25 research outputs found
A K-band Selected Photometric Redshift Catalog in the HDF-S: Sampling the Rest-Frame V-Band to z=3
We present the first results from the Faint Infra-Red Extragalactic Survey
(FIRES) of the Hubble Deep Field South. Using a combination of deep near
infrared data obtained with ISAAC at the VLT with the WFPC2 HST data, we
construct a K-band selected sample of 136 galaxies with K(AB)<=23.5. We derive
zphot's using a newly developed technique which models the observed spectral
energy distribution with a linear combination of empirical galaxy templates.
Testing our zphot technique against spectroscopic redshifts in the HDF-N yields
dz/(1+z)~0.07 for z<6. We show that we can derive realistic error estimates in
zphot by combining the systematic uncertainties derived from the HDF-N with
errors in zphot which depend on the observed flux errors. The redshift
histogram of galaxies in the HDF-S shows distinct structure with a sharp peak
at z~0.5 and a broad enhancement at z~1-1.4. We find that 12% of our galaxies
with K(vega)=2. While this is higher than the fraction predicted
in Omega_M=1 hierarchical models of galaxy formation we find that published
predictions using pure luminosity evolution models produce too many bright
galaxies at redshifts greater than unity. Finally, we use our broad wavelength
coverage to measure the rest-frame UBV luminosities Lrest for z<=3. There is a
paucity of galaxies brighter than Lrest_V>=1.4e10 h^{-2}Lsun at z~1.5-2,
however, at z>2 we find very luminous galaxies with Lrest_V>=5e10 h^{-2}Lsun
(for Omega_M=0.3,Lambda=0.7, H_o=100 h km s^{-1}Mpc^{-1}). Local B-band
luminosity functions predict 0.1 galaxies in the redshift range 2<=z<=3.5 and
with Lrest_B>= 5e10 h^{-2}Lsun,B but we find 9. The discrepancy can be
explained if L*_B increases by a factor of 2.4-3.2 with respect to locally
determined values (abridged).Comment: 46 pages, 15 figures, 3 Tables, Accepted for publication in
Astronomical Journal, paper and high resolution figures available at
http://www.strw.leidenuniv.nl/~fires/, minor changes to comply with referee's
comment
The Rest-Frame Optical Luminosity Density, Color, and Stellar Mass Density of the Universe from z=0 to z=3
We present the evolution of the rest-frame optical luminosity density, of the
integrated rest-frame optical color, and of the stellar mass density for a
sample of Ks-band selected galaxies in the HDF-S. We derived the luminosity
density in the rest-frame U, B, and V-bands and found that the luminosity
density increases by a factor of 1.9+-0.4, 2.9+-0.6, and 4.9+-1.0 in the V, B,
and U rest-frame bands respectively between a redshift of 0.1 and 3.2. We
derived the luminosity weighted mean cosmic (U-B)_rest and (B-V)_rest colors as
a function of redshift. The colors bluen almost monotonically with increasing
redshift; at z=0.1, the (U-B)_rest and (B-V)_rest colors are 0.16 and 0.75
respectively, while at z=2.8 they are -0.39 and 0.29 respectively. We derived
the luminosity weighted mean M/LV using the correlation between (U-V)_rest and
log_{10} M/LV which exists for a range in smooth SFHs and moderate extinctions.
We have shown that the mean of individual M/LV estimates can overpredict the
true value by ~70% while our method overpredicts the true values by only ~35%.
