INSIGHTS ON THE FORMATION, EVOLUTION, AND ACTIVITY OF MASSIVE GALAXIES FROM ULTRACOMPACT AND DISKY GALAXIES AT z = 2–3
- Additional Document Info
- View All
We present our results on the structure and activity of massive galaxies at z = 1-3 using one of the largest (166 with M*⊙ ≥ 5 × 1010 M ⊙) and most diverse samples of massive galaxies derived from the GOODS-NICMOS survey: (1) Sérsic 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 ultracompact (r e ≤ 2kpc), compared to less than 1% at z ∼ 0. Furthermore, most (∼65%) systems at z = 2-3 have a low Sérsic 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 (SFRs). The majority (85%) of non-active galactic nucleus (AGN) massive galaxies at z = 2-3, with SFR high enough to yield a 5σ (30 μJy) 24 μm Spitzer detection, have low n ≤ 2. Such n ≤ 2 systems host the highest SFR. (3) The frequency of AGNs is 40% at z = 2-3. Most (65%) AGN hosts have disky (n ≤ 2) morphologies. Ultracompact 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, re ). Dry minor and major mergers may play an important role in this process. © 2011. The American Astronomical Society. All rights reserved.
author list (cited authors)
Weinzirl, T., Jogee, S., Conselice, C. J., Papovich, C., Chary, R., Bluck, A., ... Bauer, A. E.