2007ApJ...663..808P -
Astrophys. J., 663, 808-815 (2007/July-2)
The mid-infrared emission of M87.
PERLMAN E.S., MASON R.E., PACKHAM C., LEVENSON N.A., ELITZUR M., SCHAEFER J.J., IMANISHI M., SPARKS W.B. and RADOMSKI J.
Abstract (from CDS):
We discuss Subaru and Spitzer Space Telescope imaging and spectroscopy of M87 in the mid-infrared (mid-IR) from 5 to 35 µm. These observations allow us to investigate mid-IR emission mechanisms in the core of M87 and to establish that the flaring, variable jet component HST-1 is not a major contributor to the mid-IR flux. The Spitzer data include a high signal-to-noise ratio 15-35 µm spectrum of the knot A/B complex in the jet, which is consistent with synchrotron emission. However, a synchrotron model cannot account for the observed nuclear spectrum, even when contributions from the jet, necessary due to the degrading of resolution with wavelength, are included. The Spitzer data show a clear excess in the spectrum of the nucleus at wavelengths longer than 25 µm, which we model as thermal emission from cool dust at a characteristic temperature of 55±10 K, with an IR luminosity ∼1039 ergs/s^. Given Spitzer's few arcsecond angular resolution, the dust seen in the nuclear spectrum could be located anywhere within ∼5" (390 pc) of the nucleus. In any case, the ratio of active galactic nucleus (AGN) thermal to bolometric luminosity indicates that M87 does not contain the IR-bright torus that classical unified AGN schemes invoke. However, this result is consistent with theoretical predictions for low-luminosity AGNs.
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Journal keyword(s):
Galaxies: Active - Galaxies: Elliptical and Lenticular, cD - Galaxies: Individual: Messier Number: M87 - Galaxies: Jets - Infrared: Galaxies
Simbad objects:
15
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