32 research outputs found
Lack of influence of the environment in the earliest stages of massive galaxy formation
We investigate how the environment affects the assembly history of massive
galaxies. For that purpose, we make use of SHARDS and HST spectro-photometric
data, whose depth, spectral resolution, and wavelength coverage allow to
perform a detailed analysis of the stellar emission as well as obtaining
unprecedentedly accurate photometric redshifts. This expedites a sufficiently
accurate estimate of the local environment and a robust derivation of the star
formation histories of a complete sample of 332 massive galaxies
() at redshift in the GOODS-N
field. We find that massive galaxies in this redshift range avoid the lowest
density environments. Moreover, we observed that the oldest galaxies in our
sample with with mass-weighted formation redshift , avoid the highest density regions, preferring intermediate
environments. Younger galaxies, including those with active star formation,
tend to live in denser environments (). This behavior could be expected if those massive
galaxies starting their formation first would merge with neighbors and sweep
their environment earlier. On the other hand, galaxies formed more recently
() are accreted into large scale structures at later
times and we are observing them before sweeping their environment or,
alternatively, they are less likely to affect their environment. However, given
that both number and mass surface densities of neighbor galaxies is relatively
low for the oldest galaxies, our results reveal a very weak correlation between
environment and the first formation stages of the earliest massive galaxies.Comment: Accepted for publication in MNRA
The Rapid Build-up of Massive Early-type Galaxies. Supersolar Metallicity, High Velocity Dispersion and Young Age for an ETG at z=3.35
Thanks to very deep spectroscopic observations carried out at the Large
Binocular Telescope, we measured simultaneously stellar age, metallicity and
velocity dispersion for C1-23152, an ETG at redshift =3.352, corresponding
to an epoch when the Universe was 1.8 Gyr old. The analysis of its
spectrum shows that this galaxy, hosting an AGN, formed and assembled
210 M shaping its morphology within the 600
Myr preceding the observations, since 4.6. The stellar population has
a mean mass-weighted age 400 Myr and it is formed between
600 Myr and 150 Myr before the observed epoch, this latter being
the time since quenching. Its high stellar velocity dispersion,
=40960 km s, confirms the high mass
(M=10 M) and the high mass density
(= M
kpc), suggesting a fast dissipative process at its origin. The analysis
points toward a supersolar metallicity, [Z/H]=0.25, in
agreement with the above picture, suggesting a star formation efficiency much
higher than the replenishment time. However, sub-solar metallicity values
cannot be firmly ruled out by our analysis. Quenching must have been extremely
efficient to reduce the star formation to SFR6.5 M yr in less
than 150 Myr. This could be explained by the presence of the AGN, even if a
causal relation cannot be established from the data. C1-23152 has the same
stellar and physical properties of the densest ETGs in the local Universe of
comparable mass, suggesting that they are C1-23152-like galaxies which evolved
to unperturbed.Comment: 20 pages, 12 figures. Accepted for publication in ApJ (revised to
match the ApJ version
Complete IRAC mapping of the CFHTLS-DEEP, MUSYC AND NMBS-II FIELDS
The IRAC mapping of the NMBS-II fields program is an imaging survey at 3.6
and 4.5m with the Spitzer Infrared Array Camera (IRAC). The observations
cover three Canada-France-Hawaii Telescope Legacy Survey Deep (CFHTLS-D)
fields, including one also imaged by AEGIS, and two MUSYC fields. These are
then combined with archival data from all previous programs into deep mosaics.