We find that the universe at z~3 had ~10 times lower stellar mass density than
it does today in galaxies with LV>1.4 \times 10^{10} h_{70}^-2 Lsol. 50% of the
stellar mass of the universe was formed by $z~1-1.5. The rate of increase in
the stellar mass density with decreasing redshift is similar to but above that
for independent estimates from the HDF-N, but is slightly less than that
predicted by the integral of the SFR(z) curve.Comment: 19 pages, 12 figures, Accepted for Publication in the Dec. 20, 2003
edition of the Astrophysical Journal. Minor changes made to match the
accepted version including short discussions on the effects of clustering and
on possible systematic effects resulting from photometric redshift error
Ultradeep Near-Infrared ISAAC Observations of the HDF-S: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts
We present deep near-infrared (NIR) Js, H, and Ks-band ISAAC imaging of the
WFPC2 field of the HDF-S. The 2.5'x 2.5' high Galactic latitude field was
observed with the VLT under the best seeing conditions with integration times
amounting to 33.6 hours in Js, 32.3 hours in H, and 35.6 hours in Ks. We reach
total AB magnitudes for point sources of 26.8, 26.2, and 26.2 respectively (3
sigma), which make it the deepest ground-based NIR observations to date, and
the deepest Ks-band data in any field. The effective seeing of the coadded
images is ~0.45" in Js, ~0.48" in H, and ~0.46" in Ks. Using published WFPC2
optical data, we constructed a Ks-limited multicolor catalog containing 833
sources down to Ks,tot ~< 26 (AB), of which 624 have seven-band optical-to-NIR
photometry. These data allow us to select normal galaxies from their rest-frame
optical properties to high redshift (z ~< 4). The observations, data reduction
and properties of the final images are discussed, and we address the detection
and photometry procedures that were used in making the catalog. In addition, we
present deep number counts, color distributions and photometric redshifts of
the HDF-S galaxies. We find that our faint Ks-band number counts are flatter
than published counts in other deep fields, which might reflect cosmic
variations or different analysis techniques. Compared to the HDF-N, we find
many galaxies with very red V-H colors at photometric redshifts 1.95 < z < 3.5.
These galaxies are bright in Ks with infrared colors redder than Js-Ks > 2.3
(in Johnson magnitudes). Because they are extremely faint in the observed
optical, they would be missed by ultraviolet-optical selection techniques, such
as the U-dropout method.Comment: LaTeX, 24 pages, 15 figures, 3 tables. Accepted for publication in
the Astronomical Journal. The paper with full resolution images and figures
is available at http://www.strw.leidenuniv.nl/~fires/papers/2002Labbe.ps.gz .
The reduced data and catalogs can be found at
http://www.strw.leidenuniv.nl/~fires/data/hdfs
A Significant Population of Red, Near-IR Selected High Redshift Galaxies
We use very deep near-infrared photometry of the Hubble Deep Field South
taken with ISAAC/VLT to identify a population of high redshift galaxies with
rest- frame optical colors similar to those of nearby galaxies. The galaxies
are chosen by their infrared colors Js-Ks > 2.3, aimed at selecting galaxies
with redshifts above 2. When applied to our dataset, we find 14 galaxies with
Ks < 22.5, corresponding to a surface density of 3+-0.8 /arcmin**2. The
photometric redshifts all lie above 1.9, with a median of 2.6 and a rms of 0.7.
The spectral energy distributions of these galaxies show a wide range: one is
very blue in the rest-frame UV, and satisfies the normal Lyman-break criteria
for high redshift, star-forming galaxies. Others are quite red throughout the
observed spectral range, and are extremely faint in the optical, with a median
V = 26.6. Hence these galaxies would not be included in photometric samples
based on optical ground-based data, and spectroscopic follow-up is difficult.
The spectral energy distributions often show a prominent break, identified as
the Balmer break or 4000 Ang. break. The median age is 1 Gyr when fit with a
constant star formation model with dust, or 0.7 Gyr when fit with a single
burst model. Although significantly younger ages cannot be excluded when a
larger range of models is allowed, the results indicate that these galaxies are
among the oldest at these redshifts. The volume density to Ks=22.5 is half that
of Lyman-break galaxies at z = 3. Since the mass-to-light ratios of the red
galaxies are likely to be higher, the stellar mass density is inferred to be
comparable to that of Lyman-break galaxies. These red galaxies may be the
descendants of galaxies which started to form stars at very high redshifts, and
they may evolve into the most massive galaxies at low redshift.Comment: LaTex, 5 pages and 4 figures. Accepted for publication in ApJ
Letters. See also related preprints on astroph today by Daddi et al and van
Dokkum et a
The size evolution of galaxies since z~3: combining SDSS, GEMS and FIRES
We present the evolution of the luminosity-size and stellar mass-size
relations of luminous (L_V>3.4x10^10h_70^-2L_sun) and of massive
(M_*>3x10^10h_70^-2M_sun) galaxies in the last ~11 Gyr. We use very deep
near-infrared images of the Hubble Deep Field-South and the MS1054-03 field in
the J_s, H and K_s bands from FIRES to retrieve the sizes in the optical
rest-frame for galaxies with z>1. We combine our results with those from GEMS
at 0.2<z<1 and SDSS at z~0.1 to achieve a comprehensive picture of the optical
rest-frame size evolution from z=0 to z=3. Galaxies are differentiated
according to their light concentration using the Sersic index n. For less
concentrated objects, the galaxies at a given luminosity were typically ~3+-0.5
(+-2 sigma) times smaller at z~2.5 than those we see today. The stellar
mass-size relation has evolved less: the mean size at a given stellar mass was
\~2+-0.5 times smaller at z~2.5, evolving proportional to (1+z)^{-0.40+-0.06}.
