413 research outputs found
Evidence of very low metallicity and high ionization state in a strongly lensed, star-forming dwarf galaxy at z=3.417
We investigate the gas-phase metallicity and Lyman Continuum (LyC) escape
fraction of a strongly gravitationally lensed, extreme emission-line galaxy at
z=3.417, J1000+0221S, recently discovered by the CANDELS team. We derive
ionization and metallicity sensitive emission-line ratios from H+K band
LBT/LUCI medium resolution spectroscopy. J1000+0221S shows high ionization
conditions, as evidenced by its enhanced [OIII]/[OII] and [OIII]/Hbeta ratios.
Consistently, strong-line methods based on the available line ratios suggest
that J1000+0221S is an extremely metal-poor galaxy, with a metallicity of
12+log(O/H) < 7.44 (< 5% solar), placing it among the most metal-poor
star-forming galaxies at z > 3 discovered so far. In combination with its low
stellar mass (2x10^8 Msun) and high star formation rate (5 Msun/yr), the
metallicity of J1000+0221S is consistent with the extrapolation to low masses
of the mass-metallicity relation traced by Lyman-break galaxies at z > 3, but
it is 0.55 dex lower than predicted by the fundamental metallicity relation at
z < 2.5. These observations suggest the picture of a rapidly growing galaxy,
possibly fed by the massive accretion of pristine gas. Additionally, deep
LBT/LBC in the UGR bands are used to derive a limit to the LyC escape fraction,
thus allowing us to explore for the first time the regime of sub-L* galaxies at
z > 3. We find a 1sigma upper limit to the escape fraction of 23%, which adds a
new observational constraint to recent theoretical models predicting that
sub-L* galaxies at high-z have high escape fractions and thus are the
responsible for the reioization of the Universe.Comment: 5 pages, 3 figures and 1 table. Accepted for publication in ApJ
Letter
The Number Density Evolution of Extreme Emission Line Galaxies in 3D-HST: Results from a Novel Automated Line Search Technique for Slitless Spectroscopy
The multiplexing capability of slitless spectroscopy is a powerful asset in
creating large spectroscopic datasets, but issues such as spectral confusion
make the interpretation of the data challenging. Here we present a new method
to search for emission lines in the slitless spectroscopic data from the 3D-HST
survey utilizing the Wide-Field Camera 3 on board the Hubble Space Telescope.
Using a novel statistical technique, we can detect compact (extended) emission
lines at 90% completeness down to fluxes of 1.5 (3.0) times 10^{-17}
erg/s/cm^2, close to the noise level of the grism exposures, for objects
detected in the deep ancillary photometric data. Unlike previous methods, the
Bayesian nature allows for probabilistic line identifications, namely redshift
estimates, based on secondary emission line detections and/or photometric
redshift priors. As a first application, we measure the comoving number density
of Extreme Emission Line Galaxies (restframe [O III] 5007 equivalent widths in
excess of 500 Angstroms). We find that these galaxies are nearly 10 times more
common above z~1.5 than at z<0.5. With upcoming large grism surveys such as
Euclid and WFIRST as well as grisms featuring prominently on the NIRISS and
NIRCam instruments on James Webb Space Telescope, methods like the one
presented here will be crucial for constructing emission line redshift catalogs
in an automated and well-understood manner.Comment: 16 pages, 14 Figures; Accepted to Ap
Ages of massive galaxies at from 3D-HST rest-frame optical spectroscopy
We present low-resolution near-infrared stacked spectra from the 3D-HST
survey up to and fit them with commonly used stellar population
synthesis models: BC03 (Bruzual & Charlot, 2003), FSPS10 (Flexible Stellar
Population Synthesis, Conroy & Gunn 2010), and FSPS-C3K (Conroy, Kurucz,
Cargile, Castelli, in prep). The accuracy of the grism redshifts allows the
unambiguous detection of many emission and absorption features, and thus a
first systematic exploration of the rest-frame optical spectra of galaxies up
to . We select massive galaxies (), we
divide them into quiescent and star-forming via a rest-frame color-color
technique, and we median-stack the samples in 3 redshift bins between
and . We find that stellar population models fit the observations well
at wavelengths below rest-frame, but show systematic residuals
at redder wavelengths. The FSPS-C3K model generally provides the best fits
(evaluated with a statistics) for quiescent galaxies, while BC03
performs the best for star-forming galaxies. The stellar ages of quiescent
galaxies implied by the models, assuming solar metallicity, vary from 4 Gyr at
to 1.5 Gyr at , with an uncertainty of a factor of 2
caused by the unknown metallicity. On average the stellar ages are half the age
of the Universe at these redshifts. We show that the inferred evolution of ages
of quiescent galaxies is in agreement with fundamental plane measurements,
assuming an 8 Gyr age for local galaxies. For star-forming galaxies the
inferred ages depend strongly on the stellar population model and the shape of
the assumed star-formation history.Comment: 13 pages, 15 figures, accepted for publication in Ap
The MUSE-Wide Survey: A first catalogue of 831 emission line galaxies
We present a first instalment of the MUSE-Wide survey, covering an area of
22.2 arcmin (corresponding to 20% of the final survey) in the
CANDELS/Deep area of the Chandra Deep Field South. We use the MUSE integral
field spectrograph at the ESO VLT to conduct a full-area spectroscopic mapping
at a depth of 1h exposure time per 1 arcmin pointing. We searched for
compact emission line objects using our newly developed LSDCat software based
on a 3-D matched filtering approach, followed by interactive classification and
redshift measurement of the sources. Our catalogue contains 831 distinct
emission line galaxies with redshifts ranging from 0.04 to 6. Roughly one third
(237) of the emission line sources are Lyman emitting galaxies with , only four of which had previously measured spectroscopic redshifts.
