Quasars and the big blue bump

Zhaohui Shang, Michael S. Brotherton, Richard F. Green, Gerard A. Kriss, Jennifer Scott, Jessica Kim Quijano, Omer Blaes, Ivan - Hubeny, John Hutchings, Mary Elizabeth Kaiser, Anuradha Koratkar, William Oegerle, Wei Zheng

Research output: Contribution to journalArticle

102 Citations (Scopus)

Abstract

We investigate the ultraviolet-to-optical spectral energy distributions of 17 active galactic nuclei (AGNs) using quasi-simultaneous spectrophotometry spanning 900-9000 Å (rest frame). We employ data from the Far Ultraviolet Spectroscopic Explorer, the Hubble Space Telescope, and the 2.1 m telescope at Kitt Peak National Observatory. Taking advantage of the short-wavelength coverage, we are able to study the so-called big blue bump, the region in which the energy output peaks, in detail. Most objects exhibit a spectral break around 1100 Å. Although this result is formally associated with large uncertainty for some objects, there is strong evidence in the data that the far-ultraviolet spectral region is below the extrapolation of the near-ultraviolet-optical slope, indicating a spectral break around 1100 Å. We compare the behavior of our sample to those of non-LTE thin-disk models covering a range in black hole mass, Eddington ratio, disk inclination, and other parameters. The distribution of ultraviolet-optical spectral indices redward of the break and far-ultraviolet indices shortward of the break are in rough agreement with the models. However, we do not see a correlation between the far-ultraviolet spectral index and the black hole mass, as seen in some accretion disk models. We argue that the observed spectral break is intrinsic to AGNs, although intrinsic reddening as well as Comptonization can strongly affect the far-ultraviolet spectral index. We make our data available online in digital format.

Original languageEnglish (US)
Pages (from-to)41-59
Number of pages19
JournalAstrophysical Journal
Volume619
Issue number1 I
DOIs
StatePublished - Jan 20 2005

Fingerprint

quasars
active galactic nuclei
spectrophotometry
spectral energy distribution
Hubble Space Telescope
accretion disks
inclination
format
energy
extrapolation
observatories
coverings
observatory
accretion
telescopes
slopes
wavelength
index
output
wavelengths

Keywords

  • Galaxies: active
  • Galaxies: nuclei
  • Quasars: general
  • Ultraviolet: general

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Shang, Z., Brotherton, M. S., Green, R. F., Kriss, G. A., Scott, J., Quijano, J. K., ... Zheng, W. (2005). Quasars and the big blue bump. Astrophysical Journal, 619(1 I), 41-59. https://doi.org/10.1086/426134

Quasars and the big blue bump. / Shang, Zhaohui; Brotherton, Michael S.; Green, Richard F.; Kriss, Gerard A.; Scott, Jennifer; Quijano, Jessica Kim; Blaes, Omer; Hubeny, Ivan -; Hutchings, John; Kaiser, Mary Elizabeth; Koratkar, Anuradha; Oegerle, William; Zheng, Wei.

In: Astrophysical Journal, Vol. 619, No. 1 I, 20.01.2005, p. 41-59.

Research output: Contribution to journalArticle

Shang, Z, Brotherton, MS, Green, RF, Kriss, GA, Scott, J, Quijano, JK, Blaes, O, Hubeny, I, Hutchings, J, Kaiser, ME, Koratkar, A, Oegerle, W & Zheng, W 2005, 'Quasars and the big blue bump', Astrophysical Journal, vol. 619, no. 1 I, pp. 41-59. https://doi.org/10.1086/426134
Shang Z, Brotherton MS, Green RF, Kriss GA, Scott J, Quijano JK et al. Quasars and the big blue bump. Astrophysical Journal. 2005 Jan 20;619(1 I):41-59. https://doi.org/10.1086/426134
Shang, Zhaohui ; Brotherton, Michael S. ; Green, Richard F. ; Kriss, Gerard A. ; Scott, Jennifer ; Quijano, Jessica Kim ; Blaes, Omer ; Hubeny, Ivan - ; Hutchings, John ; Kaiser, Mary Elizabeth ; Koratkar, Anuradha ; Oegerle, William ; Zheng, Wei. / Quasars and the big blue bump. In: Astrophysical Journal. 2005 ; Vol. 619, No. 1 I. pp. 41-59.
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