439 research outputs found
True to the Fable?: Examining the Appropriate Reach of Cat\u27s Paw Liability
In its recent decision in Staub v. Proctor Hospital, the Seventh Circuit clarified its approach to the colorfully named cat\u27s paw theory of employment discrimination. The cat\u27s paw doctrine holds employers vicariously liable when an employee involved in the decisionmaking process, other than the non-biased formal decisionmaker, possessed discriminatory intent. Currently, the circuits disagree about how much control the biased employee must possess over the decisionmaker to impose liability on the employer. In Staub, the Seventh Circuit held that liability should be imposed only when the biased employee possessed singular influence over the formal decisionmaker, aligning the court most closely with the Fourth Circuit\u27s stringent actual decisionmaker rule. In light of the current circuit split, this Note argues that a coherent and uniform standard needs to be adopted to decide these common cases. It analyzes the strengths and weaknesses of the circuits\u27 various rules, concluding that no current approach provides a satisfying solution. Accordingly, this Note suggests that courts should adopt the motivating factor standard of causation, should more carefully scrutinize whether an independent investigation breaks the causal chain, and should apply agency principles as a proper limitation on liability
True to the Fable?: Examining the Appropriate Reach of Cat\u27s Paw Liability
In its recent decision in Staub v. Proctor Hospital, the Seventh Circuit clarified its approach to the colorfully named cat\u27s paw theory of employment discrimination. The cat\u27s paw doctrine holds employers vicariously liable when an employee involved in the decisionmaking process, other than the non-biased formal decisionmaker, possessed discriminatory intent. Currently, the circuits disagree about how much control the biased employee must possess over the decisionmaker to impose liability on the employer. In Staub, the Seventh Circuit held that liability should be imposed only when the biased employee possessed singular influence over the formal decisionmaker, aligning the court most closely with the Fourth Circuit\u27s stringent actual decisionmaker rule. In light of the current circuit split, this Note argues that a coherent and uniform standard needs to be adopted to decide these common cases. It analyzes the strengths and weaknesses of the circuits\u27 various rules, concluding that no current approach provides a satisfying solution. Accordingly, this Note suggests that courts should adopt the motivating factor standard of causation, should more carefully scrutinize whether an independent investigation breaks the causal chain, and should apply agency principles as a proper limitation on liability
FUSE Detection of Galactic OVI Emission in the Halo above the Perseus Arm
Background observations obtained with the Far Ultraviolet Spectroscopic
Explorer (FUSE) toward l=95.4, b=36.1 show OVI 1032,1038 in emission. This
sight line probes a region of stronger-than-average soft X-ray emission in the
direction of high-velocity cloud Complex C above a part of the disk where
Halpha filaments rise into the halo. The OVI intensities, 1600+/-300
ph/s/cm^2/sr (1032A) and 800+/-300 ph/s/cm^2/sr (1038A), are the lowest
detected in emission in the Milky Way to date. A second sight line nearby
(l=99.3, b=43.3) also shows OVI 1032 emission, but with too low a
signal-to-noise ratio to obtain reliable measurements. The measured
intensities, velocities, and FWHMs of the OVI doublet and the CII* line at
1037A are consistent with a model in which the observed emission is produced in
the Galactic halo by hot gas ejected by supernovae in the Perseus arm. An
association of the observed gas with Complex C appears unlikely.Comment: accepted for publication in ApJL, 11 pages including 3 figure
Highly-Ionized High-Velocity Gas in the Vicinity of the Galaxy
We report the results of an extensive FUSE study of high velocity OVI
absorption along 102 complete sight lines through the Galactic halo. The high
velocity OVI traces a variety of phenomena, including tidal interactions with
the Magellanic Clouds, accretion of gas, outflow from the Galactic disk,
warm/hot gas interactions in a highly extended Galactic corona, and
intergalactic gas in the Local Group. We identify 85 high velocity OVI features
at velocities of -500 < v(LSR) < +500 km/s along 59 of the 102 sight lines.
Approximately 60% of the sky (and perhaps as much as 85%) is covered by high
velocity H+ associated with the high velocity OVI. Some of the OVI is
associated with known high velocity HI structures (e.g., the Magellanic Stream,
Complexes A and C), while some OVI features have no counterpart in HI 21cm
emission. The smaller dispersion in the OVI velocities in the GSR and LGSR
reference frames compared to the LSR is necessary (but not conclusive) evidence
that some of the clouds are extragalactic. Most of the OVI cannot be produced
by photoionization, even if the gas is irradiated by extragalactic background
radiation. Collisions in hot gas are the primary OVI ionization mechanism. We
favor production of some of the OVI at the boundaries between warm clouds and a
highly extended [R > 70 kpc], hot [T > 10^6 K], low-density [n < 10^-4 cm^-3]
Galactic corona or Local Group medium. A hot Galactic corona or Local Group
medium and the prevalence of high velocity OVI are consistent with predictions
of galaxy formation scenarios. Distinguishing between the various phenomena
producing high velocity OVI will require continuing studies of the distances,
kinematics, elemental abundances, and physical states of the different types of
high velocity OVI features found in this study. (abbreviated)Comment: 78 pages of text/tables + 31 figures, AASTeX preprint format. All
figures are in PNG format due to astro-ph space restrictions. Bound copies of
manuscript and two accompanying articles are available upon request.
