ABSTRACT We present Hubble WFC3/IR slitless grism spectra of a remarkably bright z 10 galaxy candidate, GN-z11, identified initially from CANDELS/GOODS-N imaging data. A significant spectroscopic ...continuum break is detected at . The new grism data, combined with the photometric data, rule out all plausible lower redshift solutions for this source. The only viable solution is that this continuum break is the Ly break redshifted to , just ∼400 Myr after the Big Bang. This observation extends the current spectroscopic frontier by 150 Myr to well before the Planck (instantaneous) cosmic reionization peak at z ∼ 8.8, demonstrating that galaxy build-up was well underway early in the reionization epoch at z > 10. GN-z11 is remarkably, and unexpectedly, luminous for a galaxy at such an early time: its UV luminosity is 3× larger than measured at z ∼ 6−8. The Spitzer IRAC detections up to 4.5 m of this galaxy are consistent with a stellar mass of ∼109 M . This spectroscopic redshift measurement suggests that James Webb Space Telescope (JWST) will be able to similarly and easily confirm such sources at z > 10 and characterize their physical properties through detailed spectroscopy. Furthermore, WFIRST, with its wide-field near-IR imaging, would find large numbers of similar galaxies and contribute greatly to JWST's spectroscopy, if it is launched early enough to overlap with JWST.
ABSTRACT The Large Early Galaxy Census (LEGA-C) is a Public Spectroscopic Survey of ∼3200 K-band selected galaxies at redshifts z = 0.6 − 1.0 with stellar masses M * > 10 10 M , conducted with VIMOS ...on ESO's Very Large Telescope. The survey is embedded in the COSMOS field (R.A. = 10h00; decl . = + 2 deg ). The 20 hr long integrations produce high-signal-to-noise ratio continuum spectra that reveal ages, metallicities and velocity dispersions of the stellar populations. LEGA-C's unique combination of sample size and depth will enable us for the first time to map the stellar content at large lookback time, across galaxies of different types and star formation activity. Observations started in 2014 December and are planned to be completed by mid 2018, with early data releases of the spectra and value-added products. In this paper we present the science case, the observing strategy, an overview of the data reduction process and data products, and a first look at the relationship between galaxy structure and spectral properties, as it existed 7 Gyr ago.
ABSTRACT We identify four unusually bright (H < 25.5) galaxies from Hubble Space Telescope (HST) and Spitzer CANDELS data with probable redshifts z ∼ 7-9. These identifications include the ...brightest-known galaxies to date at z 7.5. As Y-band observations are not available over the full CANDELS program to perform a standard Lyman-break selection of z > 7 galaxies, we employ an alternate strategy using deep Spitzer/IRAC data. We identify z ∼ 7.1-9.1 galaxies by selecting z 6 galaxies from the HST CANDELS data that show quite red IRAC 3.6−4.5 colors, indicating strong O iii+Hβ lines in the 4.5 m band. This selection strategy was validated using a modest sample for which we have deep Y-band coverage, and subsequently used to select the brightest z ≥ 7 sources. Applying the IRAC criteria to all HST-selected optical dropout galaxies over the full ∼900 arcmin2 of the CANDELS survey revealed four unusually bright z ∼ 7.1, 7.6, 7.9, and 8.6 candidates. The median 3.6−4.5 color of our selected z ∼ 7.1-9.1 sample is consistent with rest-frame O iii+Hβ EWs of ∼1500 in the 4.5 band. Keck/MOSFIRE spectroscopy has been independently reported for two of our selected sources, showing Ly at redshifts of 7.7302 0.0006 and , respectively. We present similar Keck/MOSFIRE spectroscopy for a third selected galaxy with a probable 4.7 Ly line at zspec = 7.4770 0.0008. All three have H160-band magnitudes of ∼25 mag and are ∼0.5 mag more luminous (M1600 ∼ −22.0) than any previously discovered z ∼ 8 galaxy, with important implications for the UV luminosity function (LF). Our three brightest and highest redshift z > 7 galaxies all lie within the CANDELS-EGS field, providing a dramatic illustration of the potential impact of field-to-field variance.
