The fundamental plane of cluster elliptical galaxies at z=1.25

Using deep Hubble Space Telescope Advanced Camera for Surveys imaging and Very Large Telescope FOcal Reducer/low dispersion Spectrograph 2 spectra, we determined the velocity dispersions, effective radii, and surface brightnesses for four early-type galaxies in the z = 1.237 cluster RDCS 1252.9 - 2927. All four galaxies are massive, greater than 10(11) M-.. These four galaxies, combined with three from RDCS 0848 + 4453 at z = 1.276, establish the fundamental plane of massive early-type cluster galaxies at (z) over bar = 1.25. The offset of the fundamental plane shows that the luminosity evolution in rest-frame B is Deltaln(M/L-B) = (-0.98 +/- 0.06)z for galaxies with M > 10(11.5) M-.. To reproduce the observed mass-to-light ratio (M/L) evolution, we determine the characteristic age of the stars in these M > 10(11.5) M-. galaxies to be 3.0(-0.3)(+0.3) Gyr; i.e., z* = 3.4(-0.4)(+0.5). Including selection effects caused by morphological bias (the "progenitor bias"), we estimate an age of 2.1(-0.2)(+0.2) Gyr, or z* = 2.3(-0.2)(+0.2) for the elliptical galaxy population. Massive cluster early-type galaxies appear to have a large fraction of stars that formed early in the history of the universe. However, there is a large scatter in the derived M/L values, which is confirmed by the spread in the galaxies' colors. Two lower mass galaxies in our sample have much lower values, implying significant star formation close to the epoch of observation. Thus, even in the centers of massive clusters, there appears to have been significant star formation in some massive, M similar or equal to 10(11) M-., galaxies at z similar or equal to 1.

Spectroscopy of z ∼ 6 i-dropout galaxies : frequency of Lyα emission and the sizes of Lyα-emitting galaxies

We report on deep spectroscopy, using LRIS on Keck I and FORS2 on the VLT, of a sample of 22 candidate z similar to 6 Lyman break galaxies (LBGs) selected by the (i)775 - z(850) > 1: 3 dropout criterion. Redshifts could be measured for eight objects. These redshifts are all in the range z = 5: 5-6.1, confirming the efficiency of the i775 - z850 color selection technique. Six of the confirmed galaxies show Ly alpha emission. Assuming that the 14 objects without redshifts are z similar to 6 LBGs that lack detectable Ly alpha emission lines, we infer that the fraction of Ly alpha-emitting LBGs with Ly alpha equivalent widths greater than 20 angstrom among z similar to 6 LBGs is approximate to 30%, similar to that found at z similar to 3. Every Ly alpha-emitting object in our sample is compact, with half-light radii r(hl) 97% confidence. We speculate that the small sizes of the Ly alpha-emitting LBGs are due to these objects being less massive than other LBGs at z similar to 6

Spectroscopic confirmation of a substantial population of luminous red galaxies at redshifts z ≳ 2

We confirm spectroscopically the existence of a population of galaxies at z greater than or similar to 2 with rest-frame optical colors similar to normal nearby galaxies. The galaxies were identified by their red near-infrared colors in deep images obtained with the Infrared Spectrometer and Array Camera on the Very Large Telescope of the field around the foreground cluster MS 1054-03. Redshifts of six galaxies with J(s)-K-s > 2.3 were measured from optical spectra obtained with the W. M. Keck telescope. Five out of six are in the range, demonstrating that the 2.43 = z = 3.52 J(s)-K-s color selection is quite efficient. The rest-frame ultraviolet spectra of confirmed z > 2 galaxies display a range of properties, with two galaxies showing emission lines characteristic of active galactic nuclei, two having Lyalpha in emission, and one showing interstellar absorption lines only. Their full spectral energy distributions are well described by constant star formation models with ages 1.4-2.6 Gyr, except for one galaxy whose colors indicate a dusty starburst. The confirmed z > 2 galaxies are very luminous: their K-s magnitudes are in the range 19.2-19.9, corresponding to rest-frame absolute V magnitudes from -24.8 to -23.2. Assuming that our bright spectroscopic sample is representative for the general population of J(s)-K-s selected objects, we find that the surface density of red z greater than or similar to 2 galaxies is approximate to0.9 arcmin(-2) to K-s = 21. The surface density is comparable to that of Lyman break-selected galaxies with K-s < 21, when corrections are made for the different redshift distributions of the two samples. Although there will be some overlap between the two populations, most "optical-break" galaxies are too faint in the rest-frame ultraviolet to be selected as Lyman break galaxies. The most straightforward interpretation is that star formation in typical optical-break galaxies started earlier than in typical Lyman break galaxies. Optical-break galaxies may be the oldest and most massive galaxies yet identified at, and they z 1 2 could evolve into early-type galaxies and bulges

