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基于投影几率的星系对统计研究方法对COSMOS巡天的新应用
Alternative TitleA New Statistical Study of Galaxy-pair Populations in the COSMOS Field Based on Chance-projection Probabilities
阮志锋
Subtype硕士
Thesis Advisor邬文弢
2015-07-01
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline天体物理
Keyword星系 演化—星系 高红移—星系 相互作用—星系 统计
Abstract在我们的研究中提出了一个新的统计方法来研究COSMOS巡天中的星系对比例演化,首先我们利用两星系的投影几率作为判断星系对的标准建立一个间接的星系对样本,然后用在空间上随机分布的星系模拟真实空间的中的投影星系对,并从样本的结果中扣除模拟中得到的投影星系对的结果。在我们的工作中发现在rp
Other AbstractWe present a new statistical study of the evolution of galaxy-pair fractions in the COSMOS survey up to z < 1. We use a simple method based on chance-projection probabilities to indirectly sample relatively isolated galaxy pairs. The method subtracts contaminations of chance-project pairs according to simulated random galaxy distributions. We for the first time assess and empirically avoid the screen effect in high-redshift pair statistics. Our sampled pairs statistically have projected separations (rp) from ~ 20 h_75^(-1) kpc to~ 30 h_75^(-1) kpc. By taking these pairs as evolutionary counterparts of the nearby CPG pairs of similar rp , which is supported by our additional statistics, we find that the pair fractions evolve with redshift as (1+z)m with m = 0.93 ± 0.20$. This result argues for a significant medium-fast pair-fraction increase toward higher $z$. We find that sampling of populations of high-redshift pairs of rp < r_p^sc is likely strongly biased by the screen effect if using sky-survey object catalogs generated with currently available algorithms (e.g. the SExtractor), withr_p^sc varying with the redshift in the range~ 15 h_75^(-1) kpc to ~ 25 h_75^(-1) kpc. Furthermore, current object identification from space-based sky-survey images may have over-deblended high-redshift galaxies and generated false galaxy pairs of rp < r_p^sc. These issues raise serious doubts about previous results suggesting fast pair-fraction evolution, m ≈ 2.2-3.1. In addition, our study shows strong and complex evolution of galaxy environment in the vicinities of relatively isolated pairs. We thus caution about directly interpreting pair-fraction increase (reflected in the m) as the galaxy merger-rate increase. Conversion of pair-fraction increase to merger-rate increase involves the merger timescales (τm) at various redshifts, but τm may evolve in an unknown complex pattern under the influences of the evolving close galaxy environments of the pairs.Overall, our study uncovers several problems that should be interesting for future research of high-redshift pairs, mainly the influences of the screen effect and cosmic environments of pairs on pair statistics and τm.
Subject Area天文学
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/9461
Collection高能天体物理研究组
Affiliation中国科学院云南天文台
Recommended Citation
GB/T 7714
阮志锋. 基于投影几率的星系对统计研究方法对COSMOS巡天的新应用[D]. 北京. 中国科学院研究生院,2015.
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