P. Rosati

The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging

This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from the Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multiband imaging data obtained with the Hubble Space Telescope and the Advanced Camera for Surveys (ACS). The survey covers roughly 320 arcmin2 in the ACS F435W, F606W, F814W, and F850LP bands, divided into two well-studied fields. Existing deep observations from the Chandra X-Ray Observatory and ground-based facilities are supplemented with new, deep imaging in the optical and near-infrared from the European Southern Observatory and from the Kitt Peak National Observatory. Deep observations with the Space Infrared Telescope Facility are scheduled. Reduced data from all facilities are being released worldwide within 3-6 months of acquisition. Together, this data set provides two deep reference fields for studies of distant normal and active galaxies, supernovae, and faint stars in our own Galaxy. This Letter serves to outline the survey strategy and describe the specific data that have been used in the accompanying letters, summarizing the reduction procedures and sensitivity limits.

The Hubble Space Telescope Cluster Supernova Survey. V. Improving the Dark-energy Constraints above z > 1 and Building an Early-type-hosted Supernova Sample

We present Advanced Camera for Surveys, NICMOS, and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on board HST. The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union.

The 4MOST instrument concept overview

The 4MOST[1] instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the ESO VISTA telescope designed to perform a massive (initially >25x106 spectra in 5 years) combined all-sky public survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of galaxies, X-ray AGN/galaxy evolution to z~5, Galactic X-ray sources and resolving the Galactic edge; Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of ~1600 targets at R~5,000 from 390-900nm and ~800 targets at R<18,000 in three channels between ~395-675nm (channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of ~ 4.1 degrees. The initial 5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: optomechanical, control, data management and operations concepts; and initial performance estimates.

The Chandra Deep Field-South: Optical Spectroscopy. I.

We present the results of our spectroscopic follow-up program of the X-ray sources detected in the 942 ks exposure of the Chandra Deep Field-South (CDFS). A total of 288 possible counterparts were observed at the VLT with the FORS1/FORS2 spectrographs for 251 of the 349 Chandra sources (including three additional faint X-ray sources). Spectra and R-band images are shown for all the observed sources and R - K colors are given for most of them. Spectroscopic redshifts were obtained for 168 X-ray sources, of which 137 have both reliable optical identification and redshift estimate (including 16 external identifications). The R 1044 ergs s-1] at z > 2 (13 sources with unambiguous spectroscopic identification); most X-ray type 1 QSOs are bright, R 24, whereas most X-ray type 2 QSOs have R 24, which may explain the difference with the CDFN results as few spectroscopic redshifts were obtained for R > 24 CDFN X-ray counterparts. There are X-ray type 1 QSOs down to z ~ 0.5, but a strong decrease at z 5) as X-ray counterparts, and their fraction strongly increases with decreasing optical flux, up to 25% for the R ? 24 sample. They cover the whole range of X-ray hardness ratios, comprise objects of various classes (in particular a high fraction of z 1 X-ray absorbed AGNs, but also elliptical and starburst galaxies) and more than half of them should be fairly bright X-ray sources [LX(0.5-10 keV) > 1042 ergs s-1]. Photometric redshifts will be necessary to derive the properties and evolution of the X-ray selected EROs.

GMASS ultradeep spectroscopy of galaxies at z ~ 2 - II. Superdense passive galaxies: How did they form and evolve?

Aims. The aim of this work is to investigate the physical, structur al and evolutionary properties of old, passive galaxies at z> 1.4 and to place new constraints on massive galaxy formation and evolution. Methods. We combine ultradeep optical spectroscopy from the GMASS project (Galaxy Mass Assembly ultradeep Spectroscopic Survey) with GOODS multi-band (optical to mid‐infrared) photometry and HST imaging to study a sample of spectroscopically identified passive galaxies at 1.39 2. No X-ray emission was found neither from individual galaxies nor from a stacking analysis of the sample. Only one galaxy shows a marginal detection at 24� m. These galaxies have morphologies that are predominantly compact and spheroidal. However, their sizes (Re. 1 kpc) are much smaller than those of spheroids in the present‐day Universe. Their stellar mass surface densities are consequently hig her by≈1 dex if compared to spheroids at z≈ 0 with the same mass. Their rest-frame B-band surface brightness scales with the effective radius, but the offset with respect to the surface brightness of the local Korme ndy relation is too large to be explained by simple passive evolution. At z≈ 1, a larger fraction of passive galaxies follows the z≈ 0 size ‐ mass relation. Superdense relics with Re≈ 1 kpc are extremely rare at z≈ 0 with respect to z> 1, and absent if Re 2. The results are compared with theoretical models and the main implications discussed in the framework of massive galaxy formation and evolution.

