315 research outputs found
3D-HST+CANDELS : the evolution of the galaxy size-mass distribution since z=3
Spectroscopic+photometric redshifts, stellar mass estimates, and rest-frame colors from the 3D-HST survey are combined with structural parameter measurements from CANDELS imaging to determine the galaxy size-mass distribution over the redshift range 0 < z < 3. Separating early- and late-type galaxies on the basis of star-formation activity, we confirm that early-type galaxies are on average smaller than late-type galaxies at all redshifts, and we find a significantly different rate of average size evolution at fixed galaxy mass, with fast evolution for the early-type population, R eff∝(1 + z)–1.48, and moderate evolution for the late-type population, R eff∝(1 + z)-0.75Peer reviewedFinal Accepted Versio
Less is less: photometry alone cannot predict the observed spectral indices of galaxies from the LEGA-C spectroscopic survey
We test whether we can predict optical spectra from deep-field photometry of
distant galaxies. Our goal is to perform a comparison in data space,
highlighting the differences between predicted and observed spectra. The Large
Early Galaxy Astrophysics Census (LEGA-C) provides high-quality optical spectra
of thousands of galaxies at redshift . Broad-band photometry of the
same galaxies, drawn from the recent COSMOS2020 catalog, is used to predict the
optical spectra with the spectral energy distribution (SED) fitting code
Prospector and the MILES stellar library. The observed and predicted spectra
are compared in terms of two age and metallicity-sensitive absorption features
(H and Fe4383). The global bimodality of star-forming and
quiescent galaxies in photometric space is recovered with the model spectra.
But the presence of a systematic offset in the Fe4383 line strength and the
weak correlation between the observed and modeled line strength imply that
accurate age or metallicity determinations cannot be inferred from photometry
alone. For now we caution that photometry-based estimates of stellar population
properties are determined mostly by the modeling approach and not the physical
properties of galaxies, even when using the highest-quality photometric
datasets and state-of-the-art fitting techniques. When exploring a new physical
parameter space (i.e. redshift or galaxy mass) high-quality spectroscopy is
always needed to inform the analysis of photometry.Comment: 13 pages, 8 figures, accepted 26 October 202
Management of epithelial precancerous conditions and lesions in the stomach (MAPS II): European Society of Gastrointestinal Endoscopy (ESGE), European Helicobacter and Microbiota Study Group (EHMSG), European Society of Pathology (ESP), and Sociedade Portuguesa de Endoscopia Digestiva (SPED) guideline update 2019
Patients with chronic atrophic gastritis or intestinal metaplasia (IM) are at risk for gastric adenocarcinoma. This underscores the importance of diagnosis and risk stratification for these patients. High definition endoscopy with chromoendoscopy (CE) is better than high definition white-light endoscopy alone for this purpose. Virtual CE can guide biopsies for staging atrophic and metaplastic changes and can target neoplastic lesions. Biopsies should be taken from at least two topographic sites (antrum and corpus) and labelled in two separate vials. For patients with mild to moderate atrophy restricted to the antrum there is no evidence to recommend surveillance. In patients with IM at a single location but with a family history of gastric cancer, incomplete IM, or persistent Helicobacter pylori gastritis, endoscopic surveillance with CE and guided biopsies may be considered in 3 years. Patients with advanced stages of atrophic gastritis should be followed up with a high quality endoscopy every 3 years. In patients with dysplasia, in the absence of an endoscopically defined lesion, immediate high quality endoscopic reassessment with CE is recommended. Patients with an endoscopically visible lesion harboring low or high grade dysplasia or carcinoma should undergo staging and treatment. H. pylori eradication heals nonatrophic chronic gastritis, may lead to regression of atrophic gastritis, and reduces the risk of gastric cancer in patients with these conditions, and it is recommended. H. pylori eradication is also recommended for patients with neoplasia after endoscopic therapy. In intermediate to high risk regions, identification and surveillance of patients with precancerous gastric conditions is cost-effective.info:eu-repo/semantics/publishedVersio
Asymmetric nuclear matter:the role of the isovector scalar channel
We try to single out some qualitative new effects of the coupling to the
-isovector-scalar meson introduced in a minimal way in a
phenomenological hadronic field theory. Results for the equation of state
() and the phase diagram of asymmetric nuclear matter () are
discussed. We stress the consistency of the -coupling introduction in a
relativistic approach. New contributions to the slope and curvature of the
symmetry energy and the neutron-proton effective mass splitting appear
particularly interesting. A more repulsive for neutron matter at high
baryon densities is expected. Effects on new critical properties of warm ,
mixing of mechanical and chemical instabilities and isospin distillation, are
also presented. The influence is mostly on the {\it isovectorlike}
collective response.
