用近红外光度学对合并率演变的稳健估计
Towards a robust estimate of the merger rate evolution using near-IR photometry
摘要：
我们使用的组合深，高角分辨率的成像数据从CDFS（HST/ACS GOODS调查）和地面近红外$K_s$图像推导星系主要合并率的红移范围$0.2 \leq z \leq 1.2$的演变。我们选择星系的唯一基础上，他们的J-波段静止框架，绝对星等，这是一个很好的示踪剂的恒星质量。我们发现随着红移的急剧变化，光学选择对的合并率为$\propto (1+z)^{3.43\pm0.49}$，近红外选择对的合并率为$\propto (1+z)^{2.18\pm0.18}$。我们的结果不太可能受到亮度变化的影响，当使用静止框架J带选择时，亮度变化相对温和。显然更快的演变，我们发现在可见光是可能造成的偏差有关的不完整性和空间分辨率影响地面近红外测光，低估了对计数在较高的红移在近IR. The主要合并率是$\sim$ 5.6倍，在$z\sim1.2$比在当前的时代。在所有具有$M_J\leq-19.5$的星系中，总共有41%的$\times$（$0.5\gyr$ / $τ$）在最近的$\sim8 \gyr$中经历了一次大合并，其中$τ$是合并的时间尺度。有趣的是，我们没有发现由于CDFS中$z=0.735$的大尺度结构的存在而对导出的主要合并率产生影响。
英文摘要：
We use a combination of deep, high angular resolution imaging data from the CDFS (HST/ACS GOODS survey) and ground based near-IR $K_s$ images to derive the evolution of the galaxy major merger rate in the redshift range $0.2 \leq z \leq 1.2$. We select galaxies on the sole basis of their J-band rest-frame, absolute magnitude, which is a good tracer of the stellar mass. We find steep evolution with redshift, with the merger rate $\propto (1+z)^{3.43\pm0.49}$ for optically selected pairs, and $\propto (1+z)^{2.18\pm0.18}$ for pairs selected in the near-IR. Our result is unlikely to be affected by luminosity evolution which is relatively modest when using rest-frame J band selection. The apparently more rapid evolution that we find in the visible is likely caused by biases relating to incompleteness and spatial resolution affecting the ground based near IR photometry, underestimating pair counts at higher redshifts in the near-IR. The major merger rate was $\sim$5.6 times higher at $z\sim1.2$ than at the current epoch. Overall 41%$\times$($0.5\gyr$/$τ$) of all galaxies with $M_J\leq-19.5$ have undergone a major merger in the last $\sim8 \gyr$, where $τ$ is the merger timescale. Interestingly, we find no effect on the derived major merger rate due to the presence of the large scale structure at $z=0.735$ in the CDFS.
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