论文标题
IA型超新星的可能距离偏差，具有不同的射出速度
A Possible Distance Bias for Type Ia Supernovae with Different Ejecta Velocities
论文作者
论文摘要
在校正其光曲线形状和颜色之后，IA型超新星（SNE IA）是精确的宇宙学指标。但是，在测得的距离与从宇宙学模型（即哈勃残差或HRS）中推断出的差异之间存在非零的固有散射，这表明SN IA IA距离可以进一步改善。我们使用开源关系数据库kaepora来生成具有相期，光曲线形状和HR的平均特性的复合光谱。在许多阶段，来自正平均HR的两个子样本的复合光谱显着差异。特别是，在峰值亮度之后的9天到15天的所有光谱中，我们发现HR平均具有比为正HRS的SNE更高的SNE射出速度（几乎在每个光谱特征中可以看到）。在相对于B波段最大值的+4天时，使用62 SNE IA的样本，我们测量具有SI II 6355线速度SNE之间的0.091 +/- 0.035 MAG HR步骤高于-11,000 km/s（中间速度）。在光曲线形状和颜色校正之后，相对于宇宙学模型，具有较高速度的SNE往往低估了距离模量。进行此校正后，我们的样品中的固有散射从0.094 mag减少到0.082 mag。使用SI II 6355 115 SNE IA的速度演化，我们估计在正hr和负HR样品之间，每个时期内都存在速度差> 500 km/s，其置信度为99.4％。最终，在+37天晚期的时期，我们观察到与阳性HR复合光谱相比，负HR复合光谱往往具有较弱的光谱特征。
After correcting for their light-curve shape and color, Type Ia supernovae (SNe Ia) are precise cosmological distance indicators. However, there remains a non-zero intrinsic scatter in the differences between measured distance and that inferred from a cosmological model (i.e., Hubble residuals or HRs), indicating that SN Ia distances can potentially be further improved. We use the open-source relational database kaepora to generate composite spectra with desired average properties of phase, light-curve shape, and HR. At many phases, the composite spectra from two subsamples with positive and negative average HRs are significantly different. In particular, in all spectra from 9 days before to 15 days after peak brightness, we find that SNe with negative HRs have, on average, higher ejecta velocities (as seen in nearly every optical spectral feature) than SNe with positive HRs. At +4 days relative to B-band maximum, using a sample of 62 SNe Ia, we measure a 0.091 +/- 0.035 mag HR step between SNe with Si II 6355 line velocities higher/lower than -11,000 km/s (the median velocity). After light-curve shape and color correction, SNe with higher velocities tend to have underestimated distance moduli relative to a cosmological model. The intrinsic scatter in our sample reduces from 0.094 mag to 0.082 mag after making this correction. Using the Si II 6355 velocity evolution of 115 SNe Ia, we estimate that a velocity difference > 500 km/s exists at each epoch between the positive-HR and negative-HR samples with 99.4% confidence. Finally at epochs later than +37 days, we observe that negative-HR composite spectra tend to have weaker spectral features in comparison to positive-HR composite spectra.
