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arXiv 0811.3714astro-ph
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Sloan数字巡天探测星系核和窄线活动星系核的光谱变率

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

Ching-Wa Yip, Andrew Connolly, Daniel Vanden Berk, Ryan Scranton, Simon Krughoff, Alex Szalay, Laszlo Dobos, Christy Tremonti, Manuchehr Taghizadeh-Popp, Tamas … 展开作者

Ching-Wa Yip, Andrew Connolly, Daniel Vanden Berk, Ryan Scranton, Simon Krughoff, Alex Szalay, Laszlo Dobos, Christy Tremonti, Manuchehr Taghizadeh-Popp, Tamas Budavari, Istvan Csabai, Rosemary Wyse, Zeljko Ivezic

摘要:

在活动星系核的统一模型下,窄线(2型)活动星系核实际上是宽线(1型)活动星系核,但每个活动星系核都有一个严重遮蔽的吸积盘。因此,我们预期2型活动星系核的光学连续辐射主要由恒星光组成,并且在几个月到几年的时间尺度上是不变的。在这项工作中,我们探测星系和窄线活动星系核的光谱变化使用的多历元数据在斯隆数字巡天(SDSS)数据发布6。样本包含18,435个源,其中存在成对的光谱观测(最大间隔约为700天),覆盖波长范围为3900-8900埃。为了获得一个可靠的重复性测量之间的每个光谱对,我们考虑了一些技术的分光光度校准,导致改进的分光光度校准的一个因素。从这些数据中,我们发现在窄线活动星系核中没有明显的连续谱和发射线的平均变率--连续谱的光谱变率在g带为0.07+/-0.26 mag,发射线比log 10([NII]/H α)和log 10([OIII]/H β)的变率分别为0.02+/-0.03 dex和0.06+/-0.08 dex。从连续光谱的变化测量,我们设置了一个上限的变化光谱分量的流量之间的比例,大概与活动星系核活动,和宿主星系的~ 30%。我们提供了相应的上限为其他光谱类,包括那些从BPT图,eClass星系分类,恒星和类星体。

英文摘要:

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.

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