246 research outputs found
Politics versus Policies: Fourth Wave Feminist Critiques of Higher Education’s Response to Sexual Violence
This article uses the lens of fourth wave feminism to examine media accounts of institutional and student responses in two cases of sexual violence at institutions of higher education. Competing discourses reveal a disconnect between what institutions say they do and students’ actual experiences of the institutional handling of sexual violence cases. When policies, actions, and values are not fully aligned, institutions of higher education are unable to respond to societal and institutional injustices. Hence, recommendations for better alignment between institutional values and actions are proposed
Possible Signatures of a Cold-Flow Disk from MUSE using a z=1 galaxy--quasar pair towards SDSSJ1422-0001
We use a background quasar to detect the presence of circum-galactic gas
around a low-mass star forming galaxy. Data from the new Multi Unit
Spectroscopic Explorer (MUSE) on the VLT show that the host galaxy has a
dust-corrected star-formation rate (SFR) of 4.70.2 Msun/yr, with no
companion down to 0.22 Msun/yr (5 ) within 240 kpc (30"). Using a
high-resolution spectrum (UVES) of the background quasar, which is fortuitously
aligned with the galaxy major axis (with an azimuth angle of only
), we find, in the gas kinematics traced by low-ionization lines,
distinct signatures consistent with those expected for a "cold flow disk"
extending at least 12 kpc (). We estimate the mass accretion
rate to be at least two to three times larger than the SFR,
using the geometric constraints from the IFU data and the HI column density of
obtained from a {\it HST}/COS NUV spectrum. From
a detailed analysis of the low-ionization lines (e.g. ZnII, CrII, TiII, MnII,
SiII), the accreting material appears to be enriched to about 0.4
(albeit with large uncertainties: ), which is
comparable to the galaxy metallicity (), implying a
large recycling fraction from past outflows. Blue-shifted MgII and FeII
absorptions in the galaxy spectrum from the MUSE data reveal the presence of an
outflow. The MgII and FeII doublet ratios indicate emission infilling due to
scattering processes, but the MUSE data do not show any signs of fluorescent
FeII* emission.Comment: 17 pages, 11 figures, in press (ApJ), minor edits after the proofs.
Data available at http://muse-vlt.eu/science/j1422
Gas Accretion and Giant Lyman-alpha Nebulae
Several decades of observations and discoveries have shown that high-redshift
AGN and massive galaxies are often surrounded by giant Lyman-alpha nebulae
extending in some cases up to 500 kpc in size. In this review, I discuss the
properties of the such nebulae discovered at z>2 and their connection with gas
flows in and around the galaxies and their halos. In particular, I show how
current observations are used to constrain the physical properties and origin
of the emitting gas in terms of the Lyman-alpha photon production processes and
kinematical signatures. These studies suggest that recombination radiation is
the most viable scenario to explain the observed Lyman-alpha luminosities and
Surface Brightness for the large majority of the nebulae and imply that a
significant amount of dense, ionized and cold clumps should be present within
and around the halos of massive galaxies. Spectroscopic studies suggest that,
among the giant Lyman-alpha nebulae, the one associated with radio-loud AGN
should have kinematics dominated by strong, ionized outflows within at least
the inner 30-50 kpc. Radio-quiet nebulae instead present more quiescent
kinematics compatible with stationary situation and, in some cases, suggestive
of rotating structures. However, definitive evidences for accretion onto
galaxies of the gas associated with the giant Lyman-alpha emission are not
unambiguously detected yet. Deep surveys currently ongoing using other bright,
non-resonant lines such as Hydrogen H-alpha and HeII1640 will be crucial to
search for clearer signatures of cosmological gas accretion onto galaxies and
AGN.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dave', to be published by
Springe
Ultra High Energy Cosmology with POLARBEAR
Observations of the temperature anisotropy of the Cosmic Microwave Background
(CMB) lend support to an inflationary origin of the universe, yet no direct
evidence verifying inflation exists. Many current experiments are focussing on
the CMB's polarization anisotropy, specifically its curl component (called
"B-mode" polarization), which remains undetected. The inflationary paradigm
predicts the existence of a primordial gravitational wave background that
imprints a unique B-mode signature on the CMB's polarization at large angular
scales. The CMB B-mode signal also encodes gravitational lensing information at
smaller angular scales, bearing the imprint of cosmological large scale
structures (LSS) which in turn may elucidate the properties of cosmological
neutrinos. The quest for detection of these signals; each of which is orders of
magnitude smaller than the CMB temperature anisotropy signal, has motivated the
development of background-limited detectors with precise control of systematic
effects. The POLARBEAR experiment is designed to perform a deep search for the
signature of gravitational waves from inflation and to characterize lensing of
the CMB by LSS. POLARBEAR is a 3.5 meter ground-based telescope with 3.8
arcminute angular resolution at 150 GHz. At the heart of the POLARBEAR receiver
is an array featuring 1274 antenna-coupled superconducting transition edge
sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a
tensor-to-scalar ratio of 0.025 after two years of observation -- more than an
order of magnitude improvement over the current best results, which would test
physics at energies near the GUT scale. POLARBEAR had an engineering run in the
Inyo Mountains of Eastern California in 2010 and will begin observations in the
Atacama Desert in Chile in 2011.Comment: 8 pages, 6 figures, DPF 2011 conference proceeding
The new generation CMB B-mode polarization experiment: POLARBEAR
We describe the Cosmic Microwave Background (CMB) polarization experiment
called Polarbear. This experiment will use the dedicated Huan Tran Telescope
equipped with a powerful 1,200-bolometer array receiver to map the CMB
polarization with unprecedented accuracy. We summarize the experiment, its
goals, and current status
Hier ist wahrhaftig ein Loch im Himmel - The NGC 1999 dark globule is not a globule
The NGC 1999 reflection nebula features a dark patch with a size of ~10,000
AU, which has been interpreted as a small, dense foreground globule and
possible site of imminent star formation. We present Herschel PACS far-infrared
70 and 160mum maps, which reveal a flux deficit at the location of the globule.
