Possible star formation in the halo of NGC 253
Possible star formation in the halo of NGC 253
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NGC 253 光环中可能形成恒星
DOI：
10.1051/0004-6361:20000336
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发表时间：
2001
影响因子：
6.5
通讯作者：
A. Gómez
中科院分区：
文献类型：
--
作者：
F. Comerón;J. Torra;R. Mendez;A. Gómez
我们提出了一个深UBV调查的方向的晕的星爆星系NGC 253，旨在调查可能存在的最近星星形成远离其磁盘，跟踪早期型恒星。我们讨论了不同类别的对象与蓝色的颜色，可能会污染区域的颜色和颜色星等图所占据的早期星族I星在距离NGC 253。强大的上限被发现对他们的贡献的测量对象计数的模型，调查的晕我们的银河系，和附近的控制领域的观察。在NGC 253的晕方向上识别出了一群$（B-V）23$的天体，在高水平的统计置信度下，在控制场中没有对应的天体。这些天体在NGC 253距离处的绝对星等与它们是主序星B 0-B2相一致。NGC 253晕中最蓝的天体的空间分布似乎聚集在两组中：一组更靠近NGC 253的盘，可能包含从其盘驱逐的逃逸恒星。另一个小组预测到星系平面的距离在9到15千秒差距之间，至少它的底部与射电连续谱中的一个峰值相吻合，这是由于宇宙射线的同步辐射逃离了星系盘。我们假设，在NGC 253的晕中的遥远的蓝色恒星群是在其核恒星爆发（也许也在磁盘中的星星形成区域）和晕中的冷气体之间的相互作用的结果，在一个类似于半人马座A附近的星星形成的现象由其喷流与HI云的相互作用引起的。如果是这样的话，NGC 253提供了一个例子，说明能量较低的星系外流能够触发星星形成晕，这种现象也可能是怀疑在距离银河系盘很远的地方存在第一星族恒星的原因。
We present a deep UBV survey in the direction of the halo of the starburst galaxy NGC 253 aimed at investigating the possible existence of recent star formation far from its disk, as traced by early-type stars. We discuss different classes of objects with blue colors that may contaminate the region of color-color and color-magnitude diagrams occupied by early Population I stars at the distance of NGC 253. Strong upper limits are found on their contribution to the measured object counts by means of models, of surveys of the halo of our Galaxy, and of observations of nearby control fields. A population of objects with $(B-V) 23$ is identified in the direction of the halo of NGC 253 that has no counterpart in the control fields to a high level of statistical confidence. The absolute magnitudes of these objects at the distance of NGC 253 is consistent with them being main sequence B0-B2 stars. The spatial distribution of the bluest objects in the halo of NGC 253 seems to cluster in two groups: one is closer to the disk of NGC 253, and may contain runaway stars expelled from its disk. The other group has projected distances to the plane of the galaxy ranging between 9 and 15 kpc, and at least its base coincides with a peak in radio continuum due to synchrotron emission of cosmic rays escaping the galactic disk. We hypothesize that the distant group of blue stars in the halo of NGC 253 is a result of the interaction between the superwind produced at its nuclear starburst (and perhaps also in star forming regions in the disk) and cold gas in the halo, in a phenomenon similar to the star formation near Centaurus A induced by the interaction of its jet with a HI cloud. If this is the case, NGC 253 provides an example of the ability of less energetic galactic outflows to trigger star formation in haloes, a phenomenon that may also be responsible for the suspected existence of Population I stars at large distances from the disk of the Milky Way.