5 research outputs found
The VANDELS ESO public spectroscopic survey
VANDELS is a uniquely deep spectroscopic survey of high-redshift galaxies with the VIMOS spectrograph on ESOâs Very Large Telescope (VLT). The survey has obtained ultradeep optical (0.48 < λ < 1.0 ÎŒ m) spectroscopy of â2100 galaxies within the redshift interval 1.0 †z †7.0, over a total area of â0.2 deg2 centred on the CANDELS Ultra Deep Survey and Chandra Deep Field South fields. Based on accurate photometric redshift pre-selection, 85âperâcent of the galaxies targeted by VANDELS were selected to be at z â„ 3. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the fundamental aim of the survey is to provide the high-signal-to-noise ratio spectra necessary to measure key physical properties such as stellar population ages, masses, metallicities, and outflow velocities from detailed absorption-line studies. Using integration times calculated to produce an approximately constant signal-to-noise ratio (20 < tint< 80 h), the VANDELS survey targeted: (a) bright star-forming galaxies at 2.4 †z †5.5, (b) massive quiescent galaxies at 1.0 †z †2.5, (c) fainter star-forming galaxies at 3.0 †z †7.0, and (d) X-ray/Spitzer-selected active galactic nuclei and Herschel-detected galaxies. By targeting two extragalactic survey fields with superb multiwavelength imaging data, VANDELS will produce a unique legacy data set for exploring the physics underpinning high-redshift galaxy evolution. In this paper, we provide an overview of the VANDELS survey designed to support the science exploitation of the first ESO public data release, focusing on the scientific motivation, survey design, and target selection
VLA and ALMA Imaging of Intense Galaxy-wide Star Formation in z ~ 2 Galaxies
We present sime0farcs4 resolution extinction-independent distributions of star formation and dust in 11 star-forming galaxies (SFGs) at z = 1.3â3.0. These galaxies are selected from sensitive blank-field surveys of the 2' Ă 2' Hubble Ultra-Deep Field at λ = 5 cm and 1.3 mm using the Karl G. Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. They have star formation rates (SFRs), stellar masses, and dust properties representative of massive main-sequence SFGs at z ~ 2. Morphological classification performed on spatially resolved stellar mass maps indicates a mixture of disk and morphologically disturbed systems; half of the sample harbor X-ray active galactic nuclei (AGNs), thereby representing a diversity of z ~ 2 SFGs undergoing vigorous mass assembly. We find that their intense star formation most frequently occurs at the location of stellar-mass concentration and extends over an area comparable to their stellar-mass distribution, with a median diameter of 4.2 ± 1.8 kpc. This provides direct evidence of galaxy-wide star formation in distant blank-field-selected main-sequence SFGs. The typical galactic-average SFR surface density is 2.5 M â yrâ1 kpcâ2, sufficiently high to drive outflows. In X-ray-selected AGN where radio emission is enhanced over the level associated with star formation, the radio excess pinpoints the AGNs, which are found to be cospatial with star formation. The median extinction-independent size of main-sequence SFGs is two times larger than those of bright submillimeter galaxies, whose SFRs are 3â8 times larger, providing a constraint on the characteristic SFR (~300 M â yrâ1) above which a significant population of more compact SFGs appears to emerge
A deep ALMA image of the Hubble Ultra Deep Field
We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full â4.5 arcmin2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera 3/IR on HST. Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching Ï1.3 â 35 ÎŒJy, at a resolution of â0.7 arcsec. From an initial list of â50 > 3.5Ï peaks, a rigorous analysis confirms 16 sources with S1.3 > 120 ÎŒJy. All of these have secure galaxy counterparts with robust redshifts (ăză = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses (M*) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z â„ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M* â„ 2 Ă 1010âMâ, and we detect only one galaxy at z > 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S1.3 â 10âÎŒJy. We find strong evidence for a steep star-forming âmain sequenceâ at z â 2, with SFR âM* and a mean specific SFR â 2.2 Gyrâ1. Moreover, we find that â85âperâcent of total star formation at z â 2 is enshrouded in dust, with â65âperâcent of all star formation at this epoch occurring in high-mass galaxies (M* > 2 Ă 1010âMâ), for which the average obscured:unobscured SF ratio is â200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z â 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z â 4