RED NUGGETS AT z ∼ 1.5: COMPACT PASSIVE GALAXIES AND THE FORMATION OF THE KORMENDY RELATION
RED NUGGETS AT z ∼ 1.5: COMPACT PASSIVE GALAXIES AND THE FORMATION OF THE KORMENDY RELATION
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DOI：
10.1088/0004-637x/695/1/101
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发表时间：
2008-07
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影响因子：
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通讯作者：
I. Damjanov;P. McCarthy;R. Abraham;K. Glazebrook;Haojing Yan;E. Mentuch;D. L. Borgne;S. Savaglio-S.-Savagli
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作者：
I. Damjanov;P. McCarthy;R. Abraham;K. Glazebrook;Haojing Yan;E. Mentuch;D. L. Borgne;S. Savaglio-S.-Savagli
我们介绍了近红外相机和多目标光谱仪（NICMOS）成像的19个高质量被动演化星系的样本，1.2 < z < 2，主要从双子座深深巡天（GDDS）的结果。在我们的GDDS样本中，大约80%的星系的光谱主要由年龄为1.1 Gyr的恒星组成。我们的休息帧R波段图像显示，这些对象中的大多数具有紧凑的规则形态，遵循经典的R1/4定律。这些星系分散沿着一个紧密的序列的大小与表面亮度参数空间，定义了Kormendy关系。GDDS样本中大约三分之一（3/10）的大质量红色天体非常紧凑，有效半径小于1 kpc。我们的NICMOS观测允许比光学（静止帧UV）数据更稳健地检测这样的系统，虽然在z <2处已经看到了类似的系统，但这是第一次在1.2 < z < 2的静止帧光学测量中检测到这样的系统。我们把这些紧凑的星系称为“红块”，并注意到在附近的宇宙中完全没有类似的紧凑的大质量星系。我们引入了一个新的“恒星质量Kormendy关系”（恒星质量密度与大小），我们用它来挑选出的亮度和颜色的演变在恒星种群的大小演变的影响。1 < z < 2的被动星系的质量密度比今天的早期星系大一个数量级，与2 < z < 3的致密遥远红星系相当。我们简要地考虑机制的大小演变，在当代的模型集中在等质量合并和绝热膨胀驱动的恒星质量损失。这两种机制似乎都不能将高红移的科门迪关系转换成它的本地对应关系，使得这些致密的“红块”的起源和命运悬而未决。
We present the results of Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) imaging of a sample of 19 high-mass passively evolving galaxies with 1.2 < z < 2, taken primarily from the Gemini Deep Deep Survey (GDDS). Around 80% of galaxies in our GDDS sample have spectra dominated by stars with ages ≳1 Gyr. Our rest-frame R-band images show that most of these objects have compact regular morphologies which follow the classical R1/4 law. These galaxies scatter along a tight sequence in the size versus surface brightness parameter space which defines the Kormendy relation. Around one-third (3/10) of the massive red objects in the GDDS sample are extraordinarily compact, with effective radii under 1 kpc. Our NICMOS observations allow the detection of such systems more robustly than is possible with optical (rest-frame UV) data, and while similar systems have been seen at z ≳ 2, this is the first time such systems have been detected in a rest-frame optical survey at 1.2 < z < 2. We refer to these compact galaxies as “red nuggets,” and note that similarly compact massive galaxies are completely absent in the nearby universe. We introduce a new “stellar mass Kormendy relation” (stellar mass density versus size) which we use to single out the effects of size evolution from those of luminosity and color evolution in stellar populations. The 1 < z < 2 passive galaxies have mass densities that are an order of magnitude larger then early-type galaxies today and are comparable to the compact distant red galaxies at 2 < z < 3. We briefly consider mechanisms for size evolution in contemporary models focusing on equal-mass mergers and adiabatic expansion driven by stellar mass loss. Neither of these mechanisms appears to be able to transform the high-redshift Kormendy relation into its local counterpart, leaving the origin and fate of these compact “red nuggets” unresolved.