The resulting imaging covers a combined area of about 3 , with at least
2 hr integration time for each field. In this work, we present our data
reduction techniques and document the resulting coverage maps at 3.6 and
4.5m. All of the images are W-registered to the reference image, which is
either the z-band stack image of the 25\% best seeing images from the CFHTLS-D
for CFHTLS-D1, CFHTLS-D3, and CFHTLS-D4, or the K-band images obtained at the
Blanco 4-m telescope at CTIO for MUSYC1030 and MUSYC1255. We make all images
and coverage maps described herein publicly available via the Spitzer Science
Center.Comment: Accepted in PASP; released IRAC mosaics available upon publication of
the pape
Panchromatic spectral energy distributions of simulated galaxies: results at redshift z = 0
We present predictions of spectral energy distributions (SEDs), from the UV to the FIR, of simulated galaxies at z = 0. These were obtained by post-processing the results of an N-body+hydro simulation of a cosmological box of side 25 Mpc, which uses the Multi-Phase Particle Integrator (MUPPI) for star formation and stellar feedback, with the grasil-3d radiative transfer code that includes reprocessing of UV light by dust. Physical properties of our sample of \u2dc500 galaxies resemble observed ones, though with some tension at small and large stellar masses. Comparing predicted SEDs of simulated galaxies with different samples of local galaxies, we find that these resemble observed ones, when normalized at 3.6 \u3bcm. A comparison with the Herschel Reference Survey shows that the average SEDs of galaxies, divided in bins of star formation rate (SFR), are reproduced in shape and absolute normalization to within a factor of \u2dc2, while average SEDs of galaxies divided in bins of stellar mass show tensions that are an effect of the difference of simulated and observed galaxies in the stellar mass-SFR plane. We use our sample to investigate the correlation of IR luminosity in Spitzer and Herschel bands with several galaxy properties. SFR is the quantity that best correlates with IR light up to 160 \u3bcm, while at longer wavelengths better correlations are found with molecular mass and, at 500 \u3bcm, with dust mass. However, using the position of the FIR peak as a proxy for cold dust temperature, we assess that heating of cold dust is mostly determined by SFR, with stellar mass giving only a minor contribution. We finally show how our sample of simulated galaxies can be used as a guide to understand the physical properties and selection biases of observed samples
Probing the Star Formation Main Sequence down to M at
We investigate the star formation main sequence (MS) (SFR-M) down
to 10 using a sample of 34,061 newly-discovered
ultra-faint ( mag) galaxies at detected in
the GOODS-N field. Virtually these galaxies are not contained in previous
public catalogs, effectively doubling the number of known sources in the field.
The sample was constructed by stacking the optical broad-band observations
taken by the HST/GOODS-CANDELS surveys as well as the 25 ultra-deep medium-band
images gathered by the GTC/SHARDS project. Our sources are faint (average
observed magnitudes mag, mag), blue (UV-slope
), star-forming (rest-frame colors mag,
mag) galaxies. These observational characteristics are
identified with young (mass-weighted age Gyr)
stellar populations subject to low attenuations (
mag). Our sample allows us to probe the MS down to
at and at , around 0.6 dex deeper than
previous analysis. In the low-mass galaxy regime, we find an average value for
the slope of 0.97 at and 1.12 at . Nearly 60% of our
sample presents stellar masses in the range M between
. If the slope of the MS remained constant in this regime, the sources
populating the low-mass tail of our sample would qualify as starburst galaxies.Comment: 34 pages, 16 figures, 9 tables. Accepted for publication to Ap
The Spitzer Coverage of HSC-Deep with IRAC for Z studies (SHIRAZ) I: IRAC mosaics
We present new Spitzer Infrared Array Camera (IRAC) 3.6 and 4.5{\mu}m mosaics
of three fields, E-COSMOS, DEEP2-F3, and ELAIS-N1. Our mosaics include both new
IRAC observations as well as re-processed archival data in these fields. These
fields are part of the HSC-Deep grizy survey and have a wealth of additional
ancillary data. The addition of these new IRAC mosaics is critical in allowing
for improved photometric redshifts and stellar population parameters at cosmic
noon and earlier epochs. The total area mapped by this work is {\sim} 17 deg2
with a mean integration time of {\sim}1200s, providing a median 5{\sigma} depth
of 23.7(23.3) at 3.6(4.5){\mu}m in AB. We perform SExtractor photometry both on
the combined mosaics as well as the single-epoch mosaics taken {\sim}6 months
apart. The resultant IRAC number counts show good agreement with previous
studies. In combination with the wealth of existing and upcoming
spectro-photometric data in these fields, our IRAC mosaics will enable a wide
range of galactic evolution and AGN studies. With that goal in mind, we make
the combined IRAC mosaics and coverage maps of these three fields publicly
available. counts show good agreement with previous studies.Comment: accepted for publication in A
Clash-VLT: Insights on the mass substructures in the frontier fields cluster MACS J0416.1-2403 through accurate strong lens modeling
We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy cluster MACS J0416.1\u20132403. We show and employ our extensive spectroscopic data set taken with the VIsible Multi-Object Spectrograph instrument as part of our CLASH-VLT program, to confirm spectroscopically 10 strong lensing systems and to select a sample of 175 plausible cluster members to a limiting stellar mass of log (M */M &09) ~= 8.6. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.''3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. The latter have total mass-to-light ratios increasing with the galaxy HST/WFC3 near-IR (F160W) luminosities. The measurement of the total enclosed mass within the Einstein radius is accurate to ~5%, including the systematic uncertainties estimated from six distinct mass models. We emphasize that the use of multiple-image systems with spectroscopic redshifts and knowledge of cluster membership based on extensive spectroscopic information is key to constructing robust high-resolution mass maps. We also produce magnification maps over the central area that is covered with HST observations. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. When compared with the outcomes of cosmological N-body simulations, our results point to a lack of massive subhalos in the inner regions of simulated clusters with total masses similar to that of MACS J0416.1\u20132403. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing tests of the assumed collisionless, cold nature of dark matter and of the role played by baryons in the process of structure formation.