The Chandra Deep Field-South: The 1 Million Second Exposure*

We present the main results from our 940 ks observation of the Chandra Deep Field-South using the source catalog described in an accompanying paper by Giacconi et al. We extend the measurement of source number counts to 5.5 × 10-17 ergs cm-2 s-1 in the soft 0.5-2 keV band and 4.5 × 10-16 ergs cm-2 s-1 in the hard 2-10 keV band. The hard-band log N-log S shows a significant flattening (slope 0.6) below ≈10-14 ergs cm-2 s-1, leaving at most 10%-15% of the X-ray background to be resolved, the main uncertainty lying in the measurement of the total flux of the X-ray background (XRB). On the other hand, the analysis in the very hard 5-10 keV band reveals a relatively steep log N-log S (slope 1.3) down to 10-15 ergs cm-2 s-1. Together with the evidence of a progressive flattening of the average X-ray spectrum near the flux limit, this indicates that there is still a nonnegligible population of faint hard sources to be discovered at energies not well probed by Chandra, which possibly contributes to the 30 keV bump in the spectrum of the XRB. We use optical redshifts and identifications, obtained with the Very Large Telescope, for one-quarter of the sample to characterize the combined optical and X-ray properties of the Chandra Deep Field-South sample. Different source types are well separated in a parameter space that includes X-ray luminosity, hardness ratio, and R-K color. Type II objects, while redder on average than the field population, have colors that are consistent with being hosted by a range of galaxy types. Type II active galactic nuclei are mostly found at z 1, in contrast with predictions based on active galactic nucleus population synthesis models, thus suggesting a revision of their evolutionary parameters.

The Morphology-Density Relation in z ~ 1 Clusters

We measure the morphology-density relation (MDR) and morphology-radius relation (MRR) for galaxies in seven z ~ 1 clusters that have been observed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope. Simulations and independent comparisons of our visually derived morphologies indicate that ACS allows one to distinguish between E, S0, and spiral morphologies down to z850 = 24, corresponding to L/L* = 0.21 and 0.30 at z = 0.83 and 1.24, respectively. We adopt density and radius estimation methods that match those used at lower redshift in order to study the evolution of the MDR and MRR. We detect a change in the MDR between 0.8 < z < 1.2 and that observed at z ~ 0, consistent with recent work; specifically, the growth in the bulge-dominated galaxy fraction, fE+S0, with increasing density proceeds less rapidly at z ~ 1 than it does at z ~ 0. At z ~ 1 and Σ ≥ 500 galaxies Mpc-2, we find fE+S0 = 0.72 ± 0.10. At z ~ 0, an E+S0 population fraction of this magnitude occurs at densities about 5 times smaller. The evolution in the MDR is confined to densities Σ 40 galaxies Mpc-2 and appears to be primarily due to a deficit of S0 galaxies and an excess of Sp+Irr galaxies relative to the local galaxy population. The fE-density relation exhibits no significant evolution between z = 1 and 0. We find mild evidence to suggest that the MDR is dependent on the bolometric X-ray luminosity of the intracluster medium. Implications for the evolution of the disk galaxy population in dense regions are discussed in the context of these observations.

