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arXiv 0709.0520astro-ph
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z~5-6星系的星暴强度极限

Starburst Intensity Limit of Galaxies at z~5-6

N. P. Hathi, S. Malhotra, J. E. Rhoads

摘要:

星暴星系中的恒星形成强度峰值从局域宇宙到红移z~6没有显著变化。我们通过对47个z~5-6的星暴星系的新的表面亮度测量得出了这一结论,使这种观测的红移范围增加了一倍。这些星系在哈勃超深场(HUDF)中通过GRism ACS计划的河外科学(GRAPES)项目进行光谱确认。在校正了宇宙学表面亮度变暗和尘埃之后,z~5-6处星系的星暴强度极限与z~3-4和z~0处的星暴强度极限在几个因子之内一致。对宇宙时间不变的最自然的解释是,相同的物理机制限制了所有红移到z~6的星暴强度(无论是星系风、引力不稳定性还是其他因素)。我们确实看到了红移的两个趋势:第一,z~5-6星系的紫外光谱斜率比z~3星系的更蓝,这表明尘埃含量随着时间的推移而增加。第二,z~3 ~ z~6尺度的星系尺度近似为哈勃参数1/H(z)。因此,z~6的星系是高红移的星暴,除了颜色稍微偏蓝,物理尺寸较小,以及相应的整体光度较低之外,与它们的本地类似物非常相似。如果我们假设恒星形成的最大强度是恒定的,那么观测到的z~0和z~6表面亮度的差异与标准膨胀宇宙学是一致的,而与疲劳光模型是强烈不一致的。

英文摘要:

The peak star formation intensity in starburst galaxies does not vary significantly from the local universe to redshift z~6. We arrive at this conclusion through new surface brightness measurements of 47 starburst galaxies at z~5-6, doubling the redshift range for such observations. These galaxies are spectroscopically confirmed in the Hubble Ultra Deep Field (HUDF) through the GRism ACS program for Extragalactic Science (GRAPES) project. The starburst intensity limit for galaxies at z~5-6 agree with those at z~3-4 and z~0 to within a factor of a few, after correcting for cosmological surface brightness dimming and for dust. The most natural interpretation of this constancy over cosmic time is that the same physical mechanisms limit starburst intensity at all redshifts up to z~6 (be they galactic winds, gravitational instability, or something else). We do see two trends with redshift: First, the UV spectral slope of galaxies at z~5-6 is bluer than that of z~3 galaxies, suggesting an increase in dust content over time. Second, the galaxy sizes from z~3 to z~6 scale approximately as the Hubble parameter 1/H(z). Thus, galaxies at z~6 are high redshift starbursts, much like their local analogs except for slightly bluer colors, smaller physical sizes, and correspondingly lower overall luminosities. If we now assume a constant maximum star formation intensity, the differences in observed surface brightness between z~0 and z~6 are consistent with standard expanding cosmology and strongly inconsistent with tired light model.

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