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首页> 外文期刊>The Astrophysical journal >TIDALLY TRIGGERED STAR FORMATION IN CLOSE PAIRS OF GALAXIES
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TIDALLY TRIGGERED STAR FORMATION IN CLOSE PAIRS OF GALAXIES

机译：星系近对中的TIGALLY恒星形成

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We analyze optical spectra of a sample of 502 galaxies in close pairs and N-tuples, separated by S50 h~-1 kpc. We extracted the sample objectively from the CfA2 redshift survey, without regard to the sur- roundings of the tight systems; we remeasure the spectra with longer exposures, to explore the spectral characteristics of the galaxies. We use the new spectra to probe the relationship between star formation and the dynamics of the systems of galaxies. The equivalent widths of Ha [EW(Hα)] and other emission lines anticorrelate strongly with pair spatial separation (ΔD) and velocity separation; the anticorrelations do not result from any large-scale environmental effects that we detect. We use the measured EW(Hα) and the starburst models of Lei- therer et al. to estimate the time since the most recent burst of star formation began for galaxies in our sample. In the absence of a large contribution from an old stellar population to the continuum around Hα that correlates with the orbit parameters, the observed ΔD-EW(Hα) correlation signifies that star- bursts with larger separations on the sky are, on average, older. We also find a population of galaxies with small to moderate amounts of Balmer absorption. These galaxies support our conclusion that the sample includes many aging bursts of star formation, they have a narrower distribution of velocity separations, consistent with a population of orbiting galaxies near apogalacticon. By matching the dynamical timescale to the burst timescale, we show that the data support a simple picture in which a close pass initiates a starburst, EW(Hα) decreases with time as the pair separation increases, accounting for the anticorrelation. Recent N-body/smoothed particle hydrodynamics simula- tions of interacting pairs suggest a physical basis for the correlation--for galaxies with shallow central potentials, they predict gas infall before the final merger. This picture leads to a method for measuring the duration and the initial mass function of interaction-induced starburstsf our data are compatible with the starburst models and orbit models in many respects, as long as the starburst lasts longer than ～10~8 yr and the delay between the close pass and the initiation of the starburst is less than a few times 10~7 yr. If there is no large contribution from an old stellar population to the continuum around Ha, the Miller-Scalo and cutoff (M ≤ 30 M⊙) Salpeter initial mass functions (IMFs) fit the data much better than a standard Salpeter lMF.
机译：我们分析了由S50 h〜-1 kpc隔开的近502对和N元组的502个星系样本的光谱。我们从CfA2红移调查中客观地提取了样本，而没有考虑紧密系统的影响。我们用更长的曝光时间重新测量光谱，以探索星系的光谱特征。我们使用新的光谱来探测恒星形成与星系系统动力学之间的关系。 Ha [EW（Hα）]与其他发射线的等效宽度与线对空间间距（ΔD）和速度间距强烈反相关;反相关性不是我们检测到的任何大规模环境影响引起的。我们使用实测的EW（Hα）和Leither等人的星爆模型。估计自我们样本中的星系最近一次恒星爆发以来的时间。在没有老恒星种群对Hα周围连续体的贡献与轨道参数相关的情况下，观测到的ΔD-EW（Hα）相关性表明，在天空上具有较大间隔的恒星爆发平均而言较老。我们还发现了大量的Balmer吸收星系。这些星系支持我们的结论，即该样本包括许多恒星形成的衰老爆发，它们具有较窄的速度间隔分布，这与近距变星的轨道星系数量一致。通过将动态时标与突发时标相匹配，我们表明数据支持一个简单的图片，其中近程通过会引发星爆，EW（Hα）随着对间距的增加而随时间减小，这说明了反相关性。最近相互作用对的N体/光滑粒子流体动力学模拟为这种相关性提供了物理基础-对于中心电位较浅的星系，他们预测了最终合并之前的气体侵入。这张图片引出了一种测量相互作用引起的星暴的持续时间和初始质量函数的方法。只要星暴持续时间超过〜10〜8年，并且星暴持续时间长，我们的数据在许多方面都与星暴模型和轨道模型兼容。近距离通行与爆发之间的延迟小于10〜7年的几倍。如果旧的恒星种群对Ha附近的连续体没有大的贡献，则Miller-Scalo和截断（M≤30M⊙）Salpeter初始质量函数（IMF）拟合数据要比标准Salpeter lMF好得多。

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