This work is based in large part on data collected at ESO VLT (prog. ID 186.A-0798) and NASA HST
Probing the earliest phases in the formation of massive galaxies with simulated HST+JWST imaging data from Illustris
We use the Illustris-1 simulation to explore the capabilities of the
and data to analyze the
stellar populations in high-redshift galaxies, taking advantage of the combined
depth, spatial resolution, and wavelength coverage. For that purpose, we use
simulated broad-band ACS, WFC3 and NIRCam data and 2-dimensional stellar
population synthesis (2D-SPS) to derive the integrated star formation history
(SFH) of massive (MM) simulated galaxies at
M galaxy. In
particular, we explore the potential of HST and JWST datasets reaching a depth
similar to those of the CANDELS and ongoing CEERS observations, respectively,
and concentrate on determining the capabilities of this dataset for
characterizing the first episodes in the SFH of local
MM galaxies by studying their progenitors at
. The 2D-SPS method presented in this paper has been calibrated to
robustly recover the cosmic times when the first star formation episodes
occurred in massive galaxies, i.e., the first stages in their integrated SFHs.
In particular, we discuss the times when the first 1% to 50% of their total
stellar mass formed in the simulation. We demonstrate that we can recover these
ages with typical median systematic offset of less than 5% and scatter around
20%-30%. According to our measurements on Illustris data, we are able to
recover that local MM galaxies would have started
their formation by , forming the first 5% of their stellar mass present
at by , 10% by , and 25% by .Comment: 28 pages, 13 figures, 4 tables. ApJ in press. Summary of changes from
original submission: the major change is that we now include in Sec. 6 the
comparison of the results obtained for our sample of massive 1 < z < 4
progenitors with those obtained by considering all massive galaxies at 1 < z
< 4 in the simulated images. Several figures and sections have been update
MIDIS: JWST/MIRI reveals the Stellar Structure of ALMA-selected Galaxies in the Hubble-UDF at Cosmic Noon
We present deep James Webb Space Telescope (JWST)/MIRI F560W observations of
a flux-limited, ALMA-selected sample of 28 galaxies at z=0.5-3.6 in the Hubble
Ultra Deep Field (HUDF). The data from the MIRI Deep Imaging Survey (MIDIS)
reveal the stellar structure of the HUDF galaxies at rest-wavelengths of >1
micron for the first time. We revise the stellar mass estimates using new JWST
photometry and find good agreement with pre-JWST analysis; the few
discrepancies can be explained by blending issues in the earlier
lower-resolution Spitzer data. At z~2.5, the resolved rest-frame near-infrared
(1.6 micron) structure of the galaxies is significantly more smooth and
centrally concentrated than seen by HST at rest-frame 450 nm (F160W), with
effective radii of Re(F560W)=1-5 kpc and S\'ersic indices mostly close to an
exponential (disk-like) profile (n~1), up to n~5 (excluding AGN). We find an
average size ratio of Re(F560W)/Re(F160W)~0.7 that decreases with stellar mass.
The stellar structure of the ALMA-selected galaxies is indistinguishable from a
HUDF reference sample of galaxies with comparable MIRI flux density. We
supplement our analysis with custom-made, position-dependent, empirical PSF
models for the F560W observations. The results imply that an older and smoother
stellar structure is in place in massive gas-rich, star-forming galaxies at
Cosmic Noon, despite a more clumpy rest-frame optical appearance, placing
additional constraints on galaxy formation simulations. As a next step,
matched-resolution, resolved ALMA observations will be crucial to further link
the mass- and light-weighted galaxy structures to the dusty interstellar
medium.Comment: 19 pages, 10 figures, 1 table, submitted to Ap