313 research outputs found
Using Virtual Observatory techniques to search for Adaptive Optics suitable AGN
Until recently, it has been possible only for nearby galaxies to study the
scaling relations between central black hole and host galaxy in detail. Because
of the small number densities at low redshift, (luminous) AGN are
underrepresented in such detailed studies. The advent of adaptive optics (AO)
at large telescopes helps overcoming this hurdle, allowing to reach small
linear scales over a wide range in redshift. Finding AO-suitable targets, i.e.,
AGN having a nearby reference star, and carrying out an initial multiwavelength
classification is an excellent use case for the Virtual Observatory. We present
our Virtual-Observatory approach to select an AO-suitable catalog of
X-ray-emitting AGN at redshifts 0.1<z<1.Comment: 4 pages, 5 figures, submitted to "EURO-VO AIDA workshop:
Multiwavelength astronomy and Virtual Observatory", ESAC, Spain, 1-3 Dec.
200
Jaw Dysfunction Is Associated with Neck Disability and Muscle Tenderness in Subjects with and without Chronic Temporomandibular Disorders
Purpose. Tender points in the neck are common in patients with temporomandibular disorders (TMD). However, the correlation among neck disability, jaw dysfunction, and muscle tenderness in subjects with TMD still needs further investigation. This study investigated the correlation among neck disability, jaw dysfunction, and muscle tenderness in subjects with and without chronic TMD. Participants. Forty females between 19 and 49 years old were included in this study.There were 20 healthy controls and 20 subjects who had chronic TMD and neck disability. Methods. Subjects completed the neck disability index and the limitations of daily functions in TMD questionnaires. Tenderness of the masticatory and cervical muscles was measured using an algometer. Results. The correlation between jaw disability and neck disability was significantly high (� = 0.915, � \u3c 0.05). The correlation between level of muscle tenderness in the masticatory and cervical muscles with jaw dysfunction and neck disability showed fair to moderate correlations (� = 0.32–0.65). Conclusion. High levels of muscle tenderness in upper trapezius and temporalis muscles correlated with high levels of jaw and neck dysfunction. Moreover, high levels of neck disability correlated with high levels of jaw disability.These findings emphasize the importance of considering the neck and its structures when evaluating and treating patients with TMD
Heavily Obscured Quasar Host Galaxies at z~2 are Disks, Not Major Mergers
We explore the nature of heavily obscured quasar host galaxies at z~2 using
deep Hubble Space Telescope WFC3/IR imaging of 28 Dust Obscured Galaxies (DOGs)
to investigate the role of major mergers in driving black hole growth. The high
levels of obscuration of the quasars selected for this study act as a natural
coronagraph, blocking the quasar light and allowing a clear view of the
underlying host galaxy. The sample of heavily obscured quasars represents a
significant fraction of the cosmic mass accretion on supermassive black holes
as the quasars have inferred bolometric luminosities around the break of the
quasar luminosity function. We find that only a small fraction (4%, at most
11-25%) of the quasar host galaxies are major mergers. Fits to their surface
brightness profiles indicate that 90% of the host galaxies are either disk
dominated, or have a significant disk. This disk-like host morphology, and the
corresponding weakness of bulges, is evidence against major mergers and
suggests that secular processes are the predominant driver of massive black
hole growth. Finally, we suggest that the co-incidence of mergers and AGN
activity is luminosity dependent, with only the most luminous quasars being
triggered mostly by major mergers.Comment: 5 pages, 4 figures, 1 table. To appear as a Letter in MNRA
Quantitative Morphology of Galaxies from the SDSS I: Luminosity in Bulges and Disks
In the first paper of this series we use the publicly available code Gim2D to
model the r- and i-band images of all galaxies in a magnitude-limited sample of
roughly 1800 morphologically classified galaxies taken from the Sloan Digital
Sky Survey. The model is a concentric superposition of two components, each
with elliptical isophotes with constant flattening and position angle. The disk
luminosity profile is assumed exponential, while the bulge is assumed to have a
de Vaucouleurs or a Sersic profile. We find that the parameters returned by
Gim2D depend little on the waveband or bulge profile used; their formal
uncertainties are usually small. Nevertheless, for bright galaxies the measured
distribution of b/a, the apparent disk flattening, deviates strongly from the
expected uniform distribution, showing that the `disk' identified by the code
frequently corresponds to an intrinsically 3-dimensional structure rather than
to a true thin disk. We correct approximately for this systematic problem using
the observed statistics of the b/a distribution and estimate, as a function of
absolute magnitude, the mean fractions of galaxy light in disks and in `pure
bulge' systems (those with no detectable disk). For the brightest galaxies the
disk light fraction is about 10% and about 80% are `pure bulge' systems. For
faint galaxies most of the light is in disks and we do not detect a `pure
bulge' population. Averaging over the galaxy population as a whole, we find
that 54 \pm 2% of the local cosmic luminosity density at both r and i comes
from disks and 32 \pm 2% from `pure bulge' systems. The remaining 14 \pm 2%
comes from bulges in galaxies with detectable disks.Comment: Submitted to MNRAS (14 pages, 14 figures). For version with higher
quality figures, see
http://www.mpa-garching.mpg.de/~tasca/MNRAS/Morph_paperI.p
Stellar populations of bulges at low redshift
This chapter summarizes our current understanding of the stellar population
properties of bulges and outlines important future research directions.Comment: Review article to appear in "Galactic Bulges", Editors: Laurikainen
E., Peletier R., Gadotti D., Springer Publishing. 34 pages, 12 figure
The bright galaxy population of five medium redshift clusters. II. Quantitative Galaxy Morphology
Aims: Following the study already presented in our previous paper, based on
the Nordic Optical Telescope (NOT) sample, which consists of five clusters of
galaxies within the redshift range 0.18 z 0.25, imaged in the
central 0.5-2 Mpc in very good seeing conditions, we have studied the
quantitative morphology of their bright galaxy population
Methods: We have analyzed the surface brightness profiles of the galaxy
population in those clusters. Previously, we have performed simulations in
order to check the reliability of the fits. We have also derived a quantitative
morphological classification.
Results: The structural parameters derived from these analysis have been
analyzed. We have obtained that the structural parameters of E/S0 galaxies are
similar to those showed by galaxies in low redshift clusters. However, the disc
scales are different. In particular, the scales of the discs of galaxies at
medium redshift clusters are statistically different than those located in
similar galaxies in the Coma cluster. But, the scales of the discs of galaxies
in medium redshift clusters are similar to nearby field galaxies.
Conclusions: The results suggest that the evolution of the disc component of
galaxies in clusters is faster than in field ones. Mechanisms like galaxy
harassment showing timescales of Gyr could be the responsible of this
disc scale evolution. This indicates that spiral galaxies in clusters have
suffered a strong evolution in the last 2.5 Gyr or that Coma is in some way
anomalous.Comment: 13 pages, 10 figures, Accepted for publication in A&
Boxy/peanut/X bulges, barlenses and the thick part of galactic bars: What are they and how did they form?
Bars have a complex three-dimensional shape. In particular their inner part
is vertically much thicker than the parts further out. Viewed edge-on, the
thick part of the bar is what is commonly known as a boxy-, peanut- or X- bulge
and viewed face-on it is referred to as a barlens. These components are due to
disc and bar instabilities and are composed of disc material. I review here
their formation, evolution and dynamics, using simulations, orbital structure
theory and comparisons to observations.Comment: 21 pages, 7 figures, invited review to appear in "Galactic Bulges",
E. Laurikainen, R. Peletier, D. Gadotti, (eds.), Springe
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