Spitzer Infrared Spectrograph (IRS)* Observations of the Redshift 3.91 Quasar APM 08279+5255 **

B. T. Soifer; V. Charmandaris; B. R. Brandl; L. Armus; P. N. Appleton; M. J. Burgdorf; D. Devost; T. Herter; S. J. U. Higdon; J. L. Higdon; J. R. Houck; C. R. Lawrence; P. W. Morris; H. I. Teplitz; K. I. Uchida; J. van Cleve; D. Weedman

doi:10.1086/421977

The Astrophysical Journal Supplement Series

Spitzer Infrared Spectrograph (IRS)^* Observations of the Redshift 3.91 Quasar APM 08279+5255 ^**

B. T. Soifer¹, V. Charmandaris^2,3, B. R. Brandl^2,4, L. Armus¹, P. N. Appleton¹, M. J. Burgdorf¹, D. Devost², T. Herter², S. J. U. Higdon², J. L. Higdon², J. R. Houck², C. R. Lawrence⁵, P. W. Morris¹, H. I. Teplitz¹, K. I. Uchida², J. van Cleve^2,6, and D. Weedman²

© 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A.
The Astrophysical Journal Supplement Series, Volume 154, Number 1 Citation B. T. Soifer et al 2004 ApJS 154 151 DOI 10.1086/421977

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Author affiliations

¹ Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125

² Astronomy Department, Cornell University, Ithaca, NY 14853-6801

³ Chercheur Associé, Observatoire de Paris, F-75014 Paris, France

⁴ Leiden University, 2300 RA Leiden, Netherlands

⁵ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109

⁶ Ball Aerospace Technologies Corporation, 1600 Commerce Street, Boulder, CO 80301

Dates

Received 2004 March 20
Accepted 2004 April 12

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Abstract

The Infrared Spectrograph (IRS) on board the Spitzer Space Telescope has been used to obtain low- and moderate-resolution spectra of the dust- and gas-rich quasar APM 08279+5255 (z = 3.91). Broad Paα and Paβ recombination lines of hydrogen were detected at wavelengths of 9.235 and 6.315 μm, respectively, as well as a strong, red continuum that is a smooth power law over the observed (rest-frame) wavelength range 5.3-35 μm (1.08-7.1 μm). The observed Paα/Paβ line flux ratio of 1.05 ± 0.2 is far from the case B value of ∼2 and simple models of high-density, high optical depth ionized-gas regions (∼1.8). This deviation is opposite in sense to the expected effect of reddening. No evidence is found in the spectrum for either the 3.3 or the 6.2 μm emission features usually attributed to aromatic hydrocarbons in gas-rich galaxies in the local universe. This is consistent with the high-luminosity active galactic nucleus (AGN) nature of APM 08279+5255.

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Footnotes

*
The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation, funded by NASA through JPL and the Ames Research Center.
**
Based on observations obtained with the Spitzer Space Telescope, which is operated by JPL, California Institute of Technology, for NASA.

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