165 research outputs found
NGDEEP Epoch 1: Spatially Resolved H Observations of Disk and Bulge Growth in Star-Forming Galaxies at 0.6-2.2 from JWST NIRISS Slitless Spectroscopy
We study the H equivalent width, EW(H), maps of 19 galaxies
at in the Hubble Ultra Deep Field (HUDF) derived from NIRISS
slitless spectroscopy as part of the Next Generation Deep Extragalactic
Exploratory Public (NGDEEP) Survey. Our galaxies mostly lie on the
star-formation main sequence with a stellar mass range of , and are therefore characteristic of "typical" star-forming
galaxies at these redshifts. Leveraging deep HST and JWST broad-band images,
spanning 0.4-4 m, we perform spatially-resolved fitting of the spectral
energy distributions (SEDs) for these galaxies and construct specific star
formation rate (sSFR) and stellar-mass-weighted age maps. We compare these to
the EW(H) maps with a spatial resolution of 1 kpc. The
pixel-to-pixel EW(H) increases with increasing sSFR and with decreasing
age, with the average trend slightly different from the relations derived from
integrated fluxes of galaxies from the literature. Quantifying the radial
profiles of EW(H), sSFR, and age, the majority (84%) of galaxies show
positive EW(H) gradients, positive sSFR gradients, and negative age
gradients, in line with the the inside-out quenching scenario. A few galaxies
(16%) show inverse (and flat) trends possibly due to merging or starbursts.
Comparing the distributions of EW(H) and sSFR to the star formation
history models as a function of galactocentric radius, the central region of
galaxies (e.g., their bulges) have experienced, at least one, rapid
star-formation episodes, which leads to the formation of bulge, while their
outer regions (e.g., disks) grow in a more steady-state. These results
demonstrate the ability to study resolved star formation in distant galaxies
with JWST NIRISS.Comment: 22 pages, 11 figure
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
The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years
We present a robust measurement and analysis of the rest-frame ultraviolet
(UV) luminosity function at z=4-8. We use deep Hubble Space Telescope imaging
over the CANDELS/GOODS fields, the Hubble Ultra Deep Field and the Year 1
Hubble Frontier Field deep parallel observations. These surveys provides an
effective volume of 0.6-1.2 x 10^6 Mpc^3 over this epoch, allowing us to
perform a robust search for faint (M_UV=-18) and bright (M_UV < -21) galaxies.
We select candidate galaxies using a well-tested photometric redshift technique
with careful screening of contaminants, finding a sample of 7446 galaxies at
3.51000 galaxies at z~6-8. We measure the luminosity function
using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At
the faint end our results agree with previous studies, yet we find a higher
abundance of UV-bright galaxies at z>6, with M* ~ -21 at z>5, different than
that inferred based on previous trends at lower redshift. At z=8, a single
power-law provides an equally good fit to the UV luminosity function, while at
z=6 and 7, an exponential cutoff at the bright-end is moderately preferred. We
compare to semi-analytical models, and find that the lack of evolution in M* is
consistent with models where the impact of dust attenuation on the bright-end
of the luminosity function decreases at higher redshift. We measure the
evolution of the cosmic star-formation rate density, correcting for dust
attenuation, and find that it declines as (1+z)^(-4.3 +/- 0.5) at z>4,
consistent with observations at z>9. Our observations are consistent with a
reionization history that starts at z>10, completes at z>6, and reaches a
midpoint (x_HII = 0.5) at 6.7<z<9.4. Finally, our observations predict that the
abundance of bright z=9 galaxies is likely higher than previous constraints,
though consistent with recent estimates of bright z~10 galaxies. [abridged]Comment: Re-submitted to the Astrophysical Journal after first referee's
report. 34 pages, 21 figures, 7 tables. The source file includes a machine
readable table of our full galaxy sampl
Optimized Photometric Redshifts for the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)
We present the first comprehensive release of photometric redshifts (photo- z's) from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) team. We use statistics based upon the Quantile-Quantile (Q-Q) plot to identify biases and signatures of underestimated or overestimated errors in photo- z probability density functions (PDFs) produced by six groups in the collaboration; correcting for these effects makes the resulting PDFs better match the statistical definition of a PDF. After correcting each groupâs PDF, we explore three methods of combining the different groupsâ PDFs for a given object into a consensus curve. Two of these methods are based on identifying the minimum f-divergence curve, i.e., the PDF that is closest in aggregate to the other PDFs in a set (analogous to the median of an array of numbers). We demonstrate that these techniques yield improved results using sets of spectroscopic redshifts independent of those used to optimize PDF modifications. The best photo- z PDFs and point estimates are achieved with the minimum f-divergence using the best four PDFs for each object (mFDa4) and the hierarchical Bayesian (HB4) methods, respectively. The HB4 photo- z point estimates produced Ï NMAD = 0.0227/0.0189 and âŁÎz/(1 + z)⣠> 0.15 outlier fraction = 0.067/0.019 for spectroscopic and 3D Hubble Space Telescope redshifts, respectively. Finally, we describe the structure and provide guidance for the use of the CANDELS photo- z catalogs, which are available at https://archive.stsci.edu/prepds/candels/.</p
Optimized Photometric Redshifts for the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS)
We present the first comprehensive release of photometric redshifts
(photo-z's) from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy
Survey (CANDELS) team. We use statistics based upon the Quantile-Quantile
(Q--Q) plot to identify biases and signatures of underestimated or
overestimated errors in photo-z probability density functions (PDFs) produced
