(2016) 'Sizes, colour gradients and resolved stellar mass distributions for the massive cluster galaxies in XMMUJ2235-2557 at z = 1.39.', Monthly notices of the Royal Astronomical Society., 458 (3). pp. 3181-3209. Further information on publisher's website: Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTWe 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 nearinfrared Hubble Space Telescope imaging. We derive light-weighted Sérsic 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 Sérsic fits: the mass-weighted sizes are ∼ 41% smaller than their restframe 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 (∇ z−H ) are mostly negative, with a median value of ∼ 0.45 mag dex −1 , twice the local value. The evolution is caused by an evolution in age gradients along the semi-major axis (a), with ∇ age = d log(age)/d log(a) ∼ −0.33, while the survival of weaker colour gradients in old, local galaxies implies that metallicity gradients are also required, with ∇ Z = d log(Z)/d log(a) ∼ −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.

We present the analysis of the fundamental plane (FP) for a sample of 19 massive red-sequence galaxies (M > 4 × 10 10 M ) in 3 known overdensities at 1.39 < z < 1.61 from the KMOS Cluster Survey, a guaranteed time program with spectroscopy from the K-band Multi-Object Spectrograph (KMOS) at the VLT and imaging from the Hubble Space Telescope. As expected, we find that the FP zero-point in B band evolves with redshift, from the value 0.443 of Coma to −0.10 ± 0.09, −0.19 ± 0.05, −0.29 ± 0.12 for our clusters at z = 1.39, z = 1.46, and z = 1.61, respectively. For the most massive galaxies (log M /M > 11) in our sample, we translate the FP zero-point evolution into a mass-to-light-ratio M/L evolution finding ∆ log M/L B = (−0.46 ± 0.10)z, ∆ log M/L B = (−0.52 ± 0.07)z, to ∆ log M/L B = (−0.55 ± 0.10)z, respectively. We assess the potential contribution of the galaxies structural and stellar velocity dispersion evolution to the evolution of the FP zeropoint and find it to be ∼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 /M > 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.

We present the goals, design, and first results of the MUSE Ultra Deep Field (MUDF) survey, a large programme using the Multi Unit Spectroscopic Explorer (MUSE) instrument at the ESO Very Large Telescope. The MUDF survey is collecting ≈ 150 hours on-source of integral field optical spectroscopy in a 1.5 × 1.2 arcmin 2 region which hosts several astrophysical structures along the line of sight, including two bright z ≈ 3.2 quasars with close separation (≈ 500 kpc). Following the description of the data reduction procedures, we present the analysis of the galaxy environment and gaseous properties of seven groups detected at redshifts 0.5 < z < 1.5, spanning a large dynamic range in halo mass, log(M h /M ) ≈ 11 − 13.5. For four of the groups, we find associated Mg ii absorbers tracing cool gas in high-resolution spectroscopy of the two quasars, including one case of correlated absorption in both sightlines at distance ≈ 480 kpc. The absorption strength associated with the groups is higher than what has been reported for more isolated galaxies of comparable mass and impact parameters. We do not find evidence for widespread cool gas giving rise to strong absorption within these groups. Combining these results with the distribution of neutral and ionised gas seen in emission in lower-redshift groups, we conclude that gravitational interactions in the group environment strip gas from the galaxy haloes into the intragroup medium, boosting the cross section of cool gas and leading to the high fraction of strong Mg ii absorbers that we detect.

Understanding the relationship between the underlying escape fraction of Lyman continuum (LyC) photons (fesc) emitted by galaxies and measuring the distribution of observed fesc values at high redshift is fundamental to the interpretation of the reionization process. In this paper, we perform a statistical exploration of the attenuation of LyC photons by neutral hydrogen in the intergalactic medium using ensembles of simulated transmission functions. We show that LyC-detected galaxies are more likely to be found in sightlines with higher than average transmission of LyC photons. This means that adopting a mean transmission at a given redshift leads to an overestimate of the true fesc for LyC-detected galaxies. We note, however, that mean values are appropriate for fesc estimates of larger parent samples that include LyC non-detected galaxies. We quantify this IGM transmission bias for LyC detections in photometric and spectroscopic surveys in the literature and show that the bias is stronger for both shallower observations and for fainter parent samples (i.e. Ly α emitters versus Lyman break galaxies). We also explore the effects of varying the underlying probability distribution function (PDF) of fesc on recovered values, showing that the underlying fesc PDF may depend on sample selection by comparing with observational surveys. This work represents a first step in improved interpretation of LyC detections in the context of understanding fesc from high-redshift galaxies.

Identifying non-contaminated sample of high-redshift galaxies with escaping Lyman continuum (LyC) flux is important for understanding the sources and evolution of cosmic reionization. We present CLAUDS u-band photometry of the COSMOS field to probe LyC radiation from spectroscopically confirmed galaxies at z 3.5 and outside the standard Lyman-break galaxy colour selection expectations. Complementary to the CLAUDS data, we use Subaru multifilter photometry, Hubble Space Telescope (HST) multi-filter imaging, and the spectroscopic surveys D10K, VUDS and 3D-HST. We present a sample of Lyman continuum galaxy (LCG) candidates in the redshift range 3.5 z 5.1. Here, we introduce 5 LCG candidates, where two are flagged quality 1 and three quality 2. The estimated f abs esc for quality 1 candidates are in the range ∼ 5% − 73% and ∼ 30% − 93%. These estimates are based on our derived parameters from individual galaxies as inputs to a range of BPASS models as well as mean intergalactic medium (IGM) and maximal intergalactic and circumgalactic media (IGM+CGM) transmission. We conclude that our search for LCGs is most likely biased to lines of sight with low HI densities or free from Lyman limit systems. Our two best LCG candidates have EW (Lyα) 50Å and we find no correlation or anti-correlation between EW (Lyα), f abs esc , and R obs , the ratio of ionizing to non-ionizing observed flux in the measured passbands. Stacking candidates without solid LyC detections (S/N < 3) results in an estimated f abs esc from galaxies not greater than 1%.