834 research outputs found
12 and 18 micron images of dust surrounding HD 32297
We present the first subarcsecond-resolution images at multiple mid-IR
wavelengths of the thermally-emitting dust around the A0 star HD 32297. Our
observations with T-ReCS at Gemini South reveal a nearly edge-on resolved disk
at both 11.7 microns and 18.3 microns that extends ~150 AU in radius. The
mid-IR is the third wavelength region in which this disk has been resolved,
following coronagraphic observations by others of the source at optical and
near-IR wavelengths. The global mid-IR colors and detailed consideration of the
radial color-temperature distribution imply that the central part of the disk
out to ~80 AU is relatively deficient in dust.Comment: 4 pages, 3 figures; accepted for publication in ApJ
High-Resolution Mid-Infrared Morphology of Cygnus A
We present subarcsecond resolution mid-infrared images at 10.8 and 18.2
microns of Cygnus A. These images were obtained with the University of Florida
mid-IR camera/spectrometer OSCIR at the Keck II 10-m telescope. Our data show
extended mid-IR emission primarily to the east of the nucleus with a possible
western extension detected after image deconvolution. This extended emission is
closely aligned with the bi-conical structure observed at optical and near-IR
wavelengths by the HST. This emission is consistent with dust heated from the
central engine of Cygnus A. We also marginally detect large-scale low level
emission extending > 1.5 kpc from the nucleus which may be caused by in-situ
star formation, line emission, and/or PAH contamination within the bandpass of
our wide N-band filter.Comment: 20 pages, 8 figures, accepted for publication in the Astrophysical
Journa
Subaru Spectroscopy and Spectral Modeling of Cygnus A
We present high angular resolution (0.5) MIR spectra
of the powerful radio galaxy, Cygnus A, obtained with the Subaru telescope. The
overall shape of the spectra agree with previous high angular resolution MIR
observations, as well as previous Spitzer spectra. Our spectra, both on and off
nucleus, show a deep silicate absorption feature. The absorption feature can be
modeled with a blackbody obscured by cold dust or a clumpy torus. The deep
silicate feature is best fit by a simple model of a screened blackbody,
suggesting foreground absorption plays a significant, if not dominant role, in
shaping the spectrum of Cygnus A. This foreground absorption prevents a clear
view of the central engine and surrounding torus, making it difficult to
quantify the extent the torus attributes to the obscuration of the central
engine, but does not eliminate the need for a torus in Cygnus A
Co-Occurrence and Characteristics of Patients With Axial Spondyloarthritis Who Meet Criteria for Fibromyalgia : Results From a UK National Register
The British Society for Rheumatology (BSR) Biologics Register in Ankylosing Spondylitis is funded by the BSR and they have receive funds for this from Pfizer, AbbVie and UCB. These companies receive advance copies of manuscripts and can provide comments but have no input into determining the topics for analysis, publication and no input into the work involved in this analysis. This analysis is part-funded by Arthritis Research UK (Grant No: 21378)Peer reviewedPublisher PD
Understanding the 8 micron vs. Pa-alpha relationship on sub-arcsecond scales in Luminous Infrared Galaxies
This work explores in detail the relation between the 8 micron and the
Pa-alpha emissions for 122 HII regions identified in a sample of 10 low-z LIRGs
with nearly constant metallicity (12 + log (O/H) ~ 8.8). We use Gemini/T-ReCS
high-spatial resolution (<~ 0.4" ~ 120 pc for the average distance of 60 Mpc of
our sample) mid-infrared imaging (at 8.7 micron or 10.3 micron) together with
HST/NICMOS continuum and Pa-alpha images. The LIRG HII regions extend the
L_8micron vs. L_Pa-alpha relation found for HII knots in the high-metallicity
SINGS galaxies by about two orders of magnitude to higher luminosities. Since
the metallicity of the LIRG sample is nearly constant, we can rule out this
effect as a cause for the scatter seen in the relationship. In turn, it is