The results are largely analytical and this makes the physical meaning quite
transparent. Implications for nuclear structure properties of drip-line nuclei
and for reaction dynamics with Radioactive Beams are finally pointed out.Comment: 12 pages, 10 Postscript figure
A census of star formation histories of massive galaxies at 0.6 < z < 1 from spectro-photometric modeling using Bagpipes and Prospector
We present individual star-formation histories of massive galaxies
(log() > 10.5) from the Large Early Galaxy Astrophysics
Census (LEGA-C) spectroscopic survey at a lookback time of 7 billion
years and quantify the population trends leveraging 20hr-deep integrated
spectra of these 1800 star-forming and 1200 quiescent galaxies at
0.6 < < 1.0. Essentially all galaxies at this epoch contain stars of age <
3 Gyr, in contrast with older massive galaxies today, facilitating better
recovery of previous generations of star formation at cosmic noon and earlier.
We conduct spectro-photometric analysis using parametric and non-parametric
Bayesian SPS modeling tools - Bagpipes and Prospector to constrain the median
star-formation histories of this mass-complete sample and characterize
population trends. A consistent picture arises for the late-time stellar mass
growth when quantified as and , corresponding to the age of
the universe when galaxies formed 50\% and 90\% of their total stellar mass,
although the two sets of models disagree at the earliest formation times (e.g.
). Our results reveal trends in both stellar mass and stellar velocity
dispersion as in the local universe - low-mass galaxies with shallower
potential wells grow their stellar masses later in cosmic history compared to
high-mass galaxies. Unlike local quiescent galaxies, the median duration of
late-time star-formation ( = - ) does not
consistently depend on the stellar mass. This census sets a benchmark for
future deep spectro-photometric studies of the more distant universe.Comment: 25 pages, 12 figures, 4 tables, submitted to Ap
Leveraging 3D-HST Grism Redshifts to Quantify Photometric Redshift Performance
We present a study of photometric redshift accuracy in the 3D-HST photometric catalogs, using 3D-HST grism redshifts to quantify and dissect trends in redshift accuracy for galaxies brighter than JH IR > 24 with an unprecedented and representative high-redshift galaxy sample. We find an average scatter of 0.0197 ± 0.0003(1 + z) in the Skelton et al. photometric redshifts. Photometric redshift accuracy decreases with magnitude and redshift, but does not vary monotonically with color or stellar mass. The 1σ scatter lies between 0.01 and 0.03 (1 + z) for galaxies of all masses and colors below z JH IR 2), dusty star-forming galaxies for which the scatter increases to ~0.1 (1 + z). We find that photometric redshifts depend significantly on galaxy size; the largest galaxies at fixed magnitude have photo-zs with up to ~30% more scatter and ~5 times the outlier rate. Although the overall photometric redshift accuracy for quiescent galaxies is better than that for star-forming galaxies, scatter depends more strongly on magnitude and redshift than on galaxy type. We verify these trends using the redshift distributions of close pairs and extend the analysis to fainter objects, where photometric redshift errors further increase to ~0.046 (1 + z) at HF160W=26. We demonstrate that photometric redshift accuracy is strongly filter dependent and quantify the contribution of multiple filter combinations. We evaluate the widths of redshift probability distribution functions and find that error estimates are underestimated by a factor of ~1.1–1.6, but that uniformly broadening the distribution does not adequately account for fitting outliers. Finally, we suggest possible applications of these data in planning for current and future surveys and simulate photometric redshift performance in the Large Synoptic Survey Telescope, Dark Energy Survey (DES), and combined DES and Vista Hemisphere surveys
Stellar Half-Mass Radii of Galaxies: Comparison with JWST/NIRCam Half-Light Radii
We use CEERS JWST/NIRCam imaging to measure rest-frame near-IR light profiles
of 500 galaxies in the redshift range .
