1,153 research outputs found
Temperature and Metallicity Gradients in the Hot Gas Outflows of M82
We utilize deep Chandra X-ray Observatory imaging and spectra of M82, the
prototype of a starbursting galaxy with a multiphase wind, to map the hot
plasma properties along the minor axis of the galaxy. We extract spectra from
11 regions up to 2.5 kpc from the starbursting midplane and model the data as a
multi-temperature, optically thin thermal plasma with contributions from a
non-thermal (power-law) component and from charge exchange (CX). We examine the
gradients in best-fit parameters, including the intrinsic column density,
plasma temperature, metal abundances, and number density of the hot gas as a
function of distance from the M82 nucleus. We find that the temperatures and
number densities of the warm-hot and hot plasma peak at the starbursting ridge
and decreases along the minor axis. The temperature and density profiles are
inconsistent with spherical adiabatic expansion of a super-heated wind and
suggest mass loading and mixing of the hot phase with colder material.
Non-thermal emission is detected in all of the regions considered, and CX
comprises 8-25% of the total absorption-corrected, broad-band (0.5-7 keV) X-ray
flux. We show that the abundances of O, Ne, Mg, and Fe are roughly constant
across the regions considered, while Si and S peak within 500 pc of the central
starburst. These findings support a direct connection between the M82 superwind
and the warm-hot, metal-rich circumgalactic medium (CGM).Comment: 15 pages, 8 figures, ApJ in pres
Evolution of Stellar Feedback in HII Regions
Stellar feedback is needed to produce realistic giant molecular clouds (GMCs)
and galaxies in simulations, but due to limited numerical resolution, feedback
must be implemented using subgrid models. Observational work is an important
means to test and anchor these models, but limited studies have assessed the
relative dynamical role of multiple feedback modes, particularly at the
earliest stages of expansion when HII regions are still deeply embedded. In
this paper, we use multiwavelength (radio, infrared, and X-ray) data to measure
the pressures associated with direct radiation (), dust-processed
radiation (), photoionization heating (), and
shock-heating from stellar winds () in a sample of 106 young,
resolved HII regions with radii 0.5 pc to determine how stellar
feedback drives their expansion. We find that the dominates in 84%
of the regions and that the median and are smaller
than the median by factors of and ,
respectively. Based on the radial dependences of the pressure terms, we show
that HII regions transition from -dominated to -dominated at radii of 3 pc. We find a median trapping factor of
8 without any radial dependence for the sample, suggesting
this value can be adopted in sub-grid feedback models. Moreover, we show that
the total pressure is greater than the gravitational pressure in the majority
of our sample, indicating that the feedback is sufficient to expel gas from the
regions.Comment: 13 pages, 8 figures, ApJ, in pres
CLEAR: High-Ionization [Ne V] 3426 Emission-line Galaxies at
We analyze a sample of 25 [Ne V] 3426 emission-line galaxies at
using Hubble Space Telescope/Wide Field Camera 3 G102 and G141
grism observations from the CANDELS Lyman- Emission at Reionization
(CLEAR) survey. [Ne V] emission probes extremely energetic photoionization
(97.11-126.21 eV), and is often attributed to energetic radiation from active
galactic nuclei (AGN), shocks from supernova, or an otherwise very hard
ionizing spectrum from the stellar continuum. In this work, we use [Ne V] in
conjunction with other rest-frame UV/optical emission lines ([O II]
3726,3729, [Ne III] 3869, H, [O III]
4959,5007, H+[N II] 6548,6583, [S II]
6716,6731), deep (2--7 Ms) X-ray observations (from Chandra),
and mid-infrared imaging (from Spitzer) to study the origin of this emission
and to place constraints on the nature of the ionizing engine. The majority of
the [Ne V]-detected galaxies have properties consistent with ionization from
AGN. However, for our [Ne V]-selected sample, the X-ray luminosities are
consistent with local () X-ray-selected Seyferts, but the [Ne V]
luminosities are more consistent with those from X-ray-selected QSOs.
