2,931 research outputs found
Infrared astronomy research and high altitude observations
Highlights are presented of studies of the emission mechanisms in the 4 to 8 micron region of the spectrum using a circular variable filter wheel spectrometer with a PbSnTe photovoltaic detector. Investigations covered include the spectroscopy of planets, stellar atmospheres, highly obscured objects in molecular clouds, planetary nebulae, H2 regions, and extragalactic objects
Spitzer Mid-Infrared Imaging of Nearby Ultraluminous Infrared Galaxies
We have observed 14 nearby (z<0.16) Ultraluminous Infrared Galaxies (ULIRGs)
with Spitzer at 3.6-24 microns. The underlying host galaxies are well-detected,
in addition to the luminous nuclear cores. While the spatial resolution of
Spitzer is poor, the great sensitivity of the data reveals the underlying
galaxy merger remnant, and provides the first look at off-nuclear mid-infrared
activity.Comment: To appear in the conference proceedings for Spitzer New Views of the
Universe, held Nov. 2004 in Pasadena, C
Selection and Mid-infrared Spectroscopy of Ultraluminous Star-Forming Galaxies at z~2
Starting from a sample of 24 \micron\ sources in the Extended Groth Strip, we
use 3.6 to 8 \micron\ color criteria to select ultraluminous infrared galaxies
(ULIRGs) at . Spectroscopy from 20-38 \micron\ of 14 objects verifies
their nature and gives their redshifts. Multi-wavelength data for these objects
imply stellar masses \Msun\ and star formation rates 410
\Msun yr. Four objects of this sample observed at 1.6 \micron\
(rest-frame visible) with {\it HST}/WFC3 show diverse morphologies, suggesting
that multiple formation processes create ULIRGs. Four of the 14 objects show
signs of active galactic nuclei, but the luminosity appears to be dominated by
star formation in all cases.Comment: 33 pages, 13 figures, accepted by Ap
Contribution of the Accretion Disk, Hot Corona, and Obscuring Torus to the Luminosity of Seyfert Galaxies: Integral and Spitzer Observations
We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spitzer mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei (AGNs) from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first HX-selected (above 15 keV) sample of AGNs with complementary high angular resolution, high signal-to-noise, MIR data. Correcting for the host galaxy contribution, we find a correlation between HX and MIR luminosities: L 15 ÎŒmâL0.74 ± 0.06 HX. Assuming that the observed MIR emission is radiation from an accretion disk reprocessed in a surrounding dusty torus that subtends a solid angle decreasing with increasing luminosity (as inferred from the declining fraction of obscured AGNs), the intrinsic disk luminosity, L Disk, is approximately proportional to the luminosity of the corona in the 2-300 keV energy band, L Corona, with the L Disk/L Corona ratio varying by a factor of 2.1 around a mean value of 1.6. This ratio is a factor of ~2 smaller than for typical quasars producing the cosmic X-ray background. Therefore, over three orders of magnitude in luminosity, HX radiation carries a large, and roughly comparable, fraction of the bolometric output of AGNs. We estimate the cumulative bolometric luminosity density of local AGNs at ~(1-3) Ă 1040 erg sâ1 Mpcâ3. Finally, the Compton temperature ranges between kT c â 2 and â6 keV for nearby AGNs, compared to kT c â 2 keV for typical quasars, confirming that radiative heating of interstellar gas can play an important role in regulating SMBH growth
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