3,791 research outputs found
Identifying galaxy candidates in WSRT HI imaging of ultra-compact high velocity clouds
Ultra-compact high velocity clouds (UCHVCs) were identified in the ALFALFA HI
survey as potential gas-bearing dark matter halos. Here we present higher
resolution neutral hydrogen (HI) observations of twelve UCHVCS with the
Westerbork Synthesis Radio Telescope (WSRT). The UCHVCs were selected based on
a combination of size, isolation, large recessional velocity and high column
density as the best candidate dark matter halos. The WSRT data were tapered to
image the UCHVCs at 210" (comparable to Arecibo) and 105" angular resolution.
In a comparison of the single-dish to interferometer data, we find that the
line flux recovered in the WSRT observations is comparable to that from the
single-dish ALFALFA data. In addition, any structure seen in the ALFALFA data
is reproduced in the WSRT maps at the same angular resolution. At 210'"
resolution all the sources are generally compact with a smooth HI morphology,
as expected from their identification as UCHVCs. At the higher angular
resolution, a majority of the sources break into small clumps contained in a
diffuse envelope. These UCHVCs also have no ordered velocity motion and are
most likely Galactic halo clouds. We identify two UCHVCs, AGC 198606 and AGC
249525, as excellent galaxy candidates based on maintaining a smooth HI
morphology at higher angular resolution and showing ordered velocity motion
consistent with rotation. A third source, AGC 249565, lies between these two
populations in properties and is a possible galaxy candidate. If interpreted as
gas-bearing dark matter halos, the three candidate galaxies have rotation
velocities of 8-15 km/s, HI masses of 0.6-50 x 10^5 Msun, HI radii of 0.3-2
kpc, and dynamical masses of 2-20 x 10^7 Msun for a range of plausible
distances. These are the UCHVCs with the highest column density values in the
ALFALFA HI data and we suggest this is the best way to identify further
candidates.Comment: Accepted for publication in A&A. 26 pages, 19 figures, 5 table
Detection of an Optical Counterpart to the ALFALFA Ultra-compact High Velocity Cloud AGC 249525
We report on the detection at 98% confidence of an optical counterpart to
AGC 249525, an Ultra-Compact High Velocity Cloud (UCHVC) discovered by the
ALFALFA blind neutral hydrogen survey. UCHVCs are compact, isolated HI clouds
with properties consistent with their being nearby low-mass galaxies, but
without identified counterparts in extant optical surveys. Analysis of the
resolved stellar sources in deep - and -band imaging from the WIYN pODI
camera reveals a clustering of possible Red Giant Branch stars associated with
AGC 249525 at a distance of 1.640.45 Mpc. Matching our optical detection
with the HI synthesis map of AGC 249525 from Adams et al. (2016) shows that the
stellar overdensity is exactly coincident with the highest-density HI contour
from that study. Combining our optical photometry and the HI properties of this
object yields an absolute magnitude of , a stellar
mass between and , and an HI to stellar mass ratio between 9 and 144. This object has
stellar properties within the observed range of gas-poor Ultra-Faint Dwarfs in
the Local Group, but is gas-dominated.Comment: 9 pages, 4 figures; accepted to ApJ
A case for associational resistance : Apparent support for the stress gradient hypothesis varies with study system
publishedVersio
The Psychology of Engagement with Indigenous Identities: A Cultural Perspective
(c) 2012 APA, all rights reserved. This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.A questionnaire study among 124 students at Haskell Indian Nations University investigated the
hypothesis that engagement with Indigenous identity—assessed along 3 dimensions including
degree (identification scale), content (pan-ethnic or tribal nation), and context (reservation or
non-reservation)—can serve as a psychological resource for well-being and liberation from
oppression. Consistent with this hypothesis, degree of identification was positively correlated
with community efficacy and perception of racism. Apparently inconsistent with this hypothesis,
degree of identification among students who had resided on a reservation was negatively
correlated with the social self-esteem subscale of the Current Thoughts Scale (Heatherton &
Polivy, 1991). Rather than evidence against the identity-as-resource hypothesis, this pattern may
reflect the cultural grounding of self-esteem and tools designed to measure it
The H I mass function of group galaxies in the ALFALFA survey
We estimate the H i mass function (HIMF) of galaxies in groups based on thousands of ALFALFA (Arecibo Legacy Fast ALFA survey) H i detections within the galaxy groups of four widely used SDSS (Sloan Digital Sky Survey) group catalogues. Although differences between the catalogues mean that there is no one definitive group galaxy HIMF, in general we find that the low-mass slope is flat, in agreement with studies based on small samples of individual groups, and that the 'knee' mass is slightly higher than that of the global HIMF of the full ALFALFA sample. We find that the observed fraction of ALFALFA galaxies in groups is approximately 22 per cent. These group galaxies were removed from the full ALFALFA source catalogue to calculate the field HIMF using the remaining galaxies. Comparison between the field and group HIMFs reveals that group galaxies make only a small contribution to the global HIMF as most ALFALFA galaxies are in the field, but beyond the HIMF 'knee' group galaxies dominate. Finally, we attempt to separate the group galaxy HIMF into bins of group halo mass, but find that too few low-mass galaxies are detected in the most massive groups to tightly constrain the slope, owing to the rarity of such groups in the nearby Universe where low-mass galaxies are detectable with existing H i surveys.© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyWe acknowledge the work of the entire ALFALFA team for
observing, flagging, and performing signal extraction. We thank
the anonymous referee for their suggestions that helped to improve
this paper. MGJ is supported by a Juan de la Cierva formacion´
fellowship (FJCI-2016-29685) from the Spanish Ministerio de
Ciencia, Innovacion y Universidades (MCIU). MGJ and LVM ´
also acknowledge support from the grants AYA2015-65973-C3-1-
R (MINECO/FEDER, UE) and RTI2018-096228-B-C31 (MCIU).
The research of KMH is supported by the under the European
Union’s Seventh Framework Programme (FP/2007-2013)/ERC
Grant Agreement nr. 291531. EAKA is supported by the WISE
research programme, which is financed by the Netherlands Organisation for Scientific Research (NWO). This work has been supported
by the State Agency for Research of the Spanish MCIU through
the ‘Centro de Excelencia Severo Ochoa’ award to the Instituto
de Astrof´ısica de Andaluc´ıa (SEV-2017-0709). This research was
supported by the Munich Institute for Astro- and Particle Physics
(MIAPP) which is funded by the Deutsche Forschungsgemeinschaft
(DFG, German Research Foundation)Peer reviewe
Inequitable Chronic Lead Exposure: A Dual Legacy of Social and Environmental Injustice
Both historic and contemporary factors contribute to the current unequal distribution of lead in urban environments and the disproportionate impact lead exposure has on the health and well-being of low-income minority communities. We consider the enduring impact of lead through the lens of environmental justice, taking into account well-documented geographic concentrations of lead, legacy sources that produce chronic exposures, and intergenerational transfers of risk. We discuss the most promising type of public health action to address inequitable lead exposure and uptake: primordial prevention efforts that address the most fundamental causes of diseases by intervening in structural and systemic inequalities
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