137 research outputs found
Velocity Segregation and Systematic Biases In Velocity Dispersion Estimates With the SPT-GMOS Spectroscopic Survey
The velocity distribution of galaxies in clusters is not universal; rather,
galaxies are segregated according to their spectral type and relative
luminosity. We examine the velocity distributions of different populations of
galaxies within 89 Sunyaev Zel'dovich (SZ) selected galaxy clusters spanning . Our sample is primarily draw from the SPT-GMOS spectroscopic
survey, supplemented by additional published spectroscopy, resulting in a final
spectroscopic sample of 4148 galaxy spectra---2868 cluster members. The
velocity dispersion of star-forming cluster galaxies is % greater than
that of passive cluster galaxies, and the velocity dispersion of bright () cluster galaxies is % lower than the velocity dispersion of
our total member population. We find good agreement with simulations regarding
the shape of the relationship between the measured velocity dispersion and the
fraction of passive vs. star-forming galaxies used to measure it, but we find a
small offset between this relationship as measured in data and simulations in
which suggests that our dispersions are systematically low by as much as 3\%
relative to simulations. We argue that this offset could be interpreted as a
measurement of the effective velocity bias that describes the ratio of our
observed velocity dispersions and the intrinsic velocity dispersion of dark
matter particles in a published simulation result. Measuring velocity bias in
this way suggests that large spectroscopic surveys can improve dispersion-based
mass-observable scaling relations for cosmology even in the face of velocity
biases, by quantifying and ultimately calibrating them out.Comment: Accepted to ApJ; 21 pages, 11 figures, 5 table
Silver release from silver nanoparticles in natural waters
Silver nanoparticles (AgNPs) are used increasingly in consumer products for their antimicrobial properties. This increased use raises ecological concern because of the release of AgNPs into the environment. Once released, zero-valent silver may be oxidized to Ag+ and the cation liberated or it may persist as AgNPs. The chemical form of Ag has implications for its toxicity; it is therefore crucial to characterize the persistence of AgNPs to predict their ecotoxicological potential. In this study, we evaluated the release of Ag from AgNPs of various sizes exposed to river and lake water for up to 4 months. Several AgNP-capping agents were also considered: polyvinylpyrrolidone (PVP), tannic acid (Tan), and citric acid (Cit). We observed a striking difference between 5, 10, and 50 nm AgNPs, with the latter being more resistant to dissolution in oxic water on a mass basis. However, the difference decreased when Ag was surface-area-normalized, suggesting an important role of the surface area in determining Ag loss. We propose that rapid initial Ag+ release was attributable to desorption of Ag+ from nanoparticle surfaces. We also observed that PVP- and Tan-AgNPs are more prone to Ag+ release than Cit-AgNPs. In addition, it is likely that oxidative dissolution also occurs but at a slower rate. This study clearly shows that small AgNPs (5 nm, PVP and Tan) dissolve rapidly and almost completely, while larger AgNPs (50 nm) have the potential to persist for an extended period of time and could serve as a continuous source of Ag ions
The ecology of human-caused mortality for a protected large carnivore
Mitigating human-caused mortality for large carnivores is a pressing global challenge for wildlife conservation. However, mortality is almost exclusively studied at local (within-population) scales creating a mismatch between our understanding of risk and the spatial extent most relevant to conservation and management of wide-ranging species. Here, we quantified mortality for 590 radio-collared mountain lions statewide across their distribution in California to identify drivers of human-caused mortality and investigate whether human-caused mortality is additive or compensatory. Human-caused mortality, primarily from conflict management and vehicles, exceeded natural mortality despite mountain lions being protected from hunting. Our data indicate that human-caused mortality is additive to natural mortality as population-level survival decreased as a function of increasing human-caused mortality and natural mortality did not decrease with increased human-caused mortality. Mortality risk increased for mountain lions closer to rural development and decreased in areas with higher proportions of citizens voting to support environmental initiatives. Thus, the presence of human infrastructure and variation in the mindset of humans sharing landscapes with mountain lions appear to be primary drivers of risk. We show that human-caused mortality can reduce population-level survival of large carnivores across large spatial scales, even when they are protected from hunting
The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star-formation in cluster infall
We investigate the properties of optically passive spirals and dusty red
galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe
near-UV-optical SEDs, 24 micron IR data and HST morphologies from the STAGES
dataset. The cluster sample is based on COMBO-17 redshifts with an rms
precision of sigma_cz~2000 km/sec. We find that 'dusty red galaxies' and
'optically passive spirals' in A901/2 are largely the same phenomenon, and that
they form stars at a substantial rate, which is only 4x lower than that in blue
spirals at fixed mass. This star formation is more obscured than in blue
galaxies and its optical signatures are weak. They appear predominantly in the
stellar mass range of log M*/Msol=[10,11] where they constitute over half of
the star-forming galaxies in the cluster; they are thus a vital ingredient for
