國立高雄大學圖資館 |

登入

回首頁

Balmer line emission from the accretion disks surrounding the supermassive black holes in active galactic nuclei.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Balmer line emission from the accretion disks surrounding the supermassive black holes in active galactic nuclei.
作者:	Strateva, Iskra V.
面頁冊數:	182 p.
附註:	Adviser: Michael A. Strauss.
附註:	Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4989.
Contained By:	Dissertation Abstracts International64-10B.
標題:	Physics, Astronomy and Astrophysics.
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3110249
ISBN:	0496577883

Balmer line emission from the accretion disks surrounding the supermassive black holes in active galactic nuclei.
Strateva, Iskra V.

Balmer line emission from the accretion disks surrounding the supermassive black holes in active galactic nuclei. [electronic resource] - 182 p.

Adviser: Michael A. Strauss.

Thesis (Ph.D.)--Princeton University, 2004.

The hydrogen Balmer emission lines are the most prominent feature in the optical spectra of low redshift Active Galactic Nuclei (AGN). Their line widths or the Balmer-to-metal line flux-ratios are used to distinguish active from star-forming galaxies. Yet the geometry and dynamics of the gas responsible for these lines are still poorly constrained. Using a large new sample of a rare class of broad-line AGN with double-peaked Balmer-line profiles indicative of an accretion disk origin, I consider the contribution of disk emission to Halpha, the strongest of the observed Balmer lines. I focus on finding an efficient method for the selection of double-peaked AGN, which constitute about 3% of all AGN with z < 0.33 discovered with the Sloan Digital Sky Survey. I proceed to define the characteristic properties which distinguish the double-peaked AGN from the general population, searching for the underlying reasons for their strong disk-emission contribution. Using both statistical comparison of line shapes and direct disk-model fitting methods, I study the sizes, inclinations, and surface emissivity profiles of accretion disks in the light of their Halpha line emission. I find that 60%--80% (depending on the strength of the asymmetry) of all observed line-shapes originate in non-axisymmetric disks, and that single-epoch observations of the Halpha line profiles are not sufficient to constrain the surface emissivity patterns of the accretion disks. With the help of theoretically motivated surface emissivity laws, it is possible to infer the distribution of inclinations and accretion disk sizes. I find evidence for the existence of obscuring material coplanar with the disks at larger distances from the central black holes, supporting unification theories for broad and narrow line AGN. The sizes of Halpha emitting rings implied by the observations suggest that they are likely limited by the onset of self-gravity, a few thousand gravitational radii from the center. The most probable causes for the small accretion disk emission contribution to the Balmer line flux in the general AGN population are the onset of self gravity, which fragments and destroys the outer parts of the disk, and/or the lack of external illumination necessary to produce detectable accretion disk contribution.

ISBN: 0496577883Subjects--Topical Terms:

227131
Physics, Astronomy and Astrophysics.

Balmer line emission from the accretion disks surrounding the supermassive black holes in active galactic nuclei.
LDR:03310nmm _2200253 _450 001 162303
005 20051017073432.5
008 230606s2004 eng d
020 $a 0496577883
035 $a 00148804
035 $a 162303
040 $a UnM $c UnM
100 0 $a Strateva, Iskra V. $3 227430
245 1 0 $a Balmer line emission from the accretion disks surrounding the supermassive black holes in active galactic nuclei. $h [electronic resource]
300 $a 182 p.
500 $a Adviser: Michael A. Strauss.
500 $a Source: Dissertation Abstracts International, Volume: 64-10, Section: B, page: 4989.
502 $a Thesis (Ph.D.)--Princeton University, 2004.
520 # $a The hydrogen Balmer emission lines are the most prominent feature in the optical spectra of low redshift Active Galactic Nuclei (AGN). Their line widths or the Balmer-to-metal line flux-ratios are used to distinguish active from star-forming galaxies. Yet the geometry and dynamics of the gas responsible for these lines are still poorly constrained. Using a large new sample of a rare class of broad-line AGN with double-peaked Balmer-line profiles indicative of an accretion disk origin, I consider the contribution of disk emission to Halpha, the strongest of the observed Balmer lines. I focus on finding an efficient method for the selection of double-peaked AGN, which constitute about 3% of all AGN with z < 0.33 discovered with the Sloan Digital Sky Survey. I proceed to define the characteristic properties which distinguish the double-peaked AGN from the general population, searching for the underlying reasons for their strong disk-emission contribution. Using both statistical comparison of line shapes and direct disk-model fitting methods, I study the sizes, inclinations, and surface emissivity profiles of accretion disks in the light of their Halpha line emission. I find that 60%--80% (depending on the strength of the asymmetry) of all observed line-shapes originate in non-axisymmetric disks, and that single-epoch observations of the Halpha line profiles are not sufficient to constrain the surface emissivity patterns of the accretion disks. With the help of theoretically motivated surface emissivity laws, it is possible to infer the distribution of inclinations and accretion disk sizes. I find evidence for the existence of obscuring material coplanar with the disks at larger distances from the central black holes, supporting unification theories for broad and narrow line AGN. The sizes of Halpha emitting rings implied by the observations suggest that they are likely limited by the onset of self-gravity, a few thousand gravitational radii from the center. The most probable causes for the small accretion disk emission contribution to the Balmer line flux in the general AGN population are the onset of self gravity, which fragments and destroys the outer parts of the disk, and/or the lack of external illumination necessary to produce detectable accretion disk contribution.
590 $a School code: 0181.
650 # 0 $a Physics, Astronomy and Astrophysics. $3 227131
710 0 # $a Princeton University. $3 212488
773 0 # $g 64-10B. $t Dissertation Abstracts International
790 $a 0181
790 1 0 $a Strauss, Michael A., $e advisor
791 $a Ph.D.
792 $a 2004
856 4 0 $u http://libsw.nuk.edu.tw/login?url=http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3110249 $z http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3110249