从z=2-3的超致密盘状星系看大质量星系的形成、演化和活动
Insights on the Formation, Evolution, and Activity of Massive Galaxies From Ultra-Compact and Disky Galaxies at z=2-3
摘要：
利用GOODS-NICMOS巡天中最大的（166个，M_star>= 5e 10 M_sun）和最多样的大质量星系样本，给出了z=1-3时大质量星系结构和活动的研究结果：（1）对深NIC 3/F160 W图像的Sersic拟合表明，与z~0相比，z=2-3时大质量星系的静止标架光学结构有很大的不同。大约40%的大质量星系是超紧凑的（r_e<=2 kpc），而在z~0时不到1%。此外，在z=2-3处的大多数（~65%）系统具有低Sersic指数n<=2，相比之下在z~0处为~13%。我们提出的证据表明，在z=2-3的n<=2系统可能包含突出的磁盘，不像大多数质量z~0系统。(2)结构和恒星形成率（SFR）之间存在相关性。大多数（~85%）z=2-3的非活动星系核大质量星系，其SFR足够高，可以产生5 sigma（30 μ Jy）24微米的斯皮策探测器，n<=2。这样的n<=2系统具有最高的SFR。(3)活动星系核的频率在z=2-3时约为40%。大多数（~65%）活动星系核的主体具有盘状（n<=2）形态。超致密星系在活动星系核活动和恒星形成方面都是静止的。(4)大的恒星表面密度意味着z=2-3的大质量星系是通过z>2的快速、高耗散事件形成的。大部分n<=2的盘状系统表明冷模吸积补充了z>2时的富气主合并。为了使z=2-3的大质量星系演化成现在的大质量E/S 0，它们需要显著增加（n，r_e）。在这一过程中，小型和大型的干合并可能发挥重要作用。
英文摘要：
We present our results on the structure and activity of massive galaxies at z=1-3 using one of the largest (166 with M_star>=5e10 M_sun) and most diverse samples of massive galaxies derived from the GOODS-NICMOS survey: (1) Sersic fits to deep NIC3/F160W images indicate that the rest-frame optical structures of massive galaxies are very different at z=2-3 compared to z~0. Approximately 40% of massive galaxies are ultra-compact (r_e<=2 kpc), compared to less than 1% at z~0. Furthermore, most (~65%) systems at z=2-3 have a low Sersic index n<=2, compared to ~13% at z~0. We present evidence that the n<=2 systems at z=2-3 likely contain prominent disks, unlike most massive z~0 systems. (2) There is a correlation between structure and star formation rates (SFR). The majority (~85%) of non-AGN massive galaxies at z=2-3, with SFR high enough to yield a 5 sigma (30 micro Jy) 24 micron Spitzer detection have low n<=2. Such n<=2 systems host the highest SFR. (3) The frequency of AGN is ~40% at z=2-3. Most (~65%) AGN hosts have disky (n<=2) morphologies. Ultra-compact galaxies appear quiescent in terms of both AGN activity and star formation. (4) Large stellar surface densities imply massive galaxies at z=2-3 formed via rapid, highly dissipative events at z>2. The large fraction of n<=2 disky systems suggests cold mode accretion complements gas-rich major mergers at z>2. In order for massive galaxies at z=2-3 to evolve into present-day massive E/S0s, they need to significantly increase (n, r_e). Dry minor and major mergers may play an important role in this process.
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