The outer halo of the nearest giant elliptical: A VLT/VIMOS survey of the resolved stellar populations in Centaurus A to 85 kpc
The outer halo of the nearest giant elliptical: A VLT/VIMOS survey of the resolved stellar populations in Centaurus A to 85 kpc
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DOI：
10.1093/mnras/stt494
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发表时间：
2013-03
影响因子：
4.8
通讯作者：
D. Crnojevi'c;A. Ferguson;M. Irwin;E. Bernard;N. Arimoto;P. Jablonka;C. I. F. Astronomy;U. Edinburgh;R. Observatory;UK.;I. O. Astronomy;Cambridge;Subaru Telescope;National Space Development Agency of Japan;Hawaii;Usa;Department of Materials Science;Graduate Studies;Tokyo;Japan.;Laboratoire d'astrophysique;E. P. F. Lausanne;Switzerland.;Gepi;O. Paris;France.;S. O. Physics;Astronomy;Mathematics;U. Hertfordshire;R. S. O. Astronomy;Astrophysics;The Australian National University;Australia.
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文献类型：
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作者：
D. Crnojevi'c;A. Ferguson;M. Irwin;E. Bernard;N. Arimoto;P. Jablonka;C. I. F. Astronomy;U. Edinburgh;R. Observatory;UK.;I. O. Astronomy;Cambridge;Subaru Telescope;National Space Development Agency of Japan;Hawaii;Usa;Department of Materials Science;Graduate Studies;Tokyo;Japan.;Laboratoire d'astrophysique;E. P. F. Lausanne;Switzerland.;Gepi;O. Paris;France.;S. O. Physics;Astronomy;Mathematics;U. Hertfordshire;R. S. O. Astronomy;Astrophysics;The Australian National University;Australia.
我们提出的第一次调查解决恒星人口在遥远的外晕我们最近的巨型椭圆（GE），半人马座A（D = 3.8百万秒差距）。利用可见多目标摄谱仪（VIMOS）/甚大望远镜（VLT）光学相机，我们获得了沿长轴和短轴沿着四个视场的深度测光，投影椭圆半径近似为30-85 kpc（对应于近似为5- 14 R（eff））。我们使用解析的星星计数来绘制红巨星分支（RGB）恒星的空间和颜色分布，直到RGB尖端以下2等。我们探测到一个扩展的晕到最远的椭圆半径探测（类似于85千秒差距或类似于14 R（eff）），展示了这个系统的巨大范围。我们检测到一个本地化的子结构在这些部分，可见（旧）RGB和（中间年龄）发光渐近巨星分支星，有一些证据表明，外晕变得更加椭圆形，并有一个浅的表面亮度剖面。我们推导出晕RGB恒星的光度金属丰度分布函数，并发现相对较高的金属丰度中值（<[Fe/H]（med）类似于-0.9至-1.0 dex），在我们的调查范围内，随着半径的变化很小。经测量，径向金属丰度梯度约为-0.002-0.004 dex kpc（-1），贫金属星（定义为[Fe/H] < -1.0）的比例在所有半径上约为40- 50%。我们讨论了这些发现的背景下，星系形成模型的建设GE晕。
We present the first survey of resolved stellar populations in the remote outer halo of our nearest giant elliptical (gE), Centaurus A (D = 3.8 Mpc). Using the VIsible Multi Object Spectrograph (VIMOS)/Very Large Telescope (VLT) optical camera, we obtained deep photometry for four fields along the major and minor axes at projected elliptical radii of similar to 30-85 kpc (corresponding to similar to 5-14R(eff)). We use resolved star counts to map the spatial and colour distribution of red giant branch (RGB) stars down to similar to 2 mag below the RGB tip. We detect an extended halo out to the furthermost elliptical radius probed (similar to 85 kpc or similar to 14R(eff)), demonstrating the vast extent of this system. We detect a localized substructure in these parts, visible in both (old) RGB and (intermediate-age) luminous asymptotic giant branch stars, and there is some evidence that the outer halo becomes more elliptical and has a shallower surface brightness profile. We derive photometric metallicity distribution functions for halo RGB stars and find relatively high median metallicity values (<[Fe/H](med) similar to -0.9 to -1.0 dex) that change very little with radius over the extent of our survey. Radial metallicity gradients are measured to be approximate to -0.002-0.004 dex kpc(-1), and the fraction of metal-poor stars (defined as [Fe/H] < -1.0) is approximate to 40-50 per cent at all radii. We discuss these findings in the context of galaxy formation models for the buildup of gE haloes.