Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey

Details Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey

2008-11-24

arxiv.org/abs/0811.3714v2

Astronomy and Astrophysics

Astrophysics

AJ accepted

Scientific paper

Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type 2 AGN to be composed mainly of stellar light and non-variable on the time-scales of months to years. In this work we probe the spectroscopic variability of galaxies and narrow-line AGNs using the multi-epoch data in the Sloan Digital Sky Survey (SDSS) Data Release 6. The sample contains 18,435 sources for which there exist pairs of spectroscopic observations (with a maximum separation in time of ~700 days) covering a wavelength range of 3900-8900 angstrom. To obtain a reliable repeatability measurement between each spectral pair, we consider a number of techniques for spectrophotometric calibration resulting in an improved spectrophotometric calibration of a factor of two. From these data we find no obvious continuum and emission-line variability in the narrow-line AGNs on average -- the spectroscopic variability of the continuum is 0.07+/-0.26 mag in the g band and, for the emission-line ratios log10([NII]/Halpha) and log10([OIII]/Hbeta), the variability is 0.02+/-0.03 dex and 0.06+/-0.08 dex, respectively. From the continuum variability measurement we set an upper limit on the ratio between the flux of varying spectral component, presumably related to AGN activities, and that of host galaxy to be ~30%. We provide the corresponding upper limits for other spectral classes, including those from the BPT diagram, eClass galaxy classification, stars and quasars.

Affiliated with

Also associated with

No associations

Rating

Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-643752