2004/05/31 by Hsiao-Wen Chen, Hsiao‐Wen Chen, Ronald O. Marzke +1 · 4 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Hubble Deep Field #Hubble Ultra-Deep Field #Luminous infrared galaxy #Physics #Redshift #Star formation #Stellar mass #astro-ph
paper · pdf · doi:10.1086/424732
published as Astrophys.J. 615 (2004) 603-609 · 14 pages, 3 figures, ApJ in press
arxiv created 2004/07/23 · openalex publication_date 2004/11/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have identified six early-type galaxies at z > 2.8 in the central 5.76 arcmin 2 Hubble Ultra Deep Field NICMOS region based on a pronounced broadband discontinuity between the NICMOS F110W and F160W bandpasses. These galaxies have red observed optical and near-infrared colors (AB F775W - AB F160W ≥ 2) that cannot be explained entirely by dust reddening (indicating advanced age), and their luminosities at rest-frame optical wavelengths suggest a substantial stellar mass. One of the galaxies is detected in the X-ray and is likely to have an active nuclear region, while the rest are estimated to be at least 1 Gyr old at z ≈ 3 and contain a total stellar mass of (0.4-9.1) × 10 10 h -2 M ☉ . We calculate a cumulative comoving stellar mass density of ρ star = (0.7-1.2) × 10 7 h M ☉ Mpc -3 for massive evolved galaxies of M > 10 9 h -2 M ☉ at z > 2.5. Comparison of the stellar mass density confined in galaxies of different types shows that massive evolved galaxies contribute ≈16%-28% of total stellar mass density even at these early epochs. Finally, an analysis of their morphology observed in the ACS and NICMOS images shows that the active galaxy has compact structure, while the rest are less concentrated. The presence of massive evolved galaxies at z ~ 3, when the universe was only 2 Gyr old, suggests that early star formation may have been particularly efficient in massive halos.