J/ApJ/732/116 IR spectra of γ-ray bright blazars (Malmrose+, 2011)
Emission from hot dust in the infrared spectra of gamma-ray bright blazars.
Malmrose M.P., Marscher A.P., Jorstad S.G., Nikutta R., Elitzur M.
<Astrophys. J., 732, 116 (2011)>
=2011ApJ...732..116M 2011ApJ...732..116M
ADC_Keywords: QSOs ; BL Lac objects ; Spectra, infrared
Keywords: BL Lacertae objects: individual (ON231) - galaxies: active -
infrared: galaxies -
quasars: individual (4C 21.35, PKS 1510-089, CTA102, ON231)
Abstract:
A possible source of γ-ray photons observed from the jets of
blazars is inverse Compton scattering by relativistic electrons of
infrared seed photons from a hot, dusty torus in the nucleus. We use
observations from the Spitzer Space Telescope to search for signatures
of such dust in the infrared spectra of four γ-ray bright
blazars, the quasars 4C 21.35, CTA102, and PKS 1510-089, and the BL
Lacertae object ON231. The spectral energy distribution (SED) of
4C 21.35 contains a prominent infrared excess indicative of dust
emission. After subtracting a non-thermal component with a power-law
spectrum, we fit a dust model to the residual SED. The model consists
of a blackbody with temperature ∼1200K, plus a much weaker optically
thin component at ∼660K. The total luminosity of the thermal dust
emission is 7.9±0.2x1045erg/s. If the dust lies in an equatorial
torus, the density of infrared photons from the torus is sufficient to
explain the γ-ray flux from 4C 21.35 as long as the scattering
occurs within a few parsecs of the central engine. We also report a
tentative detection of dust in the quasar CTA102, in which the
luminosity of the infrared excess is 7±2x1045erg/s. However, in
CTA102 the far-infrared spectra are too noisy to detect the 10um
silicate feature. Upper limits to the luminosity from thermal emission
from dust in PKS 1510-089, and ON231, are 2.3x1045, and
6.6x1043erg/s, respectively. These upper limits do not rule out the
possibility of inverse Compton upscattering of infrared photons to
γ-ray energies in these two sources.
Description:
The small sample selected for our study consists of the four blazars
detected at γ-ray energies by both the Compton EGRET and
Fermi-LAT instruments that we found to contain an apparent IR excess
over a pure power law in their continuum spectra compiled by Impey &
Neugebauer (1988AJ.....95..307I 1988AJ.....95..307I): 4C 21.35 (z=0.435), CTA102
(z=1.037), PKS 1510-089 (z=0.361), and ON231 (z=0.102).
We obtained infrared observations of these blazars with the Infrared
Array Camera (IRAC), Infrared Spectrograph (IRS), and Multi-Band
Imaging Photometer for Spitzer (MIPS) instruments aboard Spitzer
between 2007 March 20 and 2008 February 16.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 56 8 Luminosity distances and dates of observations
for the four blazars
spectra.dat 110 3052 Epoch 1 and 2 Spitzer data
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See also:
II/225 : Catalog of Infrared Observations, Edition 5 (Gezari+ 1999)
J/A+A/537/A99 : Large Quasar Astrometric Catalogue 2 (LQAC-2) (Souchay+, 2012)
J/other/NewA/16.503 : 2MASS observation of BL Lac objects II. (Mao+, 2011)
J/ApJ/716/30 : SED of Fermi bright blazars (Abdo+, 2010)
J/MNRAS/405/2062 : AGN candidates from 2MASS/ROSAT catalogs (Kouzuma+, 2010)
J/AJ/121/2843 : QSOs in 2MASS incremental release DR2 (Barkhouse+, 2001)
J/A+AS/143/357 : Tuorla Quasar Monitoring (Katajainen+ 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Source name
14- 18 F5.3 Gpc Dist Luminosity distance
20 I1 --- Ep [1/2]
22- 32 A11 "YYYY/MMM/DD" IRS.date IRS observation date
34- 44 A11 "YYYY/MMM/DD" MIPS.date MIPS observation date
46- 56 A11 "YYYY/MMM/DD" IRAC.date IRAC observation date
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Byte-by-byte Description of file: spectra.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Source name
14- 17 A4 --- Inst Spitzer instrument used
19- 32 F14.8 um lam1 Wavelength in epoch 1
34- 47 F14.8 Jy F1 ?=-9999 Flux density in epoch 1
49- 63 F15.9 Jy e_F1 ?=-9999 Error in F1
65- 78 F14.8 um lam2 Wavelength in epoch 2
80- 94 F15.9 Jy F2 ?=-9999 Flux density in epoch 2
96-110 F15.9 Jy e_F2 ?=-9999 Error in F2
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Nov-2012