25 research outputs found
Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies II. Momentum-Driven Winds Powered by Star Formation in the Early Universe
Galactic outflows of molecular gas are a common occurrence in galaxies and
may represent a mechanism by which galaxies self-regulate their growth,
redistributing gas that could otherwise have formed stars. We previously
presented the first survey of molecular outflows at z > 4 towards a sample of
massive, dusty galaxies. Here we characterize the physical properties of the
molecular outflows discovered in our survey. Using low-redshift outflows as a
training set, we find agreement at the factor-of-two level between several
outflow rate estimates. We find molecular outflow rates 150-800Msun/yr and
infer mass loading factors just below unity. Among the high-redshift sources,
the molecular mass loading factor shows no strong correlations with any other
measured quantity. The outflow energetics are consistent with expectations for
momentum-driven winds with star formation as the driving source, with no need
for energy-conserving phases. There is no evidence for AGN activity in our
sample, and while we cannot rule out deeply-buried AGN, their presence is not
required to explain the outflow energetics, in contrast to nearby obscured
galaxies with fast outflows. The fraction of the outflowing gas that will
escape into the circumgalactic medium (CGM), though highly uncertain, may be as
high as 50%. This nevertheless constitutes only a small fraction of the total
cool CGM mass based on a comparison to z~2-3 quasar absorption line studies,
but could represent >~10% of the CGM metal mass. Our survey offers the first
statistical characterization of molecular outflow properties in the very early
universe.Comment: ApJ accepted. 25 pages, 16 figures. Data and tables from Papers I and
II available at https://github.com/spt-smg/publicdat
Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies I. Sample Overview and Clumpy Structure in Molecular Outflows on 500pc Scales
Massive galaxy-scale outflows of gas are one of the most commonly-invoked
mechanisms to regulate the growth and evolution of galaxies throughout the
universe. While the gas in outflows spans a large range of temperatures and
densities, the cold molecular phase is of particular interest because molecular
outflows may be capable of suppressing star formation in galaxies by removing
the star-forming gas. We have conducted the first survey of molecular outflows
at z > 4, targeting 11 strongly-lensed dusty, star-forming galaxies (DSFGs)
with high-resolution Atacama Large Millimeter Array (ALMA) observations of OH
119um absorption as an outflow tracer. In this first paper, we give an overview
of the survey, focusing on the detection rate and structure of molecular
outflows. We find unambiguous evidence for outflows in 8/11 (73%) galaxies,
more than tripling the number known at z > 4. This implies that molecular winds
in z > 4 DSFGs must have both a near-unity occurrence rate and large opening
angles to be detectable in absorption. Lensing reconstructions reveal that
500pc-scale clumpy structures in the outflows are common. The individual clumps
are not directly resolved, but from optical depth arguments we expect that
future observations will require 50-200pc spatial resolution to do so. We do
not detect high-velocity [CII] wings in any of the sources with clear OH
outflows, indicating that [CII] is not a reliable tracer of molecular outflows.
Our results represent a first step toward characterizing molecular outflows at
z > 4 at the population level, demonstrating that large-scale outflows are
ubiquitous among early massive, dusty galaxies.Comment: ApJ accepted. 28 pages, 12 figures + appendix. Data and tables from
Papers I and II available at https://github.com/spt-smg/publicdat
Chaotic and Clumpy Galaxy Formation in an Extremely Massive Reionization-era Halo
© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. https://creativecommons.org/licenses/by/4.0/Abstract: The SPT 0311–58 system at z = 6.900 is an extremely massive structure within the reionization epoch and offers a chance to understand the formation of galaxies at an extreme peak in the primordial density field. We present 70 mas Atacama Large Millimeter/submillimeter Array observations of the dust continuum and [C ii] 158 μm emission in the central pair of galaxies and reach physical resolutions of ∼100–350 pc, among the most detailed views of any reionization-era system to date. The observations resolve the source into at least a dozen kiloparsec-size clumps. The global kinematics and high turbulent velocity dispersion within the galaxies present a striking contrast to recent claims of dynamically cold thin-disk kinematics in some dusty galaxies just 800 Myr later at z ∼ 4. We speculate that both gravitational interactions and fragmentation from massive parent disks have likely played a role in the overall dynamics and formation of clumps in the system. Each clump individually is comparable in mass to other 6 < z < 8 galaxies identified in rest-UV/optical deep field surveys, but with star formation rates elevated by a factor of ~3-5. Internally, the clumps themselves bear close resemblance to greatly scaled-up versions of virialized cloud-scale structures identified in low-redshift galaxies. Our observations are qualitatively similar to the chaotic and clumpy assembly within massive halos seen in simulations of high-redshift galaxies.Peer reviewe
