ULTRAVIOLET CONTINUUM COLOR VARIABILITY OF LUMINOUS SLOAN DIGITAL SKY SURVEY QSOs
ULTRAVIOLET CONTINUUM COLOR VARIABILITY OF LUMINOUS SLOAN DIGITAL SKY SURVEY QSOs
复制标题
DOI：
10.1088/0004-637x/731/1/50
复制
发表时间：
2011-03
期刊：
影响因子：
--
通讯作者：
Y. Sakata;T. Morokuma;T. Minezaki;Y. Yoshii;Yukiyasu Kobayashi;S. Koshida;H. Sameshima
中科院分区：
文献类型：
--
作者：
Y. Sakata;T. Morokuma;T. Minezaki;Y. Yoshii;Yukiyasu Kobayashi;S. Koshida;H. Sameshima
我们研究了活动星系核紫外连续辐射的光谱能量分布是否在流量变化过程中发生变化。我们使用斯隆数字巡天（SDSS）遗产巡天观测到的条带82中类星体的多历元光度数据，并选择了10个具有高光度精度的明亮类星体，在z = 1.0-2.4的红移范围内，其中强宽发射线如Lyα和C iv不会污染SDSS滤波器，以研究紫外连续辐射的光谱变化。在1998-2007年的监测期间，所有目标类星体都显示出明显的通量变化，同一天晚上获得的两个不同波段的多历元通量数据显示，所有目标类星体的通量与通量之间都呈线性关系。在通量-通量图中，将较长波长的通量与x轴平行，对于大多数目标，最佳拟合线性回归线的x截距为正，这意味着它们在观察波段中的颜色随着它们变得更亮而变得更蓝。然后，宿主星系的流量估计的基础上的恒星质量的凸起的宿主星系和中央黑洞质量之间的相关性，后者估计的基础上的亮度标度关系的C IV或Mg II的发射线和它们的线宽。我们发现，对于大多数目标，在相同的较短波长通量下，宿主星系的较长波长通量系统地小于最佳拟合回归线的较暗延伸。这一结果有力地表明，类星体在紫外区（静止坐标系波长为1400-3600 nm）的连续辐射的光谱形状通常随着它变得更亮而变得更蓝。发现通量-通量图中的多历元通量数据与Vanden Berk等人提出的波长依赖的变化幅度一致，其在较短波长中显示出较大的变化幅度。我们还发现，对于大多数目标，多历元通量-通量图可以很好地拟合标准吸积盘模型，即在黑洞质量不变的情况下改变质量吸积速率。这一发现有力地支持了类星体紫外连续辐射的标准吸积盘模型。
We examine whether the spectral energy distribution of UV continuum emission of active galactic nuclei changes during flux variation. We used multi-epoch photometric data of QSOs in Stripe 82 observed by the Sloan Digital Sky Survey (SDSS) Legacy Survey and selected 10 bright QSOs observed with high photometric accuracies, in the redshift range of z = 1.0–2.4 where strong broad emission lines such as Lyα and C iv do not contaminate SDSS filters, to examine spectral variation of the UV continuum emission with broadband photometries. All target QSOs showed clear flux variations during the monitoring period 1998–2007, and the multi-epoch flux data in two different bands obtained on the same night showed a linear flux-to-flux relationship for all target QSOs. Assigning the flux in the longer wavelength to the x-axis in the flux-to-flux diagram, the x-intercept of the best-fit linear regression line was positive for most targets, which means that their colors in the observing bands become bluer as they become brighter. Then, the host-galaxy flux was estimated on the basis of the correlation between the stellar mass of the bulge of the host galaxy and the central black hole mass; the latter was estimated on the basis of the luminosity scaling relations for C iv or Mg ii emission lines and their line width. We found that the longer-wavelength flux of the host galaxy was systematically smaller than that of the fainter extension of the best-fit regression line at the same shorter-wavelength flux for most targets. This result strongly indicates that the spectral shape of the continuum emission of QSOs in the UV region (∼1400–3600 Å in rest-frame wavelength) usually becomes bluer as it becomes brighter. The multi-epoch flux data in the flux-to-flux diagram were found to be consistent with the wavelength-dependent amplitude of variation presented in Vanden Berk et al., which showed a larger amplitude of variation in shorter wavelengths. We also found that the multi-epoch flux-to-flux plots could be fitted well with the standard accretion disk model changing the mass accretion rate with a constant black hole mass for most targets. This finding strongly supports the standard accretion disk model for UV continuum emission of QSOs.