by six groups in the collaboration; correcting for these effects makes the
resulting PDFs better match the statistical definition of a PDF. After
correcting each group's PDF, we explore three methods of combining the
different groups' PDFs for a given object into a consensus curve. Two of these
methods are based on identifying the minimum f-divergence curve, i.e., the PDF
that is closest in aggregate to the other PDFs in a set (analogous to the
median of an array of numbers). We demonstrate that these techniques yield
improved results using sets of spectroscopic redshifts independent of those
used to optimize PDF modifications. The best photo-z PDFs and point estimates
are achieved with the minimum f-divergence using the best 4 PDFs for each
object (mFDa4) and the Hierarchical Bayesian (HB4) methods, respectively. The
HB4 photo-z point estimates produced and
outlier fraction = 0.067/0.019 for spectroscopic and
3D-HST redshifts, respectively. Finally, we describe the structure and provide
guidance for the use of the CANDELS photo-z catalogs, which are available at
https://archive.stsci.edu/hlsp/candels.Comment: 35 pages, 19 figures, submitted to ApJ, data available at
https://archive.stsci.edu/hlsp/candel
A New Method to Search for High-redshift Clusters Using Photometric Redshifts
We describe a new method (Poisson probability method, PPM) to search for high-redshift galaxy clusters and groups by using photometric redshift information and galaxy number counts. The method relies on Poisson statistics and is primarily introduced to search for megaparsec-scale environments around a specific beacon. The PPM is tailored to both the properties of the FR I radio galaxies in the Chiaberge et al. sample, which are selected within the COSMOS survey, and to the specific data set used. We test the efficiency of our method of searching for cluster candidates against simulations. Two different approaches are adopted. (1) We use two z ~ 1 X-ray detected cluster candidates found in the COSMOS survey and we shift them to higher redshift up to z = 2. We find that the PPM detects the cluster candidates up to z = 1.5, and it correctly estimates both the redshift and size of the two clusters. (2) We simulate spherically symmetric clusters of different size and richness, and we locate them at different redshifts (i.e., z = 1.0, 1.5, and 2.0) in the COSMOS field. We find that the PPM detects the simulated clusters within the considered redshift range with a statistical 1\u3c3 redshift accuracy of ~0.05. The PPM is an efficient alternative method for high-redshift cluster searches that may also be applied to both present and future wide field surveys such as SDSS Stripe 82, LSST, and Euclid. Accurate photometric redshifts and a survey depth similar or better than that of COSMOS (e.g., I < 25) are required
Comparison of quality of life after stereotactic body radiotherapy and surgery for early-stage prostate cancer
Background: As the long-term efficacy of stereotactic body radiation therapy (SBRT) becomes established and other prostate cancer treatment approaches are refined and improved, examination of quality of life (QOL) following prostate cancer treatment is critical in driving both patient and clinical treatment decisions. We present the first study to compare QOL after SBRT and radical prostatectomy, with QOL assessed at approximately the same times pre- and post-treatment and using the same validated QOL instrument. Methods: Patients with clinically localized prostate cancer were treated with either radical prostatectomy (n = 123 Spanish patients) or SBRT (n = 216 American patients). QOL was assessed using the Expanded Prostate Cancer Index Composite (EPIC) grouped into urinary, sexual, and bowel domains. For comparison purposes, SBRT EPIC data at baseline, 3 weeks, 5, 11, 24, and 36 months were compared to surgery data at baseline, 1, 6, 12, 24,and 36 months. Differences in patient characteristics between the two groups were assessed using Chi-squared tests for categorical variables and t-tests for continuous variables. Generalized estimating equation (GEE) models were constructed for each EPIC scale to account for correlation among repeated measures and used to assess the effect of treatment on QOL. Results: The largest differences in QOL occurred in the first 1-6 months after treatment, with larger declines following surgery in urinary and sexual QOL as compared to SBRT, and a larger decline in bowel QOL following SBRT as compared to surgery. Long-term urinary and sexual QOL declines remained clinically significantly lower for surgery patients but not for SBRT patients. Conclusions: Overall, these results may have implications for patient and physician clinical decision making which are often influenced by QOL. These differences in sexual, urinary and bowel QOL should be closely considered in selecting the right treatment, especially in evaluating the value of non-invasive treatments, such as SBRT
Major merging history in CANDELS. I. Evolution of the incidence of massive galaxyâgalaxy pairs from z = 3 to z ⌠0
The rate of major galaxyâgalaxy merging is theoretically predicted to steadily increase with redshift during the peak epoch of massive galaxy development (1 †z †3). We use close-pair statistics to objectively study the incidence of massive galaxies (stellar M1 > 2 Ă 1010âMâ) hosting major companions (1 †M1/M2 †4; i.e. 4:1) companions at z > 1. We show that these evolutionary trends are statistically robust to changes in companion proximity. We find disagreements between published results are resolved when selection criteria are closely matched. If we compute merger rates using constant fraction-to-rate conversion factors (Cmerg,pair = 0.6 and Tobs,pair = 0.65âGyr), we find that MR rates disagree with theoretical predictions at z > 1.5. Instead, if we use an evolving Tobs,pair(z) â (1 + z)â2 from Snyder et al., our MR-based rates agree with theory at 0 < z < 3. Our analysis underscores the need for detailed calibration of Cmerg,pair and Tobs,pair as a function of redshift, mass, and companion selection criteria to better constrain the empirical major merger history
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