STAR FORMATION IN SELF-GRAVITATING DISKS IN ACTIVE GALACTIC NUCLEI. I. METALLICITY GRADIENTS IN BROAD-LINE REGIONS

Journal Article · Tue Sep 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/739/1/3; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21587524

Jianmin, Wang; Junqiang, Ge; Chen, Hu; Yanrng, Li; Fei, Xiang; Shu, Zhang ^[1]; Baldwin, Jack A ^[2]; Ferland, Gary J ^[3]

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1. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049 (China)
2. Physics and Astronomy Department, 3270 Biomedical Physical Sciences Building, Michigan State University, East Lansing, MI 48824 (United States)
3. Department of Physics and Astronomy, 177 Chemistry/Physics Building, University of Kentucky, Lexington, KY 40506 (United States)

It has been suggested that the high metallicity generally observed in active galactic nuclei (AGNs) and quasars originates from ongoing star formation in the self-gravitating part of accretion disks around supermassive black holes (SMBHs). We designate this region as the star-forming (SF) disk, in which metals are produced from supernova explosions (SNexp) while at the same time inflows are driven by SNexp-excited turbulent viscosity to accrete onto the SMBHs. In this paper, an equation of metallicity governed by SNexp and radial advection is established to describe the metal distribution and evolution in the SF disk. We find that the metal abundance is enriched at different rates at different positions in the disk, and that a metallicity gradient is set up that evolves for steady-state AGNs. Metallicity as an integrated physical parameter can be used as a probe of the SF disk age during one episode of SMBH activity. In the SF disk, evaporation of molecular clouds heated by SNexp blast waves unavoidably forms hot gas. This heating is eventually balanced by the cooling of the hot gas, but we show that the hot gas will escape from the SF disk before being cooled, and diffuse into the broad-line regions (BLRs) forming with a typical rate of {approx}1 M{sub sun} yr{sup -1}. The diffusion of hot gas from an SF disk depends on ongoing star formation, leading to the metallicity gradients in BLR observed in AGNs. We discuss this and other observable consequences of this scenario.

• OSTI ID: 21587524
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 739; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ADVECTION
BLACK HOLES
COSMIC RADIO SOURCES
ELEMENTS
EVOLUTION
EXPLOSIONS
GALACTIC EVOLUTION
GALAXY NUCLEI
MASS TRANSFER
METALS
QUASARS
STARS