用Vista巡天的Z和Y滤波器和Spitzer巡天的IRAC滤波器确定银河系膨胀的红丛巨星的绝对星等
Determining the Absolute Magnitudes of Galactic-Bulge Red Clump Giants in the Z and Y Filters of the Vista Sky Surveys and the IRAC Filters of the Spitzer Sky Surveys
摘要：
利用红外VVV（VISTA/ESO）巡天的$Z$和$Y$测光带以及GLIMPSE（Spitzer/IRAC）银道巡天的[3.6]、[4.5]、[5.8]和[8.0]测光带，研究了银河核球中心区红团簇巨星的性质。这类天体的绝对星等首次在这些波段被测定：$M_{Z}= -0.20\pm0.04$和$M_{Y}=-0.470\pm0.045$、$M_{[3.6]}= -1.70\pm0.03$、$M_{[4.5]}= -1.60\pm0.03$、$M_{[5.8]}= -1.67\pm0.03$和$M_{[8.0]}= -1.70\pm0.03$。测量的星等与理论模型对所研究的天体光谱的预测的比较表明了良好的相互一致性，并允许获得一些重要的约束条件，以了解膨胀红团巨星的性质。特别是，与进化轨迹的比较表明，我们主要是在处理高金属丰度的膨胀红丛巨星子群。它们的金属丰度比以前认为的略高，$[M/H]\simeq0.40$（${\bf Z} \simeq 0.038$），误差为$[M/H]\simeq 0.1$ dex，而有效温度为$4250\pm150$ K。年龄在9-10 Gyr的恒星在红丛巨星中占主导地位，尽管一些年龄为$\sim8$的年轻天体也可能存在。此外，到几个银河系隆起区的距离已经被测量，D = 8200-8500 pc，在这些方向上的消光定律被证明与标准的明显不同。
英文摘要：
The properties of red clump giants in the central regions of the Galactic bulge are investigated in the photometric $Z$ and $Y$ bands of the infrared VVV (VISTA/ESO) survey and the [3.6],[4.5], [5.8] and [8.0] bands of the GLIMPSE (Spitzer/IRAC) Galactic plane survey. The absolute magnitudes for objects of this class have been determined in these bands for the first time: $M_{Z}= -0.20\pm0.04$ and $M_{Y}=-0.470\pm0.045$, $M_{[3.6]}= -1.70\pm0.03$, $M_{[4.5]}= -1.60\pm0.03$, $M_{[5.8]}= -1.67\pm0.03$ and $M_{[8.0]}= -1.70\pm0.03$. A comparison of the measured magnitudes with the predictions of theoretical models for the spectra of the objects under study has demonstrated good mutual agreement and has allowed some important constraints to be obtained for the properties of bulge red clump giants. In particular, a comparison with evolutionary tracks has shown that we are dealing predominantly with the high-metallicity subgroup of bulge red clump giants. Their metallicity is slightly higher than has been thought previously, $[M/H]\simeq0.40$ (${\bf Z} \simeq 0.038$) with an error of $[M/H]\simeq 0.1$ dex, while the effective temperature is $4250\pm150$ K. Stars with an age of 9-10 Gyr are shown to dominate among the red clump giants, although some number of younger objects with an age of $\sim8$ can also be present. In addition, the distances to several Galactic bulge regions have been measured, as D = 8200-8500 pc, and the extinction law in these directions is shown to differ noticeably from the standard one.
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