The excess [Ne V] emission requires either reduced hard X-rays, or a 0.1
keV excess. We discuss possible origins of the apparent [Ne V] excess, which
could be related to the ``soft (X-ray) excess'' observed in some QSOs and
Seyferts, and/or be a consequence of a complex/anisotropic geometry for the
narrow line region, combined with absorption from a warm, relativistic wind
ejected from the accretion disk. We also consider implications for future
studies of extreme high-ionization systems in the epoch of reionization () with JWST.Comment: 17 pages + 5 (appendix), 7 figures + 2(appendix
Using [Ne V]/[Ne III] to Understand the Nature of Extreme-Ionization Galaxies
Spectroscopic studies of extreme-ionization galaxies (EIGs) are critical to
our understanding of exotic systems throughout cosmic time. These EIGs exhibit
spectral features requiring >54.42 eV photons: the energy needed to fully
ionize helium into He2+ and emit He II recombination lines. They are likely key
contributors to reionization, and they can also probe exotic stellar
populations or accretion onto massive black holes. To facilitate the use of
EIGs as probes of high ionization, we focus on ratios constructed from strong
rest-frame UV/optical emission lines, specifically [O III] 5008, H-beta, [Ne
III] 3870, [O II] 3727,3729, and [Ne V] 3427. These lines probe the relative
intensity at energies of 35.12, 13.62, 40.96, 13.62 eV, and 97.12,
respectively, covering a wider range of ionization than traced by other common
rest-frame UV/optical techniques. We use ratios of these lines ([Ne V]/[Ne III]
= Ne53 and [Ne III]/[O II]), which are closely separated in wavelength, and
mitigates effects of dust attenuation and uncertainties in flux calibration. We
make predictions from photoionization models constructed from Cloudy that use a
broad range of stellar populations and black hole accretion models to explore
the sensitivity of these line ratios to changes in the ionizing spectrum. We
compare our models to observations from the Hubble Space Telescope and James
Webb Space Telescope of galaxies with strong high-ionization emission lines at
z ~ 0, z ~ 2, and z ~ 7. We show that the Ne53 ratio can separate galaxies with
ionization from 'normal' stellar populations from those with AGN and even
'exotic' Population III models. We introduce new selection methods to identify
galaxies with photoionization driven by Population III stars or
intermediate-mass black hole accretion disks that could be identified in
upcoming high-redshift spectroscopic surveys.Comment: 16 pages, 5 figures, 1 table. Accepted in Ap
The Transition between Telomerase and ALT Mechanisms in Hodgkin Lymphoma and Its Predictive Value in Clinical Outcomes
International audienceBackground: We analyzed telomere maintenance mechanisms (TMMs) in lymph node samples from HL patients treated with standard therapy. The TMMs correlated with clinical outcomes of patients. Materials and Methods: Lymph node biopsies obtained from 38 HL patients and 24 patients with lymphadenitis were included in this study. Seven HL cell lines were used as in vitro models. Telomerase activity (TA) was assessed by TRAP assay and verified through hTERT immunofluorescence expression; alternative telomere lengthening (ALT) was also assessed, along with EBV status. Results: Both TA and ALT mechanisms were present in HL lymph nodes. Our findings were reproduced in HL cell lines. The highest levels of TA were expressed in CD30−/CD15− cells. Small cells were identified with ALT and TA. Hodgkin and Reed Sternberg cells contained high levels of PML bodies, but had very low hTERT expression. There was a significant correlation between overall survival (p < 10−3), event-free survival (p < 10−4), and freedom from progression (p < 10−3) and the presence of an ALT profile in lymph nodes of EBV+ patients. Conclusion: The presence of both types of TMMs in HL lymph nodes and in HL cell lines has not previously been reported. TMMs correlate with the treatment outcome of EBV+ HL patients
Defining nosocomial transmission of Escherichia coli and antimicrobial resistance genes: a genomic surveillance study.
BACKGROUND: Escherichia coli is a leading cause of bloodstream infections. Developing interventions to reduce E coli infections requires an understanding of the frequency of nosocomial transmission, but the available evidence is scarce. We aimed to detect and characterise transmission of E coli and associated plasmids in a hospital setting. METHODS: In this prospective observational cohort study, patients were admitted to two adult haematology wards at the Cambridge University Hospitals NHS Foundation Trust in England. Patients aged 16 years and older who were treated for haematological malignancies were included. Stool samples were collected from study participants on admission, once per week, and at discharge. We sequenced multiple E coli isolates (both extended spectrum β-lactamase [ESBL]-producing and non-ESBL-producing) from each stool sample. A genetic threshold to infer E coli transmission was defined by maximum within-host single nucleotide polymorphism (SNP) diversity and the probability of drawing observed pairs of between-patient isolates at different SNP thresholds. Putative transmission clusters were identified when sequences were less than the genetic threshold. Epidemiological links for each transmission event were investigated. We sequenced all E coli positive blood samples from the two adult haematology wards. FINDINGS: We recruited 174 (51%) of 338 adult patients admitted to the wards between May 13 and Nov 13, 2015. We obtained and cultured 376 stool samples from 149 patients, of which 152 samples from 97 (65%) patients grew E coli. Whole-genome sequencing was done on 970 isolates. We identified extensive diversity in the bacterial population (90 sequence types) and mixed E coli sequence type carriage. 