Submitted to ApJ
Model for Gravitational Interaction between Dark Matter and Baryons
We propose a phenomenological model where the gravitational interaction
between dark matter and baryons is suppressed on small, subgalactic scales. We
describe the gravitational force by adding a Yukawa contribution to the
standard Newtonian potential and show that this interaction scheme is
effectively suggested by the available observations of the inner rotation
curves of small mass galaxies. Besides helping in interpreting the cuspy
profile of dark matter halos observed in N-body simulations, this potential
regulates the quantity of baryons within halos of different masses.Comment: 4 pages, 2 figures, final versio
Finding Galaxy Clusters using Voronoi Tessellations
We present an objective and automated procedure for detecting clusters of
galaxies in imaging galaxy surveys. Our Voronoi Galaxy Cluster Finder (VGCF)
uses galaxy positions and magnitudes to find clusters and determine their main
features: size, richness and contrast above the background. The VGCF uses the
Voronoi tessellation to evaluate the local density and to identify clusters as
significative density fluctuations above the background. The significance
threshold needs to be set by the user, but experimenting with different choices
is very easy since it does not require a whole new run of the algorithm. The
VGCF is non-parametric and does not smooth the data. As a consequence, clusters
are identified irrispective of their shape and their identification is only
slightly affected by border effects and by holes in the galaxy distribution on
the sky. The algorithm is fast, and automatically assigns members to
structures.Comment: 11 pages, 11 figures. It uses aa.cls (included). Accepted by A&
A Catalogue of Field Horizontal Branch Stars Aligned with High Velocity Clouds
We present a catalogue of 430 Field Horizontal Branch (FHB) stars, selected
from the Hamburg/ESO Survey (HES), which fortuitously align with high column
density neutral hydrogen (HI) High-Velocity Cloud (HVC) gas. These stars are
ideal candidates for absorption-line studies of HVCs, attempts at which have
been made for almost 40 years with little success. A parent sample of 8321 HES
FHB stars was used to extract HI spectra along each line-of-sight, using the HI
Parkes All-Sky Survey. All lines-of-sight aligned with high velocity HI
emission with peak brightness temperatures greater than 120mK were examined.
The HI spectra of these 430 probes were visually screened and cross-referenced
with several HVC catalogues. In a forthcoming paper, we report on the results
of high-resolution spectroscopic observations of a sample of stars drawn from
this catalogue.Comment: 7 pages, 4 figures. ApJS accepted. Full catalogue and all online-only
images available at
http://astronomy.swin.edu.au/staff/cthom/catalogue/index.htm
Optimal filtering of optical and weak lensing data to search for galaxy clusters: application to the COSMOS field
Galaxy clusters are usually detected in blind optical surveys via suitable
filtering methods. We present an optimal matched filter which maximizes their
signal-to-noise ratio by taking advantage of the knowledge we have of their
intrinsic physical properties and of the data noise properties. In this paper
we restrict our application to galaxy magnitudes, positions and photometric
redshifts if available, and we also apply the filter separately to weak lensing
data. The method is suitable to be naturally extended to a multi-band approach
which could include not only additional optical bands but also observables with
different nature such as X-rays. For each detection, the filter provides its
significance, an estimate for the richness and for the redshift even if photo-z
are not given. The provided analytical error estimate is tested against
numerical simulations. We finally apply our method to the COSMOS field and
compare the results with previous cluster detections obtained with different
methods. Our catalogue contains 27 galaxy clusters with minimal threshold at
3-sigma level including both optical and weak-lensing information.Comment: 15 pages, 15 figures, accepted for publication in MNRA
Photometric validation of a model independent procedure to extract galaxy clusters
By means of CCD photometry in three bands (Gunn g, r, i) we investigate the
existence of 12 candidate clusters extracted via a model independent peak
finding algorithm (\cite{memsait}) from DPOSS data. The derived color-magnitude
diagrams allow us to confirm the physical nature of 9 of the cluster
candidates, and to estimate their photometric redshifts. Of the other
candidates, one is a fortuitous detection of a true cluster at z~0.4, one is a
false detection and the last is undecidable on the basis of the available data.
The accuracy of the photometric redshifts is tested on an additional sample of
8 clusters with known spectroscopic redshifts. Photometric redshifts turn out
to be accurate within z~0.01 (interquartile range).Comment: A&A in pres
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