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arXiv 0808.2899astro-ph
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用Spitzer-IRS测量后发座星系团早型星系的中红外色-星等关系

The mid-infrared colour-magnitude relation of early-type galaxies in the Coma cluster as measured by Spitzer-IRS

M. S. Clemens, A. Bressan, P. Panuzzo, R. Rampazzo, L. Silva, L. Buson, G. L. Granato

摘要:

我们利用后发座星系团中50个早型星系的16微米、Spitzer-IRS、蓝色峰上光度测量来定义中红外色-星等关系。我们比较了最近简单的恒星星族模型,其中包括中红外发射的扩展,尘埃信封的演变恒星。这些模型中的Ks-[16]色对尘埃渐近巨星分支(AGB)星的相对星族非常敏感。我们发现,被动发展的早型星系定义了一个序列的近似恒定的年龄(~10 Gyr)与不同的金属丰度。有几个星系处于光学/近红外色等关系,但不处于中红外关系。这说明了Ks-[16]颜色对年龄的敏感性。在中红外线中可以看到颜色与星等的关系,这一事实强调了后发座星系团中大多数(68%)早型星系的极端被动性质。由此推论,在我们的样本中,32%的早期类型星系不是“被动的”,因为它们要么比10 Gyr年轻得多,要么在过去的几个Gyr中有一些复兴事件。

英文摘要:

We use 16 micron, Spitzer-IRS, blue peakup photometry of 50 early-type galaxies in the Coma cluster to define the mid-infrared colour-magnitude relation. We compare with recent simple stellar population models that include the mid-infrared emission from the extended, dusty envelopes of evolved stars. The Ks-[16] colour in these models is very sensitive to the relative population of dusty Asymptotic Giant Branch (AGB) stars. We find that the passively evolving early-type galaxies define a sequence of approximately constant age (~10 Gyr) with varying metallicity. Several galaxies that lie on the optical/near-infrared colour-magnitude relation do not lie on the mid-infrared relation. This illustrates the sensitivity of the Ks-[16] colour to age. The fact that a colour-magnitude relation is seen in the mid-infrared underlines the extremely passive nature of the majority (68%) of early-type galaxies in the Coma cluster. The corollary of this is that 32% of the early-type galaxies in our sample are not `passive', insofar as they are either significantly younger than 10 Gyr or they have had some rejuvenation episode within the last few Gyr.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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