the ionizing photon production and its escape fraction whose measurements are challenging for both simulations and observations. Outstanding questions include: what are the physical properties at the origin of such extreme properties? What are the smallest dark matter halos that host star formation? Are dwarf galaxies responsible for cosmic reionization? [ABSTRACT FROM AUTHOR]

Following up on the detailed results from our searches for z~ 6–10 galaxies using gravitional lensing clusters descrived in Richard et al. (2006), we have obtained new observations, which are presented here. For a general overview of the project see Schaerer et al. (2006). First, deep HST/ACS observations in the z-band confirm 17 out of 18 high redshift candidates as optical drop-out objects; the remaining object appears faint and star-like. Second, Spitzer/IRAC images at 3.6, 4.5, 5.8 and 8.0 μm have been obtained. 11 out of 18 candidates are in “free”, uncominated regions. These 11 high-z candidates are undetected, with upper limits which are compatible with their SED if these objects are blue star-forming galaxies at high redshift (see Fig. 1). In conclusion, our new observations corroborate so far the high-z nature of the majority of the candidates. [ABSTRACT FROM PUBLISHER]

We report the discovery of two peculiar galaxies infalling into the lensing clusters of galaxies Abell 1689 (z~ 0.18) and 2667 (z~ 0.23). Hubble Space Telescope images show extraordinary trails composed by blue bright knots and stellar streams associated with both these systems, an ~L* and ~0.1L* galaxy. Under the combined action of tidal interaction with the cluster potential and of ram pressure by the intra-cluster medium the morphologies and star formation histories of these two galaxies are strongly perturbed. While in the massive system tidal interactions are the dominant effect and are able to produce a sinking of gas towards the galaxy center triggering a strong burst of star formation and changing galaxy's morphology, in the smaller galaxy the effects of gravitation are reduced by ram pressure stripping which blows away the neutral hydrogen from the galactic disk, quenching the star formation activity and transforming a gas rich late type spiral into quiescent disk dominated early type system. This result is a new additional evidence that galaxy mass represents the main driver of galaxy evolution, even during their dive into the harsh cluster environment and can give additional insights on the origin of S0s and dwarf cluster galaxies. [ABSTRACT FROM PUBLISHER]

We present high-precision strong lensing models for the galaxy clusters MACS J0416.1–0403 at z =0.396 and Abell 2744 at z=0.307. The models are constrained by two of the largest data-sets of secure multiple images ever used in lensing. These are identified from the photometric images observed by the Hubble space telescope and JWST in combination with spectroscopic data obtained by the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. The same spectro-photometric data are used to create pure and complete samples of cluster member galaxies. Our models allow an extremely precise estimation of the cluster total mass distribution and produce accurate magnification maps that are fundamental to study the physical properties (mass, size, luminosity, etc.) of the lensed high-redshift galaxies. [ABSTRACT FROM AUTHOR]

Strong lensing galaxy clusters provide a powerful observational test of Cold Dark Matter (CDM) structure predictions derived from simulation. Specifically, the shape and relative alignments of the dark matter halo, stars, and hot intracluster gas tells us the extent to which theoretical structure predictions hold for clusters in various dynamical states. We measure the position angles, ellipticities, and locations/centroids of the brightest cluster galaxy (BCG), intracluster light (ICL), the hot intracluster medium (ICM), and the core lensing mass for a sample of strong lensing galaxy clusters from the SDSS Giant Arcs Survey (SGAS). We use iterative elliptical isophote fitting methods and GALFIT modeling on HST WFC3/IR imaging data to extract ICL and BCG information and use CIAO's Sherpa modeling on Chandra ACIS-I X-ray data to make measurements of the ICM. Using this multicomponent approach, we attempt to constrain the physical state of these strong lensing clusters and evaluate the different observable components in terms of their ability to trace out the gravitational potential of the cluster. [ABSTRACT FROM AUTHOR]

Galaxy-galaxy strong lensing in galaxy clusters is a unique tool for studying the subhalo mass distribution, as well as for testing predictions from cosmological simulations. We describe a novel method that simulates realistic lensed features embedded inside the complexity of observed data by exploiting high-precision cluster lens models. Such methodology is used to build a large dataset with which Convolutional Neural Networks have been trained to identify strong lensing events in galaxy clusters. In particular, we inject lensed sources around cluster members using the images acquired by the Hubble Space Telescope. The resulting simulated mock data preserve the complexity of observation by taking into account all the physical components that could affect the morphology and the luminosity of the lensing events. The trained networks achieve a purity-completeness level of ∼ 91% in detecting such events. The methodology presented can be extended to other data-intensive surveys carried out with the next-generation facilities. [ABSTRACT FROM AUTHOR]

