AKARI NEAR- AND MID-INFRARED SPECTROSCOPY OF APM 08279+5255 AT z = 3.91

Journal Article · Wed May 20 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/697/1/452; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21300588

Oyabu, S ^[1]; Kawara, K; Matsuoka, Y; Sameshima, H; Asami, N ^[2]; Tsuzuki, Y ^[3]

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1. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yosinodai, Sagamihara, Kanagawa 229-8510 (Japan)
2. Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
3. System Integration Service Department, Redfox Inc., 3-3-11, Kita-Aoyama, Minato-ku, Tokyo 107-0061 (Japan)

We present rest-frame optical/near-infrared spectra of the gravitationally lensed quasar APM 08279+5255 at z = 3.91 that has been taken using the Infrared Camera (IRC) onboard the AKARI infrared satellite. The observed continuum consists of two components; a power-law component dominating optical wavelengths which is the direct light from the central source and thermal emission dominating near-infrared wavelengths which is attributed to the emission from hot dust in the circumnuclear region. The thermal emission well represents optically thick emission by hot dust at T {approx} 1300 K with {tau}{sub 2{mu}}{sub m} > 2 and apparent mass, M {sub hot} > 10 M {sub sun}. Thus, our observations directly detected the optically thick region of hot dust in APM 08279+5255. H I recombination lines of H{alpha} (0.656 {mu}m), Pa{alpha} (1.875 {mu}m), and Pa{beta} (1.282 {mu}m) are clearly detected at 3.2, 6.3, and 9.3 {mu}m. Simulations with the photoionization models suggest that APM 08279+5255 has broad-line region (BLR) clouds characterized by log n {sub H} {approx} 12-14 for the gas density, log U {approx} -2 to -6 for the ionization parameter, and E(B - V) {approx} 0.3-0.6 for the BLR. Thus, optically thick emission of hot dust supports an idea on nonspherical distribution of dust near the central source, consistent with the active galactic nuclei model with the dust torus. The temperature of hot dust and flux ratios of these H I lines are similar to those observed in low-redshift quasars. There are significant time variations in the H I lines, which are probably caused by variations in the brightness of the central source.

• OSTI ID: 21300588
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 697; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
ABSORPTION SPECTROSCOPY
BRIGHTNESS
CAMERAS
DUSTS
GALAXIES
GALAXY NUCLEI
GAMMA-GAMMA LOGGING
INFRARED SPECTRA
MASS
PHOTOIONIZATION
QUASARS
RECOMBINATION
RED SHIFT
SATELLITES