172 research outputs found
Structure of Protocluster Galaxies: Accelerated Structural Evolution in Overdense Environments?
We present a high spatial-resolution HST/NICMOS imaging survey in the field
of a known protocluster surrounding the powerful radio galaxy MRC1138-262 at
z=2.16. Previously, we have shown that this field exhibits a substantial
surface overdensity of red J-H galaxies. Here we focus on the stellar masses
and galaxy effective radii in an effort to compare and contrast the properties
of likely protocluster galaxies with their field counterparts and to look for
correlations between galaxy structure and (projected) distance relative to the
radio galaxy.
We find a hint that quiescent, cluster galaxies are on average less dense
than quiescent field galaxies of similar stellar mass and redshift. In fact, we
find only two (of nine) quiescent protocluster galaxies are of simliar density
to the majority of the massive, quiescent compact galaxies (SEEDs) found in
several field surveys. Furthermore, there is some indication that the
structural Sersic n parameter is higher (n ~ 3-4) on average for cluster
galaxies compared to the field SEEDs (n ~ 1-2) This result may imply that the
accelerated galaxy evolution expected (and observed) in overdense regions also
extends to structural evolution presuming that massive galaxies began as dense
(low n) SEEDs and have already evolved to be more in line with local galaxies
of the same stellar mass.Comment: 11 pages, 7 figures, 1 table, Accepted for publication in Ap
Vacuum inversion and securing of distal colonic pseudodiverticula with novel spiked O-rings
Diverticular disease is increasingly prevalent in Western societies and is associated with significant morbidity.
OBJECTIVE:
Two-stage endoscopic device development for inversion and secured ligation of colonic diverticula; first, human cadaver studies were performed to measure forces required for diverticular inversion; second, a novel set of devices (elastic spiked O-ring with delivery system) was tested in animals.
DESIGN:
Prospective, observational study of human cadavers and prospective, interventional study of a porcine model.
SETTING:
University hospital pathology laboratory and animal facility.
INTERVENTION:
Full-thickness inversion of the colonic wall with a pipelike delivery instrument to produce an inverted pseudodiverticulum that was secured with a spiked O-ring.
MAIN OUTCOME MEASUREMENTS:
The forces required for diverticular inversion, the secured closure of inverted pseudodiverticula, and the time until necrotic tissue falls off.
RESULTS:
A total of 248 of 248 of cadaveric sigmoid diverticula could be inverted by means of vacuum or forceps. The forces required for inversion ranged from 0.28 to 0.47 N (median, 0.37 N). Twenty-four spiked O-rings were delivered in 6 living pigs to produce 24 inverted pseudodiverticula. One animal died the day after the procedure of a pulmonary thromboembolism. In the remaining 5 pigs, all delivered spiked O-rings remained in place for 7 to 22 days. At necropsy, none of the inverted sites showed signs of perforation but rather full-thickness reparative scarring with ingrowth of connective tissue.
LIMITATIONS:
Animal model, stiff pipelike delivery instrument, variations in diverticular location, diameter, and size.
CONCLUSIONS:
Endoluminal inversion and securing of colonic diverticula induces tissue necrosis, diverticular sloughing, and full-thickness scarring
Taking the pulse of Mars via dating of a plume-fed volcano
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the articleâs Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the articleâs Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. The attached file is the published version of the article
The SL2S Galaxy-scale Lens Sample. II. Cosmic evolution of dark and luminous mass in early-type galaxies
We present a joint gravitational lensing and stellar-dynamical analysis of 11
early-type galaxies (median deflector redshift \zd=0.5) from Strong Lenses in
the Legacy Survey (SL2S). Using newly measured redshifts and stellar velocity
dispersions from Keck spectroscopy with lens models from Paper I, we derive the
total mass density slope inside the Einstein radius for each of the 11 lenses.
