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arXiv 0707.4484astro-ph
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z~2.5红蓝星系的HST和Spitzer成像:从致密静止星系到扩展恒星形成星系的大小和恒星形成活动之间的相关性

HST and Spitzer imaging of red and blue galaxies at z~2.5: A correlation between size and star formation activity from compact quiescent galaxies to extended star forming galaxies

S. Toft, P. van Dokkum, M. Franx, I. Labbe, N. M. Forster Schreiber, S. Wuyts, T. Webb, G. Rudnick, A. Zirm, M. Kriek, P. van der Werf, J. P. Blakeslee, G. Illi… 展开作者

S. Toft, P. van Dokkum, M. Franx, I. Labbe, N. M. Forster Schreiber, S. Wuyts, T. Webb, G. Rudnick, A. Zirm, M. Kriek, P. van der Werf, J. P. Blakeslee, G. Illingworth, H. -W. Rix, C. Papovich, A. Moorwood

摘要:

本文介绍了在FIRES MS 1054视场中用红、蓝静止坐标系光学色对41个2<z<3.5星系进行的HST NICMOS+ACS和Spitzer IRAC+MIPS观测。在静止坐标系光波长下,约有一半的星系是非常紧凑的(有效半径r_e < 1 kpc),其余的星系是伸展的(1< r_e < 10 kpc)。作为参考,1千秒差距对应于所采用的宇宙学中z=2.5时的0.12角秒。我们分离活跃的恒星形成的星系从静止的星系通过建模他们的休息帧UV-NIR SED。恒星形成星系的大小范围很广,而静止星系的r_e都小于2kpc。在红移范围内,MIPS 24微米成像是再辐射尘埃发射(z<2.5)的敏感探针,24微米通量证实了小静止星系的光由老恒星主导,而不是尘埃笼罩的恒星形成或活动星系核活动。静止星系的表面质量密度和速度色散的推断是非常高的本地星系相比。星系遵循一个Kormendy关系(表面亮度和大小之间),其斜率与局部的相似,但向更亮的表面亮度移动,与平均恒星形成红移z_f~5一致。本文证明了恒星形成活动与z~2.5的大小之间的直接关系,以及存在大量的大质量,极密,古老的恒星系统,在局部宇宙中没有容易识别的对应物。

英文摘要:

We present HST NICMOS+ACS and Spitzer IRAC+MIPS observations of 41 galaxies at 2<z<3.5 in the FIRES MS1054 field with red and blue rest-frame optical colors. About half of the galaxies are very compact (effective radii r_e < 1 kpc) at rest-frame optical wavelengths, the others are extended (1< r_e < 10 kpc). For reference, 1 kpc corresponds to 0.12 arcsec at z=2.5 in the adopted cosmology. We separate actively star forming galaxies from quiescent galaxies by modeling their rest-frame UV-NIR SEDs. The star forming galaxies span the full range of sizes, while the quiescent galaxies all have r_e<2kpc. In the redshift range where MIPS 24 micron imaging is a sensitive probe of re-radiated dust emission (z<2.5), the 24 micron fluxes confirm that the light of the small quiescent galaxies is dominated by old stars, rather than dust-enshrouded star formation or AGN activity. The inferred surface mass densities and velocity dispersions for the quiescent galaxies are very high compared to those in local galaxies. The galaxies follow a Kormendy relation (between surface brightness and size) with approximately the same slope as locally, but shifted to brighter surface brightnesses, consistent with a mean stellar formation redshift of z_f~5. This paper demonstrates a direct relation between star formation activity and size at z~2.5, and the existence of a significant population of massive, extremely dense, old stellar systems without readily identifiable counterparts in the local universe.

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