22,250 research outputs found
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
Older people's experiences of changed medication appearance : a survey
This report details a survey of older people's experiences of changed medication appearance. The aims of the study were:
• To develop a questionnaire in partnership with older people to survey older people’s views on fluctuating medication appearance
• To elicit older people’s experiences of medication that changed appearance due to ‘generic prescribing’ and ‘parallel import’ practices and its impact on their medication taking practices.
These common pharmacy practices mean that the same tablet medication can be issued to older people in different colours, sizes and shapes to their previous prescriptions. Older people from a local User/Carer Forum highlighted these problems to the research team and asked that we investigate to explore the extent of the problem.
An eight-item questionnaire was developed and distributed to 2000 older people (50 years+) across participating PCTs in Greater Manchester in 2008. A 29% response rate was achieved. The data was analysed using the SPSS statistical package. Findings include:
•63.3% experienced a change in the appearance of their tablet medications.
•74.1% did not seek advice regarding the change in the appearance of their tablet medications.
•Older people noted changes to the actual tablets, tablet packaging and written information that accompanies tablets. Changes are occurring to the colour, size and shape of tablets more than changes to packaging and written information.
The majority of respondents had experienced changes in the appearance of their prescribed tablet medication in the previous two years which were not due to change in medication or dose etc. Worryingly, for some respondents, these changes prompted negative experiences such as anxiety, confusion and upset. Of particular concern was that a small number omitted the affected tablet medications and did not seek help or advice from GPs, pharmacists or relatives.
Six older people have been study advisors from inception to dissemination of this study and significantly added to its quality. The study demonstrates substantive public engagement / user involvement in research. The findings suggest nurses and others have a role to play in promoting better medicines management and identifying those most at risk from changed appearance of medications
Similarity of ionized gas nebulae around unobscured and obscured quasars
Quasar feedback is suspected to play a key role in the evolution of massive
galaxies, by removing or reheating gas in quasar host galaxies and thus
limiting the amount of star formation. In this paper we continue our
investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini
Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1)
quasars, to determine the morphology and kinematics of ionized gas around these
objects, predominantly via observations of the [O III]5007 emission line. We
find that ionized gas nebulae extend out to ~13 kpc from the quasar, that they
are smooth and round, and that their kinematics are inconsistent with gas in
dynamical equilibrium with the host galaxy. The observed morphological and
kinematic properties are strikingly similar to those of ionized gas around
obscured (type 2) quasars with matched [O III] luminosity, with marginal
evidence that nebulae around unobscured quasars are slightly more compact.
Therefore in samples of obscured and unobscured quasars carefully matched in [O
III] luminosity we find support for the standard geometry-based unification
model of active galactic nuclei, in that the intrinsic properties of quasars,
of their hosts and of their ionized gas appear to be very similar. Given the
apparent ubiquity of extended ionized regions, we are forced to conclude that
either the quasar is at least partially illuminating pre-existing gas or that
both samples of quasars are seen during advanced stages of quasar feedback. In
the latter case, we may be biased by our [O III]-based selection against
quasars in the early "blow-out" phase, for example due to dust obscuration.Comment: 17 pages, 10 figures, 2 tables. Published in MNRAS, 201
Intermediate-mass Black Holes in Galactic Nuclei
We present the first homogeneous sample of intermediate-mass black hole
candidates in active galactic nuclei. Starting with broad-line active nuclei
from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling
relation to select a sample of 19 galaxies in the mass range M_BH ~ 8 x 10^4 -
10^6 solar masses. In contrast to the local active galaxy population, the host
galaxies are ~1 mag fainter than M* and thus are probably late-type systems.
The active nuclei are also faint, with M_g ~ -15 to -18 mag, while the
bolometric luminosities are close to the Eddington limit. The spectral
properties of the sample are compared to the related class of objects known as
narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as
observational analogues of primordial black holes, contributors to the
integrated signal for future gravitational wave experiments, and as a valuable
tool in the calibration of the M-sigma relation.Comment: 4 pages, 4 figures. To appear in "The Interplay among Black Holes,
Stars and ISM in Galactic Nuclei," Proc. IAU 222 (Gramado, Brazil), eds Th.