In the past decade, submillimeter surveys have been employed to define samples of gravitationally-lensed dusty star-forming galaxies (DSFGs) at z ∼ 1 − 4. These extreme objects () appear to form stars prodigiously at rates of. Using all-sky Planck and WISE surveys, and wide-area Herschel surveys, we have identified the PASSAGES sample, with some of the rarest hyper-luminous IR galaxies ever discovered. We have found that their globally-averaged star formation surface densities are always sub-Eddington, typically by an order of magnitude. This may suggest that our understanding of how radiation pressure from massive stars disrupts the collapse of molecular clouds (thereby quenching star formation) is flawed—or simply that smaller physical resolutions are necessary. With the aid of lensing, we can now capture the source-plane distribution of star formation at ∼ 100pc scales, letting us identify isolated super-Eddington regions where quenching is occurring. [ABSTRACT FROM AUTHOR]

Rare systems with multiple sources strongly lensed by a single galaxy provide the most robust way to explore the geometry of the Universe and to study the inner mass structure of lens galaxies. We present here a study of the SDSS J0100+1818 deflector, analyzing its total and baryonic mass distributions. The system comprises an ultra-massive early-type galaxy, surrounded by ten multiple images of three background sources. Exploiting high-resolution HST photometry and VLT/X-shooter spectroscopy we conduct a strong lensing analysis with the software GLEE to reconstruct the complex surface brightness distributions of the background sources over approximately 7200 HST pixels. These results are presented in our recent paper, Bolamperti et al. (2023). Finally, we present some preliminary results from new VLT/MUSE observations, that will allow us to build a new strong lensing+dynamics joint model and measure the values of the total matter density and of the cosmological constant parameters, Ω m and ΩΛ. [ABSTRACT FROM AUTHOR]

Strong gravitational magnification in the core of lensing clusters allows to probe the faint-end of the galaxy luminosity function up to very high redshift. In particular, the Frontier Fields have allowed us to identify a large number of faint dropouts and constrain the Lyman-break luminosity function at z~5-7. I present here the results of an ongoing program with MUSE, a new integral field spectrograph on the Very Large Telescope having a large field of view (1 arcmin2), to confirm these candidate high redshift dropouts through Lyman-α emission and identify additional emitters with high equivalent width, fainter than the depth of the Frontier Fields Hubble images. Combined with similar deep exposures taken with MUSE in blank fields, this gives us the best opportunity to probe the Lyman-α luminosity function over a wide range in luminosity. [ABSTRACT FROM PUBLISHER]

Selection effects in the submillimeter/far-infrared inhibit detailed analysis of extreme starbursts in the early Universe. Submillimeter Galaxy (SMG) detection and characterization biases against warm temperature SEDs Tdust ~50 K, against the highest redshift ULIRGs z > 3, and has so far been limited to a small sample of ~100 sources that have reliably identified optical or radio counterparts and spectroscopic redshifts. Recent observations by Herschel ⋅ ⋅ ⋅ ⋅ and ⋅ ⋅ ⋅⋅ ⋅ in the ~70–500 μm wavelength range provide a more complete census of high-z ULIRG activity than previous SMG surveys. However, source confusion and lack of spectroscopic identification of reliable counterparts limit the analysis of extreme ULIRGs to the most basic calculations, frought with a priori assumptions (e.g. Tdust/(1+z) degeneracy, far-IR/radio relation, confusion boosting factors, etc). Herein I address the biases on conclusions of SMG work and I demonstrate the need for thorough, spectroscopic follow-up of high-z ULIRGs in order to infer their physical conditions. [ABSTRACT FROM PUBLISHER]

The gravitationally lensing clusters A370, A2218, A1689 and Cl0024+1654 were observed with the Infrared Space Observatory (ISO) using ISOCAM at 6.7 $\mu$m and 14.3 $\mu$m (hereafter 7 $\mu$m and 15 $\mu$m respectively).A total of 178 sources were detected in the whole set, 70 of them being cluster objects. The spectral energy distribution of a subset of sources was calculated using GRASIL. The results for the total infrared luminosity and the estimation of the star formation rate are presented for the non stellar objects for which the SED has been determined. The majority of the cluster galaxies in A2218 are best fit by models of quiescent ellipticals. In Cl0024+1654, most of the galaxies lying on the Butcher-Oemler region of the colour-magnitude diagram are best fit by disk galaxies, while those on the main sequence area have in general SEDs corresponding to post-starburst galaxies.The population of each cluster is compared with the field population, as well as with the population of other clusters. A significant number of Luminous IR Galaxies (LIRGs) is detected in Cl0024+1654, while only one LIRG has been observed in total in A370, A1689, and A2218. This result supports the link between LIRGs in clusters and recent or ongoing cluster merger activity as well as the need for extending the observations to the outer parts of clusters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html [ABSTRACT FROM PUBLISHER]

