193 research outputs found
The Dearth of z~10 Galaxies in all HST Legacy Fields -- The Rapid Evolution of the Galaxy Population in the First 500 Myr
We present an analysis of all prime HST legacy fields spanning >800 arcmin^2
for the search of z~10 galaxy candidates and the study of their UV luminosity
function (LF). In particular, we present new z~10 candidates selected from the
full Hubble Frontier Field (HFF) dataset. Despite the addition of these new
fields, we find a low abundance of z~10 candidates with only 9 reliable sources
identified in all prime HST datasets that include the HUDF09/12, the HUDF/XDF,
all the CANDELS fields, and now the HFF survey. Based on this comprehensive
search, we find that the UV luminosity function decreases by one order of
magnitude from z~8 to z~10 at all luminosities over a four magnitude range.
This also implies a decrease of the cosmic star-formation rate density by an
order of magnitude within 170 Myr from z~8 to z~10. We show that this
accelerated evolution compared to lower redshift can entirely be explained by
the fast build-up of the dark matter halo mass function at z>8. Consequently,
the predicted UV LFs from several models of galaxy formation are in good
agreement with this observed trend, even though the measured UV LF lies at the
low end of model predictions. In particular, the number of only 9 observed
candidate galaxies is lower, by ~50%, than predicted by galaxy evolution
models. The difference is generally still consistent within the Poisson and
cosmic variance uncertainties. However, essentially all models predict larger
numbers than observed. We discuss the implications of these results in light of
the upcoming James Webb Space Telescope mission, which is poised to find much
larger samples of z~10 galaxies as well as their progenitors at less than 400
Myr after the Big Bang.Comment: 13 pages, 6 figures, minor updates to match accepted versio
The GREATS H+[OIII] Luminosity Function and Galaxy Properties at : 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 [OIII] and H nebular emission lines. To efficiently prepare
such observations, we photometrically select a large sample of galaxies at
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 [OIII]+H fluxes and equivalent widths for our
sample, as well as the average physical properties of galaxies, such
as the ionizing photon production efficiency with
. We
find a relatively tight correlation between the [OIII]+H and UV
luminosity, which we use to derive for the first time the [OIII]+H
luminosity function (LF) at . The [OIII]+H LF is higher
at all luminosities compared to lower redshift, as opposed to the UV LF, due to
an increase of the [OIII]+H luminosity at a given UV luminosity from
to . Finally, using the [OIII]+H LF, we make
predictions for JWST/NIRSpec number counts of galaxies. We find that
the current wide-area extragalactic legacy fields are too shallow to use JWST
at maximal efficiency for spectroscopy even at 1hr depth and JWST
pre-imaging to mag will be required.Comment: 13 pages, 9 figures, accepted for publication in MNRA
Newly Discovered Bright z~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 arcmin^2 CANDELS+ERS fields. This study adds 147 arcmin^2 to the search
area we consider over the 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 HST, Spitzer/IRAC, and
ground-based imaging data. As a result of our expanded search and use of
broader color criteria, 3 new candidate z~9-10 galaxies are identified. We also
find again the z=8.683 source previously confirmed by Zitrin+2015. This brings
our sample of probable z~9-11 galaxy candidates over the CANDELS+ERS fields to
19 sources in total, equivalent to 1 candidate per 47 arcmin^2 (1 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<4. One case example is a bright z~9.4 candidate COS910-8
which seems instead to be at z~2. Based on this expanded sample, we obtain a
more robust LF at z~9 and improved constraints on the volume density of bright
z~9 and z~10 galaxies. Our improved z~9-10 results again reinforce previous
findings for strong evolution in the UV LF at z>8, with a factor of ~10
evolution seen in the luminosity density from z~10 to z~8.Comment: 22 pages, 12 figures, 6 tables, accepted for publication in the
Astrophysical Journa
Wavelength-scale stationary-wave integrated Fourier-transform spectrometry
Spectrometry is a general physical-analysis approach for investigating
light-matter interactions. However, the complex designs of existing
spectrometers render them resistant to simplification and miniaturization, both
of which are vital for applications in micro- and nanotechnology and which are
now undergoing intensive research. Stationary-wave integrated Fourier-transform
spectrometry (SWIFTS)-an approach based on direct intensity detection of a
standing wave resulting from either reflection (as in the principle of colour
photography by Gabriel Lippmann) or counterpropagative interference
phenomenon-is expected to be able to overcome this drawback. Here, we present a
SWIFTS-based spectrometer relying on an original optical near-field detection
method in which optical nanoprobes are used to sample directly the evanescent
standing wave in the waveguide. Combined with integrated optics, we report a
way of reducing the volume of the spectrometer to a few hundreds of cubic
wavelengths. This is the first attempt, using SWIFTS, to produce a very small
integrated one-dimensional spectrometer suitable for applications where
microspectrometers are essential
The Bright End of the z~9 and z~10 UV Luminosity Functions using all five CANDELS Fields
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 (LFs).
