529 research outputs found
Spatially-Resolved Spectra of the "Teacup" AGN: Tracing the History of a Dying Quasar
The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number
of spectacular galaxies possessing Extended Emission-Line Regions (EELRs), the
most famous being Hanny's Voorwerp galaxy. We present another EELR object
discovered in the SDSS endeavor: the Teacup Active Galactic Nucleus (AGN),
nicknamed for its EELR, which has a handle like structure protruding 15 kpc
into the northeast quadrant of the galaxy. We analyze physical conditions of
this galaxy with long-slit ground based spectroscopy from Lowell, Lick, and
KPNO observatories. With the Lowell 1.8m Perkin's telescope we took multiple
observations at different offset positions, allowing us to recover spatially
resolved spectra across the galaxy. Line diagnostics indicate the ionized gas
is photoionized primarily by the AGN. Additionally we are able to derive the
hydrogen density from the [S II] 6716/6731 ratio. We generated two-component
photoionization models for each spatially resolved Lowell spectrum. These
models allow us to calculate the AGN bolometric luminosity seen by the gas at
different radii from the nuclear center of the Teacup. Our results show a drop
in bolometric luminosity by more than two orders of magnitude from the EELR to
the nucleus, suggesting that the AGN has decreased in luminosity by this amount
in a continuous fashion over 46,000 years, supporting the case for a dying AGN
in this galaxy independent of any IR based evidence. We demonstrate that
spatially resolved photoionization modeling could be applied to EELRs to
investigate long time scale variability.Comment: 38 pages, 11 figures, accepted for publication in the Astrophysical
Journa
The Contribution of Copy Number Variants and Single Nucleotide Polymorphisms to the Additive Genetic Variance of Carcass Traits in Cattle
The relative contributions of both copy number variants (CNVs) and single nucleotide polymorphisms (SNPs) to the additive genetic variance of carcass traits in cattle is not well understood. A detailed understanding of the relative importance of CNVs in cattle may have implications for study design of both genomic predictions and genome-wide
association studies. The first objective of the present study was to quantify the relative contributions of CNV data and SNP genotype data to the additive genetic variance of
carcass weight, fat, and conformation for 945 Charolais, 923 Holstein-Friesian, and 974 Limousin sires. The second objective was to jointly consider SNP and CNV data in a least absolute selection and shrinkage operator (LASSO) regression model to identify genomic regions associated with carcass weight, fat, and conformation within each of the three breeds separately. A genomic relationship matrix (GRM) based on just CNV data did not capture any variance in the three carcass traits when jointly evaluated with a SNP-derived GRM. In the LASSO regression analysis, a total of 987 SNPs and 18 CNVs were associated with at least one of the three carcass traits in at least one of the three
breeds. The quantitative trait loci (QTLs) corresponding to the associated SNPs and CNVs overlapped with several candidate genes including previously reported candidate
genes such as MSTN and RSAD2, and several potential novel candidate genes such as ACTN2 and THOC1. The results of the LASSO regression analysis demonstrated that CNVs can be used to detect associations with carcass traits which were not detected using the set of SNPs available in the present study. Therefore, the CNVs and SNPs available in the present study were not redundant forms of genomic data
Extreme lowering of deglacial seawater radiocarbon recorded by both epifaunal and infaunal benthic foraminifera in a wood-dated sediment core
For over a decade, oceanographers have debated the interpretation
and reliability of sediment microfossil records indicating extremely low
seawater radiocarbon (14C) during the last deglaciation –
observations that suggest a major disruption in marine carbon cycling
coincident with rising atmospheric CO2 concentrations. Possible
flaws in these records include poor age model controls, utilization of mixed
infaunal foraminifera species, and bioturbation. We have addressed these
concerns using a glacial–interglacial record of epifaunal benthic
foraminifera 14C on an ideal sedimentary age model (wood calibrated
to atmosphere 14C). Our results affirm – with important caveats –
the fidelity of these microfossil archives and confirm previous observations
of highly depleted seawater 14C at intermediate depths in the
deglacial northeast Pacific.</p
A Preliminary Survey of Interprofessional Education
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153603/1/jddj002203372006704tb04096x.pd
Pretty Picky for a Generalist: Impacts of Toxicity and Nutritional Quality on Mantid Prey Processing
Prey have evolved a number of defenses against predation, and predators have developed means of countering these protective measures. Although caterpillars of the monarch butterfly, Danaus plexippus L., are defended by cardenolides sequestered from their host plants, the Chinese mantid Tenodera sinensis Saussure guts the caterpillar before consuming the rest of the body. We hypothesized that this gutting behavior might be driven by the heterogeneous quality of prey tissue with respect to toxicity and/or nutrients. We conducted behavioral trials in which mantids were offered cardenolide-containing and cardenolide-free D. plexippus caterpillars and butterflies. In addition, we fed mantids starved and unstarved D. plexippus caterpillars from each cardenolide treatment and nontoxic Ostrinia nubilalis Hübner caterpillars. These trials were coupled with elemental analysis of the gut and body tissues of both D. plexippus caterpillars and corn borers. Cardenolides did not affect mantid behavior: mantids gutted both cardenolide-containing and cardenolide-free caterpillars. In contrast, mantids consumed both O. nubilalis and starved D. plexippus caterpillars entirely. Danaus plexippus body tissue has a lower C:N ratio than their gut contents, while O. nubilalis have similar ratios; gutting may reflect the mantid’s ability to regulate nutrient uptake. Our results suggest that post-capture prey processing by mantids is likely driven by a sophisticated assessment of resource quality
