140 research outputs found
Stellar populations of galaxies in the ALHAMBRA survey up to . I. MUFFIT: A Multi-Filter Fitting code for stellar population diagnostics
We present MUFFIT, a new generic code optimized to retrieve the main stellar
population parameters of galaxies in photometric multi-filter surveys, and we
check its reliability and feasibility with real galaxy data from the ALHAMBRA
survey. Making use of an error-weighted -test, we compare the
multi-filter fluxes of galaxies with the synthetic photometry of mixtures of
two single stellar populations at different redshifts and extinctions, to
provide through a Monte Carlo method the most likely range of stellar
population parameters (mainly ages and metallicities), extinctions, redshifts,
and stellar masses. To improve the diagnostic reliability, MUFFIT identifies
and removes from the analysis those bands that are significantly affected by
emission lines. We highlight that the retrieved age-metallicity locus for a
sample of early-type galaxies in ALHAMBRA at different stellar
mass bins are in very good agreement with the ones from SDSS spectroscopic
diagnostics. Moreover, a one-to-one comparison between the redshifts, ages,
metallicities, and stellar masses derived spectroscopically for SDSS and by
MUFFIT for ALHAMBRA reveals good qualitative agreements in all the parameters.
In addition, and using as input the results from photometric-redshift codes,
MUFFIT improves the photometric-redshift accuracy by -, and it
also detects nebular emissions in galaxies, providing physical information
about their strengths. Our results show the potential of multi-filter galaxy
data to conduct reliable stellar population studies with the appropiate
analysis techniques, as MUFFIT.Comment: 31 pages, 18 figures, accepted for publication in A&
The ALHAMBRA Survey: Bayesian Photometric Redshifts with 23 bands for 3 squared degrees
The ALHAMBRA (Advance Large Homogeneous Area Medium Band Redshift
Astronomical) survey has observed 8 different regions of the sky, including
sections of the COSMOS, DEEP2, ELAIS, GOODS-N, SDSS and Groth fields using a
new photometric system with 20 contiguous ~ filters covering the
optical range, combining them with deep imaging. The observations,
carried out with the Calar Alto 3.5m telescope using the wide field (0.25 sq.
deg FOV) optical camera LAICA and the NIR instrument Omega-2000, correspond to
~700hrs on-target science images. The photometric system was designed to
maximize the effective depth of the survey in terms of accurate spectral-type
and photo-zs estimation along with the capability of identification of
relatively faint emission lines. Here we present multicolor photometry and
photo-zs for ~438k galaxies, detected in synthetic F814W images, complete down
to I~24.5 AB, taking into account realistic noise estimates, and correcting by
PSF and aperture effects with the ColorPro software. The photometric ZP have
been calibrated using stellar transformation equations and refined internally,
using a new technique based on the highly robust photometric redshifts measured
for emission line galaxies. We calculate photometric redshifts with the BPZ2
code, which includes new empirically calibrated templates and priors. Our
photo-zs have a precision of for I<22.5 and 1.4% for
22.5<I<24.5. Precisions of less than 0.5% are reached for the brighter
spectroscopic sample, showing the potential of medium-band photometric surveys.