understanding the overall picture of star formation quenching in clusters. We
find that the mean specific SFR of star-forming galaxies in the cluster is
clearly lower than in the field, in contrast to the specific SFR properties of
blue galaxies alone, which appear similar in cluster and field. Such a rich red
spiral population is best explained if quenching is a slow process and
morphological transformation is delayed even more. At log M*/Msol<10, such
galaxies are rare, suggesting that their quenching is fast and accompanied by
morphological change. We note, that edge-on spirals play a minor role; despite
being dust-reddened they form only a small fraction of spirals independent of
environment.Comment: Accepted for publication in MNRA
CMB-S4 Science Book, First Edition
This book lays out the scientific goals to be addressed by the
next-generation ground-based cosmic microwave background experiment, CMB-S4,
envisioned to consist of dedicated telescopes at the South Pole, the high
Chilean Atacama plateau and possibly a northern hemisphere site, all equipped
with new superconducting cameras. CMB-S4 will dramatically advance cosmological
studies by crossing critical thresholds in the search for the B-mode
polarization signature of primordial gravitational waves, in the determination
of the number and masses of the neutrinos, in the search for evidence of new
light relics, in constraining the nature of dark energy, and in testing general
relativity on large scales
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
Assessing the Role of CD103 in Immunity to an Intestinal Helminth Parasite
In the intestine, the integrin CD103 is expressed on a subset of T regulatory (T(reg)) cells and a population of dendritic cells (DCs) that produce retinoic acid and promote immune homeostasis. However, the role of CD103 during intestinal helminth infection has not been tested.We demonstrate that CD103 is dispensable for the development of protective immunity to the helminth parasite Trichuris muris. While we observed an increase in the frequency of CD103(+) DCs in the lamina propria (LP) following acute high-dose infection with Trichuris, lack of CD103 had no effect on the frequency of CD11c(+) DCs in the LP or mesenteric lymph nodes (mLN). CD103-deficient (CD103(-/-)) mice develop a slightly increased and earlier T cell response but resolve infection with similar kinetics to control mice. Similarly, low-dose chronic infection of CD103(-/-) mice with Trichuris resulted in no significant difference in immunity or parasite burden. Absence of CD103 also had no effect on the frequency of CD4(+)CD25(+)Foxp3(+) T(reg) cells in the mLN or LP.These results suggest that CD103 is dispensable for intestinal immunity during helminth infection. Furthermore, lack of CD103 had no effect on DC or T(reg) recruitment or retention within the large intestine
Renal amyloidosis in children
Renal amyloidosis is a detrimental disease caused by the deposition of amyloid fibrils. A child with renal amyloidosis may present with proteinuria or nephrotic syndrome. Chronic renal failure may follow. Amyloid fibrils may deposit in other organs as well. The diagnosis is through the typical appearance on histopathology. Although chronic infections and chronic inflammatory diseases used to be the causes of secondary amyloidosis in children, the most frequent cause is now autoinflammatory diseases. Among this group of diseases, the most frequent one throughout the world is familial Mediterranean fever (FMF). FMF is typically characterized by attacks of clinical inflammation in the form of fever and serositis and high acute-phase reactants. Persisting inflammation in inadequately treated disease is associated with the development of secondary amyloidosis. The main treatment is colchicine. A number of other monogenic autoinflammatory diseases have also been identified. Among them cryopyrin-associated periodic syndrome (CAPS) is outstanding with its clinical features and the predilection to develop secondary amyloidosis in untreated cases. The treatment of secondary amyloidosis mainly depends on the treatment of the disease. However, a number of new treatments for amyloid per se are in the pipeline
Detecting Radio AGN Signatures in Red Geysers
A new class of quiescent galaxies harboring possible AGN-driven winds has been discovered using spatially resolved optical spectroscopy from the ongoing SDSS-IV MaNGA survey. These galaxies, termed "red geysers", constitute 5−10% of the local quiescent population and are characterized by narrow bisymmetric patterns in ionized gas emission features. Cheung et al. argued that these galaxies host large-scale AGN-driven winds that may play a role in suppressing star formation at late times. In this work, we test the hypothesis that AGN activity is ultimately responsible for the red geyser phenomenon. We compare the nuclear radio activity of the red geysers to a matched control sample with similar stellar mass, redshift, rest frame NUV−r color, axis ratio and presence of ionized gas. We have used the 1.4 GHz radio continuum data from VLA FIRST survey to stack the radio flux from the red geyser and control samples. In addition to a 3 times higher FIRST detection rate, we find that red geysers have a 5σ higher level of average radio flux than control galaxies. After restricting to rest-frame NUV−r color > 5 and checking mid-IR WISE photometry, we rule out star formation contamination and conclude that red geysers are associated with more active AGN. Red geysers and a possibly-related class with disturbed Hα emission account for 40\% of all radio-detected red galaxies with log (M⋆/M⊙)<11. Our results support a picture in which episodic AGN activity drives large-scale-relatively weak ionized winds that may provide a feedback mechanism for many early-type galaxies
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