AN EXTREMELY TOP-HEAVY INITIAL MASS FUNCTION IN THE GALACTIC CENTER STELLAR DISKS
AN EXTREMELY TOP-HEAVY INITIAL MASS FUNCTION IN THE GALACTIC CENTER STELLAR DISKS
复制标题
DOI：
10.1088/0004-637x/708/1/834
复制
发表时间：
2009-08
期刊：
影响因子：
--
通讯作者：
H. Bartko;Fabrice Martins;S. Trippe;T. Fritz;R. Genzel;T. Ott;F. Eisenhauer;S. Gillessen;
中科院分区：
文献类型：
--
作者：
H. Bartko;Fabrice Martins;S. Trippe;T. Fritz;R. Genzel;T. Ott;F. Eisenhauer;S. Gillessen;
我们在ESO/VLT上用自适应光学辅助积分场光谱仪SINFONI对银河系中央部分的核星团进行了新的观测。我们的工作允许对早类型和晚类型恒星的光谱探测到MK⩾16，比我们之前的数据集深2 MAG以上。我们的观测结果是，总共有177颗真正的早期恒星样本。我们发现，这些Wolf Rayet(WR)星、O星和B星大多位于距离SgrA*0.“8到12”的两个强翘曲圆盘中，以及以SgrA*为中心的致密星团(S星团)。后一类B星(MK和GT；15)在0.“8-12”之间的径向间隔内，似乎在盘外呈更各向同性的分布。即使在考虑到恒星碰撞的情况下，在中心几角秒内观察到的晚型恒星的稀少也令人费解。盘星的恒星质量函数是极重的，其最好的幂函数为dN/dm∝m−0.45±0.3。WR/O-星是在6Myr前的单个恒星形成事件∼中就地形成的，这个质量函数可能反映了初始质量函数。0.“8”内的S星和距离超过12“的早期类型星的质量函数符合标准的Salpeter/Kroupa IMF(dN/dm∝m−的最佳拟合幂定律2.15±0.3)。
We present new observations of the nuclear star cluster in the central parsec of the Galaxy with the adaptive optics assisted, integral field spectrograph SINFONI on the ESO/VLT. Our work allows the spectroscopic detection of early- and late-type stars to mK ⩾ 16, more than 2 mag deeper than our previous data sets. Our observations result in a total sample of 177 bona fide early-type stars. We find that most of these Wolf Rayet (WR), O-, and B-stars reside in two strongly warped disks between 0.″8 and 12″ from Sgr A*, as well as a central compact concentration (the S-star cluster) centered on Sgr A*. The later type B-stars (mK>15) in the radial interval between 0.″8 and 12″ seem to be in a more isotropic distribution outside the disks. The observed dearth of late-type stars in the central few arcseconds is puzzling, even when allowing for stellar collisions. The stellar mass function of the disk stars is extremely top heavy with a best-fit power law of dN/dm ∝ m−0.45± 0.3. WR/O-stars were formed in situ in a single star formation event ∼6 Myr ago, this mass function probably reflects the initial mass function (IMF). The mass functions of the S-stars inside 0.″8 and of the early-type stars at distances beyond 12″ are compatible with a standard Salpeter/Kroupa IMF (best-fit power law of dN/dm ∝ m−2.15± 0.3).