2,856 research outputs found
Improved and Quality-assessed Emission and Absorption Line measurements in Sloan Digital Sky Survey galaxies
We present a new database of absorption and emission-line measurements based
on the entire spectral atlas from the Sloan Digital Sky Survey (SDSS) 7th data
release of galaxies within a redshift of 0.2. Our work makes use of the
publicly available penalized pixel-fitting(pPXF) and gas and absorption line
fitting (gandalf) IDL codes, aiming to improve the existing measurements for
stellar kinematics, the strength of various absorption-line features, and the
flux and width of the emissions from different species of ionised gas. Our fit
to the stellar continuum uses both standard stellar population models and
empirical templates obtained by combining a large number of stellar spectra in
order to fit a subsample of high-quality SDSS spectra for quiescent galaxies.
Furthermore, our fit to the nebular spectrum includes an exhaustive list of
both recombination and forbidden lines. Foreground Galactic extinction is
implicitly treated in our models, whereas reddening in the SDSS galaxies is
included in the form of a simple dust screen component affecting the entire
spectrum that is accompanied by a second reddening component affecting only the
ionised gas emission. In order to check for systematic departures, we provide a
quality assessment for our fit to the SDSS spectra in our sample. This quality
assessment also allows the identification of objects with either problematic
data or peculiar features. For example, based on the quality assessment,
approximately 1% of the SDSS spectra classified as "galaxies" by the SDSS
pipeline do in fact require additional broad lines to be matched, even though
they do not show a strong continuum from an active nucleus, as do the SDSS
objects classified as "quasars". Finally, we provide new spectral templates for
galaxies of different Hubble types, obtained by combining the results of our
spectral fit for a subsample of 452 morphologically selected objects.Comment: Accepted for publication in ApJS. 23 pages, 14 figures, 4 tables. A
version with high-resolution figures is available at
http://gem.yonsei.ac.kr/~ksoh/ossy/arXiv/Oh_11_OSSY.pd
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The M87 Black Hole Mass From Gas-Dynamical Models Of Space Telescope Imaging Spectrograph Observations
The supermassive black hole of M87 is one of the most massive black holes known and has been the subject of several stellar and gas-dynamical mass measurements; however, the most recent revision to the stellar-dynamical black hole mass measurement is a factor of about two larger than the previous gas-dynamical determinations. Here, we apply comprehensive gas-dynamical models that include the propagation of emission-line profiles through the telescope and spectrograph optics to new Space Telescope Imaging Spectrograph observations from the Hubble Space Telescope. Unlike the previous gas-dynamical studies of M87, we map out the complete kinematic structure of the emission-line disk within similar to 40 pc from the nucleus, and find that a small amount of velocity dispersion internal to the gas disk is required to match the observed line widths. We examine a scenario in which the intrinsic velocity dispersion provides dynamical support to the disk, and determine that the inferred black hole mass increases by only 6%. Incorporating this effect into the error budget, we ultimately measure a mass of M-BH = (3.5(-0.7)(+0.9)) x 10(9)M circle dot (68% confidence). Our gas-dynamical black hole mass continues to differ from the most recent stellar-dynamical mass by a factor of two, underscoring the need for carrying out more cross-checks between the two main black hole mass measurement methods.NSF Astronomy and Astrophysics Postdoctoral Fellowship 1102845Space Telescope Science Institute 12162NASA NAS 5-26555NSF AST-1108835Astronom
A black-hole mass measurement from molecular gas kinematics in NGC4526
The masses of the supermassive black-holes found in galaxy bulges are
correlated with a multitude of galaxy properties, leading to suggestions that
galaxies and black-holes may evolve together. The number of reliably measured
black-hole masses is small, and the number of methods for measuring them is
limited, holding back attempts to understand this co-evolution. Directly
measuring black-hole masses is currently possible with stellar kinematics (in
early-type galaxies), ionised-gas kinematics (in some spiral and early-type
galaxies) and in rare objects which have central maser emission. Here we report
that by modelling the effect of a black-hole on the kinematics of molecular gas
it is possible to fit interferometric observations of CO emission and thereby
accurately estimate black hole masses. We study the dynamics of the gas in the
early-type galaxy NGC4526, and obtain a best fit which requires the presence of
a central dark-object of 4.5(+4.2-3.0)x10^8 Msun (3 sigma confidence limit).
