Search

We introduce a novel Interval Bound Propagation (IBP) approach for the formal verification of object detection models, specifically targeting the Intersection over Union (IoU) metric. The approach has been implemented in an open source code, named IBP IoU, compatible with popular abstract interpretation based verification tools. The resulting verifier is evaluated on landing approach runway detection and handwritten digit recognition case studies. Comparisons against a baseline (Vanilla IBP IoU) highlight the superior performance of IBP IoU in ensuring accuracy and stability, contributing to more secure and robust machine learning applications.

Surrogate Neural Networks are nowadays routinely used in industry as substitutes for computationally demanding engineering simulations (e.g., in structural analysis). They allow to generate faster predictions and thus analyses in industrial applications e.g., during a product design, testing or monitoring phases. Due to their performance and time-efficiency, these surrogate models are now being developed for use in safety-critical applications. Neural network verification and in particular the assessment of their robustness (e.g., to perturbations) is the next critical step to allow their inclusion in real-life applications and certification. We assess the applicability and scalability of empirical and formal methods in the context of aircraft predictive maintenance for surrogate neural networks designed to predict the stress sustained by an aircraft part from external loads. The case study covers a high-dimensional input and output space and the verification process thus accommodates multi-objective constraints. We explore the complementarity of verification methods in assessing the local stability property of such surrogate models to input noise. We showcase the effectiveness of sequentially combining methods in one verification 'pipeline' and demonstrate the subsequent gain in runtime required to assess the targeted property., Comment: Peer-reviewed and accepted at the 29th International Conference on Formal Methods for Industrial Critical Systems (FMICS 2024) - 15 pages

As deep neural networks (DNNs) are becoming the prominent solution for many computational problems, the aviation industry seeks to explore their potential in alleviating pilot workload and in improving operational safety. However, the use of DNNs in this type of safety-critical applications requires a thorough certification process. This need can be addressed through formal verification, which provides rigorous assurances -- e.g.,~by proving the absence of certain mispredictions. In this case-study paper, we demonstrate this process using an image-classifier DNN currently under development at Airbus and intended for use during the aircraft taxiing phase. We use formal methods to assess this DNN's robustness to three common image perturbation types: noise, brightness and contrast, and some of their combinations. This process entails multiple invocations of the underlying verifier, which might be computationally expensive; and we therefore propose a method that leverages the monotonicity of these robustness properties, as well as the results of past verification queries, in order to reduce the overall number of verification queries required by nearly 60%. Our results provide an indication of the level of robustness achieved by the DNN classifier under study, and indicate that it is considerably more vulnerable to noise than to brightness or contrast perturbations., Comment: This is a preprint version of the paper in the proceedings of 43rd Digital Avionics Systems Conference (DASC)

Passive early-type galaxies dominate cluster cores at z $\lesssim$1.5. At higher redshift, cluster core galaxies are observed to have still on-going star-formation, fuelled by cold molecular gas. We measure the molecular gas reservoir of the central region around the radio-loud AGN in the cluster CARLA J1103+3449 at z=1.44 with NOEMA. The AGN synchrotron emission dominates the continuum emission at 94.48 GHz, and we measure its flux at the AGN position and at the position of two radio jets. Combining our measurements with published results over the range 4.71 GHz-94.5 GHz, we obtain a flat spectral index $\alpha = 0.14 \pm 0.03$ for the AGN core emission, and a steeper index $\alpha = 1.43 \pm 0.04$ and $\alpha = 1.15 \pm 0.04$ at positions close to the western and eastern lobe, respectively. The total spectral index is $\alpha = 0.92 \pm 0.02$ over the range 73.8 MHz-94.5 GHz. We detect two CO(2-1) emission lines, both blue-shifted with respect to the AGN. Their emission corresponds to two regions, ~17 kpc south-east and ~14 kpc south-west of the AGN, not associated with galaxies. In these two regions, we find a total massive molecular gas reservoir of $M_{gas}$ = 3.9 $\pm$ 0.4 $10^{10} M_{\odot}$, which dominates (~ 60%) the central total molecular gas reservoir. These results can be explained by massive cool gas flows in the center of the cluster. The AGN early-type host is not yet quenched; its star formation rate is consistent with being on the main sequence of star-forming galaxies in the field (SFR~30-140 $M_{\odot}$/yr), and the cluster core molecular gas reservoir is expected to feed the AGN and the host star-formation before quiescence. The other cluster confirmed members show star formation rates at ~2 $\sigma$ below the field main sequence at similar redshifts and do not have molecular gas masses larger than galaxies of similar stellar mass in the field., Comment: 18 pages, 14 figures, A&A, accepted for publication

We study the dynamical properties of massive quiescent galaxies at $1.4 < z < 2.1$ using deep Hubble Space Telescope WFC3/F160W imaging and a combination of literature stellar velocity dispersion measurements and new near-infrared spectra obtained using KMOS on the ESO VLT. We use these data to show that the typical dynamical-to-stellar mass ratio has increased by $\sim$0.2 dex from $z = 2$ to the present day, and investigate this evolution in the context of possible changes in the stellar initial mass function (IMF) and/or fraction of dark matter contained within the galaxy effective radius, $f_\mathrm{DM}$. Comparing our high-redshift sample to their likely descendants at low-redshift, we find that $f_\mathrm{DM}$ has increased by a factor of more than 4 since $z \approx 1.8$, from $f_\mathrm{DM}$ = $6.6\pm1.0$% to $\sim$24%. The observed increase appears robust to changes in the methods used to estimate dynamical masses or match progenitors and descendants. We quantify possible variation of the stellar IMF through the offset parameter $\alpha$, defined as the ratio of dynamical mass in stars to the stellar mass estimated using a Chabrier IMF. We demonstrate that the correlation between stellar velocity dispersion and $\alpha$ reported among quiescent galaxies at low-redshift is already in place at $z = 2$, and argue that subsequent evolution through (mostly minor) merging should act to preserve this relation while contributing significantly to galaxies overall growth in size and stellar mass., Comment: 40 pages, 21 figures; accepted for publication in ApJ

This paper is one in a series that explores the importance of radius as a second parameter in galaxy evolution. The topic investigated here is the relationship between star formation rate (SFR) and galaxy radius ($R_{\rm e}$) for main-sequence star-forming galaxies. The key observational result is that, over a wide range of stellar mass and redshift in both CANDELS and SDSS, there is little trend between SFR and $R_{\rm e}$ at fixed stellar mass. The Kennicutt-Schmidt law, or any similar density-related star formation law, then implies that smaller galaxies must have lower gas fractions than larger galaxies (at fixed $M_{\ast}$), and this is supported by observations of local star-forming galaxies. We investigate the implication by adopting the equilibrium "bathtub" model: the ISM gas mass is assumed to be constant over time and the net star formation rate is the difference between the accretion rate of gas onto the galaxy from the halo and the outflow rate due to winds. To match the observed null correlation between SFR and radius, the bathtub model requires that smaller galaxies at fixed mass have weaker galactic winds. Our hypothesis is that galaxies are a 2-dimensional family whose properties are set mainly by halo mass and concentration. Galaxy radius and accretion rate plausibly both depend on halo concentration, which predicts how wind strength should vary with $R_{\rm e}$ and SFR., Comment: 21 pages, 9 figures, ApJ accepted