24 (26%) patients carried two sequence types, 12 (13%) carried three, and six (6%) patients carried four or more sequence types. Using a 17 SNP cutoff we identified ten clusters in 20 patients. The largest cluster contained seven patients, whereas four patients were included in multiple clusters. Strong epidemiological links were found between patients in seven clusters. 17 (11%) of 149 patients had stool samples positive for ESBL-producing E coli, the most common of which was associated with bla CTX-M-15 (12 [71%] of 17). Long-read sequencing revealed that bla CTX-M-15 was often integrated into the chromosome, with little evidence for plasmid transmission. Seven patients developed E coli bloodstream infection, four with identical strains to those in their stool; two of these had documented nosocomial acquisition. INTERPRETATION: We provide evidence of bacterial transmission and endogenous infection during routine care by integrating genomic and epidemiological data and by determining a genetic cutoff informed by within-host diversity in the studied population. Our findings challenge single colony-based investigations, and the widely accepted notion of plasmid spread. FUNDING: UK Department of Health, Wellcome Trust, UK National Institute for Health Research
JWST's TEMPLATES for Star Formation: The First Resolved Gas-Phase Metallicity Maps of Dust-Obscured Star-Forming Galaxies at 4
We present the first spatially resolved maps of gas-phase metallicity for
dust-obscured star-forming galaxies (DSFGs) at 4, from the JWST
TEMPLATES Early Release Science program, derived from NIRSpec integral field
unit spectroscopy of the H and [NII] emission lines. Empirically
derived literature optical line calibrations are used to determine that the
sources are highly metal rich, with both appearing to display regions of
supersolar metallicity, particularly in SPT2147-50. While we cannot rule out
shocks or AGN in these regions, we suggest that the two systems have already
undergone significant enrichment as a result of their extremely high
star-formation rates. Utilising ALMA rest-frame 380m continuum and
[CI](P-P) line maps we compare metallicity and gas-to-dust
ratio variations in the two galaxies, finding the two to be anticorrelated on
highly resolved spatial scales, consistent with various literature studies of
0 galaxies. The data are indicative of the enormous potential of
JWST to probe the enrichment of the interstellar medium on kpc scales in
extremely dust-obscured systems at 4 and beyond.Comment: 12 pages, 5 figures, submitted to Ap
JWST's TEMPLATES for Star Formation: The First Resolved Gas-phase Metallicity Maps of Dust-obscured Star-forming Galaxies at z ∼ 4
We present the first spatially resolved maps of gas-phase metallicity for two dust-obscured star-forming galaxies at z ∼ 4, from the JWST TEMPLATES Early Release Science program, derived from NIRSpec integral field unit spectroscopy of the Hα and [N ii] emission lines. Empirical optical line calibrations are used to determine that the sources are globally enriched to near-solar levels. While one source shows elevated [N ii]/Hα ratios and broad Hα emission consistent with the presence of an active galactic nucleus in a ≳1 kpc region, we argue that both systems have already undergone significant metal enrichment as a result of their extremely high star formation rates. Utilizing Atacama Large Millimeter/submillimeter Array rest-frame 380 μm continuum and [Ci](3P2–3P1) line maps we compare the spatial variation of the metallicity and gas-to-dust ratio in the two galaxies, finding the two properties to be anticorrelated on highly resolved spatial scales, consistent with various literature studies of z ∼ 0 galaxies. The data are indicative of the enormous potential of JWST to probe the enrichment of the interstellar medium on ∼kpc scales in extremely dust-obscured systems at z ∼ 4 and beyond
LSST Science Book, Version 2.0
A survey that can cover the sky in optical bands over wide fields to faint
magnitudes with a fast cadence will enable many of the exciting science
opportunities of the next decade. The Large Synoptic Survey Telescope (LSST)
will have an effective aperture of 6.7 meters and an imaging camera with field
of view of 9.6 deg^2, and will be devoted to a ten-year imaging survey over
20,000 deg^2 south of +15 deg. Each pointing will be imaged 2000 times with
fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a
total point-source depth of r~27.5. The LSST Science Book describes the basic
parameters of the LSST hardware, software, and observing plans. The book
discusses educational and outreach opportunities, then goes on to describe a
broad range of science that LSST will revolutionize: mapping the inner and
outer Solar System, stellar populations in the Milky Way and nearby galaxies,
the structure of the Milky Way disk and halo and other objects in the Local
Volume, transient and variable objects both at low and high redshift, and the
properties of normal and active galaxies at low and high redshift. It then
turns to far-field cosmological topics, exploring properties of supernovae to
z~1, strong and weak lensing, the large-scale distribution of galaxies and
baryon oscillations, and how these different probes may be combined to
constrain cosmological models and the physics of dark energy.Comment: 596 pages. Also available at full resolution at
http://www.lsst.org/lsst/sciboo
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