DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY
Abstract
We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona fide Compton-thick (N{sub H} > 1.5 Multiplication-Sign 10{sup 24} cm{sup -2}) active galactic nuclei (AGNs) with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at {lambda} {approx} 9.7 {mu}m in archival low-resolution (R {approx} 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority ( Almost-Equal-To 45%) of nearby Compton-thick AGNs have strong Si-absorption features (S{sub 9.7} = ln (f{sub int}/f{sub obs}) {approx}> 0.5) which would indicate significant dust attenuation. The majority ( Almost-Equal-To 60%) are star formation dominated (AGN:SB < 0.5) at mid-IR wavelengths and lack the spectral signatures of AGN activity at optical wavelengths, most likely because the AGN emission lines are optically extinguished. Those Compton-thick AGNs hosted in low-inclination-angle galaxies exhibit a narrow range in Si-absorption (S{sub 9.7} {approx} 0-0.3), which is consistent with that predicted by clumpy-torus models. However, on the basis of the IR spectra and additional lines of evidence, we conclude that the dominant contribution to the observed mid-IR dust extinction is dust located in the host galaxy (i.e., due to disturbed morphologies, dust lanes, galaxy inclination angles)more »
- Authors:
-
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom)
- Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)
- Publication Date:
- OSTI Identifier:
- 22039190
- Resource Type:
- Journal Article
- Journal Name:
- Astrophysical Journal
- Additional Journal Information:
- Journal Volume: 755; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ASTRONOMY; ASTROPHYSICS; COSMIC DUST; EMISSION SPECTROSCOPY; GALAXY NUCLEI; INCLINATION; INFRARED SPECTRA; KEV RANGE; PHOTON EMISSION; SEYFERT GALAXIES; SILICATES; STARS; X RADIATION; X-RAY GALAXIES
Citation Formats
Goulding, A D, Forman, W R, Jones, C, Trichas, M, Alexander, D M, Mullaney, J R, Bauer, F E, and Hickox, R. C., E-mail: agoulding@cfa.harvard.edu. DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY. United States: N. p., 2012.
Web. doi:10.1088/0004-637X/755/1/5.
Goulding, A D, Forman, W R, Jones, C, Trichas, M, Alexander, D M, Mullaney, J R, Bauer, F E, & Hickox, R. C., E-mail: agoulding@cfa.harvard.edu. DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY. United States. https://doi.org/10.1088/0004-637X/755/1/5
Goulding, A D, Forman, W R, Jones, C, Trichas, M, Alexander, D M, Mullaney, J R, Bauer, F E, and Hickox, R. C., E-mail: agoulding@cfa.harvard.edu. 2012.
"DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY". United States. https://doi.org/10.1088/0004-637X/755/1/5.
@article{osti_22039190,
title = {DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY},
author = {Goulding, A D and Forman, W R and Jones, C and Trichas, M and Alexander, D M and Mullaney, J R and Bauer, F E and Hickox, R. C., E-mail: agoulding@cfa.harvard.edu},
abstractNote = {We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona fide Compton-thick (N{sub H} > 1.5 Multiplication-Sign 10{sup 24} cm{sup -2}) active galactic nuclei (AGNs) with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at {lambda} {approx} 9.7 {mu}m in archival low-resolution (R {approx} 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority ( Almost-Equal-To 45%) of nearby Compton-thick AGNs have strong Si-absorption features (S{sub 9.7} = ln (f{sub int}/f{sub obs}) {approx}> 0.5) which would indicate significant dust attenuation. The majority ( Almost-Equal-To 60%) are star formation dominated (AGN:SB < 0.5) at mid-IR wavelengths and lack the spectral signatures of AGN activity at optical wavelengths, most likely because the AGN emission lines are optically extinguished. Those Compton-thick AGNs hosted in low-inclination-angle galaxies exhibit a narrow range in Si-absorption (S{sub 9.7} {approx} 0-0.3), which is consistent with that predicted by clumpy-torus models. However, on the basis of the IR spectra and additional lines of evidence, we conclude that the dominant contribution to the observed mid-IR dust extinction is dust located in the host galaxy (i.e., due to disturbed morphologies, dust lanes, galaxy inclination angles) and not necessarily a compact obscuring torus surrounding the central engine.},
doi = {10.1088/0004-637X/755/1/5},
url = {https://www.osti.gov/biblio/22039190},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 755,
place = {United States},
year = {Fri Aug 10 00:00:00 EDT 2012},
month = {Fri Aug 10 00:00:00 EDT 2012}
}