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arXiv 1006.0488astro-ph.COastro-ph.GAastro-ph.HE
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星系核“冲刷”质量的非参数估计

A Non-Parametric Estimate of Mass 'Scoured' in Galaxy Cores

Philip F. Hopkins, Lars Hernquist

摘要:

我们提出了一个简单的估计的质量“赤字”的核心球状体,作为星系内的星系质量和半径的函数。以前的尝试来衡量这种赤字依赖于拟合一些功能形式的配置文件在大半径和向内外推,这是敏感的假设功能形式,不允许核轮廓形状的变化。我们利用较大的数据集,直接构建观测系统的恒星质量剖面和测量恒星质量包围在一系列的物理半径(M(<R)),在相同的恒星质量的尖点和核心球状体的样本。在小半径处,该分布存在显著的双峰性,并且我们非参数化地测量核心和尖点群体之间的中位偏移(赤字Delta_M(<R))。我们构造的冲刷质量作为半径的函数,没有参考任何假设的功能形式。质量亏损以幂律方式(Δ_M(<R)R^{1.3-1.8})从R<10 pc时的一个显著但很小的质量增加到在~ 100 pc时的最大值~0.5-2 M_BH。在较大的半径处,种群之间没有统计上显著的分离;在~kpc处累积冲刷质量的上限为~2-4 M_BH。这并不强烈依赖于恒星质量。在核心人口中,M(<R)的分散度似乎较大,这可能反映了冲刷增加了剖面形状的分散度。这些结果与BH二元系的冲刷模型符合得很好。

英文摘要:

We present a simple estimate of the mass 'deficits' in cored spheroids, as a function of galaxy mass and radius within the galaxy. Previous attempts to measure such deficits depended on fitting some functional form to the profile at large radii and extrapolating inwards; this is sensitive to the assumed functional form and does not allow for variation in nuclear profile shapes. We take advantage of larger data sets to directly construct stellar mass profiles of observed systems and measure the stellar mass enclosed in a series of physical radii (M(<R)), for samples of cusp and core spheroids at the same stellar mass. There is a significant bimodality in this distribution at small radii, and we non-parametrically measure the median offset between core and cusp populations (the deficit Delta_M(<R)). We construct the scoured mass profile as a function of radius, without reference to any assumed functional form. The mass deficit rises in power-law fashion (Delta_M(<R) R^{1.3-1.8}) from a significant but small mass at R<10pc, to asymptote to a maximum ~0.5-2 M_BH at ~100pc. At larger radii there is no statistically significant separation between populations; the upper limit to the cumulative scoured mass at ~kpc is ~2-4 M_BH. This does not depend strongly on stellar mass. The dispersion in M(<R) appears larger in the core population, possibly reflecting the fact that scouring increases the scatter in profile shapes. These results are in good agreement with models of scouring from BH binary systems.

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