ABSTRACT
The deep, wide-area (∼800–900 arcmin
2
) near-infrared/WFC3/IR +
Spitzer
/IRAC observations over the CANDELS fields have been a remarkable resource for constraining the bright end of ...high-redshift UV luminosity functions. However, the lack of
Hubble Space Telescope
(
HST
) 1.05
μ
m observations over the CANDELS fields has made it difficult to identify
z
∼ 9–10 sources robustly, since such data are needed to confirm the presence of an abrupt Lyman break at 1.2
μ
m. Here, we report on the successful identification of many such
z
∼ 9–10 sources from a new
HST
program (z9-CANDELS) that targets the highest-probability
z
∼ 9–10 galaxy candidates with observations at 1.05
μ
m, to search for a robust Lyman-break at 1.2
μ
m. The potential
z
∼ 9–10 candidates were preselected from the full
HST
,
Spitzer
/IRAC S-CANDELS observations, and the deepest-available ground-based optical+near-infrared observations (CFHTLS-DEEP+HUGS+UltraVISTA+ZFOURGE). We identified 15 credible
z
∼ 9–10 galaxies over the CANDELS fields. Nine of these galaxies lie at
z
∼ 9 and five are new identifications. Our targeted follow-up strategy has proven to be very efficient in making use of scarce
HST
time to secure a reliable sample of
z
∼ 9–10 galaxies. Through extensive simulations, we replicate the selection process for our sample (both the preselection and follow-up) and use it to improve current estimates for the volume density of bright
z
∼ 9 and
z
∼ 10 galaxies. The volume densities we find are 5
and
lower, respectively, than those found at
z
∼ 8. When compared with the best-fit evolution (i.e.,
) in the UV luminosity densities from
z
∼ 8 to
z
∼ 4 integrated to
(−20 mag), these luminosity densities are
and
lower, respectively, than the extrapolated trends. Our new results are broadly consistent with the “accelerated evolution” scenario at
z
> 8, consistent with that seen in many models.
Abstract
We present six galaxies at
that show evidence of Lyman continuum (LyC) emission based on the newly acquired UV imaging of the Hubble Deep UV legacy survey (HDUV) conducted with the WFC3/UVIS ...camera on the
Hubble Space Telescope
(
HST
). At the redshift of these sources, the HDUV F275W images partially probe the ionizing continuum. By exploiting the
HST
multiwavelength data available in the HDUV/GOODS fields, models of the UV spectral energy distributions, and detailed Monte Carlo simulations of the intergalactic medium absorption, we estimate the absolute ionizing photon escape fractions of these galaxies to be very high—typically
(
for all sources at 90% likelihood). Our findings are in broad agreement with previous studies that found only a small fraction of galaxies with high escape fraction. These six galaxies compose the largest sample yet of LyC leaking candidates at
whose inferred LyC flux has been observed at
HST
resolution. While three of our six candidates show evidence of hosting an active galactic nucleus, two of these are heavily obscured and their LyC emission appears to originate from star-forming regions rather than the central nucleus. Extensive multiwavelength data in the GOODS fields, especially the near-IR grism spectra from the 3D-
HST
survey, enable us to study the candidates in detail and tentatively test some recently proposed indirect methods to probe LyC leakage. High-resolution spectroscopic follow-up of our candidates will help constrain such indirect methods, which are our only hope of studying
f
esc
at
in the
JWST
era.
The IRAC ultradeep field and IRAC Legacy over GOODS programs are two ultradeep imaging surveys at 3.6 and 4.5 mum with the Spitzer Infrared Array Camera (IRAC). The primary aim is to directly detect ...the infrared light of reionization epoch galaxies at z > 7 and to constrain their stellar populations. The observations cover the Hubble Ultra Deep Field (HUDF), including the two HUDF parallel fields, and the CANDELS/GOODS-South, and are combined with archival data from all previous deep programs into one ultradeep data set. The resulting imaging reaches unprecedented coverage in IRAC 3.6 and 4.5 mum ranging from >50 hr over 150 arcmin super(2), >100 hr over 60 sq arcmin super(2), to ~200 hr over 5-10 arcmin super(2). This paper presents the survey description, data reduction, and public release of reduced mosaics on the same astrometric system as the CANDELS/GOODS-South Wide Field Camera 3 (WFC3) data. To facilitate prior-based WFC3+IRAC photometry, we introduce a new method to create high signal-to-noise PSFs from the IRAC data and reconstruct the complex spatial variation due to survey geometry. The PSF maps are included in the release, as are registered maps of subsets of the data to enable reliability and variability studies. Simulations show that the noise in the ultradeep IRAC images decreases approximately as the square root of integration time over the range 20-200 hr, well below the classical confusion limit, reaching 1sigma point-source sensitivities as faint as 15 nJy (28.5 AB) at 3.6 mum and 18 nJy (28.3 AB) at 4.5 mum. The value of such ultradeep IRAC data is illustrated by direct detections of z = 7-8 galaxies as faint as H sub(AB) = 28.