Berkeley Supernova Ia Program I: Observations, Data Reduction, and Spectroscopic Sample of 582 Low-Redshift Type Ia Supernovae
In this first paper in a series we present 1298 low-redshift (z\leq0.2)
optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 through
2008 as part of the Berkeley SN Ia Program (BSNIP). 584 spectra of 199 SNe Ia
have well-calibrated light curves with measured distance moduli, and many of
the spectra have been corrected for host-galaxy contamination. Most of the data
were obtained using the Kast double spectrograph mounted on the Shane 3 m
telescope at Lick Observatory and have a typical wavelength range of
3300-10,400 Ang., roughly twice as wide as spectra from most previously
published datasets. We present our observing and reduction procedures, and we
describe the resulting SN Database (SNDB), which will be an online, public,
searchable database containing all of our fully reduced spectra and companion
photometry. In addition, we discuss our spectral classification scheme (using
the SuperNova IDentification code, SNID; Blondin & Tonry 2007), utilising our
newly constructed set of SNID spectral templates. These templates allow us to
accurately classify our entire dataset, and by doing so we are able to
reclassify a handful of objects as bona fide SNe Ia and a few other objects as
members of some of the peculiar SN Ia subtypes. In fact, our dataset includes
spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present
spectroscopic host-galaxy redshifts of some SNe Ia where these values were
previously unknown. [Abridged]Comment: 34 pages, 11 figures, 11 tables, revised version, re-submitted to
MNRAS. Spectra will be released in January 2013. The SN Database homepage
(http://hercules.berkeley.edu/database/index_public.html) contains the full
tables, plots of all spectra, and our new SNID template
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
An Experiment to Search for Systematic Effects in Long-Lived Radioactive Decays
Franz Zwicky first discovered “Dunkle Materie,” or “Dark Matter” over 100 years ago, when he realized galaxy clusters must consist predominately of non-luminous matter. Since then, mounting evidence, has shown that a paltry 4% of the energy density of the universe is baryonic matter. We realize that the energy density of the universe is, in fact, dominated by dark matter and dark energy. Despite the evidence for dark matter, there is a long-standing discrepancy in the interpretation of results from direct dark matter experiments. The Italian DArk MAtter project (DAMA) claims to have discovered WIMPs, a particular variety of dark matter, since 1999. However, other direct detection experiments, provide results that directly contradict DAMA’s claims. For years, the dark matter community has worked to reconcile the two opposing sets of results through improved experiments in direct detection and alternative Dark Matter models. This thesis outlines the Modulation Experiment, which is designed to identify and determine possible systematic sources of error that could explain the annually modulating signal attributed to Dark Matter by DAMA. We present a dedicated experiment for the long-term measurement of gamma emissions resulting from beta decays that provides high-quality data and allows for the identification of systematic influences. Up to 16 sources are monitored redundantly by 32 3×3” NaI(Tl) detectors in four separate setups across three continents. In each setup, monitoring of environmental and operational conditions facilitates correlation studies. The deadtime-free performance of the data acquisition system is confirmed and monitored by LED pulsers. Waveforms of all events are recorded individually, enabling a study of time-dependent effects spanning microseconds to years, using both time-binned and unbinned analyses. In this thesis, we show that the experiment is successfully acquiring data, and environmental effects are well-understood. Because of the experimental design, the Modulation Experiment is particularly well-suited to monitor decay rates of various isotopes. Though decay rates are generally considered to be Poisson processes, standards offices such as the National Institute of Standards (NIST) and Physikalisch-Technische Bundesanstalt (PTB) have reported annually modulating rates due to an unknown influence. Some scientists hypothesize that these effects may be due to a solar neutrino influence. Furthermore, some