With next generation mm-interferometers (e.g. ALMA) these observations could be
reproduced in galaxies out to 75 megaparsecs in less the 5 hours of observing
time. The use of molecular gas as a kinematic tracer should thus allow one to
estimate black-hole masses in hundreds of galaxies in the local universe, many
more than accessible with current techniques.Comment: To appear in Nature online on 30/01/2013. 3 Pages, 2 Figures (plus
two pages of supplementary information
Pain in systemic connective tissue diseases
Pain is frequent in patients with connective tissue diseases
(CTDs), particularly those affected by systemic sclerosis (SSc) and
systemic lupus erythematosus (SLE) in which it is virtually
ubiquitous and can have different causes. The SLE classi
fi
cation
criteria include pain associated with musculoskeletal involve-
ment, which are frequently the initial symptom of SLE and can
include arthralgia, arthritis and/or myalgia. Chronic widespread
pain, the cornerstone of
fi
bromyalgia (FM), is also frequently
associated with CTDs.
Chronic pain has a considerable impact on mental health, and the
professional and family lives of patients. It can be due to many
disorders, but there are few reports concerning its prevalence
during the course of other diseases.
It is essential to identify the origin of pain in CTDs in order to avoid
dangerous over-treatment in patients with co-existing widespread
pain. Effective pain management is a primary goal of patient
care, although it has not been investigated in detail in patients
with SSc
Building bridges between doctors and patients: the design and pilot evaluation of a training session in argumentation for chronic pain experts
Shared decision-making requires doctors to be competent in exchanging views with patients to identify the appropriate course of action. In this paper we focus on the potential of a course in argumentation as a promising way to empower doctors in presenting their viewpoints and addressing those of patients. Argumentation is the communication process in which the speaker, through the use of reasons, aims to convince the interlocutor of the acceptability of a viewpoint. The value of argumentation skills for doctors has been addressed in the literature. Yet, there is no research on what a course on argumentation might look like. In this paper, we present the content and format of a training session in argumentation for doctors and discuss some insights gained from a pilot study that examined doctors' perceived strengths and limitations vis-Ã -vis this training
On the fragility of nuclear stellar discs against galaxy mergers: surviving photometric and kinematic signatures of nuclear discs
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.Nuclear stellar discs (NSDs) can help to constrain the assembly history of their host galaxies, as long as we can assume them to be fragile structures that are disrupted during merger events. In this work we investigate the fragility of NSDs by means of N-body simulations reproducing the last phases of a galaxy encounter, when the nuclear regions of the two galaxies merge. For this, we exposed an NSD set in the gravitational potential of the bulge and supermassive black hole of a primary galaxy to the impact of the supermassive black hole from a secondary galaxy. We explored merger events of different mass ratios, from major mergers with a 1:1 mass ratio to intermediate and minor interactions with 1:5 and 1:10 ratios, while considering various impact geometries. We analyse the end results of such mergers from different viewing angles and look for possible photometric and kinematic signatures of the presence of a disc in the remnant surface density and velocity maps, while adopting detection limits from real observations. Our simulations show that indeed NSDs are fragile against major mergers, which leave little trace of NSDs both in images and velocity maps, while signatures of a disc can be found in the majority of the intermediate to minor-merger remnants and in particular when looking at their kinematics. These results show that NSDs could allow us to distinguish between these two modes of galaxy assembly, which may indeed pertain to different kinds of galaxies or galactic environments.Peer reviewe
MUSE observations of M87: radial gradients for the stellar initial-mass function and the abundance of Sodium
Based on MUSE integral-field data we present evidence for a radial variation
at the low-mass end of the stellar initial-mass function (IMF) in the central
regions of the giant early-type galaxy NGC4486 (M87). We used state-of-the-art
stellar population models and the observed strength of various IMF-sensitive
