53 research outputs found
ZFOURGE: Using Composite Spectral Energy Distributions to Characterize Galaxy Populations at 1<z<4
We investigate the properties of galaxies as they shut off star formation
over the 4 billion years surrounding peak cosmic star formation. To do this we
categorize galaxies from into groups based on the shape
of their spectral energy distributions (SEDs) and build composite SEDs with
resolution. These composite SEDs show a variety of spectral shapes
and also show trends in parameters such as color, mass, star formation rate,
and emission line equivalent width. Using emission line equivalent widths and
strength of the 4000\AA\ break, , we categorize the composite SEDs
into five classes: extreme emission line, star-forming, transitioning,
post-starburst, and quiescent galaxies. The transitioning population of
galaxies show modest H emission (\AA) compared to
more typical star-forming composite SEDs at
(\AA). Together with their smaller sizes (3 kpc vs. 4 kpc)
and higher S\'ersic indices (2.7 vs. 1.5), this indicates that morphological
changes initiate before the cessation of star formation. The transitional group
shows a strong increase of over one dex in number density from to
, similar to the growth in the quiescent population, while
post-starburst galaxies become rarer at . We calculate average
quenching timescales of 1.6 Gyr at and 0.9 Gyr at and
conclude that a fast quenching mechanism producing post-starbursts dominated
the quenching of galaxies at early times, while a slower process has become
more common since .Comment: Accepted for publication in The Astrophysical Journa
Designing a Regional System of Social Indicators to Evaluate Nonpoint Source Water Projects
A collaborative team has developed a system to measure the social outcomes of nonpoint source
water projects as indicators of progress towards environmental goals. The system involves a set of core
indicators, additional supplemental indicators, and a process for collecting and using the indicators. This
process is supported by methodologies and instruments for data collection, analysis, and reporting that are
coordinated and supported through detailed written guidance and an on-line data management tool. Its
multi-state scope and application offer a unique opportunity to target, measure, and report interim resource
management accomplishments consistently at multiple levels
Evaluating Four Inosine-Uridine Preferring Nucleoside Hydrolases in Bacillus Anthracis for Decontamination Strategies
Andrew Roser is a doctoral student in the School of Biological Sciences at Louisiana Tech University.
Abigail Bass, Sophie Bott, Madison Brewton, Adam Broussard, Taylor Clement, Makenzie Cude, Hunter Currie, Claire Herke, Mary Hickman, Lauren James, Hailey Johnson, Madeline Lechtenberg, Sarah Murchison, Alex Plaisance, Wil Plants, Alex Sullivan, Sara Vandenberg, and Kaitlynn Willis are undergraduate students in the School of Biological Sciences at Louisiana Tech University.
Rebecca Giorno is an Associate Professor in the School of Biological Sciences at Louisiana Tech University
Tomographic galaxy clustering with the Subaru Hyper Suprime-Cam first year public data release
We analyze the clustering of galaxies in the first public data release of the
HSC Subaru Strategic Program. Despite the relatively small footprints of the
observed fields, the data are an excellent proxy for the deep photometric
datasets that will be acquired by LSST, and are therefore an ideal test bed for
the analysis methods being implemented by the LSST DESC. We select a magnitude
limited sample with and analyze it in four redshift bins covering
. We carry out a Fourier-space analysis of the
two-point clustering of this sample, including all auto- and
cross-correlations. We demonstrate the use of map-level deprojection methods to
account for fluctuations in the galaxy number density caused by observational
systematics. Through an HOD analysis, we place constraints on the
characteristic halo masses of this sample, finding a good fit up to scales
, including both auto- and cross-correlations.
Our results show monotonically decreasing average halo masses, which can be
interpreted in terms of the drop-out of red galaxies at high redshifts for a
flux-limited sample. In terms of photometric redshift systematics, we show that
additional care is needed in order to marginalize over uncertainties in the
redshift distribution in galaxy clustering, and that these uncertainties can be
constrained by including cross-correlations. We are able to make a
detection of lensing magnification in the HSC data. Our results
are stable to variations in and and we find constraints
that agree well with measurements from Planck and low-redshift probes. Finally,
we use our pipeline to study the clustering of galaxies as a function of
limiting flux, and provide a simple fitting function for the linear galaxy bias
for magnitude limited samples as a function of limiting magnitude and redshift.
[abridged]Comment: 65 pages, 30 figures, 5 tables, to be submitted to JCA
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
US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in
Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference
The Lyman Continuum Escape Fraction of Star-forming Galaxies at from UVCANDELS
The UltraViolet Imaging of the Cosmic Assembly Near-infrared Deep
Extragalactic Legacy Survey Fields (UVCANDELS) survey is a Hubble Space
Telescope (HST) Cycle-26 Treasury Program, allocated in total 164 orbits of
primary Wide-Field Camera 3 Ultraviolet and Visible light F275W imaging with
coordinated parallel Advanced Camera for Surveys F435W imaging, on four of the
five premier extragalactic survey fields: GOODS-N, GOODS-S, EGS, and COSMOS. We
introduce this survey by presenting a thorough search for galaxies at
that leak significant Lyman continuum (LyC) radiation, as well as
a stringent constraint on the LyC escape fraction () from stacking
the UV images of a population of star-forming galaxies with secure redshifts.
Our extensive search for LyC emission and stacking analysis benefit from the
catalogs of high-quality spectroscopic redshifts compiled from archival
ground-based data and HST slitless spectroscopy, carefully vetted by dedicated
visual inspection efforts. We report a sample of five galaxies as individual
LyC leaker candidates, showing estimated
using detailed Monte Carlo analysis of intergalactic medium attenuation. We
develop a robust stacking method to apply to five samples of in total 85
non-detection galaxies in the redshift range of . Most stacks
give tight 2- upper limits below . A stack
for a subset of 32 emission-line galaxies shows tentative LyC leakage detected
at 2.9-, indicating at ,
supporting the key role of such galaxies in contributing to the cosmic
reionization and maintaining the UV ionization background. These new F275W and
F435W imaging mosaics from UVCANDELS have been made publicly available on the
Barbara A. Mikulski Archive for Space Telescopes.Comment: 33 pages, 21 figures, and 5 tables. Resubmitted after addressing the
referee repor
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