scientists have also examined a potential link from solar effects (e.g. flares and storms) to discrepancies in decay rate. However, these effects may simply be the by-products of some seasonal effects. This thesis explores the reported claims of decay rate modulation, and limits annual modulation amplitudes to \u3c 5.95×10-5 for Ti-44, 1.46×10-4 for Co-60, and 1.8×10-4 Cs-137 at a 3σ confidence level. No additional periodicities were found to be statistically significant. The Modulation experiment is beginning to explore the true nature of the impact of systematic effects on the measured decay rate. As data continues to be collected and more setups come online, we will be able to lower statistical uncertainties on measurements the half life, measure or set further limits on time-dependent modulations and search for correlations between locations
Multiphase ISM in the z = 5.7 Hyperluminous Starburst SPT 0346-52
International audienceWith ΣSFR ~ 4200 M ⊙ yr-1 kpc-2, SPT 0346-52 (z = 5.7) is the most intensely star-forming galaxy discovered by the South Pole Telescope. In this paper, we expand on previous spatially resolved studies, using ALMA observations of dust continuum, [N II] 205 μm, [C II] 158 μm, [O I] 146 μm, and undetected [N II] 122 μm and [O I] 63 μm emission to study the multiphase interstellar medium (ISM) in SPT 0346-52. We use pixelated, visibility-based lens modeling to reconstruct the source-plane emission. We also model the source-plane emission using the photoionization code CLOUDY and find a supersolar metallicity system. We calculate T dust = 48.3 K and λ peak = 80 μm and see line deficits in all five lines. The ionized gas is less dense than comparable galaxies, with n e -3, while ~20% of the [C II] 158 μm emission originates from the ionized phase of the ISM. We also calculate the masses of several phases of the ISM. We find that molecular gas dominates the mass of the ISM in SPT 0346-52, with the molecular gas mass ~4× higher than the neutral atomic gas mass and ~100× higher than the ionized gas mass
A dense, solar metallicity ISM in the
We present a study of six far-infrared fine structure lines in the z = 4.225 lensed dusty star-forming galaxy SPT 0418−47 to probe the physical conditions of its interstellar medium (ISM). In particular, we report Atacama Pathfinder EXperiment (APEX) detections of the [OI] 145 μm and [OIII] 88 μm lines and Atacama Compact Array (ACA) detections of the [NII] 122 and 205 μm lines. The [OI] 145 μm/[CII] 158 μm line ratio is ∼5× higher compared to the average of local galaxies. We interpret this as evidence that the ISM is dominated by photo-dissociation regions with high gas densities. The line ratios, and in particular those of [OIII] 88 μm and [NII] 122 μm imply that the ISM in SPT 0418−47 is already chemically enriched to nearly solar metallicity. While the strong gravitational amplification was required to detect these lines with APEX, larger samples can be observed with the Atacama Large Millimeter/submillimeter Array (ALMA), and should allow observers to determine if the dense, solar metallicity ISM is common among these highly star-forming galaxies
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Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies. II. Momentum-driven Winds Powered by Star Formation in the Early Universe
Galactic outflows of molecular gas are a common occurrence in galaxies and
may represent a mechanism by which galaxies self-regulate their growth,
redistributing gas that could otherwise have formed stars. We previously
presented the first survey of molecular outflows at z > 4 towards a sample of
massive, dusty galaxies. Here we characterize the physical properties of the
molecular outflows discovered in our survey. Using low-redshift outflows as a
training set, we find agreement at the factor-of-two level between several
outflow rate estimates. We find molecular outflow rates 150-800Msun/yr and
infer mass loading factors just below unity. Among the high-redshift sources,
the molecular mass loading factor shows no strong correlations with any other
measured quantity. The outflow energetics are consistent with expectations for
momentum-driven winds with star formation as the driving source, with no need
for energy-conserving phases. There is no evidence for AGN activity in our
sample, and while we cannot rule out deeply-buried AGN, their presence is not
required to explain the outflow energetics, in contrast to nearby obscured
galaxies with fast outflows. The fraction of the outflowing gas that will
escape into the circumgalactic medium (CGM), though highly uncertain, may be as
high as 50%. This nevertheless constitutes only a small fraction of the total
cool CGM mass based on a comparison to z~2-3 quasar absorption line studies,
but could represent >~10% of the CGM metal mass. Our survey offers the first
statistical characterization of molecular outflow properties in the very early
universe