The wealth of strong lensing features observed in the Frontier Fields clusters offers insights on the nature of dark energy. The large number of multiple-images systems with redshifts allows to simultaneously estimate the lens model parameters and the cosmological parameters involved in the distances calculations. In particular for the ΛCDM model, it is possible to estimate the matter density Ωm and the dark energy equations parameters wX. In this talk, I will present recent analyses of systematic errors based on Frontier Fields observed and simulated data. [ABSTRACT FROM PUBLISHER]

Constraints on the masses of dark matter haloes associated with galaxies in the field and in clusters have been successfully obtained used galaxy-galaxy lensing techniques. Weak lensing thus provides important information on the mass distribution in galaxies at large radii in a statistical fashion. Current work suggests that all galaxies possess extended dark matter haloes, however those that host galaxies in clusters are less extended and less massive. [ABSTRACT FROM PUBLISHER]

Using an ultra-deep, untargeted survey with the MUSE integral field spectrograph on the ESO Very Large Telescope, we obtain spectroscopic redshifts to a depth never explored before: galaxies with observed magnitudes m > 30–32. Specifically, we detect objects via Lyman-α emission at 2.9 < z < 6.7 without individual continuum counterparts in areas covered by the deepest optical/near-infrared imaging taken by the Hubble Space Telescope, the Hubble Ultra Deep Field. In total, we find more than 100 such objects in 9 square arcminutes at these redshifts, also including a number of sources that are visible only in the HST band that contains Lyman-α. Detailed HST and IRAC stacking analyses confirm the Lyman-α emission as well as the 1216 Å breaks, faint UV continua (MUV ∼ −15), and optical emission lines: these objects are the faintest spectroscopically-confirmed galaxies at high-z. The blue UV continuum slopes and measurements/limits on the equivalent widths of Lyman-α, which in some cases exceeds 300 Å, are consistent with ages < 10 Myr, metallicities < 5% solar, and stellar masses < 107–8 solar masses. The nature of these types of objects is intriguing as they could be the faint star-forming sources of Reionization and could represent the initial (strong) phase of stellar mass growth in galaxies. [ABSTRACT FROM AUTHOR]

Early-type galaxies (ETGs) are of crucial importance to trace back the galaxy mass assembly across cosmic time, yet their formation and quenching remain remarkably elusive. The discoveries of massive, dead galaxies at ever-growing redshifts provided compelling evidence to push their formation up to redshift > 4–5 when the Universe was barely 1 Gyr old. In this talk I will present our results on the ages of a new sample of ETGs at z ∼ 3, built by exploiting HST WFC3/G141 rest-frame optical/near-UV grism spectroscopy to study the nature of 10 passive galaxy candidates at 2.5 < z < 3.5 in COSMOS. This work is part of a PhD project aimed at quantifying the parent space density of distant genuine passive galaxies. I will also discuss the importance of multi-wavelength data in clarifying the degree of contamination by dusty star-forming galaxies affecting the color selection. [ABSTRACT FROM AUTHOR]

Studying the transformation of cluster galaxies contributes a lot to have a clear picture of evolution of the universe. Towards that we are studying different properties (morphology, star formation, AGN contribution and metallicity) of galaxies in clusters up to z ∼ 1.0 taking three different clusters: ZwCl0024 + 1652 at z ∼ 0.4, RXJ1257 + 4738 at z ∼ 0.9 and Virgo at z ∼ 0.0038. For ZwCl0024 + 1652 and RXJ1257 + 4738 clusters we used tunable filters data from GLACE survey taken with GTC 10.4 m telescope and other public data, while for Virgo we used public data. We did the morphological classification of 180 galaxies in ZwCl0024 + 1652 using galSVM, where 54 % and 46 % of galaxies were classified as early-type (ET) and late-type (LT) respectively. We did a comparison between the three clusters within the clustercentric distance of 1 Mpc and found that ET proportion (decreasing with redshift) dominates over the LT (increasing with redshift) throughout. We finalized the data reduction for ZwCl0024 + 1652 cluster and identified 46 [OIII] and 73 Hβ emission lines. For this cluster we have classified 22 emission line galaxies (ELGs) using BPT-NII diagnostic diagram resulting with 14 composite, 1 AGN and 7 star forming (SF) galaxies. We are using these results, together with the public data, for further analysis of the variations of properties in relation to redshift within z < 1.0. [ABSTRACT FROM AUTHOR]

