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arXiv 1209.4952astro-ph.COastro-ph.GAastro-ph.IM
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定位红巨星枝尖星等(Part II)的贝叶斯方法;到M31卫星的距离

A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude (Part II); Distances to the Satellites of M31

Anthony R. Conn, Rodrigo A. Ibata, Geraint F. Lewis, Quentin A. Parker, Daniel B. Zucker, Nicolas F. Martin, Alan W. McConnachie, Mike J. Irwin, Nial Tanvir, Ma… 展开作者

Anthony R. Conn, Rodrigo A. Ibata, Geraint F. Lewis, Quentin A. Parker, Daniel B. Zucker, Nicolas F. Martin, Alan W. McConnachie, Mike J. Irwin, Nial Tanvir, Mark A. Fardal, Annette M. N. Ferguson, Scott C. Chapman, David Valls-Gabaud

摘要:

在“确定红巨星枝尖星等的贝叶斯方法(第一部分)”中,介绍了一种使用TRGB标准烛光获取距离的新技术。在这里,我们描述了一个有用的补充技术的潜力,以进一步减少我们的距离测量的不确定性,通过将匹配滤波器加权方案到模型的似然计算。在这个方案中,恒星根据它们是真正天体成员的概率进行加权。然后,我们重新测试我们的修改后的算法,使用随机实现的人工数据,以验证所生成的后验概率分布(PPD)的有效性,并继续将该算法应用于卫星系统的M31,最终在三维视图的系统。进一步由此获得的分布,我们应用卫星特定的卫星距离的先验权重的距离后验分布,基于晕密度分布。因此,在一份出版物中,使用一种方法,全面覆盖了M31的同伴星系的距离,包括矮球状体仙女座I - III,V,IX-XXVII和XXX以及NGC 147,NGC 185,M33和M31本身。其中,仙女座XXIV - XXVII和仙女座XXX的距离以前从未使用TRGB推导过。物距是由高分辨率的尖端星等后验分布确定的,这些分布是使用马尔可夫链蒙特卡罗(MCMC)技术和相关的采样来产生的,以考虑前景消光的不确定性和TRGB的绝对星等以及光度误差。对于每个对象获得的距离PPD,无论是否具有上述先验,都以表格形式提供给读者。

英文摘要:

In `A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude (PART I),' a new technique was introduced for obtaining distances using the TRGB standard candle. Here we describe a useful complement to the technique with the potential to further reduce the uncertainty in our distance measurements by incorporating a matched-filter weighting scheme into the model likelihood calculations. In this scheme, stars are weighted according to their probability of being true object members. We then re-test our modified algorithm using random-realization artificial data to verify the validity of the generated posterior probability distributions (PPDs) and proceed to apply the algorithm to the satellite system of M31, culminating in a 3D view of the system. Further to the distributions thus obtained, we apply a satellite-specific prior on the satellite distances to weight the resulting distance posterior distributions, based on the halo density profile. Thus in a single publication, using a single method, a comprehensive coverage of the distances to the companion galaxies of M31 is presented, encompassing the dwarf spheroidals Andromedas I - III, V, IX-XXVII and XXX along with NGC147, NGC 185, M33 and M31 itself. Of these, the distances to Andromeda XXIV - XXVII and Andromeda XXX have never before been derived using the TRGB. Object distances are determined from high-resolution tip magnitude posterior distributions generated using the Markov Chain Monte Carlo (MCMC) technique and associated sampling of these distributions to take into account uncertainties in foreground extinction and the absolute magnitude of the TRGB as well as photometric errors. The distance PPDs obtained for each object both with, and without the aforementioned prior are made available to the reader in tabular form...

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