TIDAL TAILS OF MINOR MERGERS: STAR FORMATION EFFICIENCY IN THE WESTERN TAIL OF NGC 2782
TIDAL TAILS OF MINOR MERGERS: STAR FORMATION EFFICIENCY IN THE WESTERN TAIL OF NGC 2782
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小型合并的潮汐尾部：NGC 2782 西部尾部的恒星形成效率
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
E. Wehner
中科院分区：
文献类型：
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作者：
K. Knierman;P. Knezek;P. Scowen;R. Jansen;E. Wehner
虽然对大合并及其潮汐碎片进行了充分的研究，但它们不如小合并（质量比> 0.3）常见。奇特的螺旋星系NGC 2782是两个盘状星系合并的结果，两个星系的质量比为1.4：1，发生在2.2亿年前。这种合并产生了一个分子和H i丰富，光学明亮的东部尾巴和H i丰富，光学暗淡的西部尾巴。Braine等人在西尾没有探测到CO，这表明在潮汐尾还没有开始形成星星。然而，深Hα窄带图像显示了在西尾最近形成星星的证据。在整个西尾，我们发现每单位面积的全球星星形成率（GSFR）比总气体密度的预期低几个数量级。再加上银河演化探测器沿着尾部的扩展FUV+NUV发射，这表明在潮汐尾部产生较低质量星星团的全球星星形成效率较低。我们观测到的H ii区域与Hα的局部（几千秒差距尺度）相对SFR小于总气体密度的预期值，这与潮汐碎片的其他观测结果一致。从总气体密度推断的这个H ii区的星星形成效率较低，但从分子气体密度推断时正常。这些结果表明，在NGC 2782的西部尾部存在一个非常小的局部致密区域，或者是一个低金属量和/或低压恒星形成区域。
While major mergers and their tidal debris are well studied, they are less common than minor mergers (mass ratios ≲ 0.3). The peculiar spiral NGC 2782 is the result of a merger between two disk galaxies with a mass ratio of ∼4: 1 occurring ∼200 Myr ago. This merger produced a molecular and H i-rich, optically bright eastern tail and an H i-rich, optically faint western tail. Non-detection of CO in the western tail by Braine et al. suggested that star formation had not yet begun to occur in that tidal tail. However, deep Hα narrowband images show evidence of recent star formation in the western tail. Across the entire western tail, we find the global star formation rate per unit area (ΣSFR) to be several orders of magnitude less than expected from the total gas density. Together with extended FUV+NUV emission from Galaxy Evolution Explorer along the tail, this indicates a low global star formation efficiency in the tidal tail producing lower mass star clusters. The H ii region that we observed has a local (few-kiloparsec scale) ΣSFR from Hα that is less than that expected from the total gas density, which is consistent with other observations of tidal debris. The star formation efficiency of this H ii region inferred from the total gas density is low, but normal when inferred from the molecular gas density. These results suggest the presence of a very small, locally dense region in the western tail of NGC 2782 or of a low-metallicity and/or low-pressure star-forming region.
DOI：
10.1088/0004-6256/140/5/1194
发表时间：
2010-07
期刊：
The Astronomical Journal
影响因子：
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作者：
F. Bigiel;A. Leroy;F. Walter;L. Blitz;E. Brinks;W. D. Blok;B. M. U. Berkeley;Mpia Heidelberg;Nrao;U. Hertfordshire;U. C. Town;C. Observatories
通讯作者：
F. Bigiel;A. Leroy;F. Walter;L. Blitz;E. Brinks;W. D. Blok;B. M. U. Berkeley;Mpia Heidelberg;Nrao;U. Hertfordshire;U. C. Town;C. Observatories