absorption-line features to solve for the best low-mass tapered "bimodal" form
of the IMF, while accounting also for radial variations in stellar metallicity,
the overall -elements abundance, and the abundance of individual
elements such as Ti, O, Na and Ca. Our analysis reveals a strong IMF gradient
in M87, corresponding to an exceeding fraction of low-mass stars compared to
the case of the Milky Way toward the center of M87 that drops to nearly
Milky-way levels by 0.4 . This IMF gradient is found to correlate well
with both the radial profile for stellar metallicity and for -elements
abundance but not with stellar velocity dispersion. Such IMF variations
correspond to over a factor two increase in stellar mass-to-light M/L ratio
compared to the case of a Milky-way like IMF, consistent with other
investigations into IMF gradients in early-type galaxies, including recent
dynamical constraints on M/L radial variations in M87 by Oldham & Auger. In
addition to constraining the IMF in M87 we also looked into the abundance of
Sodium, which turned up to be super-Solar over the entire radial range of our
MUSE observations and to exhibit a considerable negative gradient. These
findings suggest an additional role of metallicity in boosting the Na-yields in
the central, metal-rich regions of M87 during its early and brief
star-formation history. Our work adds the case of M87 to the few objects that
as of today have radial constraints on their IMF or [Na/Fe] abundance, while
also illustrating the accuracy that MUSE could bring to this kind of
investigations.Comment: 17 pages, 13 figures, re-submitted for publication on MNRAS following
the referee's comment
Star formation in the central regions of galaxies
Massive star formation in the central regions of spiral galaxies plays an
important role in the dynamical and secular evolution of their hosts. Here, we
summarise a number of recent investigations of the star formation history and
the physical conditions of the gas in circumnuclear regions, to illustrate not
only the detailed results one can achieve, but also the potential of using
state-of-the-art spectroscopic and analysis techniques in researching the
central regions of galaxies in general. We review how the star formation
history of nuclear rings confirms that they are long-lived and stable
configurations. Gas flows in from the disk, through the bar, and into the ring,
where successive episodes of massive star formation occur. Analysing the ring
in NGC 7742 in particular, we determine the physical conditions of the line
emitting gas using a combination of ionisation and stellar population
modelling, concluding that the origin of the nuclear ring in this non-barred
galaxy lies in a recent minor merger with a small gas-rich galaxy.Comment: Invited contribution, to appear in "Mapping the Galaxy and other
galaxies", Eds. K. Wada and F. Combes, Springer, in pres
Diffuse Gas in Retired Galaxies: Nebular Emission Templates and Constraints on the Sources of Ionization
We present emission line templates for passively evolving ("retired")
galaxies, useful for investigation of the evolution of the ISM in these
galaxies, and characterization of their high-temperature source populations.
The templates are based on high signal-to-noise () co-added spectra
(\AA) of gas-rich Sloan Digital Sky Survey galaxies
devoid of star-formation and active galactic nuclei. Stacked spectra are
provided for the entire sample and sub-samples binned by mean stellar age. In
Johansson~et al (2014), these spectra provided the first measurements of the He
II 4686\AA\ line in passively-evolving galaxies, and the observed He
II/H ratio constrained the contribution of accreting white dwarfs (the
"single-degenerate" scenario) to the type Ia supernova rate. In this paper, the
full range of unambiguously detected emission lines are presented. Comparison
of the observed [O I] 6300\AA/H ratio with photoionization models
further constrains any high-temperature single-degenerate scenario for type Ia
supernovae (with 1.5 T/ 10) to 3-6\%
of the observed rate in the youngest age bin (i.e. highest SN Ia rate). Hence,
for the same temperatures, in the presence of an ambient population of post-AGB
stars, we exclude additional high-temperature sources with a combined ionizing
luminosity of for stellar
populations with mean ages of 1 - 4 Gyrs. Furthermore, we investigate the
extinction affecting both the stellar and nebular continuum. The latter shows
about five times higher values. This contradicts isotropically distributed dust
and gas that renders similar extinction values for both cases.Comment: Accepted for publication in MNRAS, 16 pages, 12 figure
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