Measuring Ωm with the ROSAT Deep Cluster Survey

We analyze the ROSAT Deep Cluster Survey (RDCS) to derive cosmological constraints from the evolution of the cluster X-ray luminosity distribution. The sample contains 103 galaxy clusters out to z 0.85 and flux limit Flim = 3 × 10-14 ergs s-1 cm-2 (RDCS-3) in the [0.5-2.0] keV energy band, with a high-redshift extension containing four clusters at 0.90 ≤ z ≤ 1.26 and brighter than Flim = 1 × 10-14 ergs s-1 cm-2 (RDCS-1). We assume cosmological models to be specified by the matter density parameter Ωm, the rms fluctuation amplitude at the 8 h-1 Mpc scale σ8, and the shape parameter for the cold dark matter-like power spectrum Γ. Model predictions for the cluster mass function are converted into the X-ray luminosity function in two steps. First, we convert mass into intracluster gas temperature by assuming hydrostatic equilibrium. Then, temperature is converted into X-ray luminosity by using the most recent data on the LX-TX relation for nearby and distant clusters. These include the Chandra data for six distant clusters at 0.57 ≤ z ≤ 1.27. From RDCS-3 we find Ωm = 0.35 and σ8 = 0.66 for a spatially flat universe with a cosmological constant, with no significant constraint on Γ (errors correspond to 1 σ confidence levels for three fitting parameters). Even accounting for both theoretical and observational uncertainties in the mass-X-ray luminosity conversion, an Einstein-de Sitter model is always excluded at far more than the 3 σ level. We also show that the number of X-ray-bright clusters in RDCS-1 at z > 0.9 is expected from the evolution inferred at z < 0.9 data.

CLASH: three strongly lensed images of a candidate z ≈ 11 galaxy

We present a candidate for the most distant galaxy known to date with a photometric redshift of z = 10.7+0.6 –0.4 (95% confidence limits; with z < 9.5 galaxies of known types ruled out at 7.2σ). This J-dropout Lyman break galaxy, named MACS0647-JD, was discovered as part of the Cluster Lensing and Supernova survey with Hubble (CLASH). We observe three magnified images of this galaxy due to strong gravitational lensing by the galaxy cluster MACSJ0647.7+7015 at z = 0.591. The images are magnified by factors of ~80, 7, and 2, with the brighter two observed at ~26th magnitude AB (~0.15 μJy) in the WFC3/IR F160W filter (~1.4-1.7 μm) where they are detected at 12σ. All three images are also confidently detected at 6σ in F140W (~1.2-1.6 μm), dropping out of detection from 15 lower wavelength Hubble Space Telescope filters (~0.2-1.4 μm), and lacking bright detections in Spitzer/IRAC 3.6 μm and 4.5 μm imaging (~3.2-5.0 μm). We rule out a broad range of possible lower redshift interlopers, including some previously published as high-redshift candidates. Our high-redshift conclusion is more conservative than if we had neglected a Bayesian photometric redshift prior. Given CLASH observations of 17 high-mass clusters to date, our discoveries of MACS0647-JD at z ~ 10.8 and MACS1149-JD at z ~ 9.6 are consistent with a lensed luminosity function extrapolated from lower redshifts. This would suggest that low-luminosity galaxies could have reionized the universe. However, given the significant uncertainties based on only two galaxies, we cannot yet rule out the sharp drop-off in number counts at z 10 suggested by field searches.

A magnified young galaxy from about 500 million years after the Big Bang

Re-ionization of the intergalactic medium occurred in the early Universe at redshift z ≈ 6–11, following the formation of the first generation of stars. Those young galaxies (where the bulk of stars formed) at a cosmic age of less than about 500 million years (z ≲ 10) remain largely unexplored because they are at or beyond the sensitivity limits of existing large telescopes. Understanding the properties of these galaxies is critical to identifying the source of the radiation that re-ionized the intergalactic medium. Gravitational lensing by galaxy clusters allows the detection of high-redshift galaxies fainter than what otherwise could be found in the deepest images of the sky. Here we report multiband observations of the cluster MACS J1149+2223 that have revealed (with high probability) a gravitationally magnified galaxy from the early Universe, at a redshift of z = 9.6 ± 0.2 (that is, a cosmic age of 490 ± 15 million years, or 3.6 per cent of the age of the Universe). We estimate that it formed less than 200 million years after the Big Bang (at the 95 per cent confidence level), implying a formation redshift of ≲14. Given the small sky area that our observations cover, faint galaxies seem to be abundant at such a young cosmic age, suggesting that they may be the dominant source for the early re-ionization of the intergalactic medium.Johns Hopkins University, 3701 San Martin Drive, Baltimore , MD 21218, U.S.A. Space Telescope Science Institute Universität Heidelberg University of California, San Diego University of Science and Technology of China University College London Institute de Ciencies de l’Espai Instituto de Astrofı́sica de Andalucı́a Jet Propulsion Laboratory, California Institute of Techno logy Pontificia Universidad Católica de Chile National Optical Astronomical Observatory Universitas Sternwarte, München Leiden Observatory University of Basque Country