CaltechAUTHORS
  A Caltech Library Service

Is the dependence of spectral index on luminosity real in optically selected AGN samples?

Tang, Su Min and Zhang, Shuang Nan and Hopkins, Philip F. (2007) Is the dependence of spectral index on luminosity real in optically selected AGN samples? Monthly Notices of the Royal Astronomical Society, 377 (3). pp. 1113-1121. ISSN 0035-8711. doi:10.1111/j.1365-2966.2007.11589.x. https://resolver.caltech.edu/CaltechAUTHORS:20200529-093432189

[img] PDF - Published Version
See Usage Policy.

949kB
[img] PDF - Accepted Version
See Usage Policy.

1MB

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20200529-093432189

Abstract

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 α_(OX), the spectral index between the rest-frame 2500 Å and 2 keV, with optical luminosity. We examine this relationship by means of Monte Carlo simulations and conclude that a constant αOX 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, α_(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 αOX independent of optical luminosity is also consistent with the data. By comparing X-ray and optical luminosity functions, we find that a luminosity-independent α_(OX) is in fact more preferred than the luminosity-dependent α_(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 α_(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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1111/j.1365-2966.2007.11589.xDOIArticle
https://arxiv.org/abs/astro-ph/0702082arXivDiscussion Paper
ORCID:
AuthorORCID
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:© 2007 The Authors. Journal compilation © 2007 RAS. Accepted 2007 February 2. Received 2007 January 11; in original form 2006 June 26. We thank the anonymous referee for helpful comments and stimulating suggestions that improved the manuscript. SMT thanks J. X. Wang, G. T. Richards, N. Brandt and X. L. Zhou for helpful discussion. SNZ acknowledges partial funding support by the Ministry of Education of China, Directional Research Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China under project no. 10233010 and 10521001.
Funders:
Funding AgencyGrant Number
Ministry of Education (China)UNSPECIFIED
Chinese Academy of SciencesUNSPECIFIED
National Natural Science Foundation of China10233010
National Natural Science Foundation of China10521001
Subject Keywords:methods: statistical, galaxies: active, quasars: general, X-rays: galaxies
Issue or Number:3
DOI:10.1111/j.1365-2966.2007.11589.x
Record Number:CaltechAUTHORS:20200529-093432189
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200529-093432189
Official Citation:Su Min Tang, Shuang Nan Zhang, Philip F. Hopkins, Is the dependence of spectral index on luminosity real in optically selected AGN samples?, Monthly Notices of the Royal Astronomical Society, Volume 377, Issue 3, May 2007, Pages 1113–1121, https://doi.org/10.1111/j.1365-2966.2007.11589.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103546
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:01 Jun 2020 14:06
Last Modified:16 Nov 2021 18:22

Repository Staff Only: item control page