1,342 research outputs found
The Grism Lens-Amplified Survey from Space (GLASS). XII. Spatially Resolved Galaxy Star Formation Histories and True Evolutionary Paths at z > 1
Modern data empower observers to describe galaxies as the spatially and
biographically complex objects they are. We illustrate this through case
studies of four, systems based on deep, spatially resolved, 17-band
+ G102 + G141 Hubble Space Telescope grism spectrophotometry. Using full
spectrum rest-UV/-optical continuum fitting, we characterize these galaxies'
observed kpc-scale structures and star formation rates (SFRs) and
reconstruct their history over the age of the universe. The sample's
diversity---passive to vigorously starforming; stellar masses to ---enables us to draw spatio-temporal inferences
relevant to key areas of parameter space (Milky Way- to super-Andromeda-mass
progenitors). Specifically, we find signs that bulge mass-fractions () and
SF history shapes/spatial uniformity are linked, such that higher s
correlate with "inside-out growth" and central specific SFRs that peaked above
the global average for all starforming galaxies at that epoch. Conversely, the
system with the lowest had a flat, spatially uniform SFH with normal peak
activity. Both findings are consistent with models positing a feedback-driven
connection between bulge formation and the switch from rising to falling SFRs
("quenching"). While sample size forces this conclusion to remain tentative,
this work provides a proof-of-concept for future efforts to refine or refute
it: JWST, WFIRST, and the 30-m class telescopes will routinely produce data
amenable to this and more sophisticated analyses. These samples---spanning
representative mass, redshift, SFR, and environmental regimes---will be ripe
for converting into thousands of sub-galactic-scale empirical windows on what
individual systems actually looked like in the past, ushering in a new dialog
between observation and theory.Comment: 18 pp, 15 figs, 3 tables (main text); 5 pp, 5 figs, 1 table
(appendix); Submitted to AAS Journals 1 October 201
CaracterĆsticas morfolĆ³gicas e citogenĆ©ticas na avaliaĆ§Ć£o da uniformidade genĆ©tica de cultivares brasileiras de trigo.
Monosomic analysis of adult-plant resistance to leaf rust in the Brazilian wheat cultivar 'Toropi'.
Through the looking GLASS: HST spectroscopy of faint galaxies lensed by the Frontier Fields cluster MACS0717.5+3745
The Grism Lens-Amplified Survey from Space (GLASS) is a Hubble Space
Telescope (HST) Large Program, which will obtain 140 orbits of grism
spectroscopy of the core and infall regions of 10 galaxy clusters, selected to
be among the very best cosmic telescopes. Extensive HST imaging is available
from many sources including the CLASH and Frontier Fields programs. We
introduce the survey by analyzing spectra of faint multiply-imaged galaxies and
galaxy candidates obtained from the first seven orbits out of
fourteen targeting the core of the Frontier Fields cluster MACS0717.5+3745.
Using the G102 and G141 grisms to cover the wavelength range 0.8-1.7m, we
confirm 4 strongly lensed systems by detecting emission lines in each of the
images. For the 9 galaxy candidates clear from contamination, we do
not detect any emission lines down to a seven-orbit 1 noise level of
510erg scm. Taking lensing magnification
into account, our flux sensitivity reaches 0.2-510erg
scm. These limits over an uninterrupted wavelength range rule out
the possibility that the high- galaxy candidates are instead strong line
emitters at lower redshift. These results show that by means of careful
modeling of the background - and with the assistance of lensing magnification -
interesting flux limits can be reached for large numbers of objects, avoiding
pre-selection and the wavelength restrictions inherent to ground-based
multi-slit spectroscopy. These observations confirm the power of slitless HST
spectroscopy even in fields as crowded as a cluster core.Comment: Accepted by ApJ letters, 8 pages, 4 figures, GLASS website at
http://glass.physics.ucsb.ed
The Grism Lens-Amplified Survey from Space (GLASS). I. Survey overview and first data release
We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a
large Hubble Space Telescope program aimed at obtaining grism spectroscopy of
the fields of ten massive clusters of galaxies at redshift z=0.308-0.686,
including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 yields near
infrared spectra of the cluster cores, covering the wavelength range
0.81-1.69mum through grisms G102 and G141, while the Advanced Camera for
Surveys in parallel mode provides G800L spectra of the infall regions of the
clusters. The WFC3 spectra are taken at two almost orthogonal position angles
