arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1012.0005astro-ph.CO
收藏

光谱能改善Ia型超新星的距离测量吗?

Do spectra improve distance measurements of Type Ia supernovae?

Stéphane Blondin, Kaisey S. Mandel, Robert P. Kirshner

摘要:

[摘要]我们研究了使用各种光谱测量来确定低红移Ia型超新星(SN Ia)的距离。我们考虑线性模型预测距离超新星Ia使用光变曲线宽度和颜色参数(使用SALT 2光变曲线拟合器确定)和光谱指标,并评估所得的哈勃图散射使用交叉验证程序。我们确认的能力,光谱通量比单独在最大的光,以减少约10%的光曲线宽度和颜色的标准组合的哈勃残差的散射。当与SALT 2颜色参数结合使用时,最大光下的颜色校正通量比R^c(6420/5290)导致甚至更低的散射,尽管考虑到我们的样本大小(26 SN Ia),该改进具有较低的统计显著性(<2 sigma)。我们强调了一个准确的相对通量校准的重要性,这种方法的失败高度红化的对象。与二维延迟爆炸模型合成光谱的比较表明,R(6630/4400)与超新星Ia绝对星等的相关性在很大程度上可以归因于固有的颜色变化,而不是由宿主星系中的尘埃变红。我们考虑了其他年龄的通量比,以及对通量比的使用,揭示了在~4300 A和~4800 A附近铁族主导的吸收特征中存在小尺度的本征光谱变化。总体上最佳的通量比是在距离最大光t=-2.5d处的颜色校正的R^c(4610/4260),这导致相对于光曲线宽度和颜色的标准组合低约30%的散射。我们研究了其他光谱指标相关的线轮廓形态,但没有出现导致一个显着的改善,超过标准的光曲线宽度和颜色参数。

英文摘要:

[Abridged] We investigate the use of a wide variety of spectroscopic measurements to determine distances to low-redshift Type Ia supernovae (SN Ia). We consider linear models for predicting distances to SN Ia using light-curve width and color parameters (determined using the SALT2 light-curve fitter) and a spectroscopic indicator, and evaluate the resulting Hubble diagram scatter using a cross-validation procedure. We confirm the ability of spectral flux ratios alone at maximum light to reduce the scatter of Hubble residuals by ~10% with respect to the standard combination of light-curve width and color. When used in combination with the SALT2 color parameter, the color-corrected flux ratio R^c(6420/5290) at maximum light leads to an even lower scatter, although the improvement has low statistical significance (<2 sigma) given the size of our sample (26 SN Ia). We highlight the importance of an accurate relative flux calibration and the failure of this method for highly-reddened objects. Comparison with synthetic spectra from 2D delayed-detonation explosion models shows that the correlation of R(6630/4400) with SN Ia absolute magnitudes can be largely attributed to intrinsic color variations and not to reddening by dust in the host galaxy. We consider flux ratios at other ages, as well as the use of pairs of flux ratios, revealing the presence of small-scale intrinsic spectroscopic variations in the iron-group dominated absorption features around ~4300 A and ~4800 A. The best flux ratio overall is the color-corrected R^c(4610/4260) at t=-2.5d from maximum light, which leads to ~30% lower scatter with respect to the standard combination of light-curve width and color. We examine other spectroscopic indicators related to line-profile morphology, but none appear to lead to a significant improvement over the standard light-curve width and color parameters.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