Galaxy pairs in the Sloan Digital Sky Survey – V. Tracing changes in star formation rate and metallicity out to separations of 80 kpc
Galaxy pairs in the Sloan Digital Sky Survey – V. Tracing changes in star formation rate and metallicity out to separations of 80 kpc
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DOI：
10.1111/j.1365-2966.2012.21749.x
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发表时间：
2012-07
影响因子：
4.8
通讯作者：
J. Scudder;S. Ellison;P. Torrey;D. Patton;J. Mendel
中科院分区：
文献类型：
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作者：
J. Scudder;S. Ellison;P. Torrey;D. Patton;J. Mendel
我们提出了一个样本的1899个星系与密切的同伴从斯隆数字巡天数据发布7。选择的星系对的速度差Δv < 300 km s−1，投影间距（rp）< 80 kpc，质量比在0.1和10之间，并且对星星形成率和气相金属丰度进行了可靠的测量。我们匹配的星系的总恒星质量，红移和本地密度的一组10个控制星系每对星系。因此，对于每一对星系，我们可以计算与相互作用过程相关的星星形成率（SFR）和金属丰度的统计变化。相对于对照样本，我们发现成对的星系显示出典型的SFR增强，平均比rp < 30 kpc的对照样本高60%。正是在这些小的分离处，SFR的增强最强（最高可达1000倍），尽管这样的星爆是罕见的，即使在最近的双星对中也是如此。此外，这两对显示出更适度的SFR增强，从30%到至少80 kpc（我们样本中最宽的分离）。这是第一次在如此大的预计分离中稳健地检测到增强的SFR。在大合并和小合并的星系团在所有的rp上都显示出显著的SFR增强，尽管最强的星爆（SFR增强因子为1000）似乎只出现在大合并中。我们还发现证据表明，SFR增强同步在一个相互作用的对，这样一个更高的SFR在一个星系是伴随着一个增加的SFR在其同伴。这是第一次，我们还能够跟踪星系对中金属丰度的变化作为预测分离的函数。在星系对中，金属丰度通常会被稀释约0.02 dex，在最小的距离处，平均金属丰度减少约-0.03 dex，这一趋势反映了SFR增强作为rp的函数。通过与理论模型的比较，解释了预测分离的SFR和金属丰度趋势。这些模拟表明，在小分离的SFR增强的峰值是由于合并过程接近尾声的系统。SFR增强的扩展高原至少达到80 kpc，主要是由已经进行了近心通道的星系主导，现在正在经历触发星星形成的轨道上朝向远银河，或随后的密切方法。
We present a sample of 1899 galaxies with a close companion taken from the Sloan Digital Sky Survey Data Release 7. The galaxy pairs are selected to have velocity differences Δv < 300 km s−1, projected separations (rp) < 80 kpc, mass ratios between 0.1 and 10, and robust measurements of star formation rates and gas-phase metallicities. We match the galaxies in total stellar mass, redshift and local density to a set of 10 control galaxies per pair galaxy. For each pair galaxy, we can therefore calculate the statistical change in star formation rate (SFR) and metallicity associated with the interaction process. Relative to the control sample, we find that galaxies in pairs show typical SFR enhancements that are, on average, 60 per cent higher than the control sample at rp < 30 kpc. It is at these small separations that the strongest enhancements in SFR (by up to a factor of ∼10) are measured, although such starbursts are rare, even amongst the closest pairs. In addition, the pairs demonstrate more modest SFR enhancements of ∼30 per cent out to at least 80 kpc (the widest separations in our sample). This is the first time that enhanced SFRs have been robustly detected out to such large projected separations. Galaxies in both major and minor mergers show significant SFR enhancements at all rp, although the strongest starbursts (with SFR enhancements of a factor of ∼10) appear to be found only in the major mergers. We also find evidence that SFR enhancements are synchronized in an interacting pair, such that a higher SFR in one galaxy is accompanied by an increased SFR in its companion. For the first time, we are also able to trace the metallicity changes in galaxy pairs as a function of projected separation. The metallicity is generally diluted in galaxy pairs by ∼0.02 dex, with an average metallicity decrement of −0.03 dex at the smallest separations, a trend that mirrors the SFR enhancements as a function of rp. The SFR and metallicity trends with projected separation are interpreted through a comparison with theoretical models. These simulations indicate that the peak in SFR enhancements at small separations is due to systems near the end of the merger process. The extended plateau in SFR enhancements out to at least 80 kpc is dominated by galaxies that have made a pericentric passage and are now experiencing triggered star formation on their trajectory towards apogalacticon, or on a subsequent close approach.