52 research outputs found
CLASSY III: The Properties of Starburst-Driven Warm Ionized Outflows
We report the results of analyses of galactic outflows in a sample of 45
low-redshift starburst galaxies in the COS Legacy Archive Spectroscopic SurveY
(CLASSY), augmented by five additional similar starbursts with COS data. The
outflows are traced by blueshifted absorption-lines of metals spanning a wide
range of ionization potential. The high quality and broad spectral coverage of
CLASSY data enable us to disentangle the absorption due to the static ISM from
that due to outflows. We further use different line multiplets and doublets to
determine the covering fraction, column density, and ionization state as a
function of velocity for each outflow. We measure the outflow's mean velocity
and velocity width, and find that both correlate in a highly significant way
with the star-formation rate, galaxy mass, and circular velocity over ranges of
four orders-of-magnitude for the first two properties. We also estimate outflow
rates of metals, mass, momentum, and kinetic energy. We find that, at most,
only about 20% of silicon created and ejected by supernovae in the starburst is
carried in the warm phase we observe. The outflows' mass-loading factor
increases steeply and inversely with both circular and outflow velocity
(log-log slope -1.6), and reaches for dwarf galaxies. We find
that the outflows typically carry about 10 to 100% of the momentum injected by
massive stars and about 1 to 20% of the kinetic energy. We show that these
results place interesting constraints on, and new insights into, models and
simulations of galactic winds.Comment: 34 pages, 16 figures, 6 tables, submitted to Ap
The COS Legacy Archive Spectroscopy SurveY (CLASSY) Treasury Atlas
Far-ultraviolet (FUV; ~1200-2000 angstroms) spectra are fundamental to our
understanding of star-forming galaxies, providing a unique window on massive
stellar populations, chemical evolution, feedback processes, and reionization.
The launch of JWST will soon usher in a new era, pushing the UV spectroscopic
frontier to higher redshifts than ever before, however, its success hinges on a
comprehensive understanding of the massive star populations and gas conditions
that power the observed UV spectral features. This requires a level of detail
that is only possible with a combination of ample wavelength coverage,
signal-to-noise, spectral-resolution, and sample diversity that has not yet
been achieved by any FUV spectral database.
We present the COS Legacy Spectroscopic SurveY (CLASSY) treasury and its
first high level science product, the CLASSY atlas. CLASSY builds on the HST
archive to construct the first high-quality (S/N_1500 >~ 5/resel),
high-resolution (R~15,000) FUV spectral database of 45 nearby (0.002 < z <
0.182) star-forming galaxies. The CLASSY atlas, available to the public via the
CLASSY website, is the result of optimally extracting and coadding 170
archival+new spectra from 312 orbits of HST observations.
The CLASSY sample covers a broad range of properties including stellar mass
(6.2 < logM_star(M_sol) < 10.1), star formation rate (-2.0 < log SFR (M_sol/yr)
< +1.6), direct gas-phase metallicity (7.0 < 12+log(O/H) < 8.8), ionization
(0.5 < O_32 < 38.0), reddening (0.02 < E(B-V < 0.67), and nebular density (10 <
n_e (cm^-3) < 1120). CLASSY is biased to UV-bright star-forming galaxies,
resulting in a sample that is consistent with z~0 mass-metallicity
relationship, but is offset to higher SFRs by roughly 2 dex, similar to z >~2
galaxies. This unique set of properties makes the CLASSY atlas the benchmark
training set for star-forming galaxies across cosmic time.Comment: Accepted for publication in Ap
The science of scale for violence prevention: a new agenda for family strengthening in low- and middle-income countries
Ending all violence against children by 2030 is a core part of Sustainable Development Goals 5 and 16. A number of promising violence reduction strategies have been identified in research studies. However, we lack an understanding of the implementation and impact of these programs in respect to their delivery at a large scale or within existing service systems, particularly in low- and middle-income countries (LMICs). We advocate for greater collaboration between researchers, policymakers, donors, governments, non-governmental organizations, and program managers and staff to study how violence prevention programs operate on a large scale. We describe a new initiative aiming to foster such collaborations in the field of family strengthening programs
Direct Constraints on the Extremely Metal-poor Massive Stars Underlying Nebular C IV Emission from Ultra-deep HST/COS Ultraviolet Spectroscopy
International audienceMetal-poor nearby galaxies hosting massive stars have a fundamental role to play in our understanding of both high-redshift galaxies and low-metallicity stellar populations. But while much attention has been focused on their bright nebular gas emission, the massive stars that power it remain challenging to constrain. Here we present exceptionally deep Hubble Space Telescope ultraviolet spectra targeting six local (z 6. We find that the strength and spectral profile of the nebular C IV in these new spectra follow a sequence evocative of resonant scattering models, indicating that the hot circumgalactic medium likely plays a key role in regulating C IV escape locally. We constrain the metallicity of the massive stars in each galaxy by fitting the forest of photospheric absorption lines, reporting measurements driven by iron that lie uniformly below 10% solar. Comparison with the gas-phase oxygen abundances reveals evidence for enhancement in O/Fe 2-4 times above solar across the sample, robust to assumptions about the absolute gas-phase metallicity scale. This supports the idea that these local systems are more chemically similar to their primordial high-redshift counterparts than to the bulk of nearby galaxies. Finally, we find significant tension between the strong stellar wind profiles observed and our population synthesis models constrained by the photospheric forest in our highest-quality spectra. This reinforces the need for caution in interpreting wind lines in isolation at high redshift, but also suggests a unique path toward validating fundamental massive star physics at extremely low metallicity with integrated ultraviolet spectra
Evaluating the dissemination and scale-up of two evidence-based parenting interventions to reduce violence against children: Study protocol
Background
Eliminating violence against children is a prominent policy goal, codified in the Sustainable Development Goals, and parenting programs are one approach to preventing and reducing violence. However, we know relatively little about dissemination and scale-up of parenting programs, particularly in low- and middle-income countries (LMICs). The scale-up of two parenting programs, Parenting for Lifelong Health (PLH) for Young Children and PLH for Parents and Teens, developed under Creative Commons licensing and tested in randomized trials, provides a unique opportunity to study their dissemination in 25 LMICs.