In this study, we analysed active galactic nuclei in the "green valley" by comparing active and non-active galaxies using data from the COSMOS field. We found that most of our X-ray detected active galactic nuclei with far-infrared emission have star formation rates higher than the ones of normal galaxies of the same stellar mass range. [ABSTRACT FROM AUTHOR]

Early-type galaxies (ETGs) are of crucial importance to trace back the galaxy mass assembly across cosmic time, yet their formation and quenching remain remarkably elusive. The discoveries of massive, dead galaxies at ever-growing redshifts provided compelling evidence to push their formation up to redshift > 4–5 when the Universe was barely 1 Gyr old. In this talk I will present our results on the ages of a new sample of ETGs at z ∼ 3, built by exploiting HST WFC3/G141 rest-frame optical/near-UV grism spectroscopy to study the nature of 10 passive galaxy candidates at 2.5 < z < 3.5 in COSMOS. This work is part of a PhD project aimed at quantifying the parent space density of distant genuine passive galaxies. I will also discuss the importance of multi-wavelength data in clarifying the degree of contamination by dusty star-forming galaxies affecting the color selection. [ABSTRACT FROM AUTHOR]

During the Epoch of Reionization (EoR), feedback effects reduce the efficiency of star formation process in small halos or even fully quench it. The galaxy luminosity function (LF) may then turn over at the faint-end. We analyze the number counts of z > 5 galaxies observed in the fields of four Frontier Fields (FFs) clusters and obtain constraints on the LF faint-end: for the turn-over magnitude at z ∼ 6, M UV T ≳-13.3; for the circular velocity threshold of quenching star formation process, v c * ≲ 47 km s−1. We have not yet found significant evidence of the presence of feedback effects suppressing the star formation in small galaxies. [ABSTRACT FROM AUTHOR]

Euclid is a Europe-led cosmology space mission dedicated to a visible and near infrared survey of the entire extra-galactic sky. Its purpose is to deepen our knowledge of the dark content of our Universe. After an overview of the Euclid mission and science, this contribution describes how the community is getting organized to face the data analysis challenges, both in software development and in operational data processing matters. It ends with a more specific account of some of the main contributions of the Swiss Science Data Center (SDC-CH). [ABSTRACT FROM PUBLISHER]

Throughout the processing and analysis of survey data, a ubiquitous issue nowadays is that we are spoilt for choice when we need to select a methodology for some of its steps. The alternative methods usually fail and excel in different data regions, and have various advantages and drawbacks, so a combination that unites the strengths of all while suppressing the weaknesses is desirable. We propose to use a two-level hierarchy of learners. Its first level consists of training and applying the possible base methods on the first part of a known set. At the second level, we feed the output probability distributions from all base methods to a second learner trained on the remaining known objects. Using classification of variable stars and photometric redshift estimation as examples, we show that the hierarchical combination is capable of achieving general improvement over averaging-type combination methods, correcting systematics present in all base methods, is easy to train and apply, and thus, it is a promising tool in the astronomical “Big Data” era. [ABSTRACT FROM PUBLISHER]

Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the component of the interstellar medium (ISM) that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We here present results that demonstrate the capability of the Atacama Large (sub-)Millimeter Array (ALMA) to detect the cold ISM and dust in “normal” galaxies at redshifts z=5–6. We also show detailed studies of the ISM in massive, dust-obscured starburst galaxies out to z>6 with ALMA, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the Plateau de Bure Interferometer (PdBI), and the Karl G. Jansky Very Large Array (VLA). These observations place some of the most direct constraints on the dust-obscured fraction of the star formation history of the universe at z>5 to date, showing that “typical” galaxies at these epochs have low dust content, but also that highly-enriched, dusty starbursts already exist within the first billion years after the Big Bang. [ABSTRACT FROM PUBLISHER]

Abell 2744 was the first HFF cluster completed. It displays a fascinating complexity in its distribution of dark and luminous matter, which led to its nickname of the Pandora cluster. In late 2014 we obtained a deep (110 ks) observation of this cluster with XMM-Newton, with the aim of making a detailed comparison between the optical, X-ray and lensing properties of this system. The new X-ray observation unveiled the presence of three hot gas filaments extending on scales of several Mpc and connected to the cluster core. The X-ray structures coincide spatially with the distribution of galaxies and dark matter and provide strong evidence for the existence of the elusive warm-hot intergalactic medium (WHIM). The new observation also reveals the complexity of the thermodynamic structure of the cluster core and a probable shock front associated with the radio relic located 1 Mpc NW of the cluster core. [ABSTRACT FROM PUBLISHER]