The global shows a mean redshift =0.56 for I=0.86 for
I<24.5 AB. The data presented here covers an effective area of 2.79 sq. deg,
split into 14 strips of 58.5'x15.5' and represents ~32 hrs of on-target.Comment: The catalog data and a full resolution version of this paper is
available at https://cloud.iaa.csic.es/alhambra
Discovery of a rich proto-cluster at z=2.9 and associated diffuse cold gas in the VIMOS Ultra-Deep Survey (VUDS)
[Abridged] We characterise a massive proto-cluster at z=2.895 that we found
in the COSMOS field using the spectroscopic sample of the VIMOS Ultra-Deep
Survey (VUDS). This is one of the rare structures at z~3 not identified around
AGNs or radio galaxies, so it is an ideal laboratory to study galaxy formation
in dense environments. The structure comprises 12 galaxies with secure
spectroscopic redshift in an area of 7'x8', in a z bin of Dz=0.016. The
measured galaxy number overdensity is delta_g=12+/-2. This overdensity has
total mass of M~8.1x10^(14)M_sun in a volume of 13x15x17 Mpc^3. Simulations
indicate that such an overdensity at z~2.9 is a proto-cluster that will
collapse in a cluster of total mass M~2.5x10^(15)M_sun at z=0. We compare the
properties of the galaxies within the overdensity with a control sample at the
same z but outside the overdensity. We did not find any statistically
significant difference between the properties (stellar mass, SFR, sSFR, NUV-r,
r-K) of the galaxies inside and outside the overdensity. The stacked spectrum
of galaxies in the overdensity background shows a significant absorption
feature at the wavelength of Lya redshifted at z=2.895 (lambda=4736 A), with a
rest frame EW = 4+/- 1.4 A. Stacking only background galaxies without
intervening sources at z~2.9 along their line of sight, we find that this
absorption feature has a rest frame EW of 10.8+/-3.7 A, with a detection S/N of
~4. These EW values imply a high column density (N(HI)~3-20x10^(19)cm^(-2)),
consistent with a scenario where such absorption is due to intervening cold gas
streams, falling into the halo potential wells of the proto-cluster galaxies.
However, we cannot exclude the hypothesis that this absorption is due to the
diffuse gas within the overdensity.Comment: 15 pages, 9 figures, accepted for publication in A&A (revised version
after referee's comments and language editing
The zCOSMOS redshift survey : Influence of luminosity, mass and environment on the galaxy merger rate
The contribution of major mergers to galaxy mass assembly along cosmic time
is an important ingredient to the galaxy evolution scenario. We aim to measure
the evolution of the merger rate for both luminosity/mass selected galaxy
samples and investigate its dependence with the local environment. We use a
sample of 10644 spectroscopically observed galaxies from the zCOSMOS redshift
survey to identify pairs of galaxies destined to merge, using only pairs for
which the velocity difference and projected separation of both components with
a confirmed spectroscopic redshift indicate a high probability of merging. We
have identified 263 spectroscopically confirmed pairs with r_p^{max} = 100
h^{-1} kpc. We find that the density of mergers depends on luminosity/mass,
being higher for fainter/less massive galaxies, while the number of mergers a
galaxy will experience does not depends significantly on its intrinsic
luminosity but rather on its stellar mass. We find that the pair fraction and
merger rate increase with local galaxy density, a property observed up to
redshift z=1. We find that the dependence of the merger rate on the luminosity
or mass of galaxies is already present up to redshifts z=1, and that the
evolution of the volumetric merger rate of bright (massive) galaxies is
relatively flat with redshift with a mean value of 3*10^{-4} (8*10^{-5}
respectively) mergers h^3 Mpc^{-3} Gyr^{-1}. The dependence of the merger rate
with environment indicates that dense environments favors major merger events
as can be expected from the hierarchical scenario. The environment therefore
has a direct impact in shapping-up the mass function and its evolution
therefore plays an important role on the mass growth of galaxies along cosmic
time.Comment: submitted to A&A, 17 pages, 12 figure
The VIMOS Ultra Deep Survey First Data Release: spectra and spectroscopic redshifts of 698 objects up to z~6 in CANDELS
This paper describes the first data release (DR1) of the VIMOS Ultra Deep
Survey (VUDS). The DR1 includes all low-resolution spectroscopic data obtained
in 276.9 arcmin2 of the CANDELS-COSMOS and CANDELS-ECFDS survey areas,