Storchi Bergmann, L.C. Ho, H.R. Schmit
Sizes and Kinematics of Extended Narrow-Line Regions in Luminous Obscured AGN Selected by Broadband Images
To study the impact of active galactic nuclei (AGN) feedback on the galactic
ISM, we present Magellan long-slit spectroscopy of 12 luminous nearby type 2
AGN (L_bol~10^{45.0-46.5} erg/s, z~0.1). These objects are selected from a
parent sample of spectroscopically identified AGN to have high
[OIII]{\lambda}5007 and WISE mid-IR luminosities and extended emission in the
SDSS r-band images, suggesting the presence of extended [OIII]{\lambda}5007
emission. We find spatially resolved [OIII] emission (2-35 kpc from the
nucleus) in 8 out of 12 of these objects. Combined with samples of higher
luminosity type 2 AGN, we confirm that the size of the narrow-line region
(R_NLR) scales with the mid-IR luminosity until the relation flattens at ~10
kpc. Nine out of 12 objects in our sample have regions with broad [OIII]
linewidths (w_80>600 km/s), indicating outflows. We define these regions as the
kinematically-disturbed region (KDR). The size of the KDR (R_KDR) is typically
smaller than R_NLR by few kpc but also correlates strongly with the AGN mid-IR
luminosity. Given the unknown density in the gas, we derive a wide range in the
energy efficiency {\eta}=dot{E}/L_bol=0.01%-30%. We find no evidence for an AGN
luminosity threshold below which outflows are not launched. To explain the
sizes, velocity profiles, and high occurrence rates of the outflows in the most
luminous AGN, we propose a scenario in which energy-conserving outflows are
driven by AGN episodes with ~10^8-year durations. Within each episode the AGN
flickers on shorter timescales, with a cadence of ~10^6 year active phases
separated by ~10^7 years.Comment: 32 pages, 21 figures, ApJ in revie
A Study of Polymers Containing Silicon-nitrogen Bonds Annual Summary Report, 4 May 1966 - 3 Jun. 1967
Polymers containing silicon-nitrogen bond
Strong [O III] Objects Among SDSS Broad-Line Active Galaxies
We present the results of a spectral principal component analysis on 9046
broad-line AGN from the Sloan Digital Sky Survey. We examine correlations
between spectral regions within various eigenspectra (e.g., between Fe II
strength and H width) and confirm that the same trends are apparent in
spectral measurements, as validation of our technique. Because we found that
our sample had a large range in the equivalent width of [O III] 5007,
we divided the data into three subsets based on [O III] strength. Of these,
only in the sample with the weakest equivalent width of [O III] were we able to
recover the known correlation between [O III] strength and full width at half
maximum of H and their anticorrelation with Fe II strength. At the low
luminosities considered here ( of erg
s), interpretation of the principal components is considerably
complicated particularly because of the wide range in [O III] equivalent width.
We speculate that variations in covering factor are responsible for this wide
range in [O III] strength.Comment: 26 pages, 11 figures, published in Ap
Feedback In Luminous Obscured Quasars
We use spatially resolved long-slit spectroscopy from Magellan to investigate the extent, kinematics, and ionization structure in the narrow-line regions of 15 luminous, obscured quasars with z < 0.5. Increasing the dynamic range in luminosity by an order of magnitude, as well as improving the depth of existing observations by a similar factor, we revisit relations between narrow-line region size and the luminosity and linewidth of the narrow emission lines. We find a slope of 0.22 +/- 0.04 for the power-law relationship between size and luminosity, suggesting that the nebulae are limited by availability of gas to ionize at these luminosities. In fact, we find that the active galactic nucleus is effectively ionizing the interstellar medium over the full extent of the host galaxy. Broad (similar to 300-1000 km s(-1)) linewidths across the galaxies reveal that the gas is kinematically disturbed. Furthermore, the rotation curves and velocity dispersions of the ionized gas remain constant out to large distances, in striking contrast to normal and starburst galaxies. We argue that the gas in the entire host galaxy is significantly disturbed by the central active galactic nucleus. While only similar to 10(7)-10(8) M-circle dot worth of gas are directly observed to be leaving the host galaxies at or above their escape velocities, these estimates are likely lower limits because of the biases in both mass and outflow velocity measurements and may in fact be in accord with expectations of recent feedback models. Additionally, we report the discovery of two dual obscured quasars, one of which is blowing a large-scale (similar to 10 kpc) bubble of ionized gas into the intergalactic medium.NSF AST-0548198Astronom
Steep-Spectrum Radio Emission from the Low-Mass Active Galactic Nucleus GH 10
GH 10 is a broad-lined active galactic nucleus (AGN) energized by a black
hole of mass 800,000 Solar masses. It was the only object detected by Greene et
al. in their Very Large Array (VLA) survey of 19 low-mass AGNs discovered by
Greene & Ho. New VLA imaging at 1.4, 4.9, and 8.5 GHz reveals that GH 10's
emission has an extent of less than 320 pc, has an optically-thin synchrotron
spectrum with a spectral index -0.76+/-0.05, is less than 11 percent linearly
polarized, and is steady - although poorly sampled - on timescales of weeks and
years. Circumnuclear star formation cannot dominate the radio emission, because
the high inferred star formation rate, 18 Solar masses per year, is
inconsistent with the rate of less than 2 Solar masses per year derived from
narrow Halpha and [OII] 3727 emission. Instead, the radio emission must be
mainly energized by the low-mass black hole. GH 10's radio properties match
those of the steep-spectrum cores of Palomar Seyfert galaxies, suggesting that,
like those Seyferts, the emission is outflow-driven. Because GH 10 is radiating
close to its Eddington limit, it may be a local analog of the starting
conditions, or seeds, for supermassive black holes. Future imaging of GH 10 at
higher resolution thus offers an opportunity to study the relative roles of
radiative versus kinetic feedback during black-hole growth.Comment: 7 pages; 2 figures; emulateapj; to appear in Ap
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