At lower redshifts 351 galaxies are detected primarily by their [OII] emission
line (), 189 by their [OIII] line (), and 46 by their H line (). Comparing our spectroscopic redshifts to photometric redshift estimates
from the literature, we find excellent agreement for with a median
of only and an outlier rate of 6%, however a
significant systematic offset of and an outlier rate of 23%
for Ly emitters at . Together with the catalogue we also release
1D PSF-weighted extracted spectra and small 3D datacubes centred on each of the
831 sources.Comment: 24 pages, 14 figures, accepted for publication in A&A, data products
are available for download from http://muse-vlt.eu/science/muse-wide-survey/
and later via the CD
The MUSE-Wide Survey: Survey Description and First Data Release
We present the MUSE-Wide survey, a blind, 3D spectroscopic survey in the
CANDELS/GOODS-S and CANDELS/COSMOS regions. Each MUSE-Wide pointing has a depth
of 1 hour and hence targets more extreme and more luminous objects over 10
times the area of the MUSE-Deep fields (Bacon et al. 2017). The legacy value of
MUSE-Wide lies in providing "spectroscopy of everything" without photometric
pre-selection. We describe the data reduction, post-processing and PSF
characterization of the first 44 CANDELS/GOODS-S MUSE-Wide pointings released
with this publication. Using a 3D matched filtering approach we detected 1,602
emission line sources, including 479 Lyman- (Lya) emitting galaxies
with redshifts . We cross-match the emission line
sources to existing photometric catalogs, finding almost complete agreement in
redshifts and stellar masses for our low redshift (z < 1.5) emitters. At high
redshift, we only find ~55% matches to photometric catalogs. We encounter a
higher outlier rate and a systematic offset of z0.2 when
comparing our MUSE redshifts with photometric redshifts. Cross-matching the
emission line sources with X-ray catalogs from the Chandra Deep Field South, we
find 127 matches, including 10 objects with no prior spectroscopic
identification. Stacking X-ray images centered on our Lya emitters yielded no
signal; the Lya population is not dominated by even low luminosity AGN. A total
of 9,205 photometrically selected objects from the CANDELS survey lie in the
MUSE-Wide footprint, which we provide optimally extracted 1D spectra of. We are
able to determine the spectroscopic redshift of 98% of 772 photometrically
selected galaxies brighter than 24th F775W magnitude. All the data in the first
data release - datacubes, catalogs, extracted spectra, maps - are available on
the website https://musewide.aip.de. [abridged]Comment: 25 pages 15+1 figures. Accepted, A&A. Comments welcom
The Spatial Extent and Distribution of Star Formation in 3D-HST Mergers at z~1.5
We present an analysis of the spatial distribution of star formation in a
sample of 60 visually identified galaxy merger candidates at z>1. Our sample,
drawn from the 3D-HST survey, is flux-limited and was selected to have high
star formation rates based on fits of their broad-band, low spatial resolution
spectral energy distributions. It includes plausible pre-merger (close pairs)
and post-merger (single objects with tidal features) systems, with total
stellar masses and star formation rates derived from multi-wavelength
photometry. Here we use near-infrared slitless spectra from 3D-HST which
produce Halpha or [OIII] emission line maps as proxies for star-formation maps.
This provides a first comprehensive high-resolution, empirical picture of where
star formation occurred in galaxy mergers at the epoch of peak cosmic star
formation rate. We find that detectable star formation can occur in one or both
galaxy centres, or in tidal tails. The most common case (58%) is that star
formation is largely concentrated in a single, compact region, coincident with
the centre of (one of) the merger components. No correlations between star
formation morphology and redshift, total stellar mass, or star formation rate
are found. A restricted set of hydrodynamical merger simulations between
similarly massive and gas-rich objects implies that star formation should be
detectable in both merger components, when the gas fractions of the individual
components are the same. This suggests that z~1.5 mergers typically occur
between galaxies whose gas fractions, masses, and/or star formation rates are
distinctly different from one another.Comment: Accepted for publication in MNRAS, 16 pages, 10 figure
Prevalence of and Risk Factors for Biliary Carriage of Bacteria Showing Worrisome and Unexpected Resistance Traits
Data on biliary carriage of bacteria and, specifically, of bacteria with worrisome and unexpected resistance traits (URB) are lacking.
