Dust and the Infrared Kinematic Properties of Early-Type Galaxies
Dust and the Infrared Kinematic Properties of Early-Type Galaxies
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尘埃和早期星系的红外运动学特性
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
K. Gebhardt
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作者：
Julia Silge;K. Gebhardt
我们用2.29 μm近红外CO吸收带头获得了25个邻近早型星系（速度色散小于100 km s ~（-1）到大于300 km s ~（-1））的光谱，并测量了它们的恒星运动学。我们的分散体的不确定性中位数为10%。我们研究现有的光学运动学测量灰尘的影响。我们发现，近红外速度色散是，在一般情况下，小于光学速度色散，差异高达30%。中位差异小11%，并且对于更高色散的星系，这种影响更大。透镜状星系（25个中的18个）似乎导致了向低色散的转变，而经典椭圆星系（25个中的7个）在两个波长区域之间是一致的。如果均匀分布的尘埃导致了这些差异，我们会期望在星系中尘埃的相对数量和色散的分数变化之间找到相关性，但我们没有找到这样的相关性。我们确实看到了速度色散和CO带头等效宽度之间的相关性，以及速度色散和Mg 2指数之间的相关性。目前的灰尘吸收模型不能很好地解释分散的差异。尘埃的相对数量和分散度的变化之间缺乏相关性，这可能表明尘埃在星系之间的分布并不相似。这些星系的CO等效宽度相当高（几乎所有星系都是10 μ m），要求这些波长的光由非常冷的恒星主导。
We have obtained spectra and measured the stellar kinematics in a sample of 25 nearby early-type galaxies (with velocity dispersions from less than 100 km s-1 to over 300 km s-1) using the near-infrared CO absorption band head at 2.29 μm. Our median uncertainty for the dispersions is ∼10%. We examine the effects of dust on existing optical kinematic measurements. We find that the near-infrared velocity dispersions are, in general, smaller than optical velocity dispersions, with differences as large as 30%. The median difference is 11% smaller, and the effect is of greater magnitude for higher dispersion galaxies. The lenticular galaxies (18 out of 25) appear to be causing the shift to lower dispersions, while the classical elliptical galaxies (7 out of 25) are consistent between the two wavelength regimes. If uniformly distributed dust causes these differences, we would expect to find a correlation between the relative amount of dust in a galaxy and the fractional change in dispersion, but we do not find such a correlation. We do see correlations between both velocity dispersion and CO band head equivalent width, and velocity dispersion and Mg2 index. The differences in dispersion are not well explained by current models of dust absorption. The lack of correlation between the relative amount of dust and shift in dispersion possibly suggests that dust does not have a similar distribution from galaxy to galaxy. The CO equivalent widths of these galaxies are quite high (≳10 Å for almost all), requiring the light at these wavelengths to be dominated by very cool stars.