Experiments were conducted to characterize the detonation phase-velocity dependence on charge thickness for two-dimensional detonation in condensed-phase explosive slabs of PBX 9501, PBX 9502 and ANFO. In combination with previous diameter-effect measurements from a cylindrical rate-stick geometry, these data permit examination of the relative scaling of detonation phase velocity between axisymmetric and two-dimensional detonation. We find that the ratio of cylinder radius ($R$) to slab thickness ($T$) at each detonation phase velocity ($D_{0}$) is such that $R(D_{0})/T(D_{0})<1$. The variation in the $R(D_{0})/T(D_{0})$ scaling is investigated with two detonation shock dynamics (DSD) models: a lower-order model relates the normal detonation velocity to local shock curvature, while a higher-order model includes the effect of front acceleration and transverse flow. The experimentally observed $R(D_{0})/T(D_{0})$ (${<}1$) scaling behaviour for PBX 9501 and PBX 9502 is captured by the lower-order DSD theory, revealing that the variation in the scale factor is due to a difference in the slab and axisymmetric components of the curvature along the shock in the cylindrical geometry. The higher-order DSD theory is required to capture the observed $R(D_{0})/T(D_{0})$ (${<}1$) scaling behaviour for ANFO. An asymptotic analysis of the lower-order DSD formulation describes the geometric scaling of the detonation phase velocity between the cylinder and slab geometries as the detonation phase velocity approaches the Chapman–Jouguet value. [ABSTRACT FROM PUBLISHER]

In this review, I discuss the use of galaxy-galaxy weak lensing measurements to study the masses of dark matter halos in which galaxies reside. After summarizing how weak gravitational lensing measurements can be interpreted in terms of halo mass, I review measurements that were used to derive the relationship between optical galaxy mass tracers, such as stellar mass or luminosity, and dark matter halo mass. Measurements of galaxy-galaxy lensing from the past decade have led to increasingly tight constraints on the connection between dark matter halo mass and optical mass tracers, including both the mean relationships between these quantities and the intrinsic scatter between them. I also review some of the factors that can complicate analysis, such as the choice of modeling procedure, and choices made when dividing up samples of lens galaxies. [ABSTRACT FROM PUBLISHER]

Searching for massive, dusty starbursts offers the great opportunity to trace galaxy overdensities and thus the cosmic web in the distant universe. I will present our APEX-LABOCA 870 μm imaging of the protocluster field of the radio galaxy MRC1138–262 — the so-called Spiderweb Galaxy — at z = 2.16, uncovering a large number of so-called submm galaxies (SMGs). The number counts already indicate an excess of SMGs compared to blank fields. Based on an exquisite multi-wavelength dataset, I will show that a large fraction of these massive, dusty starbursts are physically associated with the protocluster at z = 2.16. Finally, I will discuss both the properties of this starburst overdensity and their individual members. [ABSTRACT FROM PUBLISHER]

The four-year X-ray all-sky survey (eRASS) of the eROSITA telescope aboard the Spektrum-Roentgen-Gamma satellite will detect ~ 3 million active galactic nuclei (AGN) with a median redshift of z≈1. We show that this unprecedented AGN sample, complemented with redshift information, will supply us with outstanding opportunities for large-scale structure research. For the first time with a sample of X-ray selected AGN, it will become possible to perform detailed redshift- and luminosity-resolved studies of the linear bias factor, and to convincingly detected baryonic acoustic oscillations (BAOs). To exploit the full potential of the eRASS AGN sample, photometric and spectroscopic surveys of large areas and a sufficient depth will be needed. [ABSTRACT FROM PUBLISHER]

X-ray and extreme ultraviolet emission from galaxy clusters can be interpreted as thermal emission from a hot plasma gravitationally bound to the cluster and constituting a significant amount of the mass of the cluster. The origin of this plasma and its thermal energy content can be linked to the formation process through the theory of self-organization of these structures. [ABSTRACT FROM PUBLISHER]

