A panoramic VISTA of the stellar halo of NGC 253
A panoramic VISTA of the stellar halo of NGC 253
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NGC 253 星晕的全景 VISTA
DOI：
10.1051/0004-6361/201322759
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发表时间：
2014
影响因子：
6.5
通讯作者：
Greggio L
中科院分区：
文献类型：
--
作者：
Greggio L
大星系的外围包含着星系形成和聚集的重要信息。分辨恒星数的研究可以探测到外晕极低的表面亮度。AimsNGC 253是雕刻家星系群中一个接近边缘的盘状星系，我们从地基图像中分辨出它的光晕恒星，目的是研究它的恒星人口含量、结构和光晕的总体范围。方法利用安装在VISTA望远镜上的VIRCAM相机的zandj波段图像构建空间分辨的djv。z - j彩色星等图（cmd）。非常深的光度测量和覆盖的广泛区域使我们能够沿着星系的小轴追踪属于NGC 253晕的红巨星分支（RGB）和渐近巨星分支（AGB）恒星。结果：我们确认了盘面外恒星成分的存在，其南部有一个非常突出的架子，北部有一个对称的特征。唯一额外可见的子结构是位于光环西北部的超密度区域，距离平面约28 kpc，平行于星系盘延伸超过20 kpc。我们的数据不够深，无法将它的恒星群与周围光晕的恒星群区分开来，但光滑光晕上多余的恒星可以追溯到~7.5 × 106M⊙的母恒星群的质量。根据恒星计数，我们测量了从圆盘到光晕的转变，径向距离约为25kpc，在数量密度剖面上有明显的断裂。等密度等高线显示，内晕是一个扁平的结构，与一个更延伸、扩散、更圆的外晕混合在一起。这样的外部结构可以追溯到我们的图像的边缘，从磁盘平面到50kpc。星晕中恒星的数量密度分布遵循指数为- 1.6的幂律，是半径的函数。CMD显示了整个磁场中非常均匀的恒星群。通过与CMD等时线的比较，我们得出结论，RGB恒星的年龄在~ 8gyr以上，而AGB恒星的年龄在~0.5到几Gyr之间，形成了大约2 × 108M⊙的恒星群。令人惊讶的是，后者的一部分似乎分散在一个广泛的地区。我们探索了几种想法来解释NGC 253内部晕中相对年轻的成分的起源。
ContextOutskirts of large galaxies contain important information about galaxy formation and assembly. Resolved star count studies can probe the extremely low surface brightness of the outer halos.AimsNGC 253 is a nearly edge-on disk galaxy in the Sculptor group, of which we resolved the halo stars from ground-based images, with the aim of studying its stellar population content, the structure and the overall extent of the halo.MethodsWe useZandJ-band images from the VIRCAM camera mounted on the VISTA telescope to construct the spatially resolvedJvs.Z-Jcolor–magnitude diagrams (CMDs). The very deep photometry and the wide area covered allow us to trace the red giant branch (RGB) and asymptotic giant branch (AGB) stars that belong to the halo of NGC 253 out to 50 kpc along the galaxy’s minor axis.ResultsWe confirm the existence of an extra-planar stellar component of the disk, with a very prominent southern shelf and a symmetrical feature on the north side. The only additional visible substructure is an overdensity in the north-west part of the halo ~28 kpc distant from the plane and extending over 20 kpc parallel with the disk of the galaxy. Our data are not deep enough to distinguish its stellar population from that of the surrounding halo, but the excess of stars above the smooth halo traces the mass of the parent population of ~7.5 × 106M⊙. From stellar counts, we measure the transition from the disk to the halo at a radial distance of about 25 kpc with a clear break in the number density profile. The isodensity contours show that the inner halo is a flattened structure that blends with a more extended, diffuse, rounder outer halo. Such external structure can be traced to the very edge of our image out to 50 kpc from the disk plane. The number density profile of the stars in the stellar halo follows a power law with index −1.6, as a function of radius. The CMD shows a very homogeneous stellar population across the field. By comparing isochrones with the CMD, we conclude that the RGB stars are ~8 Gyr old or more, while the AGB stars trace a population of about 2 × 108M⊙formed from ~0.5 to a few Gyr ago. Surprisingly, part of the latter population appears scattered over a wide area. We explore several ideas to explain the origin of this relatively young component in the inner halo of NGC 253.
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NGC 253 光环中可能形成恒星
影响因子：
6.5
作者：
F. Comerón;J. Torra;R. Mendez;A. Gómez
通讯作者：
A. Gómez
玉夫座星系团中矮椭圆星系的表面亮度涨落距离
DOI：
10.1086/300635
发表时间：
1998
期刊：
The Astronomical Journal
影响因子：
--
作者：
H. Jerjen;K. Freeman;B. Binggeli
通讯作者：
B. Binggeli
DOI：
10.1088/0004-637x/692/2/955
发表时间：
2008-01
期刊：
The Astrophysical Journal
影响因子：
--
作者：
D. Martinez-Delgado;D. Martinez-Delgado;M. Pohlen;M. Pohlen;R. J. Gabany;S. Majewski;J. Peñarrubia;C. Palma;C. Palma;C. Palma
通讯作者：
D. Martinez-Delgado;D. Martinez-Delgado;M. Pohlen;M. Pohlen;R. J. Gabany;S. Majewski;J. Peñarrubia;C. Palma;C. Palma;C. Palma
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DOI：
--
发表时间：
2011
期刊：
影响因子：
--
作者：
E. Zackrisson;R. D. Jong;G. Micheva
通讯作者：
G. Micheva
银河系 NGC 253 中的暗丝：沸腾的银盘
DOI：
10.1086/117222
发表时间：
1994
期刊：
The Astronomical Journal
影响因子：
--
作者：
Y. Sofue;K. Wakamatsu;D. Malin
通讯作者：
D. Malin