We present a WFC3 F160W ($H$-band) selected catalog in the CANDELS/GOODS-N field containing photometry from the ultraviolet (UV) to the far-infrared (IR), photometric redshifts and stellar parameters derived from the analysis of the multi-wavelength data. The catalog contains 35,445 sources over the 171 arcmin$^{2}$ of the CANDELS F160W mosaic. The 5$\sigma$ detection limits (within an aperture of radius 0\farcs17) of the mosaic range between $H=27.8$, 28.2 and 28.7 in the wide, intermediate and deep regions, that span approximately 50\%, 15\% and 35\% of the total area. The multi-wavelength photometry includes broad-band data from UV (U band from KPNO and LBC), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), near-to-mid IR (HST/WFC3 F105W, F125W, F140W and F160W, Subaru/MOIRCS Ks, CFHT/Megacam K, and \spitzer/IRAC 3.6, 4.5, 5.8, 8.0 $\mu$m) and far IR (\spitzer/MIPS 24$\mu$m, HERSCHEL/PACS 100 and 160$\mu$m, SPIRE 250, 350 and 500$\mu$m) observations. In addition, the catalog also includes optical medium-band data (R$\sim50$) in 25 consecutive bands, $\lambda=500$ to 950~nm, from the SHARDS survey and WFC3 IR spectroscopic observations with the G102 and G141 grisms (R$\sim210$ and 130). The use of higher spectral resolution data to estimate photometric redshifts provides very high, and nearly uniform, precision from $z=0-2.5$. The comparison to 1,485 good quality spectroscopic redshifts up to $z\sim3$ yields $\Delta z$/(1+$z_{\rm spec}$)$=$0.0032 and an outlier fraction of $\eta=$4.3\%. In addition to the multi-band photometry, we release added-value catalogs with emission line fluxes, stellar masses, dust attenuations, UV- and IR- based star formation rates and rest-frame colors., Comment: The catalogs, images and spectra are available in Rainbow-slicer (https://bit.ly/2OxKKx1 ), navigator (https://bit.ly/2GDS180 ) and MAST (https://bit.ly/2YtoBQ4 ). In addition to the photometry and other added-value catalogs we release UV+IR star formation rates based on Spitzer (MIPS) and Herschel (PACS and SPIRE) in the 5 CANDELS fields

We present the $0.6

The Complete Calibration of the Color-Redshift Relation (C3R2) survey is a multi-institution, multi-instrument survey that aims to map the empirical relation of galaxy color to redshift to i~24.5 (AB), thereby providing a firm foundation for weak lensing cosmology with the Stage IV dark energy missions Euclid and WFIRST. Here we present 3171 new spectroscopic redshifts obtained in the 2016B and 2017A semesters with a combination of DEIMOS, LRIS, and MOSFIRE on the Keck telescopes. The observations come from all of the Keck partners: Caltech, NASA, the University of Hawaii, and the University of California. Combined with the 1283 redshifts published in DR1, the C3R2 survey has now obtained and published 4454 high quality galaxy redshifts. We discuss updates to the survey design and provide a catalog of photometric and spectroscopic data. Initial tests of the calibration method performance are given, indicating that the sample, once completed and combined with extensive data collected by other spectroscopic surveys, should allow us to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for WFIRST. We use the full spectroscopic sample to demonstrate that galaxy brightness is weakly correlated with redshift once a galaxy is localized in the Euclid or WFIRST color space, with potentially important implications for the spectroscopy needed to calibrate redshifts for faint WFIRST and LSST sources., Comment: ApJ accepted. Survey website with links to the C3R2 redshift catalog and spectroscopic data hosted by KOA can be found at https://sites.google.com/view/c3r2-survey/home

Galaxy mergers are expected to have a significant role in the mass assembly of galaxies in the early Universe, but there are very few observational constraints on the merger history of galaxies at $z>2$. We present the first study of galaxy major mergers (mass ratios $>$ 1:4) in mass-selected samples out to $z\approx6$. Using all five fields of the HST/CANDELS survey and a probabilistic pair count methodology that incorporates the full photometric redshift posteriors and corrections for stellar mass completeness, we measure galaxy pair-counts for projected separations between 5 and 30 kpc in stellar mass selected samples at $9.7 < \log_{10}(\rm{M}_{*}/\rm{M}_{\odot}) < 10.3$ and $\log_{10}(\rm{M}_{*}/\rm{M}_{\odot}) > 10.3$. We find that the major merger pair fraction rises with redshift to $z\approx6$ proportional to $(1+z)^{m}$, with $m = 0.8\pm0.2$ ($m = 1.8\pm0.2$) for $\log_{10}(\rm{M}_{*} / \rm{M}_{\odot}) > 10.3$ ($9.7 < \log_{10}(\rm{M}_{*}/\rm{M}_{\odot}) < 10.3$). Investigating the pair fraction as a function of mass ratio between 1:20 and 1:1, we find no evidence for a strong evolution in the relative numbers of minor to major mergers out to $z<3$. Using evolving merger timescales we find that the merger rate per galaxy ($\mathcal{R}$) rises rapidly from $0.07\pm 0.01$ Gyr$^{-1}$ at $z < 1$ to $7.6\pm 2.7$ Gyr$^{-1}$ at $z = 6$ for galaxies at $\log_{10}(\rm{M}_{*}/\rm{M}_{\odot}) > 10.3$. The corresponding co-moving major merger rate density remains roughly constant during this time, with rates of $\Gamma \approx 10^{-4}$ Gyr$^{-1}$ Mpc$^{-3}$. Based on the observed merger rates per galaxy, we infer specific mass accretion rates from major mergers that are comparable to the specific star-formation rates for the same mass galaxies at $z>3$ - observational evidence that mergers are as important a mechanism for building up mass at high redshift as in-situ star-formation., Comment: 36 pages, 17 figures. Accepted for publication in ApJ

We report spectroscopic results from our 40-orbit $Hubble~Space~Telescope$ slitless grism spectroscopy program observing the 20 densest CARLA candidate galaxy clusters at $1.4 < z < 2.8$. These candidate rich structures, among the richest and most distant known, were identified on the basis of $[3.6]-[4.5]$ color from a $408~$hr multi-cycle $Spitzer$ program targeting $420$ distant radio-loud AGN. We report the spectroscopic confirmation of $16$ distant structures at $1.4 < z < 2.8$ associated with the targeted powerful high-redshift radio-loud AGN. We also report the serendipitous discovery and spectroscopic confirmation of seven additional structures at $0.87 < z < 2.12$ not associated with the targeted radio-loud AGN. We find that $10^{10} - 10^{11}\,M_{\odot}$ member galaxies of our confirmed CARLA structures form significantly fewer stars than their field counterparts at all redshifts within $1.4\leq z\leq 2$. We also observe higher star-forming activity in the structure cores up to $z = 2$, finding similar trends as cluster surveys at slightly lower redshifts ($1.0 < z < 1.5$). By design, our efficient strategy of obtaining just two grism orbits per field only obtains spectroscopic confirmation of emission-line galaxies. Deeper spectroscopy will be required to study the population of evolved, massive galaxies in these (forming) clusters. Lacking multi-band coverage of the fields, we adopt a very conservative approach of calling all confirmations "structures", although we note that a number of features are consistent with some of them being bona fide galaxy clusters. Together, this survey represents a unique and large homogenous sample of spectroscopically confirmed structures at high redshifts, potentially more than doubling the census of confirmed, massive clusters at $z > 1.4$., Comment: Accepted for publication in the Astrophysical Journal

