arXiv 0811.15792008-11astro-ph

Local Group矮球状体中的银河潮汐特征

The Signature of Galactic Tides in Local Group Dwarf Spheroidals

Jorge Penarrubia, Julio F. Navarro, Alan W. McConnachie, Nicolas F. Martin

备注：: 14 pages, ApJ accepted
发表信息：: Astrophys.J.698:222-232,2009
DOI：: 10.1088/0004-637X/698/1/222

摘要：

我们利用N体模拟研究了潮汐剥离对矮球状星系结构的影响。我们的模型dSphs国王领域嵌入NFW暗晕的轨道上偏心轨道的银河系的潜力。我们发现，恒星质量损失的插曲删除绑定恒星核心的初始截止。一旦平衡被重新建立，外部质量轮廓在投影中接近幂律，该幂律由简单的Plummer模型很好地描述。潮汐也会在外层密度剖面中产生瞬变特征。由于系统重新平衡，向外移动的“多余”的恒星被发现在半径的地方，当地的交叉时间超过了时间流逝，因为近心。如果轨道是已知的，这些结果提供了一个简单的方法来评估是否“休息”和“颠簸”的轮廓dSphs实际上是潮汐的起源。我们将此应用于人马座矮星，并令人惊讶地，确定两个功能的配置文件，可以追溯到其最后两个近心点通道。应用到狮子座I，我们发现，任何潮汐突破将位于超出目前的数据调查的区域，怀疑最近声称的潮汐碎片在这个星系周围的检测。对于船底座来说，潮汐中断应该发生在比观测到的半径大两倍的地方，这表明外部多余的恒星不是潮汐起源的，除非它的轨道是错误的。类似的评论也适用于玉夫座，它的近心似乎太大，银河潮汐不重要，但它的外部轮廓，像德拉科一样，仍然严格遵循普卢默定律。天炉座和狮子座II没有显示出幂律外轮廓的迹象，这表明它们没有遭受恒星潮汐剥离。已发表的其他较暗的银河系dSph伴星的资料没有延伸到足够远的地方，无法进行结论性的评估。

英文摘要：

(Abridged) We use N-body simulations to explore the effects of tidal stripping on the structure of dwarf spheroidal galaxies (dSphs). We model dSphs as King spheres embedded in NFW dark halos that orbit the Galactic potential on eccentric orbits. We find that episodes of stellar mass loss remove the initial cutoff of the bound stellar core. Once equilibrium has been re-established the outer mass profile approaches a power-law in projection that is well described by a simple Plummer model. Tides also result in transient features in the outer density profile. As the system re-equilibrates, an outward-moving "excess" of stars is found at radii where the local crossing time exceeds the time elapsed since pericenter. If the orbit is known, these results provide a simple way to assess whether "breaks" and "bumps" in the profile of dSphs are actually tidal in origin. We apply this to the Sagittarius dwarf and, encouragingly, identify two features in the profile that may be traced to its two last pericentric passages. Applied to Leo I, we find that any tidal break would locate beyond the area surveyed by current data, casting doubt on recent claims of the detection of tidal debris around this galaxy. For Carina, the tidal break should occur at a radius twice farther than observed, suggesting that the outer excess of stars is not tidal in origin unless its orbit is in error. A similar comment applies to Sculptor, whose pericenter appears too large for Galactic tides to be important but whose outer profile, like that of Draco, nonetheless follows closely a Plummer-law. Fornax and Leo II show no sign of a power-law outer profile, suggesting that they have not suffered stellar tidal stripping. Published profiles for other, fainter Milky Way dSph companions do not extend sufficiently far to allow for conclusive assessment.

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