in order to minimize the effects of confusion. After summarizing the scientific
drivers of GLASS, we describe the sample selection as well as the observing
strategy and data processing pipeline. We then utilize MACSJ0717.5+3745, a HFF
cluster and the first one observed by GLASS, to illustrate the data quality and
the high-level data products. Each spectrum brighter than H_AB=23 is visually
inspected by at least two co-authors and a redshift is measured when sufficient
information is present in the spectra. Furthermore, we conducted a thorough
search for emission lines through all the GLASS WFC3 spectra with the aim of
measuring redshifts for sources with continuum fainter than H_AB=23. We provide
a catalog of 139 emission-line based spectroscopic redshifts for extragalactic
sources, including three new redshifts of multiple image systems (one probable,
two tentative). In addition to the data itself we also release software tools
that are helpful to navigate the data.Comment: ApJ in press. GLASS data available at
https://archive.stsci.edu/prepds/glass/ . More info on GLASS available at
http://glass.physics.ucsb.edu
JWST/NIRSpec Measurements of the Relationships Between Nebular Emission-line Ratios and Stellar Mass at z~3-6
We analyze the rest-optical emission-line ratios of star-forming galaxies at
2.7<=z<6.5 drawn from the Cosmic Evolution Early Release Science (CEERS)
Survey, and their relationships with stellar mass (M_*). Our analysis includes
both line ratios based on the [NII]6583 feature -- [NII]6583/Ha,
([OIII]5007/Hb)/([NII]6583/Ha) (O3N2), and [NII]6583/[OII]3727 -- and those
those featuring alpha elements -- [OIII]5007/Hb, [OIII]5007/[OII]3727 (O_32),
([OIII]4959,5007+[OII]3727)/Hb (R_23), and [NeIII]3869/[OII]3727. Given the
typical flux levels of [NII]6583 and [NeIII]3869, which are undetected in the
majority of individual CEERS galaxies at 2.7<=z<6.5, we construct composite
spectra in bins of M_* and redshift. Using these composite spectra, we compare
the relationships between emission-line ratios and M_* at 2.7<=z<6.5 with those
observed at lower redshift. While there is significant evolution towards higher
excitation (e.g., higher [OIII]5007/Hb, O_32, O3N2), and weaker nitrogen
emission (e.g., lower [NII]6583/Ha and [NII]6583/[OII]3727) between z~0 and
z~3, we find in most cases that there is no significant evolution in the
relationship between line ratio and M_* beyond z~3. The [NeIII]3869/[OII]3727
ratio is anomalous in showing evidence for significant elevation at 4.0<=z<6.5
at fixed mass, relative to z~3.3. Collectively, however, our empirical results
suggest that there is no significant evolution in the mass-metallicity
relationship at 2.7<=z<6.5. Representative galaxy samples and metallicity
calibrations based on existing and upcoming JWST/NIRSpec observations will be
required to translate these empirical scaling relations into ones tracing
chemical enrichment and gas cycling, and distinguish among the descriptions of
star-formation feedback in simulations of galaxy formation at z>3.Comment: 10 pages, 4 figures, ApJL, in pres
JWST/NIRSpec Balmer-line Measurements of Star Formation and Dust Attenuation at z~3-6
We present an analysis of the star-formation rates (SFRs) and dust
attenuation properties of star-forming galaxies at drawn from
the Cosmic Evolution Early Release Science (CEERS) Survey. Our analysis is
based on {\it JWST}/NIRSpec Micro-Shutter Assembly (MSA)
spectroscopic observations covering approximately m. Our primary
rest-frame optical spectroscopic measurements are H/H Balmer
decrements, which we use as an indicator of nebular dust attenuation. In turn,
we use Balmer decrements to obtain dust-corrected H-based SFRs (i.e.,
SFR(H)). We construct the relationship between SFR(H) and
stellar mass () in three bins of redshift (, , and ), which represents the first time the star-forming
main sequence has been traced at these redshifts using direct spectroscopic
measurements of Balmer emission as a proxy for SFR. In tracing the relationship
between SFR(H) and back to such early times (), it is
essential to use a conversion factor between H and SFR that accounts
for the subsolar metallicity prevalent among distant galaxies. We also use
measured Balmer decrements to investigate the relationship between dust
attenuation and stellar mass out to . The lack of significant redshift
evolution in attenuation at fixed stellar mass, previously confirmed using
Balmer decrements out to , appears to hold out to . Given
the rapidly evolving gas, dust, and metal content of star-forming galaxies at
fixed mass, this lack of significant evolution in attenuation provides an
ongoing challenge to explain.Comment: 9 pages, 4 figures, ApJ, in pres
HibridizaĆ§Ć£o genĆ“mica in situ em triticeae: um enfoque metodolĆ³gico.