However, the lack of HST 1.05-micron 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 microns. We
report here 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 microns, to search for a robust
Lyman-break at 1.2 microns. The potential z~9-10 candidates are preselected
from the full HST, Spitzer/IRAC S-CANDELS observations, and the
deepest-available ground-based optical+near-infrared observations. We
identified 15 credible z~9-10 galaxies over the CANDELS fields. Nine of these
galaxies lie at z~9 and 5 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(-2)(+3)x and
8(-3)(+9)x lower, respectively, than found at z~8. When compared with the
best-fit evolution (i.e., dlog_{10} rho(UV)/dz=-0.29+/-0.02) in the UV
luminosities densities from z~8 to z~4 integrated to 0.3L*(z=3) (-20 mag),
these luminosity densities are 2.6(-0.9)(+1.5)x and 2.2(-1.1)(+2.0)x lower,
respectively, than the extrapolated trends. Our new results are broadly
consistent with the "accelerated evolution" scenario at z>8, as seen in many
theoretical models.Comment: 23 pages, 15 figures, 7 tables, updated to match the version in
press, including some minor textual corrections identified at the proof stag
New Determinations of the UV Luminosity Functions from z~9 to z~2 show a remarkable consistency with halo growth and a constant star formation efficiency
Here we provide the most comprehensive determinations of the rest-frame
LF available to date with HST at z~2, 3, 4, 5, 6, 7, 8, and 9. Essentially all
of the non-cluster extragalactic legacy fields are utilized, including the
Hubble Ultra Deep Field (HUDF), the Hubble Frontier Field parallel fields, and
all five CANDELS fields, for a total survey area of 1136 arcmin^2. Our
determinations include galaxies at z~2-3 leveraging the deep HDUV, UVUDF, and
ERS WFC3/UVIS observations available over a ~150 arcmin^2 area in the GOODS
North and GOODS South regions. All together, our collective samples include
>24,000 sources, >2.3x larger than previous selections with HST. 5766, 6332,
7240, 3449, 1066, 601, 246, and 33 sources are identified at z~2, 3, 4, 5, 6,
7, 8, and 9, respectively. Combining our results with an earlier z~10 LF
determination by Oesch+2018a, we quantify the evolution of the LF. Our
results indicate that there is (1) a smooth flattening of the faint-end slope
alpha from alpha~-2.4 at z~10 to -1.5 at z~2, (2) minimal evolution in the
characteristic luminosity M* at z>~2.5, and (3) a monotonic increase in the
normalization log_10 phi* from z~10 to z~2, which can be well described by a
simple second-order polynomial, consistent with an "accelerated" evolution
scenario. We find that each of these trends (from z~10 to z~2.5 at least) can
be readily explained on the basis of the evolution of the halo mass function
and a simple constant star formation efficiency model.Comment: 18 pages, 10 figures, 5 tables, in submission to ApJ, figures 9 and
10 show the main resul
The alhambra survey: evolution of galaxy spectral segregation
We study the clustering of galaxies as a function of spectral type and redshift in the range 0.35 <z <1.1 using data from the Advanced Large Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The data cover 2.381 deg2 in 7 fields, after applying a detailed angular selection mask, with accurate photometric redshifts down to IAB <24. From this catalog we draw five fixed number density redshift-limited bins. We estimate the clustering evolution for two different spectral populations selected using the ALHAMBRA-based photometric templates: quiescent and star-forming galaxies. For each sample we measure the real-space clustering using the projected correlation function. Our calculations are performed over the range [0.03, 10.0] h-1 Mpc, allowing us to find a steeper trend for Mpc, which is especially clear for star-forming galaxies. Our analysis also shows a clear early differentiation in the clustering properties of both populations: star-forming galaxies show weaker clustering with evolution in the correlation length over the analyzed redshift range, while quiescent galaxies show stronger clustering already at high redshifts and no appreciable evolution. We also perform the bias calculation where similar segregation is found, but now it is among the quiescent galaxies where a growing evolution with redshift is clearer (abrigatted). These findings clearly corroborate the well-known color-density relation, confirming that quiescent galaxies are mainly located in dark matter halos that are more massive than those typically populated by star-forming galaxies.Ministerio de Economía y Competitividad y FEDER AYA2010-22111-C03-02 AYA2013-48623-C2-2 AYA2012-39620 AYA2013-40611-P AYA2013-42227-P AYA2013-43188-P AYA2013-48623-C2-1 ESP2013-48274 AYA2014-58861-C3-1Junta de Andalucía TIC114 JA2828 P10-FQM-644
The ALHAMBRA survey: evolution of galaxy spectral segregation
We study the clustering of galaxies as a function of spectral type and
redshift in the range using data from the Advanced Large
Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The data
cover 2.381 deg in 7 fields, after applying a detailed angular selection
mask, with accurate photometric redshifts [] down to
. From this catalog we draw five fixed number density,
redshift-limited bins. We estimate the clustering evolution for two different
spectral populations selected using the ALHAMBRA-based photometric templates:
quiescent and star-forming galaxies. For each sample, we measure the real-space
clustering using the projected correlation function. Our calculations are
performed over the range Mpc, allowing us to find a
steeper trend for Mpc, which is especially clear for
star-forming galaxies. Our analysis also shows a clear early differentiation in
the clustering properties of both populations: star-forming galaxies show
weaker clustering with evolution in the correlation length over the analysed
redshift range, while quiescent galaxies show stronger clustering already at
high redshifts, and no appreciable evolution. We also perform the bias
calculation where similar segregation is found, but now it is among the
quiescent galaxies where a growing evolution with redshift is clearer. These
findings clearly corroborate the well known colour-density relation, confirming
that quiescent galaxies are mainly located in dark matter halos that are more
massive than those typically populated by star-forming galaxies.Comment: 14 pages, 9 figures, accepted by Ap
A Spectroscopic Follow-up Program of Very Massive Galaxies at 3 < z < 4: Confirmation of Spectroscopic Redshifts, and a High Fraction of Powerful AGNs
Large scale structure and cosmolog
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