Simple scaling relations between dark matter halos and baryons in a
hierarchical cosmogony predict a stronger (although consistent within the error
bars) than observed evolution of the stellar mass-size relation. The observed
luminosity-size evolution out to z~2.5 matches well recent infall model
predictions for Milky-Way type objects. For low-n galaxies, the evolution of
the stellar mass-size relation would follow naturally if the individual
galaxies grow inside-out. For highly concentrated objects, the situation is as
follows: at a given luminosity, these galaxies were ~2.7+-1.1 times smaller at
z~2.5 (or put differently, were typically ~2.2+-0.7 mag brighter at a given
size than they are today), and at a given stellar mass the size has evolved
proportional to (1+z)^{-0.45+-0.10}.Comment: Accepted for publication in ApJ. The new version includes several
improvements: much accurate size estimations and a better completeness and
robustness analysis. Tables of data are included. 29 pages and 14 figures
(one low resolution
Ultradeep near-infrared imaging of the HDF-South: rest-frame optical properties of high redshift galaxies
We have obtained ultradeep J_s, H and K_s near-infrared imaging of the Hubble Deep Field South WFPC2 field with the ISAAC camera on the VLT. The total integration time of 100 hours resulted in the deepest ground-based infrared observations to date and the deepest K_s-band data ever taken. This depth allows us to determine the spectral energy distributions of the high-redshift galaxies with unprecendented accuracy. Together with existing optical observations, we use the multicolor data to select high-redshift galaxies by their rest-frame optical light, and study their statistical properties and morphologies. We find a wide variety of morphologies: some are large in the rest-frame optical and resemble normal spiral galaxies, others are barely detected in the observers optical and have red NIR colors. The latter belong to a new population of galaxies at redshifts z>2, that is notably absent in the HDF-North. The spectral energy distributions of many of such red galaxies show distinct breaks, which we identify as the balmer break/4000 Angstrom break, and their contribution to the stellar mass density is estimated to be substantial. At redshift z~3, we find a clear excess of superluminious galaxies (> 5 L*_B(z = 0)), which is consistent with 1 magnitude of luminosity evolution. Overall, the results show the necessity of deep near-infrared imaging to obtain a full census of the high redshift universe
Large disk-like galaxies at high redshift
Using deep near-infrared imaging of the Hubble Deep Field South with ISAAC on
the Very Large Telescope we find 6 large disk-like galaxies at redshifts z =
1.4-3.0. The galaxies, selected in K_s (2.2 micron), are regular and
surprisingly large in the near-infrared (rest-frame optical), with face-on
effective radii r_e = 0.65"-0.9" or 5.0-7.5 h_70^-1 kpc in a Lambda-CDM
cosmology, comparable to the Milky Way. The surface brightness profiles are
consistent with an exponential law over 2-3 effective radii. The WFPC2
morphologies in Hubble Space Telescope imaging (rest-frame UV) are irregular
and show complex aggregates of star-forming regions ~2" (~15 h_70^-1 kpc)
across, symmetrically distributed around the K_s-band centers. The spectral
energy distributions show clear breaks in the rest-frame optical. The breaks
are strongest in the central regions of the galaxies, and can be identified as
the age-sensitive Balmer/4000 Angstrom break. The most straightforward
interpretation is that these galaxies are large disk galaxies; deep NIR data
are indispensable for this classification. The candidate disks constitute 50%
of galaxies with L_V > 6 x 10^10 h_70^-2 L_sun at z = 1.4-3.0. This discovery
was not expected on the basis of previously studied samples. In particular, the
Hubble Deep Field North is deficient in large galaxies with the morphologies
and profiles we report here.Comment: LaTeX, 5 pages, 2 figures, 1 table. Accepted for publication in the
Astrophysical Journal Letter
HDF-South K photometric redshift catalog
VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title 'A K-band-selected photometric redshift catalog in the Hubble Deep Field South: sampling the rest-frame V band to z=3.' (bibcode: 2001AJ....122.2205R