REVISITING THE INFLUENCE OF UNIDENTIFIED BINARIES ON VELOCITY DISPERSION MEASUREMENTS IN ULTRA-FAINT STELLAR SYSTEMS
REVISITING THE INFLUENCE OF UNIDENTIFIED BINARIES ON VELOCITY DISPERSION MEASUREMENTS IN ULTRA-FAINT STELLAR SYSTEMS
复制标题
重新审视未知双星对超暗恒星系统速度色散测量的影响
DOI：
10.1088/2041-8205/722/2/l209
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
P. Côté
中科院分区：
文献类型：
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作者：
A. McConnachie;P. Côté
对最近发现的MV≤−7的银河系卫星的速度色散测量表明，它们具有很高的质量光比。由于它们的重子质量，预期的速度色散为~ 0.2 km s - 1，但测量值为~ 3 km s - 1。我们对这些系统的模拟径向速度测量进行了蒙特卡罗模拟，假设它们具有与球状星团相似的质量与光比，并拥有未识别的双星群，以确定这些恒星是否可以提高速度色散到观测值。我们发现这一假设不太可能产生远超过~ 4.5 km s−1的色散，这与之前的工作一致。然而，对于可能具有最小速度色散的系统，我们的模拟中有5% - 40%的数值与观测值一致，这些数值超过fbin(P≤10 yr) ~ 5%。这个样本包括在MV - rh空间中最接近经典球状星团的候选矮星系。作为一个整体考虑，不太可能所有这些候选矮星系都具有典型的球状星团的质量光比，但是对于几个单独的候选矮星系，在高置信度下，不能排除双星观测到的色散从接近零的值增加。考虑到获得最微弱卫星的精确速度色散和动力质量的重要性，显然需要直接排除双星对这些系统的可能影响。这需要多历元径向速度测量，单个不确定度为1 km s−1，以识别轨道速度与观测到的速度色散数量级的光谱双星。
Velocity dispersion measurements of recently discovered Milky Way satellites with MV ≳ −7 imply that they posses high mass-to-light ratios. The expected velocity dispersions due to their baryonic mass are ∼0.2 km s−1, but values ≳3 km s−1 are measured. We perform Monte Carlo simulations of mock radial velocity measurements of these systems assuming that they have mass-to-light ratios similar to globular clusters and posses an unidentified binary star population, to determine if these stars could boost the velocity dispersion to the observed values. We find that this hypothesis is unlikely to produce dispersions much in excess of ∼4.5 km s−1, in agreement with previous work. However, for the systems with the potentially smallest velocity dispersions, values consistent with observations are produced in 5%–40% of our simulations for binary fractions in excess of fbin(P ⩽ 10 yr)∼ 5%. This sample includes the dwarf galaxy candidates that lie closest to classical globular clusters in MV − rh space. Considered as a population, it is unlikely that all of these dwarf galaxy candidates have mass-to-light ratios typical of globular clusters, but boosting of the observed dispersion by binaries from near-zero values cannot be ruled out at high confidence for several individual dwarf galaxy candidates. Given the importance of obtaining accurate velocity dispersions and dynamical masses for the faintest satellites, it is clearly desirable to directly exclude the possible effect of binaries on these systems. This requires multi-epoch radial velocity measurements with individual uncertainties of ≲1 km s−1 to identify spectroscopic binaries with orbital velocities of the order of the observed velocity dispersion.
DOI：
10.1088/2041-8205/712/1/l103
发表时间：
2010-02
期刊：
The Astrophysical Journal Letters
影响因子：
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作者：
V. Belokurov;M. Walker;N. Evans;G. Gilmore;M. Irwin;D. Just;Sergey E. Koposov;M. Mateo;E. Olszewski;L. Watkins;L. W. IoA;Cambridge;S. Observatory;Tucson;U. Michigan
通讯作者：
V. Belokurov;M. Walker;N. Evans;G. Gilmore;M. Irwin;D. Just;Sergey E. Koposov;M. Mateo;E. Olszewski;L. Watkins;L. W. IoA;Cambridge;S. Observatory;Tucson;U. Michigan
DOI：
10.1086/590336
发表时间：
2008-05
期刊：
The Astrophysical Journal
影响因子：
--
作者：
N. Martin;J. D. de Jong;H. Rix
通讯作者：
N. Martin;J. D. de Jong;H. Rix