The Hα Luminosity Function of Galaxies at z ∼ 4.5

We present the Hα luminosity function (LF) derived from a large sample of Lyman break galaxies at z ∼ 4.5 over the GOODS-South and North fields. This study makes use of the new, full-depth Spitzer/IRAC [3.6] and [4.5] imaging from the GOODS Re-ionization Era wide-Area Treasury from the Spitzer program. The Hα flux is derived from the offset between the continuum flux estimated from the best-fit spectral energy distribution, and the observed photometry in IRAC [3.6]. From these measurements, we build the Hα LF and study its evolution providing the best constraints of this property at high redshift, where spectroscopy of Hα is not yet available. Schechter parameterizations of the Hα LF show a decreasing evolution of Φ∗ with redshift, increasing evolution in L ∗, and no significant evolution in the faint-end slope at high z. We find that star formation rates (SFRs) derived from Hα are higher than those derived from the rest-frame UV for low SFR galaxies but the opposite happens for the highest SFRs. This can be explained by lower mass galaxies (also lower SFR) having, on average, rising star formation histories (SFHs), while at the highest masses the SFHs may be declining. The SFR function is steeper, and because of the excess SFR(Hα) compared to SFR(UV) at low SFRs, the SFR density estimated from Hα is higher than the previous estimates based on UV luminosities

Newly Discovered Bright z similar to 9-10 Galaxies and Improved Constraints on Their Prevalence Using the Full CANDELS Area

We report the results of an expanded search for z ~ 9–10 candidates over the ~883 arcmin2 CANDELS+ERS fields. This study adds 147 arcmin2 to the search area we consider over the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) COSMOS, UDS, and EGS fields, while expanding our selection to include sources with bluer J 125 − H 160 colors than our previous J 125 − H 160 > 0.5 mag selection. In searching for new z ~ 9–10 candidates, we make full use of all available Hubble Space Telescope (HST), Spitzer/IRAC, and ground-based imaging data. As a result of our expanded search and use of broader color criteria, three new candidate z ~ 9–10 galaxies are identified. We also find again the z = 8.683 source previously confirmed by Zitrin et al. This brings our sample of probable z ~ 9–11 galaxy candidates over the CANDELS+ERS fields to 19 sources in total, equivalent to one candidate per 47 arcmin2 (one per 10 WFC3/IR fields). To be comprehensive, we also discuss 28 mostly lower likelihood z ~ 9–10 candidates, including some sources that seem to be reliably at z > 8 using the HST+IRAC data alone, but which the ground-based data show are much more likely at z 8, with a factor of ~10 evolution seen in the luminosity density from z ~ 10 to z ~ 8

The GREATS H β + [O III] luminosity function and galaxy properties at z ∼ 8: walking the way of JWST

The James Webb Space Telescope will allow to spectroscopically study an unprecedented number of galaxies deep into the reionization era, notably by detecting [O III]λλ4959, 5007, and H β nebular emission lines. To efficiently prepare such observations, we photometrically select a large sample of galaxies at z ∼ 8 and study their rest-frame optical emission lines. Combining data from the GOODS Re-ionization Era wide-Area Treasury from Spitzer (GREATS) survey and from HST we perform spectral energy distribution (SED) fitting, using synthetic SEDs from a large grid of photoionization models. The deep Spitzer/IRAC data combined with our models exploring a large parameter space enables to constrain the [O III] + H β fluxes and equivalent widths for our sample, as well as the average physical properties of z ∼ 8 galaxies, such as the ionizing photon production efficiency with log(ξion/erg−1Hz)≥25.77⁠. We find a relatively tight correlation between the [O III] + H β and UV luminosity, which we use to derive for the first time the [O III]λλ4959, 5007 + H β luminosity function (LF) at z ∼ 8. The z ∼ 8 [O III] + H β LF is higher at all luminosities compared to lower redshift, as opposed to the UV LF, due to an increase of the [O III] + H β luminosity at a given UV luminosity from z ∼ 3 to z ∼ 8. Finally, using the [O III] + H β LF, we make predictions for JWST/NIRSpec number counts of z ∼ 8 galaxies. We find that the current wide-area extragalactic legacy fields are too shallow to use JWST at maximal efficiency for z ∼ 8 spectroscopy even at 1 h depth and JWST pre-imaging to ≳30 mag will be required

UV-continuum slopes of &gt;4000 z ∼ 4-8 galaxies from the HUDF/XDF, HUDF09, ERS, CANDELS-south, and CANDELS-north fields

