Spatially resolved variations of the IMF mass normalization in early-type galaxies as probed by molecular gas kinematics
Spatially resolved variations of the IMF mass normalization in early-type galaxies as probed by molecular gas kinematics
复制标题
DOI：
10.1093/mnras/stw2366
复制
发表时间：
2016-09
影响因子：
4.8
通讯作者：
T. Davis;R. McDermid
中科院分区：
文献类型：
--
作者：
T. Davis;R. McDermid
在这里，我们提出了第一个空间分辨的研究IMF在外部星系使用的质量-光比的动态示踪剂。我们使用的运动学松弛分子气体盘在7个早期类型的星系（ETGs）从ATLAS 3D调查选择动态确定质光比（M/L）梯度。这些M/L梯度在这些物体的内部并不很强，并且确实显示出变化的星系是那些具有最高特定星星形成率的星系。从星星形成历史中得到的恒星布居参数被用来估计恒星初始质量函数函数（IMF）失配参数，并揭示了它在ETG中的变化。我们的一些目标物体需要一个轻的IMF，否则它们的恒星人口质量将大于它们的动力学质量。相反，其他系统似乎需要更重的IMF来解释它们的气体运动学。我们的分析再次证实了IMF的变化似乎发生在大规模的ETG中。我们发现我们的IMF归一化使用分子气体运动学和使用其他技术得到的很好的协议。尽管如此，我们没有看到找到任何相关的IMF归一化和星系动力学性质或恒星的人口参数，无论是本地或全球。在未来更大规模的研究中，使用分子作为星系动力学的示踪剂，可以用来帮助我们解开IMF变化的根本原因。
We here present the first spatially-resolved study of the IMF in external galaxies derived using a dynamical tracer of the mass-to-light ratio. We use the kinematics of relaxed molecular gas discs in seven early-type galaxies (ETGs) selected from the ATLAS3D survey to dynamically determine mass-to-light ratio (M/L) gradients. These M/L gradients are not very strong in the inner parts of these objects, and galaxies that do show variations are those with the highest specific star formation rates. Stellar population parameters derived from star formation histories are then used in order to estimate the stellar initial mass function function (IMF) mismatch parameter, and shed light on its variation within ETGs. Some of our target objects require a light IMF, otherwise their stellar population masses would be greater than their dynamical masses. In contrast, other systems seem to require heavier IMFs to explain their gas kinematics. Our analysis again confirms that IMF variation seems to be occurring within massive ETGs. We find good agreement between our IMF normalisations derived using molecular gas kinematics and those derived using other techniques. Despite this, we do not see find any correlation between the IMF normalisation and galaxy dynamical properties or stellar population parameters, either locally or globally. In the future larger studies which use molecules as tracers of galaxy dynamics can be used to help us disentangle the root cause of IMF variation.