A Multi-Wavelength Study of the Nature of Type 1.8/1.9 Seyfert Galaxies
We focus on determining the underlying physical cause of a Seyfert galaxy's
appearance as type a 1.8 or 1.9. Are these "intermediate" Seyfert types typical
Seyfert 1 nuclei with reddened broad-line regions? Or are they objects with
intrinsically weak continua and broad emission lines? We compare measurements
of the optical reddening of the narrow and broad-line regions with each other
and with the X-ray column derived from XMM-Newton 0.5-10 keV spectra to
determine the presence and location of dust in the line of sight. We also
searched the literature to see if the objects showed evidence for broad-line
variability, and determined if the changes were consistent with a change in
reddening or a change in the intrinsic ionizing continuum flux. We find that 10
of 19 objects previously classified as Seyfert 1.8/1.9s received this
designation due to their low continuum flux. In four objects the classification
was due to BLR reddening, either by the torus or dust structures in the
vicinity of the NLR; in the remaining five objects there is not sufficient
evidence to favor one scenario over the other. These findings imply that, in
general, samples of 1.8/1.9s are not suitable for use in studies of the gas and
dust in the central torus.Comment: 85 pages, accepted by Ap
Deglacial-Holocene Pulses of Old Carbon-Enriched Mediterranean Water Masses: Implications for Aragonite Mounds Growth and Global Carbon Cycle
Major changes in the Mediterranean Thermohaline Circulation (MedTHC) related to deglaciation and monsoon dynamics have been documented, while in turn, Mediterranean waters have been proposed to play a role back in global climate variability, ocean circulation and carbon cycle budgets, for instance via changes in water mass residence times. The 14C offset between coeval planktonic and benthic foraminifera over time is a very useful tool to infer variations in the water column ventilation (with no biological interference) that becomes more accurate when combined with local paired 14C-U/Th analyses in cold-water corals (CWC). Here, we present a multi-proxy-archive study (i.e., estimates of reservoir ages, εNd, [CO3 2-], O2 and current speed) carried out on the on-mound sediment core MD13-3452 (305 m, West Melilla, Alboran Sea, Western Mediterranean), which investigates potential deglacial changes and triggers in deep reservoir ages, as well as possible impacts on CWC aragonite mound growth and on global carbon cycle.Our combined foraminifera-CWC radioactive isotopes results show: 1) the arrival of two pulses of aged waters at intermediate depth corresponding to the Younger Dryas (YD) and to the end of the last sapropel (S1), when low CWC mound growth rates dominated, and 2) a very well-ventilated water mass between those two events, parallel to a CWC mound flourishing stage. In combination with the other proxies, poorer ventilated water pulses seem to have had a different origin, but common higher content in respired carbon. Our results allow, for the first time, changes in ventilation rates to be shown, quantified, and timed in association with a periodical MedTHC weakening, as well as suggesting significant aragonite dissolution as a cause of decreased mound growth rate when higher CO2 episodes. Our findings may have implications for past hydrographic interconnexions between Mediterranean basins and for global marine carbon storage and alkalinity budget in particular
Photo-centric variability of quasars caused by variations in their inner structure: Consequences on Gaia measurements
We study the photocenter position variability due to variations in the quasar
inner structure. We consider variability in the accretion disk emissivity and
torus structure variability due to different illumination by the central
source. We discuss possible detection of these effects by Gaia. Observations of
the photocenter variability in two AGNs, SDSS J121855+020002 and SDSS
J162011+1724327 have been reported and discussed. With investigation of the
variations in the quasar inner structure we explore how much this effect can
affect the position determination and whether it can be (or not) detected with
Gaia mission. We used (a) a model of a relativistic disk, including the
perturbation that can increase brightness of a part of the disk, and
consequently offset the photocenter position, and (b) a model of a dusty torus
which absorbs and re-emits the incoming radiation from accretion disk. We
estimated the value of the photocenter offset due to these two effects. We
found that perturbations in the inner structure can significantly offset the
photocenter. It depends on the characteristics of perturbation and accretion
disk and structure of the torus. In the case of two considered QSOs the
observed photocenter offsets cannot be explained by variations in the accretion
disk and other effects should be considered. We discussed possibility of
exploding stars very close to the AGN source, and also possibility that there
are two variable sources in the center of these two AGNs that may indicate a
binary super-massive black hole system on a kpc (pc) scale. The Gaia mission
seems to be very perspective, not only for astrometry, but also for exploring
the inner structure of AGNs. We conclude that variations in the quasar inner
structure can affect the observed photocenter (up to several mas). There is a
chance to observe such effect in the case of bright and low-redshifted QSOs.Comment: 12 pages, 8 figures, 3 tables. Accepted for publication in Astronomy
and Astrophysics. Language improved, typos correcte
Narratives of self and identity in women's prisons: stigma and the struggle for self-definition in penal regimes
A concern with questions of selfhood and identity has been central to penal practices in women's prisons, and to the sociology of women's imprisonment. Studies of women's prisons have remained preoccupied with women prisoners’ social identities, and their apparent tendency to adapt to imprisonment through relationships. This article explores the narratives of women in two English prisons to demonstrate the importance of the self as a site of meaning for prisoners and the central place of identity in micro-level power negotiations in prisons
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