Methods
The Scale-Up of Parenting Evaluation Research (SUPER) study uses a range of methods to study the dissemination of these two programs. The study will examine (1) process and extent of dissemination and scale-up, (2) how the programs are implemented and factors associated with variation in implementation, (3) violence against children and family outcomes before and after program implementation, (4) barriers and facilitators to sustained program delivery, and (5) costs and resources needed for implementation.
Primary data collection, focused on three case study projects, will include interviews and focus groups with program facilitators, coordinators, funders, and other stakeholders, and a summary of key organizational characteristics. Program reports and budgets will be reviewed as part of relevant contextual information. Secondary data analysis of routine data collected within ongoing implementation and existing research studies will explore family enrolment and attendance, as well as family reports of parenting practices, violence against children, child behavior, and child and caregiver wellbeing before and after program participation. We will also examine data on staff sociodemographic and professional background, and their competent adherence to the program, collected as part of staff training and certification.
Discussion
This project will be the first study of its kind to draw on multiple data sources and methods to examine the dissemination and scale-up of a parenting program across multiple LMIC contexts. While this study reports on the implementation of two specific parenting programs, we anticipate that our findings will be of relevance across the field of parenting, as well as other violence prevention and social programs
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CLASSY III. The Properties of Starburst-driven Warm Ionized Outflows*
Abstract
We report the results of analyses of galactic outflows in a sample of 45 low-redshift starburst galaxies in the COS Legacy Archive Spectroscopic SurveY (CLASSY), augmented by five additional similar starbursts with Cosmic Origins Spectrograph (COS) data. The outflows are traced by blueshifted absorption lines of metals spanning a wide range of ionization potential. The high quality and broad spectral coverage of CLASSY data enable us to disentangle the absorption due to the static interstellar medium (ISM) from that due to outflows. We further use different line multiplets and doublets to determine the covering fraction, column density, and ionization state as a function of velocity for each outflow. We measure the outflowâs mean velocity and velocity width, and find that both correlate in a highly significant way with the star formation rate, galaxy mass, and circular velocity over ranges of four orders of magnitude for the first two properties. We also estimate outflow rates of metals, mass, momentum, and kinetic energy. We find that, at most, only about 20% of silicon created and ejected by supernovae in the starburst is carried out in the warm phase we observe. The outflowsâ mass-loading factor increases steeply and inversely with both circular and outflow velocity (logâlog slope âŒâ1.6), and reaches âŒ10 for dwarf galaxies. We find that the outflows typically carry about 10%â100% of the momentum injected by massive stars and about 1%â20% of the kinetic energy. We show that these results place interesting constraints on, and new insights into, models and simulations of galactic winds
Recommended from our members
The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas*
Far-ultraviolet (FUV; ~1200-2000 Ă
) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before; however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) treasury and its first high-level science product, the CLASSY atlas. CLASSY builds on the Hubble Space Telescope (HST) archive to construct the first high-quality (S/N1500 Ă
? 5/resel), high-resolution (R ~ 15,000) FUV spectral database of 45 nearby (0.002 < z < 0.182) star-forming galaxies. The CLASSY atlas, available to the public via the CLASSY website, is the result of optimally extracting and coadding 170 archival+new spectra from 312 orbits of HST observations. The CLASSY sample covers a broad range of properties including stellar mass (6.2 < log M ?(M ?) < 10.1), star formation rate (-2.0 < log SFR (M ? yr-1) < +1.6), direct gas-phase metallicity (7.0 < 12+log(O/H) < 8.8), ionization (0.5 < O32 < 38.0), reddening (0.02 < E(B - V) < 0.67), and nebular density (10 < n e (cm-3) < 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with the z ~ 0 mass-metallicity relationship, but is offset to higher star formation rates by roughly 2 dex, similar to z ? 2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time
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