We estimate the globule mass needed to produce such an absorption feature to be
a few tenths to a few Msun. Inspired by this Herschel observation, we obtained
APEX LABOCA and SABOCA submillimeter continuum maps, and Magellan PANIC
near-infrared images of the region. We do not detect a submillimer source at
the location of the Herschel flux decrement; furthermore our observations place
an upper limit on the mass of the globule of ~2.4x10^-2 Msun. Indeed, the
submillimeter maps appear to show a flux depression as well. Furthermore, the
near-infrared images detect faint background stars that are less affected by
extinction inside the dark patch than in its surroundings. We suggest that the
dark patch is in fact a hole or cavity in the material producing the NGC 1999
reflection nebula, excavated by protostellar jets from the V 380 Ori multiple
system.Comment: accepted for the A&A Herschel issue; 7 page
Observational Diagnostics of Gas Flows: Insights from Cosmological Simulations
Galactic accretion interacts in complex ways with gaseous halos, including
galactic winds. As a result, observational diagnostics typically probe a range
of intertwined physical phenomena. Because of this complexity, cosmological
hydrodynamic simulations have played a key role in developing observational
diagnostics of galactic accretion. In this chapter, we review the status of
different observational diagnostics of circumgalactic gas flows, in both
absorption (galaxy pair and down-the-barrel observations in neutral hydrogen
and metals; kinematic and azimuthal angle diagnostics; the cosmological column
density distribution; and metallicity) and emission (Lya; UV metal lines; and
diffuse X-rays). We conclude that there is no simple and robust way to identify
galactic accretion in individual measurements. Rather, progress in testing
galactic accretion models is likely to come from systematic, statistical
comparisons of simulation predictions with observations. We discuss specific
areas where progress is likely to be particularly fruitful over the next few
years.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dave, to be published by
Springer. Typos correcte
Gas Accretion and Star Formation Rates
Cosmological numerical simulations of galaxy evolution show that accretion of
metal-poor gas from the cosmic web drives the star formation in galaxy disks.
Unfortunately, the observational support for this theoretical prediction is
still indirect, and modeling and analysis are required to identify hints as
actual signs of star-formation feeding from metal-poor gas accretion. Thus, a
meticulous interpretation of the observations is crucial, and this
observational review begins with a simple theoretical description of the
physical process and the key ingredients it involves, including the properties
of the accreted gas and of the star-formation that it induces. A number of
observations pointing out the connection between metal-poor gas accretion and
star-formation are analyzed, specifically, the short gas consumption time-scale
compared to the age of the stellar populations, the fundamental metallicity
relationship, the relationship between disk morphology and gas metallicity, the
existence of metallicity drops in starbursts of star-forming galaxies, the
so-called G dwarf problem, the existence of a minimum metallicity for the
star-forming gas in the local universe, the origin of the alpha-enhanced gas
forming stars in the local universe, the metallicity of the quiescent BCDs, and
the direct measurements of gas accretion onto galaxies. A final section
discusses intrinsic difficulties to obtain direct observational evidence, and
points out alternative observational pathways to further consolidate the
current ideas.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springe
The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
The Photodetector Array Camera and Spectrometer (PACS) is one of the three
science instruments on ESA's far infrared and submillimetre observatory. It
employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25
pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64
pixels, respectively, to perform integral-field spectroscopy and imaging
photometry in the 60-210\mu\ m wavelength regime. In photometry mode, it
simultaneously images two bands, 60-85\mu\ m or 85-125\mu\m and 125-210\mu\ m,
over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in
each band. In spectroscopy mode, it images a field of 47"x47", resolved into
5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral
resolution of ~175km/s. We summarise the design of the instrument, describe
observing modes, calibration, and data analysis methods, and present our
current assessment of the in-orbit performance of the instrument based on the
Performance Verification tests. PACS is fully operational, and the achieved
performance is close to or better than the pre-launch predictions
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