including accurate spectroscopic redshifts z_spec and individual spectra
obtained with VIMOS on the ESO-VLT. A total of 698 objects have a measured
redshift, with 677 galaxies, two type-I AGN and a small number of 19
contaminating stars. The targets of the spectroscopic survey are selected
primarily on the basis of their photometric redshifts to ensure a broad
population coverage. About 500 galaxies have z_spec>2, 48 with z_spec>4, and
the highest reliable redshifts reach beyond z_spec=6. This dataset
approximately doubles the number of galaxies with spectroscopic redshifts at
z>3 in these fields. We discuss the general properties of the sample in terms
of the spectroscopic redshift distribution, the distribution of Lyman-alpha
equivalent widths, and physical properties including stellar masses M_star and
star formation rates (SFR) derived from spectral energy distribution fitting
with the knowledge of z_spec. We highlight the properties of the most massive
star-forming galaxies, noting the large range in spectral properties, with
Lyman-alpha in emission or in absorption, and in imaging properties with
compact, multi-component or pair morphologies. We present the catalogue
database and data products. All data are publicly available and can be
retrieved from a dedicated query-based database available at
http://cesam.lam.fr/vuds.Comment: 11 pages, 6 figures, submitted to A&
The evolution of clustering length, large-scale bias and host halo mass at 2<z<5 in the VIMOS Ultra Deep Survey (VUDS)
We investigate the evolution of galaxy clustering for galaxies in the
redshift range 2.0<<5.0 using the VIMOS Ultra Deep Survey (VUDS). We present
the projected (real-space) two-point correlation function measured
by using 3022 galaxies with robust spectroscopic redshifts in two independent
fields (COSMOS and VVDS-02h) covering in total 0.8 deg. We quantify how the
scale dependent clustering amplitude changes with redshift making use of
mock samples to evaluate and correct the survey selection function. Using a
power-law model we find that the correlation
function for the general population is best fit by a model with a clustering
length =3.95 hMpc and slope
=1.8 at ~2.5, =4.350.60 hMpc and
=1.6 at ~3.5. We use these clustering parameters
to derive the large-scale linear galaxy bias , between galaxies and
dark matter. We find = 2.680.22 at redshift ~3 (assuming
= 0.8), significantly higher than found at intermediate and low
redshifts. We fit an HOD model to the data and we obtain that the average halo
mass at redshift ~3 is =10 hM. From
this fit we confirm that the large-scale linear galaxy bias is relatively high
at = 2.820.27. Comparing these measurements with similar
measurements at lower redshifts we infer that the star-forming population of
galaxies at ~3 should evolve into the massive and bright (<-21.5)
galaxy population which typically occupy haloes of mass =
10 h at redshift =0.Comment: 19 pages, 10 figures, submitted to A&
J-PLUS: Photometric Re-calibration with the Stellar Color Regression Method and an Improved Gaia XP Synthetic Photometry Method
We employ the corrected Gaia Early Data Release 3 (EDR3) photometric data and
spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic
Telescope (LAMOST) DR7 to assemble a sample of approximately 0.25 million FGK
dwarf photometric standard stars for the 12 J-PLUS filters using the Stellar
Color Regression (SCR) method. We then independently validated the J-PLUS DR3
photometry, and uncovered significant systematic errors: up to 15 mmag in the
results of Stellar Locus (SL) method, and up to 10 mmag mainly caused by
magnitude-, color-, and extinction-dependent errors of the Gaia XP spectra with
the Gaia BP/RP (XP) Synthetic Photometry (XPSP) method. We have also further
developed the XPSP method using the corrected Gaia XP spectra by Huang et al.
(2023) and applied it to the J-PLUS DR3 photometry. This resulted in an
agreement of 1-5 mmag with the SCR method, and a two-fold improvement in the
J-PLUS zero-point precision. Finally, the zero-point calibration for around 91%
of the tiles within the LAMOST observation footprint is determined through the
SCR method, with the remaining approximately 9% of tiles outside this footprint
relying on the improved XPSP method. The re-calibrated J-PLUS DR3 photometric
data establishes a solid data foundation for conducting research that depends
on high-precision photometric calibration.Comment: 21 papes; 20 figures, submitted, see main results in Figures 5 and 1
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