WATER VAPOR EMISSION REVEALS A HIGHLY OBSCURED, STAR-FORMING NUCLEAR REGION IN THE QSO HOST GALAXY APM 08279+5255 AT z = 3.9
- Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands)
- Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, NL-9700 AV Groningen (Netherlands)
- Astronomy Department, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
- IRAM, 300 Rue de la Piscine, 38406 St. Martin d'Heres, Grenoble (France)
- Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 16, Bonn, D-53121 (Germany)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, Heidelberg, D-69117 (Germany)
We present the detection of four rotational emission lines of water vapor, from energy levels E{sub u}/k = 101-454 K, in the gravitationally lensed z = 3.9 QSO host galaxy APM 08279+5255. While the lowest H{sub 2} O lines are collisionally excited in clumps of warm, dense gas (density of hydrogen nuclei n{sub H} = (3.1 {+-} 1.2) x 10{sup 6} cm{sup -3}, gas temperature T{sub g} {approx} 105 {+-} 21 K), we find that the excitation of the higher lines is dominated by the intense local infrared radiation field. Since only collisionally excited emission contributes to gas cooling, we conclude that H{sub 2} O is not a significant coolant of the warm molecular gas. Our excitation model requires the radiatively excited gas to be located in an extended region of high 100 {mu} m opacity ({tau}{sub 100} = 0.9 {+-} 0.2). Locally, such extended infrared-opaque regions are found only in the nuclei of ultraluminous infrared galaxies. We propose a model where the infrared-opaque circumnuclear cloud, which is penetrated by the X-ray radiation field of the QSO nucleus, contains clumps of massive star formation where the H{sub 2} O emission originates. The radiation pressure from the intense local infrared radiation field exceeds the thermal gas pressure by about an order of magnitude, suggesting close to Eddington-limited star formation in these clumps.
- OSTI ID:
- 22047367
- Journal Information:
- Astrophysical Journal Letters, Vol. 741, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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