We present results on the structural properties of massive passive galaxies in three clusters at $1.39

We present a large-scale galaxy structure Cl J021734-0513 at z~0.65 discovered in the UKIDSS UDS field, made of ~20 galaxy groups and clusters, spreading over 10 Mpc. We report on a VLT/VIMOS spectroscopic follow-up program that, combined with past spectroscopy, allowed us to confirm four galaxy clusters (M200 ~ 10^14 Msol) and a dozen associated groups and star-forming galaxy overdensities. Two additional filamentary structures at z ~ 0.62 and z ~ 0.69 and foreground and background clusters at 0.6 < z < 0.7 were also confirmed along the line-of-sight. The structure subcomponents are at different formation stages. The clusters have a core dominated by passive galaxies and an established red sequence. The remaining structures are a mix of star-forming galaxy overdensities and forming groups. The presence of quiescent galaxies in the core of the latter shows that `preprocessing' has already happened before the groups fall into their more massive neighbours. Our spectroscopy allows us to derive spectral index measurements e.g. emission/absorption line equivalent widths, strength of the 4000A break, valuable to investigate the star formation history of structure members. Based on these line measurements, we select a population of `poststarburst' galaxies. These galaxies are preferentially found within the virial radius of clusters, supporting a scenario in which their recent quenching could be prompted by gas stripping by the dense intracluster medium. We derive stellar age estimates using MCMC-based spectral fitting for quiescent galaxies and find a correlation between ages and colours/stellar masses which favours a top-down formation scenario of the red sequence. A catalogue of ~650 redshifts in UDS will be released alongside the paper., Comment: 23 pages, 19 figures, 4 tables, accepted for publication in MNRAS. A catalogue of ~650 VIMOS spectroscopic redshifts in UKIDSS UDS will be released alongside the paper. Feel free to contact the authors for early access to the catalogue

The rate of major galaxy-galaxy merging is theoretically predicted to steadily increase with redshift during the peak epoch of massive galaxy development ($1{\leq}z{\leq}3$). We use close-pair statistics to objectively study the incidence of massive galaxies (stellar $M_{1}{\geq}2{\times}10^{10}M_{\odot}$) hosting major companions ($1{\leq}M_{1}/M_{2}{\leq}4$; i.e., $<$4:1) at six epochs spanning $0{<}z{<}3$. We select companions from a nearly complete, mass-limited ($\geq5{\times}10^{9}M_{\odot}$) sample of 23,696 galaxies in the five CANDELS fields and the SDSS. Using $5-50$ kpc projected separation and close redshift proximity criteria, we find that the major companion fraction $f_{\mathrm{mc}}(z)$ based on stellar mass-ratio (MR) selection increases from 6% ($z{\sim}0$) to 16% ($z{\sim}0.8$), then turns over at $z{\sim}1$ and decreases to 7% ($z{\sim}3$). Instead, if we use a major F160W flux ratio (FR) selection, we find that $f_{\mathrm{mc}}(z)$ increases steadily until $z=3$ owing to increasing contamination from minor (MR$>$4:1) companions at $z>1$. We show that these evolutionary trends are statistically robust to changes in companion proximity. We find disagreements between published results are resolved when selection criteria are closely matched. If we compute merger rates using constant fraction-to-rate conversion factors ($C_{\mathrm{merg,pair}}{=}0.6$ and $T_{\mathrm{obs,pair}}{=}0.65\mathrm{Gyr}$), we find that MR rates disagree with theoretical predictions at $z{>}1.5$. Instead, if we use an evolving $T_{\mathrm{obs,pair}}(z){\propto}(1+z)^{-2}$ from Snyder et al., our MR-based rates agree with theory at $0{<}z{<}3$. Our analysis underscores the need for detailed calibration of $C_{\mathrm{merg,pair}}$ and $T_{\mathrm{obs,pair}}$ as a function of redshift, mass and companion selection criteria to better constrain the empirical major merger history., Comment: 27 pages, 15 figures, 5 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

We present data for 16 galaxies in the overdensity JKCS 041 at $z \simeq 1.80$ as part of the K-band Multi-Object Spectrograph (KMOS) Cluster Survey (KCS). With 20-hour integrations, we have obtained deep absorption-line spectra from which we derived velocity dispersions for seven quiescent galaxies. We combined photometric parameters derived from Hubble Space Telescope images with the dispersions to construct a fundamental plane (FP) for quiescent galaxies in JKCS 041. From the zero-point evolution of the FP, we derived a formation redshift for the galaxies of $z_{form} = 3.0\pm0.3$, corresponding to a mean age of $1.4\pm0.2$ Gyrs. We tested the effect of structural and velocity dispersion evolution on our FP zero point and found a negligible contribution when using dynamical mass-normalized parameters ($\sim 3\%$), but a significant contribution from stellar-mass-normalized parameters ($\sim 42 \%$). From the relative velocities of the galaxies, we probed the three-dimensional structure of these 16 confirmed members of JKCS 041, and found that a group of galaxies in the south west of the overdensity had systematically higher velocities. We derived ages for the galaxies in the different groups from the FP. We found the east-extending group had typically older galaxies ($2.1\substack{+0.3\\-0.2}$ Gyrs), than those in the south-west group ($0.3\pm0.2$ Gyrs). Although based on small numbers, the overdensity dynamics, morphology, and age results could indicate that JKCS 041 is in formation and may comprise two merging groups of galaxies. The result could link large-scale structure to ages of galaxies for the first time at this redshift., Comment: Accepted for publication in ApJ. 24 pages, 12 figures

This is the first in a series of papers examining the demographics of star-forming galaxies at $0.2

We present the analysis of the fundamental plane (FP) for a sample of 19 massive red-sequence galaxies ($M_{\star} >4\times10^{10} M_{\odot}$) in 3 known overdensities at $1.3911$) in our sample, we translate the FP zero-point evolution into a mass-to-light-ratio $M/L$ evolution finding $\Delta \log M/L_{B}=(-0.46\pm0.10)z$, $\Delta \log M/L_{B}=(-0.52\pm0.07)z$, to $\Delta \log M/L_{B}=(-0.55\pm0.10)z$, respectively. We assess the potential contribution of the galaxies structural and stellar velocity dispersion evolution to the evolution of the FP zero-point and find it to be $\sim$6-35 % of the FP zero-point evolution. The rate of $M/L$ evolution is consistent with galaxies evolving passively. By using single stellar population models, we find an average age of $2.33^{+0.86}_{-0.51}$ Gyr for the $\log M_{\star}/M_{\odot}>11$ galaxies in our massive and virialized cluster at $z=1.39$, $1.59^{+1.40}_{-0.62}$ Gyr in a massive but not virialized cluster at $z=1.46$, and $1.20^{+1.03}_{-0.47}$ Gyr in a protocluster at $z=1.61$. After accounting for the difference in the age of the Universe between redshifts, the ages of the galaxies in the three overdensities are consistent within the errors, with possibly a weak suggestion that galaxies in the most evolved structure are older., Comment: 24 pages, 10 figures, 4 tables. Accepted for publication in ApJ

