THE Hα GALAXY SURVEY. VIII. CLOSE COMPANIONS AND INTERACTIONS, AND THE DEFINITION OF STARBURSTS
THE Hα GALAXY SURVEY. VIII. CLOSE COMPANIONS AND INTERACTIONS, AND THE DEFINITION OF STARBURSTS
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DOI：
10.1088/0004-637x/698/2/1437
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发表时间：
2009-04
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影响因子：
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通讯作者：
J. Knapen;P. James
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作者：
J. Knapen;P. James
我们考虑的大质量星星的形成特性，径向配置文件，和原子气体质量的星系在我们的Hα星系巡天，有密切的同伴星系，与一个匹配的控制样本的星系没有同伴。我们的分析是基于327个盘状星系的Hα和连续图像，这些星系构成了局部宇宙的代表性样本。我们发现，近伴星的存在使星星的形成速率提高了将近2倍，而几乎没有增加Hα发射的等效宽度。这意味着，虽然从统计学上说，有密切伴星的星系形成恒星的速度更快，但它们形成恒星的时间很长，而不是爆发。我们发现，没有显着增加的中心浓度的星星形成的一个密切的同伴的存在的结果。真正相互作用或合并的星系在局部宇宙中的比例非常小，约为2%，可能是明亮星系的4%。这些相互作用的星系中的大多数目前都具有不起眼的星星形成特性。我们还研究了调查中的星系的属性与最极端的值的星星形成指标，如率，等效宽度，星星形成率每面积，和气体耗尽的时间尺度。我们发现，这些指标有利于不同的星系子集，并使用这些信息来讨论关键的术语星爆的可能定义来描述增强星星形成活动的星系。我们的结论是，没有一个星爆的定义可以设计，是客观的，一般判别。除非人们将“星暴”一词的使用限制在极少数星系，否则这个词将继续用于各种各样的、范围广泛的天体集合，这些天体没有将其归类为星暴的物理基础。我们的总体结论是：（1）虽然很少发生相互作用和合并的星系可能促进了星星的形成，反之亦然，但那些星星形成最高的星系往往是相互作用或合并的，近伴星的存在对星系中星星形成的影响一般很小，而且持续时间很长;（2）“星爆”一词不容易用物理术语客观地、概括地加以定义。
We consider the massive star formation properties, radial profiles, and atomic gas masses of those galaxies in our Hα Galaxy Survey that have close companion galaxies, in comparison with a matched control sample of galaxies without companions. Our analysis is based on Hα and continuum images of 327 disk galaxies that form a representative sample of the local universe. We find that the presence of a close companion raises the star formation rate by a factor of just below two, while hardly at all increasing the equivalent width of the Hα emission. This means that although statistically galaxies with close companions form stars at a higher rate, they do this over extended periods of time and not as bursts. We find no significant increase in the central concentration of the star formation as a result of the presence of a close companion. The fraction of truly interacting or merging galaxies is very small in the local universe, at around 2%, and possibly 4% of bright galaxies. Most of these interacting galaxies currently have unremarkable star formation properties. We also study the properties of the galaxies in the survey with the most extreme values for star formation indicators such as rate, equivalent width, star formation rate per area, and gas-depletion timescale. We find that each of these indicators favors a different subset of galaxies, and use this information to discuss critically the possible definitions of the term starburst to describe galaxies with enhanced star formation activity. We conclude that no one starburst definition can be devised that is objective and generally discriminant. Unless one restricts the use of the term “starburst” to a very small number of galaxies indeed, the term will continue to be used for a heterogeneous and wide-ranging collection of objects with no physical basis for their classification as starburst. Our overall conclusions are that (1) whereas the rare interacting and merging galaxies may have enhanced star formation, and vice versa, those galaxies with the highest star formation are often interacting or merging, the influence of the presence of a close companion on the star formation in galaxies is in general very small, and long lasting; and (2) the term “starburst” cannot be easily defined objectively and generally in physical terms.