The average total density slope is found to be (), with an intrinsic
scatter of . We also determine the dark matter fraction
for each lens within half the effective radius, and find the average projected
dark matter mass fraction to be with a scatter of
for a Salpeter IMF. By combining the SL2S results with
those from the Sloan Lens ACS Survey (median \zd=0.2) and the Lenses
Structure and Dynamics survey (median \zd=0.8), we investigate cosmic
evolution of and find a mild trend \partial/\partial\zd =
-0.25^{+0.10}_{-0.12}. This suggests that the total density profile of massive
galaxies has become slightly steeper over cosmic time. If this result is
confirmed by larger samples, it would indicate that dissipative processes
played some role in the growth of massive galaxies since .Comment: 21 pages, 16 figures, submitted to Ap
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
Discovering extremely compact and metal-poor, star-forming dwarf galaxies out to z ~ 0.9 in the VIMOS Ultra-Deep Survey
We report the discovery of 31 low-luminosity (-14.5 > M_{AB}(B) > -18.8),
extreme emission line galaxies (EELGs) at 0.2 < z < 0.9 identified by their
unusually high rest-frame equivalent widths (100 < EW[OIII] < 1700 A) as part
of the VIMOS Ultra Deep Survey (VUDS). VIMOS optical spectra of unprecedented
sensitivity ( ~ 25 mag) along with multiwavelength photometry and HST
imaging are used to investigate spectrophotometric properties of this unique
sample and explore, for the first time, the very low stellar mass end (M* <
10^8 M) of the luminosity-metallicity (LZR) and mass-metallicity
(MZR) relations at z < 1. Characterized by their extreme compactness (R50 < 1
kpc), low stellar mass and enhanced specific star formation rates (SFR/M* ~
10^{-9} - 10^{-7} yr^{-1}), the VUDS EELGs are blue dwarf galaxies likely
experiencing the first stages of a vigorous galaxy-wide starburst. Using
T_e-sensitive direct and strong-line methods, we find that VUDS EELGs are
low-metallicity (7.5 < 12+log(O/H) < 8.3) galaxies with high ionization
conditions, including at least three EELGs showing HeII 4686A emission and four
EELGs of extremely metal-poor (<10% solar) galaxies. The LZR and MZR followed
by EELGs show relatively large scatter, being broadly consistent with the
extrapolation toward low luminosity and mass from previous studies at similar
redshift. However, we find evidences that galaxies with younger and more
vigorous star formation -- as characterized by their larger EWs, ionization and
sSFR -- tend to be more metal-poor at a given stellar mass.Comment: Letter in A&A 568, L8 (2014). This replacement matches the published
versio
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&
The VIMOS Ultra Deep Survey: Ly Emission and Stellar Populations of Star-Forming Galaxies at 2<z<2.5
The aim of this paper is to investigate spectral and photometric properties
of 854 faint (<~25 mag) star-forming galaxies (SFGs) at 2<z<2.5 using
the VIMOS Ultra-Deep Survey (VUDS) spectroscopic data and deep multi-wavelength
photometric data in three extensively studied extragalactic fields (ECDFS,
VVDS, COSMOS). These SFGs were targeted for spectroscopy based on their
photometric redshifts. The VUDS spectra are used to measure the UV spectral
slopes () as well as Ly equivalent widths (EW). On average, the
spectroscopically measured (-1.360.02), is comparable to the
photometrically measured (-1.320.02), and has smaller measurement
uncertainties. The positive correlation of with the Spectral Energy
Distribution (SED)-based measurement of dust extinction, E(B-V),
emphasizes the importance of as an alternative dust indicator at high
redshifts. To make a proper comparison, we divide these SFGs into three
subgroups based on their rest-frame Ly EW: SFGs with no Ly
emission (SFG; EW0\AA), SFGs with Ly emission (SFG; EW0\AA), and Ly emitters (LAEs; EW20\AA). The fraction of
LAEs at these redshifts is 10%, which is consistent with previous
observations. We compared best-fit SED-estimated stellar parameters of the
SFG, SFG and LAE samples. For the luminosities probed here
(L), we find that galaxies with and without Ly in emission
have small but significant differences in their SED-based properties. We find
that LAEs have less dust, and lower star-formation rates (SFR) compared to
non-LAEs. We also find that LAEs are less massive compared to non-LAEs, though
the difference is smaller and less significant compared to the SFR and E(B-V). [abridged]Comment: Accepted for publication in A&A, 19 pages, 10 figures, 1 tabl
The impact of the Star Formation Histories on the SFR-M relation at z2
In this paper we investigate the impact of different star formation histories
(SFHs) on the relation between stellar mass M and star formation rate
(SFR) using a sample of galaxies with reliable spectroscopic redshift zspec>2
drawn from the VIMOS Ultra-Deep Survey (VUDS). We produce an extensive database
of dusty model galaxies, calculated starting from the new library of single
stellar population (SSPs) models presented in Cassara' et al. 2013 and weighted
by a set of 28 different SFHs based on the Schmidt function, and characterized
by different ratios of the gas infall time scale to the star
formation efficiency . The treatment of dust extinction and re-emission
has been carried out by means of the radiative transfer calculation. The
spectral energy distribution (SED) fitting technique is performed by using
GOSSIP+, a tool able to combine both photometric and spectroscopic information
to extract the best value of the physical quantities of interest, and to
consider the Intergalactic Medium (IGM) attenuation as a free parameter. We
find that the main contribution to the scatter observed in the
plane is the possibility of choosing between different families of SFHs in the
SED fitting procedure, while the redshift range plays a minor role. The
majority of the galaxies, at all cosmic times, are best-fit by models with SFHs
characterized by a high ratio. We discuss the
reliability of the presence of a small percentage of dusty and highly star
forming galaxies, in the light of their detection in the FIR.Comment: 14 pages, 13 figures, accepted for pubblication in A&
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&
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