811 research outputs found
The Stellar Haloes of Massive Elliptical Galaxies III: Kinematics at Large Radius
We present a 2D kinematic analysis out to ~2-5 effective radii (Re) of 33
massive elliptical galaxies with stellar velocity dispersions larger than 150
km/s. Our observations were taken using the Mitchell Spectrograph (formerly
VIRUS-P), a spectrograph with a large 107 x 107 square arcsecond field-of-view
that allows us to construct robust, spatially resolved kinematic maps of the
mean velocity and velocity dispersion for each galaxy extending to at least 2
Re. Using these maps we study the radial dependence of the stellar angular
momentum and other kinematic properties. We see the familiar division between
slow and fast rotators persisting out to large radius in our sample. Centrally
slow rotating galaxies, which are almost universally characterised by some form
of kinematic decoupling or misalignment, remain slowly rotating in their halos.
The majority of fast rotating galaxies show either increases in specific
angular momentum outwards or no change beyond . The generally triaxial
nature of the slow rotators suggests that they formed through mergers,
consistent with a "two-phase" picture of elliptical galaxy formation. However,
we do not observe the sharp transitions in kinematics proposed in the
literature as a signpost of moving from central dissipationally-formed
components to outer accretion-dominated haloes.Comment: 19 pages, 13 figures. 17 Appendix pages, 19 Appendix figure
Offset Active Galactic Nuclei as Tracers of Galaxy Mergers and Supermassive Black Hole Growth
Offset active galactic nuclei (AGNs) are AGNs that are in ongoing galaxy
mergers, which produce kinematic offsets in the AGNs relative to their host
galaxies. Offset AGNs are also close relatives of dual AGNs. We conduct a
systematic search for offset AGNs in the Sloan Digital Sky Survey, by selecting
AGN emission lines that exhibit statistically significant line-of-sight
velocity offsets relative to systemic. From a parent sample of 18314 Type 2
AGNs at z<0.21, we identify 351 offset AGN candidates with velocity offsets of
50 km/s < |v| < 410 km/s. When we account for projection effects in the
observed velocities, we estimate that 4% - 8% of AGNs are offset AGNs. We
designed our selection criteria to bypass velocity offsets produced by rotating
gas disks, AGN outflows, and gravitational recoil of supermassive black holes,
but follow-up observations are still required to confirm our candidates as
offset AGNs. We find that the fraction of AGNs that are offset candidates
increases with AGN bolometric luminosity, from 0.7% to 6% over the luminosity
range 43 < log(L_bol) [erg/s] < 46. If these candidates are shown to be bona
fide offset AGNs, then this would be direct observational evidence that galaxy
mergers preferentially trigger high-luminosity AGNs. Finally, we find that the
fraction of AGNs that are offset AGN candidates increases from 1.9% at z=0.1 to
32% at z=0.7, in step with the growth in the galaxy merger fraction over the
same redshift range.Comment: 14 pages, 14 figures, accepted for publication in Ap
Active Galaxies and the Study of Black Hole Demographics
We discuss the critical importance of black hole mass indicators based on
scaling relations in active galaxies. We highlight outstanding uncertainties in
these methods and potential paths to substantial progress in the next decade.Comment: 4 pages, 1 figure, Invited review to appear in PAS
Quasar feedback and the origin of radio emission in radio-quiet quasars
We conduct kinematic analysis of the SDSS spectra of 568 obscured luminous
quasars, with the emphasis on the kinematic structure of the [OIII]5007
emission line. [OIII] emission tends to show blueshifts and blue excess, which
indicates that at least part of the narrow-line gas is undergoing an organized
outflow. The velocity width containing 90% of line power ranges from 370 to
4780 km/sec, suggesting outflow velocities up to 2000 km/sec. The velocity
width of the [OIII] emission is positively correlated with the radio luminosity
among the radio-quiet quasars. We propose that radio emission in radio-quiet
quasars is due to relativistic particles accelerated in the shocks within the
quasar-driven outflows; star formation in quasar hosts is insufficient to
explain the observed radio emission. The median radio luminosity of the sample
of nu L_nu[1.4GHz] = 10^40 erg/sec suggests a median kinetic luminosity of the
quasar-driven wind of L_wind=3x10^44 erg/sec, or about 4% of the estimated
median bolometric luminosity L_bol=8x10^45 erg/sec. Furthermore, the velocity
width of [OIII] is positively correlated with mid-infrared luminosity, which
suggests that outflows are ultimately driven by the radiative output of the
quasar. As the outflow velocity increases, some emission lines characteristic
of shocks in quasi-neutral medium increase as well, which we take as further
evidence of quasar-driven winds propagating into the interstellar medium of the
host galaxy. None of the kinematic components show correlations with the
stellar velocity dispersions of the host galaxies, so there is no evidence that
any of the gas in the narrow-line region of quasars is in dynamical equilibrium
with the host galaxy. Quasar feedback appears to operate above the threshold
luminosity of L_bol=3x10^45 erg/sec.Comment: 23 pages, accepted to MNRA
A Comprehensive Archival Chandra Search for X-ray Emission from Ultracompact Dwarf Galaxies
We present the first comprehensive archival study of the X-ray properties of
ultracompact dwarf (UCD) galaxies, with the goal of identifying
weakly-accreting central black holes in UCDs. Our study spans 578 UCDs
distributed across thirteen different host systems, including clusters, groups,
fossil groups, and isolated galaxies. Of the 336 spectroscopically-confirmed
UCDs with usable archival Chandra imaging observations, 21 are X-ray-detected.