We explore the H-alpha emission in the massive quiescent galaxies observed by the KMOS-3D survey at 0.7 < z < 2.7. The H-alpha line is robustly detected in 20 out of 120 UVJ-selected quiescent galaxies, and we classify the emission mechanism using the H-alpha line width and the [NII]/H-alpha line ratio. We find that AGN are likely to be responsible for the line emission in more than half of the cases. We also find robust evidence for star formation activity in nine quiescent galaxies, which we explore in detail. The H-alpha kinematics reveal rotating disks in five of the nine galaxies. The dust-corrected H-alpha star formation rates are low (0.2 - 7 Msun/yr), and place these systems significantly below the main sequence. The 24micron-based infrared luminosities, instead, overestimate the star formation rates. These galaxies present a lower gas-phase metallicity compared to star-forming objects with similar stellar mass, and many of them have close companions. We therefore conclude that the low-level star formation activity in these nine quiescent galaxies is likely to be fueled by inflowing gas or minor mergers, and could be a sign of rejuvenation events., Comment: 7 pages, 5 figures, published in ApJ Letters

We present a 0.4-8$\mu$m multi-wavelength photometric catalog in the Extended Groth Strip (EGS) field. This catalog is built on the Hubble Space Telescope (HST) WFC3 and ACS data from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), and it incorporates the existing HST data from the All-wavelength Extended Groth strip International Survey (AEGIS) and the 3D-HST program. The catalog is based on detections in the F160W band reaching a depth of F160W=26.62 AB (90% completeness, point-sources). It includes the photometry for 41457 objects over an area of $\approx 206$ arcmin$^2$ in the following bands: HST ACS F606W and F814W; HST WFC3 F125W, F140W and F160W; CFHT/Megacam $u^*$, $g'$, $r'$, $i'$ and $z'$; CFHT/WIRCAM $J$, $H$ and $K_\mathrm{S}$; Mayall/NEWFIRM $J1$, $J2$, $J3$, $H1$, $H2$, $K$; Spitzer IRAC $3.6\mu$m, $4.5\mu$m, $5.8\mu$m and $8.0\mu$m. We are also releasing value-added catalogs that provide robust photometric redshifts and stellar mass measurements. The catalogs are publicly available through the CANDELS repository., Comment: ApJS in press. Catalogs can be accessed through the MAST archive at https://archive.stsci.edu/prepds/candels/

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)., Comment: 10 pages, 4 figures, IAU Symposium 325 on Astroinformatics

We present a MUSE and KMOS dynamical study 405 star-forming galaxies at redshift z=0.28-1.65 (median redshift z=0.84). Our sample are representative of star-forming, main-sequence galaxies, with star-formation rates of SFR=0.1-30Mo/yr and stellar masses M=10^8-10^11Mo. For 49+/-4% of our sample, the dynamics suggest rotational support, 24+/-3% are unresolved systems and 5+/-2% appear to be early-stage major mergers with components on 8-30kpc scales. The remaining 22+/-5% appear to be dynamically complex, irregular (or face-on systems). For galaxies whose dynamics suggest rotational support, we derive inclination corrected rotational velocities and show these systems lie on a similar scaling between stellar mass and specific angular momentum as local spirals with j*=J/M*\propto M^(2/3) but with a redshift evolution that scales as j*\propto M^{2/3}(1+z)^(-1). We identify a correlation between specific angular momentum and disk stability such that galaxies with the highest specific angular momentum, log(j*/M^(2/3))>2.5, are the most stable, with Toomre Q=1.10+/-0.18, compared to Q=0.53+/-0.22 for galaxies with log(j*/M^(2/3))<2.5. At a fixed mass, the HST morphologies of galaxies with the highest specific angular momentum resemble spiral galaxies, whilst those with low specific angular momentum are morphologically complex and dominated by several bright star-forming regions. This suggests that angular momentum plays a major role in defining the stability of gas disks: at z~1, massive galaxies that have disks with low specific angular momentum, appear to be globally unstable, clumpy and turbulent systems. In contrast, galaxies with high specific angular have evolved in to stable disks with spiral structures., Comment: MNRAS in press. 21 pages; 12 figures. The full pdf, which includes an additional 32 pages of supplementary figures and data tables are available from http://astro.dur.ac.uk/~ams/MUSEcubes/

We present quantified visual morphologies of approximately 48,000 galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic And Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. 90% of galaxies have z < 3 and are observed in rest-frame optical wavelengths by CANDELS. Each galaxy received an average of 40 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. We apply a consensus-based classifier weighting method that preserves classifier independence while effectively down-weighting significantly outlying classifications. After analysing the effect of varying image depth on reported classifications, we also provide depth-corrected classifications which both preserve the information in the deepest observations and also enable the use of classifications at comparable depths across the full survey. Comparing the Galaxy Zoo classifications to previous classifications of the same galaxies shows very good agreement; for some applications the high number of independent classifications provided by Galaxy Zoo provides an advantage in selecting galaxies with a particular morphological profile, while in others the combination of Galaxy Zoo with other classifications is a more promising approach than using any one method alone. We combine the Galaxy Zoo classifications of "smooth" galaxies with parametric morphologies to select a sample of featureless disks at 1 < z < 3, which may represent a dynamically warmer progenitor population to the settled disk galaxies seen at later epochs., Comment: 30 pages, 14 figures, MNRAS accepted. Galaxy classifications available at data.galaxyzoo.org

The outcome of upcoming cosmological surveys will depend on the accurate estimates of photometric redshifts. In the framework of the implementation of the photo-z algorithm for Euclid, we are exploring new avenues to improve template-fitting methods. The paper focusses on the prescription of the extinction of source light by dust in the Milky Way. Since Galactic extinction strongly correlates with wavelength and photometry is commonly obtained in broad-band filters, the amount of absorption depends on the source SED, a point often neglected as the SED is not known a-priori. A consequence of this is that the observed E(B-V) (=A_B-A_V) will be different from the E(B-V) used to normalise the absorption law k_lambda (=A_lambda/E(B-V)). Band-pass corrections are required to renormalise the law for a given SED. We assess the band-pass corrections of a range of SEDs and find they vary by up to 20%. We investigate how dust-to-reddening scaling factors depend of the sources used for their calibration. We derive scaling factors from the color excesses of z<0.4 SDSS red galaxies and show that band-pass corrections predict the observed differences. Extinction is then estimated for a range of SEDs and filters relevant to Euclid and other cosmological ground-based surveys. For high extinction line-of-sights (E(B-V)>0.1, ~8% of the Euclid survey), the variations in corrections can be ~0.1mag in the `bluer' optical filters and ~0.04mag in the NIR filters. An inaccurate correction of extinction critically affects photo-z. In particular, for high extinctions and z<0.5, the bias (mean D_z=z_phot-z_real) exceeds 0.2%(1+z), the precision required by weak-lensing analyses. Additional uncertainty on the MW extinction law further reduces the photo-z precision. We propose a new prescription of Galactic absorption for template-fitting algorithms that takes into consideration the dependence of extinction with SED., Comment: 16 pages, 15 figures, 3 appendices. Accepted for publication in Astronomy & Astrophysics. A set of online routines will be made available in the near future. These routines will allow to derive Galactic extinction estimates for a given line of sight and galaxy type in a number of common filters. In the meantime, please feel free to contact the authors for early access to the routines