attributed to two effects: age and PAH features. The L_8micron/L_Pa-alpha
ratio, which varies by a factor of ten for the LIRG HII regions, is reproduced
by a model with instantaneous star formation and ages ranging from ~ 4 to 7.5
Myr. The remaining dispersion around the model predictions for a given age is
probably due to differential contributions of the PAH features (the 8.6 micron,
in our case) to the 8 micron emission from galaxy to galaxy.Comment: 16 pages, 9 figures, accepted for publication in ApJ; paper with
full-resolution figures can be found at:
http://damir.iem.csic.es/extragalactic
Mid-Infrared T-ReCS Spectroscopy of Local LIRGs
We present T-ReCS high spatial resolution N-band (8-13 micron) spectroscopy of the central regions (a few kpc) of 3 local LIRGs. The nuclear spectra show deep 9.7 micron silicate absorption feature and the high ionization [SIV]10.5 micron emission line, consistent with their optical classification as AGN. The two LIRGs with unresolved mid-IR emission do not show PAH emission at 11.3 micron in their nuclear spectra. The spatially resolved mid-IR spectroscopy of NGC 5135 allows us to separate out the spectra of the Seyfert nucleus, an HII region, and the diffuse region between them on scales of less than 2.5 arcsec ~ 600 pc. The diffuse region spectrum is characterized by strong PAH emission with almost no continuum, whereas the HII region shows PAH emission with a smaller equivalent width as well as [NeII]12.8 micron line
Isotropic Mid-Infrared Emission from the Central 100 pc of Active Galaxies
Dust reprocesses the intrinsic radiation of active galactic nuclei (AGNs) to
emerge at longer wavelengths. The observed mid-infrared (MIR) luminosity
depends fundamentally on the luminosity of the central engine, but in detail it
also depends on the geometric distribution of the surrounding dust. To quantify
this relationship, we observe nearby normal AGNs in the MIR to achieve spatial
resolution better than 100 pc, and we use absorption-corrected X-ray luminosity
as a proxy for the intrinsic AGN emission. We find no significant difference
between optically classified Seyfert 1 and 2 galaxies. Spectroscopic
differences, both at optical and IR wavelengths, indicate that the immediate
surroundings of AGNs is not spherically symmetric, as in standard unified AGN
models. A quantitative analysis of clumpy torus radiative transfer models shows
that a clumpy local environment can account for this dependence on viewing
geometry while producing MIR continuum emission that remains nearly isotropic,
as we observe, although the material is not optically thin at these
wavelengths. We find some luminosity dependence on the X-ray/MIR correlation in
the smallest scale measurements, which may indicate enhanced dust emission
associated with star formation, even on these sub-100 pc scales.Comment: 10 pages, 5 figures; accepted for publication in Ap
Crystalline Silicate Emission in the Protostellar Binary Serpens--SVS20
We present spatially resolved mid-infrared spectroscopy of the class
I/flat-spectrum protostellar binary system SVS20 in the Serpens cloud core. The
spectra were obtained with the mid-infrared instrument T-ReCS on Gemini-South.
SVS20-South, the more luminous of the two sources, exhibits a mid-infrared
emission spectrum peaking near 11.3 \micron, while SVS20-North exhibits a
shallow amorphous silicate absorption spectrum with a peak optical depth of
. After removal of the the line-of-sight extinction by the
molecular common envelope, the ``protostar-only'' spectra are found to be
dominated by strong amorphous olivine emission peaking near 10 \micron. We also
find evidence for emission from crystalline forsterite and enstatite associated
with both SVS20-S and SVS20-N. The presence of crystalline silicate in such a
young binary system indicates that the grain processing found in more evolved
HAeBe and T Tauri pre-main sequence stars likely begins at a relatively young
evolutionary stage, while mass accretion is still ongoing.Comment: Accepted for publication by The Astrophysical Journa
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