标题： Ia型超新星及其宿主星系的亮度函数来自斯隆数字天空调查 显示英文标题

标题： Luminosity Functions of Type Ia Supernovae and their Host Galaxies from the Sloan Digital Sky Survey

摘要： 使用来自SDSS-II超新星巡天的137个低红移（0.05 < z < 0.3）Ia型超新星样本，该样本覆盖了赤道南部300平方度的条带，我们推导出这些超新星及其宿主星系在gri波段的亮度函数。 结果显示Ia型超新星宿主星系的亮度函数与一般场中星系的亮度函数很好地匹配，这表明Ia型超新星的发生并不青睐特定类型的星系，而是主要与星系的亮度成正比。 唯一指向超新星率与恒星形成活动可能存在相关性的证据是晚期星系中的超新星率比早期星系中的高31±35%。 样本中包含8个未识别宿主星系的Ia型超新星，但研究表明它们的出现与出现在超出调查范围的低光度星系中是一致的。 Ia型超新星的亮度函数近似为高斯分布，半高全宽在亮度上是1.4倍。 如果消光与消色散的比例R_V低于银河系的特征值，并且亮度修正了光曲线形状，则高斯分布会变得更紧凑。 颜色过剩约为0.07星等，显著小于场星系预期的消色散。 这种颜色过剩不随超新星距离宿主星系中心的距离（到15 kpc）而变化。 这表明大部分颜色过剩要么是固有的，要么是在超新星附近环境中产生的消色散，而不是宿主星系中的星际消色散。 显示英文摘要

摘要： The sample of 137 low-redshift type Ia supernovae with 0.05 < z < 0.3 obtained from the SDSS-II Supernova Survey for the southern equatorial stripe of 300 square degrees is used to derive the luminosity functions of type Ia supernovae and of their host galaxies in the gri passbands. We show that the luminosity function of type Ia supernova host galaxies matches well with that of galaxies in the general field, suggesting that the occurrence of type Ia supernovae does not favour a particular type of galaxies but is predominantly proportional to the luminosity of galaxies. The only evidence that points to possible correlation between the supernova rate and star formation activity is that the supernova rate in late-type galaxies is higher than that in early-type galaxies by 31+/-35%. The sample contains 8 type Ia supernovae whose host galaxies were not identified, but it is shown that their occurrence is consistent with them occurred in low luminous galaxies beyond the survey. The luminosity function of type Ia supernovae is approximately Gaussian with the full-width half maximum being a factor of 1.4 in luminosity. The Gaussian distribution becomes tighter if the ratio of extinction to reddening, R_V, is lower than the characteristic value for the Milky Way and if luminosity is corrected for the light curve shape. The colour excess is ~0.07 mag which is significantly smaller than reddening expected for field galaxies. This colour excess does not vary with the distance of the supernovae from the centre of the host galaxy to 15 kpc. This suggests that the major part of the colour excess appears to be either intrinsic or reddening that arises in the immediate environment of supernova, rather than interstellar reddening in host galaxies.