Using HST slitless grism data, we report the spectroscopic confirmation of two distant structures at $z \sim 2$ associated with powerful high-redshift radio-loud AGN. These rich structures, likely (forming) clusters, are among the most distant currently known and were identified on the basis of Spitzer/IRAC [3.6] - [4.5] color. We spectroscopically confirm 9 members in the field of MRC 2036-254, comprising eight star-forming galaxies and the targeted radio galaxy. The median redshift is $z = 2.000$. We spectroscopically confirm 10 members in the field of B3 0756+406, comprising eight star-forming galaxies and two AGN, including the targeted radio-loud quasar. The median redshift is $z = 1.986$. All confirmed members are within 500 kpc (1 arcmin) of the targeted AGN. We derive median (mean) star-formation rates of $\sim 35~M_{\odot}\rm ~ yr^{-1}$ ($\sim 50~M_{\odot}\rm ~ yr^{-1}$) for the confirmed star-forming members of both structures based on their [OIII]$\lambda5007$ luminosities, and estimate average galaxy stellar masses $\lesssim 1 \times 10^{11} ~M_{\odot}$ based on mid-infrared fluxes and SED modeling. Most of our confirmed members are located above the star-forming main-sequence towards starburst galaxies, consistent with clusters at these early epochs being the sites of significant levels of star formation. The structure around MRC 2036-254 shows an overdensity of IRAC-selected candidate galaxy cluster members consistent with being quiescent galaxies, while the structure around B3 0756+406 shows field values, albeit with many lower limits to colors that could allow an overdensity of faint red quiescent galaxies. The structure around MRC 2036-254 shows a red sequence of passive galaxy candidates., Comment: Accepted to ApJ

We present an overview of the "KIFF" project, which provides ultra-deep Ks-band imaging of all six of the Hubble Frontier Fields clusters Abell 2744, MACS-0416, Abell S1063, Abell 370, MACS-0717 and MACS-1149. All of these fields have recently been observed with large allocations of Directors' Discretionary Time with the HST and Spitzer telescopes covering 0.4 < lambda < 1.6 microns and 3.6--4.5 microns, respectively. VLT/HAWK-I integrations of the first four fields reach 5-sigma limiting depths of Ks~26.0 (AB, point sources) and have excellent image quality (FWHM ~ 0."4). Shorter Keck/MOSFIRE integrations of the MACS-0717 (MACS-1149) field better observable in the north reach limiting depths Ks=25.5 (25.1) with seeing FWHM ~0."4 (0."5). In all cases the Ks-band mosaics cover the primary cluster and parallel HST/ACS+WFC3 fields. The total area of the Ks-band coverage is 490 arcmin^2. The Ks-band at 2.2 microns crucially fills the gap between the reddest HST filter (1.6 micron ~ H-band) and the IRAC 3.6 micron passband. While reaching the full depths of the space-based imaging is not currently feasible from the ground, the deep Ks-band images provide important constraints on both the redshifts and the stellar population properties of galaxies extending well below the characteristic stellar mass across most of the age of the universe, down to, and including, the redshifts of the targeted galaxy clusters (z < 0.5)., Comment: Submitted to ApJS, includes revisions after the first referee report. Reduced mosaics of all six survey fields are provided via the ESO Phase 3 query form at http://www.eso.org/sci/observing/phase3/news.html#kiff

We present a detailed, multi-wavelength study of star formation (SF) and AGN activity in 11 near-infrared (IR) selected, spectroscopically confirmed, massive ($\gtrsim10^{14}\,\rm{M_{\odot}}$) galaxy clusters at $1

We present measurements of the [NII]/Ha ratio as a probe of gas-phase oxygen abundance for a sample of 419 star-forming galaxies at z=0.6-2.7 from the KMOS3D near-IR multi-IFU survey. The mass-metallicity relation (MZR) is determined consistently with the same sample selection, metallicity tracer, and methodology over the wide redshift range probed by the survey. We find good agreement with long-slit surveys in the literature, except for the low-mass slope of the relation at z~2.3, where this sample is less biased than previous samples based on optical spectroscopic redshifts. In this regime we measure a steeper slope than some literature results. Excluding the AGN contribution from the MZR reduces sensitivity at the high mass end, but produces otherwise consistent results. There is no significant dependence of the [NII]/Ha ratio on SFR or environment at fixed redshift and stellar mass. The IFU data allow spatially resolved measurements of [NII]/Ha, from which we can infer abundance gradients for 180 galaxies, thus tripling the current sample in the literature. The observed gradients are on average flat, with only 15 gradients statistically offset from zero at >3sigma. We have modelled the effect of beam-smearing, assuming a smooth intrinsic radial gradient and known seeing, inclination and effective radius for each galaxy. Our seeing-limited observations can recover up to 70% of the intrinsic gradient for the largest, face-on disks, but only 30% for the smaller, more inclined galaxies. We do not find significant trends between observed or corrected gradients and any stellar population, dynamical or structural galaxy parameters, mostly in agreement with existing studies with much smaller sample sizes. In cosmological simulations, strong feedback is generally required to produce flat gradients at high redshift., Comment: submitted to ApJ

We analyse the sizes, colour gradients, and resolved stellar mass distributions for 36 massive and passive galaxies in the cluster XMMUJ2235-2557 at z=1.39 using optical and near-infrared Hubble Space Telescope imaging. We derive light-weighted S\'ersic fits in five HST bands ($i_{775},z_{850},Y_{105},J_{125},H_{160}$), and find that the size decreases by ~20% going from $i_{775}$ to $H_{160}$ band, consistent with recent studies. We then generate spatially resolved stellar mass maps using an empirical relationship between $M_{*}/L_{H_{160}}$ and $(z_{850}-H_{160})$ and use these to derive mass-weighted S\'ersic fits: the mass-weighted sizes are ~41% smaller than their rest-frame $r$-band counterparts compared with an average of ~12% at z~0. We attribute this evolution to the evolution in the $M_{*}/L_{H_{160}}$ and colour gradient. Indeed, as expected, the ratio of mass-weighted to light-weighted size is correlated with the $M_{*}/L$ gradient, but is also mildly correlated with the mass surface density and mass-weighted size. The colour gradients $(\nabla_{z-H})$ are mostly negative, with a median value of $\sim0.45$ mag dex$^{-1}$, twice the local value. The evolution is caused by an evolution in age gradients along the semi-major axis ($a$), with $\nabla_{age} = d \log(age) / d \log(a)$ $\sim-0.33$, while the survival of weaker colour gradients in old, local galaxies implies that metallicity gradients are also required, with $\nabla_{Z} = d \log(Z) / d \log(a)$ $\sim-0.2$. This is consistent with recent observational evidence for the inside-out growth of passive galaxies at high redshift, and favours a gradual mass growth mechanism, such as minor mergers., Comment: 30 pages, 25 figures, 4 tables, accepted for publication in MNRAS

