FORMATION EPOCHS, STAR FORMATION HISTORIES, AND SIZES OF MASSIVE EARLY-TYPE GALAXIES IN CLUSTER AND FIELD ENVIRONMENTS AT z = 1.2: INSIGHTS FROM THE REST-FRAME ULTRAVIOLET
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD (United States)
- ESO-European Southern Observatory, Garching bei Muenchen, D- 85748 (Germany)
- INAF-Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste (Italy)
- ST-ECF-Karl Schwarzschild strasse, 2, Garching bei Muenchen, D- 85748 (Germany)
- INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040, Monteporzio (Italy)
- National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
- GEPI, Observatoire de Paris, Section de Meudon, Meudon Cedex (France)
We derive stellar masses, ages, and star formation histories (SFHs) of massive early-type galaxies in the z = 1.237 RDCS1252.9-2927 cluster and compare them with those measured in a similarly mass-selected sample of field contemporaries drawn from the Great Observatories Origin Deep Survey South Field. Robust estimates of these parameters are obtained by comparing a large grid of composite stellar population models with 8-9 band photometry in the rest-frame near-ultraviolet, optical, and IR, thus sampling the entire relevant domain of emission of the different stellar populations. Additionally, we present new, deep U-band photometry of both fields, giving access to the critical far-ultraviolet rest frame, in order to empirically constrain the dependence of the most recent star formation processes on the environment. We also analyze the morphological properties of both samples to examine the dependence of their scaling relations on their mass and environment. We find that early-type galaxies, both in the cluster and in the field, show analogous optical morphologies, follow comparable mass versus size relation, have congruent average surface stellar mass densities, and lie on the same Kormendy relation. We also show that a fraction of early-type galaxies in the field employ longer timescales, tau, to assemble their mass than their cluster contemporaries. Hence, we conclude that while the formation epoch of early-type galaxies only depends on their mass, the environment does regulate the timescales of their SFHs. Our deep U-band imaging strongly supports this conclusion. We show that cluster galaxies are at least 0.5 mag fainter than their field contemporaries of similar mass and optical-to-infrared colors, implying that the last episode of star formation must have happened more recently in the field than in the cluster.
- OSTI ID:
- 21392329
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 709; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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