Observing galaxies in the radio and submillimeter continuum has the advantage of being unaffected by dust extinction, which is a major drawback of studying galaxy evolution using optical data. Submillimeter single-dish surveys have made tremendous progress in understanding the high-redshift dusty population, but the low angular resolution of single-dish telescopes has also hampered these studies. Our recent JCMT and SMA imaging of high-redshift submillimeter sources revealed z > 4 objects that are radio and optically faint. Such objects cannot be easily identified with the combination of submillimeter single-dish and radio imaging. We also found a large fraction of multiple objects that are blended in single-dish images. Such objects may be early-stage mergers, or dusty starbursts in group environments. Since our work, larger surveys with PdBI and ALMA have been carried out to further address these issues. Additional to submillimeter imaging, future ultradeep EVLA imaging at 20 cm can also detect large samples of ultraluminous star forming galaxies at z ≳ 2. Sensitivities in radio and submillimeter observations have different redshift and dust temperature dependencies. Radio observations are also less affected by confusion. It will be necessary to combine deep surveys in both wavebands in order to achieve a more complete picture of the evolution of high-redshift star forming galaxies. [ABSTRACT FROM PUBLISHER]

The period 2009-2011 has seen a consolidation of our theoretical understanding around the Flat-Λ CDM Universe model, with experiments on several fronts providing observations consistent with this model, and leading to improved constraints on the values of H0, ΩB, ΩM, and ΩΛ. The recently launched Planck Satellite has started to provide a wealth of new observations of the Cosmic Microwave Background (CMB) and should lead to substantial progress in the physics of the CMB over the coming years. There has also be a steady progress in mapping the formation of structure and galaxies to higher and higher redshifts. Observations of objects at the highest redshifts are suggestive that the reionization of the Universe might not be complete at these epochs. This epoch will be probed in the near future with low-frequency radio surveys. This report, prepared from the inputs received from the committee members, concentrates on these areas. [ABSTRACT FROM PUBLISHER]

We highlight and discuss the importance of accounting for nebular emission in the SEDs of high redshift galaxies, as lines and continuum emission can contribute significantly or subtly to broad-band photometry. Physical parameters such as the galaxy age, mass, star-formation rate, dust attenuation and others inferred from SED fits can be affected to different extent by the treatment of nebular emission.We analyse a large sample of Lyman break galaxies from z ~ 3–6, and show some main results illustrating e.g. the importance of nebular emission for determinations of the mass–SFR relation, attenuation and age. We suggest that a fairly large scatter in such relations could be intrinsic. We find that the majority of objects (~ 60–70%) is better fit with SEDs accounting for nebular emission; the remaining galaxies are found to show relatively weak or no emission lines. Our modeling, and supporting empirical evidence, suggests the existence of two categories of galaxies, “starbursts” and “post-starbursts” (lower SFR and older galaxies) among the LBG population, and relatively short star-formation timescales. [ABSTRACT FROM PUBLISHER]

I present an overview of the molecular gas observations in high redshift galaxies. This field has seen tremendous progress in the past few years, with an increased number of detections of other molecules than CO. The molecular line observations are done towards different classes of massive starbursts, including submillimeter galaxies, quasars, and massive gas-rich disks. I will highlight results of detections of HCN, HCO+, and other small molecules, as well as the Spitzer detections of PAHs. Additionally, I will discuss about the excitation of CO and other species in the high-z galaxies and put this in the context of new telescopes such as ALMA. [ABSTRACT FROM PUBLISHER]

Star formation histories of local dwarf galaxies, derived through resolved stellar populations, appear complex and varied. The general picture derived from hydrodynamical simulations is one of cold gas accretion and bursty star formation, followed by feedback from supernovae and winds that heat and eject the central gas reservoirs. This ejection halts star formation until the material cools and re-accretes, resulting in an episodic SFH, particularly at stellar masses below ~ 109 M⊙. Such feedback has often been cited as the driving force behind the observed slowly-rising rotation curves in local dwarfs, due to an under-density of dark matter compared to theoretical models, which is one of the primary challenges to LCDM cosmology. However, these events have not yet been directly observed at high-redshift. Recently, using HST imaging and grism spectroscopy, we have uncovered an abundant population of low-mass galaxies (M* < 109 M⊙) at z = 1 - 2 that are undergoing strong bursts of star formation, in agreement with the theoretical predictions. These Extreme Emission Line Galaxies, with high specific SFRs and shallow gravitational potential wells, are ideal places to test the theoretical prediction of strong feedback-driven outflows. Here we use deep MUSE spectroscopy to search these galaxies for signatures of outflowing material, namely kinematic offsets between absorption lines (in the restframe optical and UV), which trace cool gas, and the nebular emission lines, which define the systemic redshift of the galaxy. Although the EELGs are intrinsically very faint, stacked spectra reveal blueshifted velocity centroids for Fe II absorption, which is indicative of outflowing cold gas. This represents the first constraint on outflows in M* < 109 M⊙ galaxies at z = 1 - 2. These outflows should regulate the star formation histories of low-mass galaxies at early cosmic times and thus play a crucial role in galaxy growth and evolution. [ABSTRACT FROM PUBLISHER]

