Is the dependence of spectral index on luminosity real in optically selected AGN samples ? | |
Tang, Su Min ; Zhang, Shuang Nan ; Hopkins, Philip F. | |
2010-05-06 ; 2010-05-06 | |
关键词 | methods : statistical galaxies : active quasars : general X-rays : galaxies SOFT-X-RAY ACTIVE GALACTIC NUCLEI DIGITAL-SKY-SURVEY COSMOLOGICAL EVOLUTION ENERGY-DISTRIBUTION QUASAR SURVEY RADIO-QUIET CHANDRA EMISSION REGRESSION Astronomy & Astrophysics |
中文摘要 | We critically examine the dependence of spectral index on luminosity in optically selected AGN samples. An analysis of optically selected high-z quasars showed an anticorrelation of alpha(OX), the spectral index between the rest-frame 2500 angstrom and 2 keV, with optical luminosity. We examine this relationship by means of Monte Carlo simulations and conclude that a constant alpha(OX) independent of optical luminosity is still consistent with this high-z sample. We further find that contributions of large dispersions and narrow range of optical luminosity are most important for the apparent, yet artificial, alpha(OX)-l(o) correlation reported. We also examine another, but more complete, low-z optical selected AGN sub-sample from Steffen et al., and our analysis shows that a constant alpha(OX) independent of optical luminosity is also consistent with the data. By comparing X-ray and optical luminosity functions, we find that a luminosity-independent alpha(OX) is in fact more preferred than the luminosity-dependent alpha(OX) model. We also discuss the selection effects caused by flux limits, which might systematically bias the l(X)-l(o) relation and cause discrepancy in optically selected and X-ray selected AGN samples. To correctly establish a dependence of alpha(OX) of AGNs on their luminosity, a larger and more complete sample is needed and consequences of luminosity dispersions and selection effects in flux-limited samples must be taken into account properly. |
语种 | 英语 ; 英语 |
出版者 | BLACKWELL PUBLISHING ; OXFORD ; 9600 GARSINGTON RD, OXFORD OX4 2DQ, OXON, ENGLAND |
内容类型 | 期刊论文 |
源URL | [http://hdl.handle.net/123456789/14956] |
专题 | 清华大学 |
推荐引用方式 GB/T 7714 | Tang, Su Min,Zhang, Shuang Nan,Hopkins, Philip F.. Is the dependence of spectral index on luminosity real in optically selected AGN samples ?[J],2010, 2010. |
APA | Tang, Su Min,Zhang, Shuang Nan,&Hopkins, Philip F..(2010).Is the dependence of spectral index on luminosity real in optically selected AGN samples ?.. |
MLA | Tang, Su Min,et al."Is the dependence of spectral index on luminosity real in optically selected AGN samples ?".(2010). |
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