A prospective study (April 2010 to December 2011) was performed that included all patients admitted for<48 h for elective
laparoscopic cholecystectomy in a Spanish hospital. Bile samples were cultured and epidemiological/clinical data recorded. Logistic
regression models (stepwise) were performed using bactobilia or bactobilia by URB as dependent variables. Models (P<
0.001) showing the highest R2 values were considered. A total of 198 patients (40.4% males; age, 55.3 17.3 years) were included.
Bactobilia was found in 44 of them (22.2%). The presence of bactobilia was associated (R2 Cox, 0.30) with previous biliary endoscopic
retrograde cholangiopancreatography (ERCP) (odds ratio [OR], 8.95; 95% confidence interval [CI], 2.96 to 27.06; P<
0.001), previous admission (OR, 2.82; 95% CI, 1.10 to 7.24; P 0.031), and age (OR, 1.09 per year; 95% CI, 1.05 to 1.12; P<
0.001). Ten out of the 44 (22.7%) patients with bactobilia carried URB: 1 Escherichia coli isolate (CTX-M), 1 Klebsiella pneumoniae
isolate (OXA-48), 3 high-level gentamicin-resistant enterococci, 1 vancomycin-resistant Enterococcus isolate, 3 Enterobacter
cloacae strains, and 1 imipenem-resistant Pseudomonas aeruginosa strain. Bactobilia by URB (versus those by non-URB)
was only associated (R2 Cox, 0.19) with previous ERCP (OR, 11.11; 95% CI, 1.98 to 62.47; P 0.006). For analyses of patients
with bactobilia by URB versus the remaining patients, previous ERCP (OR, 35.284; 95% CI, 5.320 to 234.016; P<0.001), previous
intake of antibiotics (OR, 7.200; 95% CI, 0.962 to 53.906; P 0.050), and age (OR, 1.113 per year of age; 95% CI, 1.028 to
1.206; P 0.009) were associated with bactobilia by URB (R2 Cox, 0.19; P<0.001). Previous antibiotic exposure (in addition to
age and previous ERCP) was a risk driver for bactobilia by URB. This may have implications in prophylactic/therapeutic
measures
Stars, gas, and star formation of distant post-starburst galaxies
We present a comprehensive multi-wavelength study of 5 poststarburst galaxies
with at , examining their stars, gas, and
current and past star-formation activities. Using optical images from the
Subaru telescope and Hubble Space Telescope, we observe a high incidence of
companion galaxies and low surface brightness tidal features, indicating that
quenching is closely related to interactions between galaxies. From optical
spectra provided by the LEGA-C survey, we model the stellar continuum to derive
the star-formation histories and show that the stellar masses of progenitors
ranging from to , undergoing a burst of
star formation several hundred million years prior to observation, with a decay
time scale of million years. Our ALMA observations detect CO(2-1)
emission in four galaxies, with the molecular gas spreading over up to ,
or kpc, with a mass of up to . However,
star-forming regions are unresolved by either the slit spectra or 3~GHz
continuum observed by the Very Large Array. Comparisons between the
star-formation rates and gas masses, and the sizes of CO emission and
star-forming regions suggest a low star-forming efficiency. We show that the
star-formation rates derived from IR and radio luminosities with commonly-used
calibrations tend to overestimate the true values because of the prodigious
amount of radiation from old stars and the contribution from AGN, as the
optical spectra reveal weak AGN-driven outflows.Comment: Accepted by Ap
The Surgical Infection Society revised guidelines on the management of intra-abdominal infection
Background: Previous evidence-based guidelines on the management of intra-abdominal infection (IAI) were published by the Surgical Infection Society (SIS) in 1992, 2002, and 2010. At the time the most recent guideline was released, the plan was to update the guideline every five years to ensure the timeliness and appropriateness of the recommendations.
Methods: Based on the previous guidelines, the task force outlined a number of topics related to the treatment of patients with IAI and then developed key questions on these various topics. All questions were approached using general and specific literature searches, focusing on articles and other information published since 2008. These publications and additional materials published before 2008 were reviewed by the task force as a whole or by individual subgroups as to relevance to individual questions. Recommendations were developed by a process of iterative consensus, with all task force members voting to accept or reject each recommendation. Grading was based on the GRADE (Grades of Recommendation Assessment, Development, and Evaluation) system; the quality of the evidence was graded as high, moderate, or weak, and the strength of the recommendation was graded as strong or weak. Review of the document was performed by members of the SIS who were not on the task force. After responses were made to all critiques, the document was approved as an official guideline of the SIS by the Executive Council.
Results: This guideline summarizes the current recommendations developed by the task force on the treatment of patients who have IAI. Evidence-based recommendations have been made regarding risk assessment in individual patients; source control; the timing, selection, and duration of antimicrobial therapy; and suggested approaches to patients who fail initial therapy. Additional recommendations related to the treatment of pediatric patients with IAI have been included.
Summary: The current recommendations of the SIS regarding the treatment of patients with IAI are provided in this guideline
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