bitstream/CNPT-2010/40760/1/p-co270.pd
Neural correlates of visuospatial working memory in the āat-risk mental stateā
Background. Impaired spatial working memory (SWM) is a robust feature of schizophrenia and has been linked to
the risk of developing psychosis in people with an at-risk mental state (ARMS). We used functional magnetic
resonance imaging (fMRI) to examine the neural substrate of SWM in the ARMS and in patients who had just
developed schizophrenia.
Method. fMRI was used to study 17 patients with an ARMS, 10 patients with a first episode of psychosis and 15 agematched
healthy comparison subjects. The blood oxygen level-dependent (BOLD) response was measured while
subjects performed an objectālocation paired-associate memory task, with experimental manipulation of mnemonic
load.
Results. In all groups, increasing mnemonic load was associated with activation in the medial frontal and medial
posterior parietal cortex. Significant between-group differences in activation were evident in a cluster spanning the
medial frontal cortex and right precuneus, with the ARMS groups showing less activation than controls but greater
activation than first-episode psychosis (FEP) patients. These group differences were more evident at the most
demanding levels of the task than at the easy level. In all groups, task performance improved with repetition of the
conditions. However, there was a significant group difference in the response of the right precuneus across repeated
trials, with an attenuation of activation in controls but increased activation in FEP and little change in the ARMS.
Conclusions. Abnormal neural activity in the medial frontal cortex and posterior parietal cortex during an SWM task
may be a neural correlate of increased vulnerability to psychosis
SN Refsdal: Classification as a Luminous and Blue SN 1987A-like Type II Supernova
We have acquired Hubble Space Telescope (HST) and Very Large Telescope
near-infrared spectra and images of supernova (SN) Refsdal after its discovery
as an Einstein cross in Fall 2014. The HST light curve of SN Refsdal matches
the distinctive, slowly rising light curves of SN 1987A-like supernovae (SNe),
and we find strong evidence for a broad H-alpha P-Cygni profile in the HST
grism spectrum at the redshift (z = 1.49) of the spiral host galaxy. SNe IIn,
powered by circumstellar interaction, could provide a good match to the light
curve of SN Refsdal, but the spectrum of a SN IIn would not show broad and
strong H-alpha absorption. From the grism spectrum, we measure an H-alpha
expansion velocity consistent with those of SN 1987A-like SNe at a similar
phase. The luminosity, evolution, and Gaussian profile of the H-alpha emission
of the WFC3 and X-shooter spectra, separated by ~2.5 months in the rest frame,
provide additional evidence that supports the SN 1987A-like classification. In
comparison with other examples of SN 1987A-like SNe, SN Refsdal has a blue B-V
color and a high luminosity for the assumed range of potential magnifications.
If SN Refsdal can be modeled as a scaled version of SN 1987A, we estimate it
would have an ejecta mass of 20+-5 solar masses. The evolution of the light
curve at late times will provide additional evidence about the potential
existence of any substantial circumstellar material (CSM). Using MOSFIRE and
X-shooter spectra, we estimate a subsolar host-galaxy metallicity (8.3+-0.1 dex
and <8.4 dex, respectively) near the explosion site.Comment: Submitted to ApJ; 26 page
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