Ultra-luminous infrared galaxies (LIR > 1012L⊙) are locally rare, but appear to dominate the co-moving energy density at higher redshifts (z > 2). Many of these are optically faint, dust-obscured galaxies that have been identified by the detection of their thermal dust emission in the sub-mm. Multi-wavelength spectroscopic follow-up observations of these sub-mm galaxies (SMGs) have shown that they are massive (Mstellar ~ 1011M⊙) objects undergoing intense star-formation (SFRs ~ 102–103M⊙ yr−1) with a mean redshift of z ~ 2, coinciding with the epoch of peak quasar activity. Furthermore, the presence of AGNs in ~ 28–50% of SMGs has been unveiled in the X-ray and near-IR. When both AGN and star-formation activity are present, long-slit spectroscopic techniques face difficulties in disentangling their independent contributions from integrated spectra. We have observed Hα emission from a sample of three SMGs in the redshift range z ~ 1.4–2.4 with the integral field spectrograph OSIRIS on Keck, in conjunction with Laser Guide Star Adaptive Optics. The spatially resolved, two-dimensional spectroscopic insight that these observations provide is the only viable probe of the spatial distribution and line-of-sight motion of ionized gas within these galaxies. We detect multiple galactic-scale sub-components, distinguishing the compact, broad Hα emission arising from an AGN from the more extended narrow-line emission of star-forming regions spreading over ~ 8–17 kpc. We explore the dynamics of gas in the inner galaxy halo to improve our understanding of the internal dynamics of this enigmatic galaxy population. We find no evidence of ordered orbital motion such as would be found in a gaseous disk, but rather large velocity offsets of a few hundred kilometers per second between distinct galactic-scale sub-components. Considering the disturbed morphology of SMGs, these sub-components are likely remnants of originally independent gas-rich galaxies that are in the process of merging, hence triggering the ultraluminous SMG phase. [ABSTRACT FROM PUBLISHER]

We review the expected properties of Pop III and very metal-poor starbursts and the behaviour the Lyα and He ii λ1640 emission lines, which are most likely the best/easiest signatures to single out such objects. Existing claims of Pop III signatures in distant galaxies are critically examined, and the searches for He ii λ1640 emission at high redshift are summarised. Finally, we briefly summarise ongoing and future deep observations at z > 6 aiming in particular at detecting the sources of cosmic reionisation as well as primeval/Pop III galaxies. [ABSTRACT FROM PUBLISHER]

We present recent progress in searching for galaxies at redshift from z ≃ 5 to z ∼ 10. Wide-field and sensitive surveys with 8m class telescopes have been providing more than several hundreds of star forming galaxies at z ∼ 5 − 7 that are probed in the optical window. These galaxies are used to study the early cosmic star formation activity as well as the early structure formation in the universe. Moreover, near infrared deep imaging and spectroscopic surveys have found probable candidates of galaxies from z ∼ 7 to z ∼ 10. Although these candidates are too faint to be identified unambiguously, we human being are now going to the universe beyond 13 billion light years, close to the epoch of first-generations stars; i.e., Population III stars. We also mention about challenges to find Population III-dominated galaxies in the early universe. [ABSTRACT FROM PUBLISHER]

While the baryon fraction in galaxy groups and clusters may be expected to reflect the universal value, observations of cluster baryon fractions have generally fallen short of this expectation and indicated a possible correlation with cluster mass. We present a new determination of the total baryon budget in nearby galaxy groups and clusters that includes the contributions from stars in galaxies, intracluster stars, and the intracluster medium. We find that the baryon mass fraction within r500 is independent of system mass and lower than the WMAP value. We conclude however that the present shortfall provides no compelling evidence for additional missing baryons, since it may arise due to a theoretically predicted deficit of baryons within r500 and systematic uncertainties associated with the mass determinations. With the addition of the ICL to the stellar mass in galaxies, the increase in X-ray gas mass fraction with increasing total mass is entirely accounted for by a decrease in the total stellar mass fraction, supporting the argument that the behavior of both the stellar and X-ray gas components is dominated by a decrease in star formation efficiency in more massive environments. Within just the stellar component, the fraction of the total stellar luminosity in the central, giant brightest cluster galaxy (BCG) and ICL (hereafter the BCG+ICL component) decreases as velocity dispersion (σ) increases, suggesting that ICL may grow less efficiently in higher mass environments. The identification of low mass groups with large BCG+ICL components also demonstrates that the massive cluster environment is not required to form intracluster stars. These proceedings are a condensed version of the work presented in Gonzalez, Zaritsky & Zabludoff (2007), and we refer the reader to that paper for a more complete discussion. [ABSTRACT FROM PUBLISHER]