We present a pilot study of the z=2.923 radio galaxy MRC0943-242, where we for the first time combine information from ALMA and MUSE data cubes. Even with modest integration times, we disentangle an AGN and a starburst dominated set of components. These data reveal a highly complex morphology, as the AGN, starburst, and molecular gas components show up as widely separated sources in dust continuum, optical continuum and CO line emission observations. CO(1-0) and CO(8-7) line emission suggest that there is a molecular gas reservoir offset from both the dust and the optical continuum that is located ~90kpc from the AGN. The UV line emission has a complex structure in emission and absorption. The line emission is mostly due to i) a large scale ionisation cone energised by the AGN, ii) a Ly-alpha emitting bridge of gas between the radio galaxy and a heavily star-forming set of components. Strangely, the ionisation cone has no Ly-alpha emission. We find this is due to an optically thick layer of neutral gas with unity covering fraction spread out over a region of at least ~100kpc from the AGN. Other, less thick absorption components are associated with Ly-alpha emitting gas within a few tens of kpc from the radio galaxy and are connected by a bridge of emission. We speculate that this linear structure of dust, Ly-alpha and CO emission, and the redshifted absorption seen in the circum-nuclear region may represent an accretion flow feeding gas into this massive AGN host galaxy., Comment: 15 pages, 8 figures, accepted for publication in A&A

In this paper we perform a comprehensive study of the main sources of random and systematic errors in stellar mass measurement for galaxies using their Spectral Energy Distributions (SEDs). We use mock galaxy catalogs with simulated multi-waveband photometry (from U-band to mid-infrared) and known redshift, stellar mass, age and extinction for individual galaxies. Given different parameters affecting stellar mass measurement (photometric S/N ratios, SED fitting errors, systematic effects, the inherent degeneracies and correlated errors), we formulated different simulated galaxy catalogs to quantify these effects individually. We studied the sensitivity of stellar mass estimates to the codes/methods used, population synthesis models, star formation histories, nebular emission line contributions, photometric uncertainties, extinction and age. For each simulated galaxy, the difference between the input stellar masses and those estimated using different simulation catalogs, $\Delta\log(M)$, was calculated and used to identify the most fundamental parameters affecting stellar masses. We measured different components of the error budget, with the results listed as follows: (1). no significant bias was found among different codes/methods, with all having comparable scatter; (2). A source of error is found to be due to photometric uncertainties and low resolution in age and extinction grids; (3). The median of stellar masses among different methods provides a stable measure of the mass associated with any given galaxy; (4). The deviations in stellar mass strongly correlate with those in age, with a weaker correlation with extinction; (5). the scatter in the stellar masses due to free parameters are quantified, with the sensitivity of the stellar mass to both the population synthesis codes and inclusion of nebular emission lines studied., Comment: 33 pages, 20 Figures, Accepted for publication in Astrophysical Journal

We investigate the stellar populations of 25 massive, galaxies ($\log[M_\ast/M_\odot] \geq 10.9$) at $1.5 < z < 2$ using data obtained with the K-band Multi-Object Spectrograph (KMOS) on the ESO VLT. Targets were selected to be quiescent based on their broadband colors and redshifts using data from the 3D-HST grism survey. The mean redshift of our sample is $\bar{z} = 1.75$, where KMOS YJ-band data probe age- and metallicity-sensitive absorption features in the rest-frame optical, including the $G$ band, Fe I, and high-order Balmer lines. Fitting simple stellar population models to a stack of our KMOS spectra, we derive a mean age of $1.03^{+0.13}_{-0.08}$ Gyr. We confirm previous results suggesting a correlation between color and age for quiescent galaxies, finding mean ages of $1.22^{+0.56}_{-0.19}$ Gyr and $0.85^{+0.08}_{-0.05}$ Gyr for the reddest and bluest galaxies in our sample. Combining our KMOS measurements with those obtained from previous studies at $0.2 < z < 2$ we find evidence for a $2-3$ Gyr spread in the formation epoch of massive galaxies. At $z < 1$ the measured stellar ages are consistent with passive evolution, while at $1 < z \lesssim2$ they appear to saturate at $\sim$1 Gyr, which likely reflects changing demographics of the (mean) progenitor population. By comparing to star-formation histories inferred for "normal" star-forming galaxies, we show that the timescales required to form massive galaxies at $z \gtrsim 1.5$ are consistent with the enhanced $\alpha$-element abundances found in massive local early-type galaxies., Comment: 6 pages, 5 figures, accepted for publication in ApJL

We present photometric redshifts and associated probability distributions for all detected sources in the Extended Chandra Deep Field South (ECDFS). The work makes use of the most up-to-date data from the Cosmic Assembly Near-IR Deep Legacy Survey (CANDELS) and the Taiwan ECDFS Near-Infrared Survey (TENIS) in addition to other data. We also revisit multi-wavelength counterparts for published X-ray sources from the 4Ms-CDFS and 250ks-ECDFS surveys, finding reliable counterparts for 1207 out of 1259 sources ($\sim 96\%$). Data used for photometric redshifts include intermediate-band photometry deblended using the TFIT method, which is used for the first time in this work. Photometric redshifts for X-ray source counterparts are based on a new library of AGN/galaxy hybrid templates appropriate for the faint X-ray population in the CDFS. Photometric redshift accuracy for normal galaxies is 0.010 and for X-ray sources is 0.014, and outlier fractions are $4\%$ and $5.4\%$ respectively. The results within the CANDELS coverage area are even better as demonstrated both by spectroscopic comparison and by galaxy-pair statistics. Intermediate-band photometry, even if shallow, is valuable when combined with deep broad-band photometry. For best accuracy, templates must include emission lines., Comment: The paper has been accepted by ApJ. The materials we provide are available under [Surveys] > [CDFS] through the portal http://www.mpe.mpg.de/XraySurveys

The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features in dynamically mature disks should be extremely rare. Here we report the discovery of strong barred structures in massive disk galaxies at z ~ 1.5 in deep rest-frame optical images from CANDELS. From within a sample of 876 disk galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a sub-sample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5< z < 2 (f_bar = 10.7 +6.3 -3.5% after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disk galaxies have evolved over the last 11 billion years., Comment: 11 pages, 6 figures; accepted for publication in MNRAS

We present the discovery of two galaxy overdensities in the Hubble Space Telescope UDF: a proto-cluster, HUDFJ0332.4-2746.6 at $z = 1.84 \pm 0.01$, and a group, HUDFJ0332.5-2747.3 at $z =1.90 \pm 0.01$. Assuming viralization, the velocity dispersion of HUDFJ0332.4-2746.6 implies a mass of $M_{200}= (2.2 \pm 1.8) \times 10^{14} M_{\odot}$, consistent with the lack of extended X-ray emission. Neither overdensity shows evidence of a red sequence. About $50\%$ of their members show interactions and/or disturbed morphologies, which are signatures of merger remnants or disk instability. Most of their ETGs have blue colors and show recent star-formation. These observations reveal for the first time large fractions of spectroscopically confirmed star-forming blue ETGs in proto-clusters at $z\approx 2$. These star-forming ETGs are most likely among the progenitors of the quiescent population in clusters at more recent epochs. Their mass-size relation is consistent with that of passive ETGs in clusters at $z\sim0.7-1.5$. If these galaxies are the progenitors of cluster ETGs at these lower redshifts, their size would evolve according to a similar mass-size relation. It is noteworthy that quiescent ETGs in clusters at $z=1.8-2$ also do not show any significant size evolution over this redshift range, contrary to field ETGs. The ETG fraction is $\lesssim 50\%$, compared to the typical quiescent ETG fraction of $\approx 80\%$ in cluster cores at $z< 1$. The fraction, masses, and colors of the newly discovered ETGs imply that other cluster ETGs will be formed/accreted at a later time., Comment: 33 pages, 13 figures. ApJ, in press