Imposing a completeness limit of erg s, the global
X-ray detection fraction for the UCD population is . Of the 21
X-ray-detected UCDs, seven show evidence of long-term X-ray time variability on
the order of months to years. X-ray-detected UCDs tend to be more compact than
non-X-ray-detected UCDs, and we find tentative evidence that the X-ray
detection fraction increases with surface luminosity density and global stellar
velocity dispersion. The X-ray emission of UCDs is fully consistent with
arising from a population of low-mass X-ray binaries (LMXBs). In fact, there
are fewer X-ray sources than expected using a naive extrapolation from globular
clusters. Invoking the fundamental plane of black hole activity for SUCD1 near
the Sombrero galaxy, for which archival Jansky Very Large Array imaging at 5
GHz is publicly available, we set an upper limit on the mass of a hypothetical
central black hole in that UCD to be . While the
majority of our sources are likely LMXBs, we cannot rule out central black
holes in some UCDs based on X-rays alone, and so we address the utility of
follow-up radio observations to find weakly-accreting central black holes.Comment: 20 pages, 6 figures, re-submitted to ApJ after minor revision
Education for Healthcare Providers, Nurses, and the Public on Opioid Induced Hyperalgesia
This project evaluated the knowledge of the public, healthcare providers, and nurses regarding opioid induced hyperalgesia (OIH). OIH is an elevated pain response because of high dosage or chronic use of opioids. Opioids are a problem not only in the United States but throughout the world; addiction, constipation, and overdose are the most frequently mentioned consequences of opioids. Little is known about other consequences to the body caused by chronic or high dose opioid usage, such as OIH. This project sought to increase awareness and caution against the utilization of opioids by patients and their healthcare providers and nurses practice. Two healthcare providers and nurses’ education sessions were held via Zoom meetings with the material presented based on results from a Facebook survey that was used to assess current knowledge. Pre- and post-session surveys were given to healthcare providers and nurses to evaluate their education and current and future practices. Upon evaluation of the data, it showed that over half the participants were unable to correctly define OIH, that the majority were nurse practitioners in the clinic, and back pain was the most frequent reason for opioids utilized in their practice, with Tramadol being the biggest culprit. Post-session surveys displayed a decrease in the number of healthcare providers and nurses that would utilize opioids for back pain
Size and Abundance of Pismo Clams in the Intertidal and Subtidal
Pismo clams, Tivela stultorum, were observed at Rincon Beach, CA to find patterns of abundance and size distribution along a depth gradient from the intertidal, where recreational clammers have access on foot, to the subtidal, where clammers only have access with more specialized snorkeling or SCUBA equipment. Size and abundance patterns were compared between the intertidal and subtidal regions. A heuristic model was created to predict the effects of predation and wave action on clam density. Clam abundance was significantly greater in the intertidal than the subtidal and displayed a Gaussian distribution across the entire distance sampled. While Pismo clam abundance was greater in the intertidal region, the mean clam size was significantly greater in the subtidal region. Moreover there was no difference in the distribution of sublegal clams between regions. However, there were significantly more legal sized clams in the subtidal than the intertidal. Our results suggest that recreational fishing pressure and exposure to the wash zone, in addition to other factors, influence the distribution of clams at Rincon Beach, CA. Further elucidating the patterns and mechanisms contributing to the distribution trends of the Pismo clam could aid in overall population estimates and the future management of the Pismo clam fishery
Testing the presence of multiple photometric components in nearby early-type galaxies using SDSS
We investigate two-dimensional image decomposition of nearby, morphologically
selected early-type galaxies (ETGs). We are motivated by recent observational
evidence of significant size growth of quiescent galaxies and theoretical
development advocating a two-phase formation scenario for ETGs. We find that a
significant fraction of nearby ETGs show changes in isophotal shape that
require multi-component models. The characteristic sizes of the inner and outer
component are and kpc. The inner component lies on the
mass-size relation of ETGs at , while the outer component
tends to be more elliptical and hints at a stochastic buildup process. We find
real physical differences between the single- and double-component ETGs, with
the double-component galaxies being younger and more metal-rich. The fraction
of double component ETGs increases with increasing and decreases in
denser environments. We hypothesize that double-component systems were able to
accrete gas and small galaxies until later times, boosting their central
densities, building up their outer parts, and lowering their typical central
ages. In contrast, the oldest galaxies, perhaps due to residing in richer
environments, have no remaining hints of their last accretion episode.Comment: resubmitted to ApJ after referee's repor
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