We measure the UV-continuum slope beta for over 4000 high-redshift galaxies over a wide range of redshifts z~4-8 and luminosities from the HST HUDF/XDF, HUDF09-1, HUDF09-2, ERS, CANDELS-N, and CANDELS-S data sets. Our new beta results reach very faint levels at z~4 (-15.5 mag: 0.006 L*(z=3)), z~5 (-16.5 mag: 0.014L*(z=3)), and z~6 and z~7 (-17 mag: 0.025 L*(z=3)). Inconsistencies between previous studies led us to conduct a comprehensive review of systematic errors and develop a new technique for measuring beta that is robust against biases that arise from the impact of noise. We demonstrate, by object-by-object comparisons, that all previous studies, including our own and those done on the latest HUDF12 dataset, suffer from small systematic errors in beta. We find that after correcting for the systematic errors (typically d(beta) ~0.1-0.2) all beta results at z~7 from different groups are in excellent agreement. The mean beta we measure for faint (-18 mag: 0.1L*(z=3)) z~4, z~5, z~6, and z~7 galaxies is -2.03+/-0.03+/-0.06 (random and systematic errors), -2.14+/-0.06+/-0.06, -2.24+/-0.11+/-0.08, and -2.30+/-0.18+/-0.13, respectively. Our new beta values are redder than we have reported in the past, but bluer than other recent results. Our previously reported trend of bluer beta's at lower luminosities is confirmed, as is the evolution to bluer beta's at high redshifts. beta appears to show only a mild luminosity dependence faintward of M(UV,AB) ~ -19 mag, suggesting that the mean beta asymptotes to ~ -2.2 to -2.4 for faint z>~4 galaxies. At z~7, the observed beta's suggest non-zero, but low dust extinction, and they agree well with values predicted in cosmological hydrodynamical simulations

Evolution in the Cluster Early-type Galaxy Size-Surface Brightness Relation at z =~ 1

We investigate the evolution in the distribution of surface brightness, as a function of size, for elliptical and S0 galaxies in the two clusters RDCS J1252.9-2927, z=1.237 and RX J0152.7-1357, z=0.837. We use multi-color imaging with the Advanced Camera for Surveys on the Hubble Space Telescope to determine these sizes and surface brightnesses. Using three different estimates of the surface brightnesses, we find that we reliably estimate the surface brightness for the galaxies in our sample with a scatter of < 0.2 mag and with systematic shifts of \lesssim 0.05 mag. We construct samples of galaxies with early-type morphologies in both clusters. For each cluster, we use a magnitude limit in a band which closely corresponds to the rest-frame B, to magnitude limit of M_B = -18.8 at z=0, and select only those galaxies within the color-magnitude sequence of the cluster or by using our spectroscopic redshifts. We measure evolution in the rest-frame B surface brightness, and find -1.41 \+/- 0.14 mag from the Coma cluster of galaxies for RDCS J1252.9-2927 and -0.90 \+/- 0.12 mag of evolution for RX J0152.7-1357, or an average evolution of (-1.13 \+/- 0.15) z mag. Our statistical errors are dominated by the observed scatter in the size-surface brightness relation, sigma = 0.42 \+/- 0.05 mag for RX J0152.7-1357 and sigma = 0.76 \+/- 0.10 mag for RDCS J1252.9-2927. We find no statistically significant evolution in this scatter, though an increase in the scatter could be expected. Overall, the pace of luminosity evolution we measure agrees with that of the Fundamental Plane of early-type galaxies, implying that the majority of massive early-type galaxies observed at z =~ 1 formed at high redshifts.Comment: Accepted in ApJ, 16 pages in emulateapj format with 15 eps figures, 6 in colo

Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8

The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this ‘epoch of reionization’ involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C II] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C II] luminosities than would be expected from local scaling relations1,2,3,4,5, and searches for the [C II] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C II] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C II] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C II] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation-dominated disks that have been observed in Hα-emitting galaxies two billion years later, at ‘cosmic noon’

Defending the genome from the enemy within:mechanisms of retrotransposon suppression in the mouse germline

The viability of any species requires that the genome is kept stable as it is transmitted from generation to generation by the germ cells. One of the challenges to transgenerational genome stability is the potential mutagenic activity of transposable genetic elements, particularly retrotransposons. There are many different types of retrotransposon in mammalian genomes, and these target different points in germline development to amplify and integrate into new genomic locations. Germ cells, and their pluripotent developmental precursors, have evolved a variety of genome defence mechanisms that suppress retrotransposon activity and maintain genome stability across the generations. Here, we review recent advances in understanding how retrotransposon activity is suppressed in the mammalian germline, how genes involved in germline genome defence mechanisms are regulated, and the consequences of mutating these genome defence genes for the developing germline