We compare the resulting rest-frame 1.5-2m half-light radii
() with stellar half-mass radii (\rmass) derived with multi-color
light profiles from CANDELS HST imaging. In general agreement with previous
work, we find that and \rmass~are up to 40\%~smaller than the
rest-frame optical half-light radius . The agreement between
and \rmass~is excellent, with negligible systematic offset
(0.03 dex) up to for quiescent galaxies and up to for
star-forming galaxies. We also deproject the profiles to estimate \rmassd, the
radius of a sphere containing 50\% of the stellar mass. We present the
distribution of galaxies at , comparing ,
\rmass~and \rmassd. The slope is significantly flatter for \rmass~and \rmassd~
compared to , mostly due to downward shifts in size for massive
star-forming galaxies, while \rmass~and \rmassd~do not show markedly different
trends. Finally, we show rapid size evolution ()
for massive () quiescent galaxies between and
, again comparing , \rmass~and \rmassd. We conclude that
the main tenets of the size evolution narrative established over the past 20
years, based on rest-frame optical light profile analysis, still hold in the
era of JWST/NIRCam observations in the rest-frame near-IR.Comment: Submitted to ApJ. Comments welcom
Comparison of some Reduced Representation Approximations
In the field of numerical approximation, specialists considering highly
complex problems have recently proposed various ways to simplify their
underlying problems. In this field, depending on the problem they were tackling
and the community that are at work, different approaches have been developed
with some success and have even gained some maturity, the applications can now
be applied to information analysis or for numerical simulation of PDE's. At
this point, a crossed analysis and effort for understanding the similarities
and the differences between these approaches that found their starting points
in different backgrounds is of interest. It is the purpose of this paper to
contribute to this effort by comparing some constructive reduced
representations of complex functions. We present here in full details the
Adaptive Cross Approximation (ACA) and the Empirical Interpolation Method (EIM)
together with other approaches that enter in the same category
The Structural Evolution of Milky-Way-Like Star-Forming Galaxies zeta is approximately 1.3
We follow the structural evolution of star-forming galaxies (SFGs) like the Milky Way by selecting progenitors to zeta is approx. 1.3 based on the stellar mass growth inferred from the evolution of the star-forming sequence. We select our sample from the 3D-HT survey, which utilizes spectroscopy from the HST-WFC3 G141 near-IR grism and enables precise redshift measurements for our sample of SFGs. Structural properties are obtained from Sersic profile fits to CANDELS WFC3 imaging. The progenitors of zeta = 0 SFGs with stellar mass M = 10(exp 10.5) solar mass are typically half as massive at zeta is approx. 1. This late-time stellar mass grow is consistent with recent studies that employ abundance matching techniques. The descendant SFGs at zeta is approx. 0 have grown in half-light radius by a factor of approx. 1.4 zeta is approx. 1. The half-light radius grows with stellar mass as r(sub e) alpha stellar mass(exp 0.29). While most of the stellar mass is clearly assembling at large radii, the mass surface density profiles reveal ongoing mass growth also in the central regions where bulges and pseudobulges are common features in present day late-type galaxies. Some portion of this growth in the central regions is due to star formation as recent observations of H() maps for SFGs at zeta approx. are found to be extended but centrally peaked. Connecting our lookback study with galactic archeology, we find the stellar mass surface density at R - 8 kkpc to have increased by a factor of approx. 2 since zeta is approx. 1, in good agreement with measurements derived for the solar neighborhood of the Milky Way
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