We give a non-exhaustive review of the use of strong gravitational lensing in placing constraints on the quantity of dark and visible mass in galaxies. We discuss development of the methodology and summarise some recent results. [ABSTRACT FROM PUBLISHER]

Density profiles of galaxy groups can provide an insight on how large-scale structure in the Universe formed and evolved, since galaxy groups bridge the gap between individual galaxies and galaxy clusters. Studying the galaxy group that is gravitational lensing HELMS18, a submillimeter galaxy at z = 2.39 from the Herschel's HerMES Large Mode Survey (HELMS), we aim to probe the total density profile by combining strong gravitational lensing with kinematics of the centrally-located galaxies and kinematics of the group members. We have high-resolution data of HELMS18 obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) and multi-object spectroscopic data of the group members from Gemini-GMOS. Our main goal is to match these observations to probe the DM and stellar density profiles and to establish a complete description of this galaxy group. [ABSTRACT FROM AUTHOR]

The Tully-Fisher Relation (TFR) links two fundamental properties of disk galaxies: their luminosity and their rotation velocity (mass). The pioneering work of Vogt et al. in the 1990's showed that it is possible to study the TFR for spiral galaxies at considerable look-back-times, and use it as a powerful probe of their evolution. In recent years, several groups have studied the TFR for galaxies in different environments reaching redshifts beyond one. In this brief review I summarise the main results of some of these studies and their consequences for our understanding of the formation and evolution of disk galaxies. Particular emphasis is placed on the possible environment-driven differences in the behaviour of the TFR for field and cluster galaxies. [ABSTRACT FROM PUBLISHER]

We review the current status of searches for high redshift galaxies and quasars, together with their derived luminosity function, star formation history and relative contribution to the UV ionizing background. These searches have been carried out in the optical and near-infrared with the HST for very deep pencil beam surveys and ground-based telescopes for deep large area surveys. The peak of galaxy and black hole formation activity occurs at $z\sim 2$-3, with a strong decrease in UV luminosity density in the redshift interval $z\sim 3$ to 6. This decrease seems to extend beyond $z\sim 6$ for luminous galaxies, as there are only a few $z\sim 7$-8 secure galaxy candidates. The star formation rate at $z\sim 6$ is dominated by 0.1 L$^{\star}$ galaxies. The $z \gtrsim 5$ samples for both types of sources are too small to constrain the faint end of their luminosity function or even its knee. Consequently, predictions of the number density of $z \gtrsim 7$ galaxies is highly uncertain; their search with JWST and ELTs should cover areas of at least $\sim$1 deg$^2$ and will require long campaigns (${\gtrsim} 1$ month). Faint quasars of small black hole mass should also be detected in these surveys. Searches for $z\sim10$ rare, bright quasars and higher $z$ transient sources, gamma-ray bursts and population III SNe, should be undertaken with dedicated facilities. The physical properties of high $z$ galaxies and the metal-enrichment of the intergalactic medium at early epochs will be determined by high-resolution spectroscopic observations with ELTs requiring substantial exposure times (${\sim} 100$ hr). [ABSTRACT FROM PUBLISHER]

The recent development of large, complete samples which identify high-redshift galaxies at $z\sim5.7$ and $z\sim 6.5$ from deep, wide-field surveys provides detailed information on the earliest galaxies, their numbers, spatial and kinematic distributions, and implications for early reionisation of the IGM. In this contribution we present results of spectroscopic studies of $z\sim 5.7$ and $z\sim6.5$ galaxies identified from our deep, Lyman alpha narrow-band and multicolour surveys conducted with the SuprimeCam mosaic CCD camera on the 8.3-m Subaru telescope and observed with the DEIMOS multi-object spectrograph on Keck. The luminosity function of the $z\sim6.5$ galaxies is shown to be similar to the luminosity function of the $z\sim 5.7$ galaxy samples, suggesting that a substantial star-forming population is already in place at $z\sim 6.5$. Comparisons of both individual and stacked spectra of galaxies in these two samples show that the Lyman alpha emission profiles, equivalent widths, and continuum break strengths do not substantially change over this redshift interval. The wide-field nature of the surveys also permits mapping of the large-scale distribution of high-redshift galaxies in spatial structures extending across individual SuprimeCam fields ($\sim 60$ Mpc). Field-to-field variations in the number of objects at $z\sim 6.5$ may shortly be able to place constraints on the porosity of the reionisation boundary. [ABSTRACT FROM PUBLISHER]