We present 4.5 {\mu}m luminosity functions for galaxies identified in 178 candidate galaxy clusters at 1.3 < z < 3.2. The clusters were identified as Spitzer/IRAC color-selected overdensities in the Clusters Around Radio-Loud AGN (CARLA) project, which imaged 421 powerful radio-loud AGN at z > 1.3. The luminosity functions are derived for different redshift and richness bins, and the IRAC imaging reaches depths of m*+2, allowing us to measure the faint end slopes of the luminosity functions. We find that {\alpha} = -1 describes the luminosity function very well in all redshifts bins and does not evolve significantly. This provides evidence that the rate at which the low mass galaxy population grows through star formation, gets quenched and is replenished by in-falling field galaxies does not have a major net effect on the shape of the luminosity function. Our measurements for m* are consistent with passive evolution models and high formation redshifts z_f ~ 3. We find a slight trend towards fainter m* for the richest clusters, implying that the most massive clusters in our sample could contain older stellar populations, yet another example of cosmic downsizing. Modelling shows that a contribution of a star-forming population of up to 40% cannot be ruled out. This value, found from our targeted survey, is significantly lower than the values found for slightly lower redshift, z ~ 1, clusters found in wide-field surveys. The results are consistent with cosmic downsizing, as the clusters studied here were all found in the vicinity of radio-loud AGNs -- which have proven to be preferentially located in massive dark matter halos in the richest environments at high redshift -- they may therefore be older and more evolved systems than the general protocluster population., Comment: 17 pages, accepted for publication in ApJ

We present the spectroscopic confirmation of a structure of galaxies surrounding the radio galaxy MRC0156-252 at z = 2.02. The structure was initially discovered as an overdensity of both near-infrared selected z > 1.6 and mid-infrared selected z > 1.2 galaxy candidates. We used the VLT/FORS2 multi-object spectrograph to target ~80 high-redshift galaxy candidates, and obtain robust spectroscopic redshifts for more than half the targets. The majority of the confirmed sources are star-forming galaxies at z > 1.5. In addition to the radio galaxy, two of its close-by companions (< 6'') also show AGN signatures. Ten sources, including the radio galaxy, lie within |z - 2.020 | < 0.015 (i.e., velocity offsets < 1500 km/s) and within projected 2 Mpc comoving of the radio galaxy. Additional evidence suggests not only that the galaxy structure associated with MRC0156-252 is a forming galaxy cluster but also that this structure is most probably embedded in a larger scale structure., Comment: 11 pages, 9 figures, 2 tables, accepted for publication in A&A

We present results from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) photometric redshift methods investigation. In this investigation, the results from eleven participants, each using a different combination of photometric redshift code, template spectral energy distributions (SEDs) and priors, are used to examine the properties of photometric redshifts applied to deep fields with broad-band multi-wavelength coverage. The photometry used includes U-band through mid-infrared filters and was derived using the TFIT method. Comparing the results, we find that there is no particular code or set of template SEDs that results in significantly better photometric redshifts compared to others. However, we find codes producing the lowest scatter and outlier fraction utilize a training sample to optimize photometric redshifts by adding zero-point offsets, template adjusting or adding extra smoothing errors. These results therefore stress the importance of the training procedure. We find a strong dependence of the photometric redshift accuracy on the signal-to-noise ratio of the photometry. On the other hand, we find a weak dependence of the photometric redshift scatter with redshift and galaxy color. We find that most photometric redshift codes quote redshift errors (e.g., 68% confidence intervals) that are too small compared to that expected from the spectroscopic control sample. We find that all codes show a statistically significant bias in the photometric redshifts. However, the bias is in all cases smaller than the scatter, the latter therefore dominates the errors. Finally, we find that combining results from multiple codes significantly decreases the photometric redshift scatter and outlier fraction. We discuss different ways of combining data to produce accurate photometric redshifts and error estimates., Comment: 26 pages, 15 figures, ApJ in press

We present a UV-to-mid infrared multi-wavelength catalog in the CANDELS/GOODS-S field, combining the newly obtained CANDELS HST/WFC3 F105W, F125W, and F160W data with existing public data. The catalog is based on source detection in the WFC3 F160W band. The F160W mosaic includes the data from CANDELS deep and wide observations as well as previous ERS and HUDF09 programs. The mosaic reaches a 5$\sigma$ limiting depth (within an aperture of radius 0.17 arcsec) of 27.4, 28.2, and 29.7 AB for CANDELS wide, deep, and HUDF regions, respectively. The catalog contains 34930 sources with the representative 50% completeness reaching 25.9, 26.6, and 28.1 AB in the F160W band for the three regions. In addition to WFC3 bands, the catalog also includes data from UV (U-band from both CTIO/MOSAIC and VLT/VIMOS), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), and infrared (HST/WFC3 F098M, VLT/ISAAC Ks, VLT/HAWK-I Ks, and Spitzer/IRAC 3.6, 4.5, 5.8, 8.0 $\mu$m) observations. The catalog is validated via stellar colors, comparison with other published catalogs, zeropoint offsets determined from the best-fit templates of the spectral energy distribution of spectroscopically observed objects, and the accuracy of photometric redshifts. The catalog is able to detect unreddened star-forming (passive) galaxies with stellar mass of 10^{10}M_\odot at a 50% completeness level to z$\sim$3.4 (2.8), 4.6 (3.2), and 7.0 (4.2) in the three regions. As an example of application, the catalog is used to select both star-forming and passive galaxies at z$\sim$2--4 via the Balmer break. It is also used to study the color--magnitude diagram of galaxies at 0

Projected axis ratio measurements of 880 early-type galaxies at redshifts 11 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a~0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z>1 early-type galaxies. We find that the proportion of oblate versus triaxial galaxies depends both on the galaxies' stellar mass, and - at a given mass - on redshift. For present-day and z<1 early-type galaxies the oblate fraction strongly depends on galaxy mass. At z>1 this trend is much weaker over the mass range explored here (10^101, compared to 0.20+-0.02 at z~0.1. In contrast, the oblate fraction among low-mass early-type galaxies (log(M*/M_sun)<10.5) increased toward the present, from 0.38+-0.11 at z>1 to 0.72+-0.06 at z=0. [Abridged], Comment: accepted for publication in ApJ; 14 pages; 10 figures; 4 tables

We present the multiwavelength - ultraviolet to mid-infrared - catalog of the UKIDSS Ultra-Deep Survey (UDS) field observed as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). Based on publicly available data, the catalog includes: the CANDELS data from the Hubble Space Telescope (near-infrared WFC3 F125W and F160W data and visible ACS F606W and F814W data), u-band data from CFHT/Megacam, B, V, Rc, i' and z' band data from Subaru/Suprime-Cam, Y and Ks band data from VLT/HAWK-I, J, H and K bands data from UKIDSS (Data Release 8), and Spitzer/IRAC data (3.6, 4.5 from SEDS, 5.8 and 8.0um from SpUDS). The present catalog is F160W-selected and contains 35932 sources over an area of 201.7 square arcmin and includes radio and X-ray detected sources and spectroscopic redshifts available for 210 sources., Comment: 22 pages, 20 figures, ApJ in press. The CANDELS UDS catalog (in ascii & fits format) and associated ReadMe file are made available on the CANDELS website (http://candels.ucolick.org/) as well as on the MAST CANDELS page (http://archive.stsci.edu/prepds/candels/)