ABSTRACT We present a spectroscopic redshift measurement of a very bright Lyman break galaxy at using the Keck/Multi-Object Spectrometer for Infra-Red Exploration. The source was pre-selected ...photometrically in the EGS field as a robust z ∼ 8 candidate with H = 25.0 mag based on optical non-detections and a very red Spitzer/IRAC 3.6-4.5 broad-band color driven by high equivalent width O iii+Hβ line emission. The Ly line is reliably detected at and shows an asymmetric profile as expected for a galaxy embedded in a relatively neutral intergalactic medium near the Planck peak of cosmic reionization. The line has a rest-frame equivalent width of and is extended with km s−1. The source is perhaps the brightest and most massive z ∼ 8 Lyman break galaxy in the full CANDELS and BoRG/HIPPIES surveys, having already assembled of stars at only 650 Myr after the Big Bang. The spectroscopic redshift measurement sets a new redshift record for galaxies. This enables reliable constraints on the stellar mass, star formation rate, and formation epoch, as well as combined O iii+Hβ line equivalent widths. The redshift confirms that the IRAC 4.5 photometry is very likely dominated by line emission with EW0(O iii+Hβ) . This detection thus adds to the evidence that extreme rest-frame optical emission lines are a ubiquitous feature of early galaxies promising very efficient spectroscopic follow-up in the future with infrared spectroscopy using the James Webb Space Telescope and, later, ELTs.
We search the complete Hubble Frontier Field data set of Abell 2744 and its parallel field for z ~ 10 sources to further refine the evolution of the cosmic star formation rate density (SFRD) between ...z ~ 8 and z ~ 10. We independently confirm two images of the recently discovered triply imaged z ~ 9.8 source by Zitrin et al. and set an upper limit for similar z ~ 10 galaxies with red colors of J sub(125) - H sub(160) > 1.2 in the parallel field of Abell 2744. We utilize extensive simulations to derive the effective selection volume of Lyman-break galaxies at z ~ 10, both in the lensed cluster field and in the adjacent parallel field. We show that both source blending and shear reduce the completeness at a given observed magnitude in the cluster, particularly near the critical curves.
The remarkable Hubble Space Telescope (HST) data sets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map the evolution of the rest-frame UV luminosity function ...(LF) from z ~ 10 to z ~ 4. We develop new color criteria that more optimally utilize the full wavelength coverage from the optical, near-IR, and mid-IR observations over our search fields, while simultaneously minimizing the incompleteness and eliminating redshift gaps. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at z ~ 4, z ~ 5, z ~ 6, z ~ 7, z ~ 7, and z ~ 10, respectively, from the ~1000 arcmin super(2) area covered by these data sets. This sample of >10,000 galaxy candidates at z > or =, slanted 4 is by far the largest assembled to date with HST. The selection of z ~ 4-8 candidates over the five CANDELS fields allows us to assess the cosmic variance; the largest variations are at z > or =, slanted 7. Our new LF determinations at z ~ 4 and z ~ 5 span a 6 mag baseline and reach to -16 AB mag. These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of >L* galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to 3.4sigma significance for a steeper faint-end slope of the UV LF at z > 4, with alpha evolving from alpha = -1.64 + or - 0.04 at z ~ 4 to alpha = -2.06 + or - 0.13 at z ~ 7 (and alpha = -2.02 + or - 0.23 at z ~ 8), consistent with that expected from the evolution of the halo mass function. We find less evolution in the characteristic magnitude M* from z ~ 7 to z ~ 4; the observed evolution in the LF is now largely represented by changes in phi*. No evidence for a non-Schechter-like form to the z ~ 4-8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio (is proportional to(1 + z) super(-1.5)) of halos provides a good representation of the observed evolution.
Abstract
We compare the sizes and luminosities of faint
z
= 6–8 galaxies magnified by the Hubble Frontier Fields clusters with star-forming regions, as well as more evolved objects, in the nearby ...universe. Our high-redshift comparison sample includes 330
z
= 6–8 galaxies, for which size measurements were made as part of a companion study where lensing magnifications were estimated from various public models. Accurate size measurements for these sources are complicated by the lens model uncertainties, but other results and arguments suggest that faint galaxies are small, as discussed in a companion study. The measured sizes for sources in our comparison sample range from <50 pc to ∼500 pc. For many of the lowest-luminosity sources, extremely small sizes are inferred, reaching individual sizes as small as 10–30 pc, with several sources in the 10–15 pc range with our conservative magnification limits. The sizes and luminosities are similar to those of single star cluster complexes like 30 Doradus in the lower-redshift universe and—in a few cases—super star clusters. The identification of these compact, faint star-forming sources in the
z
∼ 6–8 universe also allows us to set upper limits on the proto-globular cluster luminosity function at
z
∼ 6. By comparisons of the counts and sizes with recent models, we rule out (with some caveats) proto-globular cluster formation scenarios favoring substantial (
ξ
= 10) post-formation mass loss and set useful upper limits on others. Our size results suggest we may be very close to discovering a bona fide population of forming globular clusters at high redshift.
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