Galaxy clusters are key places to study the contribution of {\it nature} (i.e. mass, morphology) and {\it nurture} (i.e.environment) in the formation and evolution of galaxies. Recently, a number of clusters at z$>$1, i.e. corresponding to the first epochs of the cluster formation, has been discovered and confirmed spectroscopically. We present new observations obtained with the {\sc LUCIFER} spectrograph at Large Binocular Telescope (LBT) of a sample of star-forming galaxies associated with a large scale structure around the radio galaxy 7C1756+6520 at z=1.42. Combining our spectroscopic data and the literature photometric data, we derived some of the properties of these galaxies: star formation rate, metallicity and stellar mass. With the aim of analyzing the effect of the cluster environment on galaxy evolution, we have located the galaxies in the plane of the so-called Fundamental Metallically Relation (FMR), which is known not to evolve with redshift up to z$=2.5$ for field galaxies, but it is still unexplored in rich environments at low and high redshift. We found that the properties of the galaxies in the cluster 7C 1756+6520 are compatible with the FMR which suggests that the effect of the environment on galaxy metallicity at this early epoch of cluster formation is marginal. As a side study, we also report the spectroscopic analysis of a bright AGN, belonging to the cluster, which shows a significant outflow of gas., Comment: Accepted for publication by MNRAS, 10 pages, 6 figures, 3 tables

We present a statistical study of the environments of 63 high-redshift radio galaxies (HzRGs) between redshifts 1

Taking advantage of the impressive sensitivity of Spitzer to detect massive galaxies at high redshift, we study the mid-infrared environments of powerful, high-redshift radio galaxies at 1.2-0.1 (AB), in the fields of 48 radio galaxies at 1.21.2. Using a counts-in-cell analysis, we identify a field as overdense when 15 or more red IRAC sources are found within 1arcmin (i.e.,~0.5Mpc at 1.21.2., Comment: 14 pages, 7 figures, 3 tables, accepted for publication in ApJ

We use the spatially-resolved, multi-band photometry in the GOODS South field acquired by the CANDELS project to constrain the nature of candidate Lyman continuum (LyC) emitters at redshift z~3.7 identified using ultra-deep imaging below the Lyman limit (1-sigma limit of ~30 AB in a 2" diameter aperture). In 18 candidates, out of a sample of 19 with flux detected at >3-sigma level, the light centroid of the candidate LyC emission is offset from that of the LBG by up to 1.5". We fit the SED of the LyC candidates to spectral population synthesis models to measure photometric redshifts and the stellar population parameters. We also discuss the differences in the UV colors between the LBG and the LyC candidates, and how to estimate the escape fraction of ionizing radiation (f_esc) in cases, like in most of our galaxies, where the LyC emission is spatially offset from the host galaxy. In all but one case we conclude that the candidate LyC emission is most likely due to lower redshift interlopers. Based on these findings, we argue that the majority of similar measurements reported in the literature need further investigation before it can be firmly concluded that LyC emission is detected. Our only surviving LyC candidate is a LBG at z=3.795, which shows the bluest (B-V) color among LBGs at similar redshift, a stellar mass of M~2 x 10^9 Msun, weak interstellar absorption lines and a flat UV spectral slope with no Lya in emission. We estimate its f_esc to be in the range 25%-100%, depending on the dust and intergalactic attenuation., Comment: Submitted to The Astrophysical Journal, 20 pages, 8 figures, 1 table

We present results from a comprehensive imaging survey of 70 radio galaxies at redshifts 13, there is tentative evidence for a factor of two decrease in stellar mass. This suggests that radio galaxies have assembled the bulk of their stellar mass by z~3, but confirmation by more detailed decomposition of stellar and AGN emission is needed. The restframe 500 MHz radio luminosities are only marginally correlated with stellar mass but are strongly correlated with the restframe 5um hot dust luminosity. This suggests that the radio galaxies have a large range of Eddington ratios. We also present new Very Large Array 4.86 and 8.46 GHz imaging of 14 radio galaxies and find that radio core dominance --- an indicator of jet orientation --- is strongly correlated with hot dust luminosity. While all of our targets were selected as narrow-lined, type 2 AGNs, this result can be understood in the context of orientation-dependent models if there is a continuous distribution of orientations from obscured type 2 to unobscured type 1 AGNs rather than a clear dichotomy. Finally, four radio galaxies have nearby (<6") companions whose mid-IR colors are suggestive of their being AGNs. This may indicate an association between radio galaxy activity and major mergers., Comment: 31 pages, 125 figures. Accepted for publication in the Astrophysical Journal

We present a study of protoclusters associated with high redshift radio galaxies. We imaged MRC1017-220 (z=1.77) and MRC0156-252 (z=2.02) using the near-infrared wide-field (7.5'x7.5') imager VLT/HAWK-I in the Y, H and Ks bands. We present the first deep Y-band galaxy number counts within a large area (200 arcmin2). We then develop a purely near-infrared colour selection technique to isolate galaxies at 1.6

We present spectroscopic follow-up of an overdensity of galaxies photometrically selected to be at 1.4

We explore the environments of two radio galaxies at z~1.5, 7C1751+6809 and 7C1756+6520, using deep optical and near-infrared imaging. Our data cover 15'x15' fields around the radio galaxies. We develop and apply BzK color criteria to select cluster member candidates around the radio galaxies and find no evidence of an overdensity of red galaxies within 2Mpc of 7C1751+6809. In contrast, 7C1756+6520 shows a significant overdensity of red galaxies within 2Mpc of the radio galaxy, by a factor of 3.1 +/- 0.8 relative to the four MUSYC fields. At small separation (r<6''), this radio galaxy also has one z~1.4 evolved galaxy candidate, one z~1.4 star-forming galaxy candidate, and an AGN candidate (at indeterminate redshift). This is suggestive of several close-by companions. Several concentrations of red galaxies are also noticed in the full 7C1756+6520 field, forming a possible large-scale structure of evolved galaxies with a NW-SE orientation. We construct the color-magnitude diagram of red galaxies found near (r<2Mpc) 7C1756+6520, and find a clear red sequence that is truncated at Ks~21.5 (AB). We also find an overdensity of mid-IR selected AGN in the surroundings of 7C1756+6520. These results are suggestive of a proto-cluster at high redshift., Comment: 21 pages, 12 figures, 6 tables, accepted for publication in A&A

We present the surface density of luminous active galactic nuclei (AGN) associated with a uniformly selected galaxy cluster sample identified in the 8.5 square degree Bootes field of the NOAO Deep Wide-Field Survey. The clusters are distributed over a large range of redshift (0 < z < 1.5) and we identify AGN using three different selection criteria: mid-IR color, radio luminosity, and X-ray luminosity. Relative to the field, we note a clear overdensity of the number of AGN within 0.5 Mpc of the cluster centers at z > 0.5. The amplitude of this AGN overdensity increases with redshift. Although there are significant differences between the AGN populations probed by each selection technique, the rise in cluster AGN surface density generally increases more steeply than that of field quasars. In particular, X-ray selected AGN are at least three times more prevalent in clusters at 1 < z < 1.5 compared to clusters at 0.5 < z < 1. This effect is stronger than can be explained by the evolving median richness of our cluster sample. We thus confirm the existence of a Butcher-Oemler type effect for AGN in galaxy clusters, with the number of AGN in clusters increasing with redshift., Comment: 9 pages, 2 figures, accepted for publication in ApJ