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Exploring the evolutionary paths of the most massive galaxies since z ~ 2



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Pérez González, Pablo Guillermo and Trujillo, Ignacio and Barro, Guillermo and Gallego Maestro, Jesús and Zamorano Calvo, Jaime and Conselice, Christopher J. (2008) Exploring the evolutionary paths of the most massive galaxies since z ~ 2. Astrophysical journal, 687 (1). pp. 50-58. ISSN 0004-637X


Official URL: http://dx.doi.org/10.1086/591843



We use Spitzer MIPS data from the FIDEL Legacy Project in the extended Groth strip to analyze the stellar mass assembly of massive (M > 1011 M_☉) galaxies at z < 2 as a function of structural parameters. We find 24 μm emission for more than 85% of the massive galaxies morphologically classified as disks, and for more than 57% of the massive systems morphologically classified as spheroids at any redshift, with about 8% of sources harboring a bright X-ray- and/or infrared-emitting AGN. More noticeably, ~60% of all compact massive galaxies at z = 1–2 are detected at 24 μm, even when rest-frame optical colors reveal that they are dead and evolving passively. For spheroid-like galaxies at a given stellar mass, the sizes of MIPS nondetections are smaller by a factor of ~1.2 in comparison with IR-bright sources. We find that disklike massive galaxies present specific SFRs ranging from 0.04 to 0.2 Gyr^−1 at z < 1 (SFRs ranging from 1 to 10 M_☉ yr^−1), typically a factor of 3-6 higher than massive spheroid-like objects in the same redshift range. At z > 1, and more pronouncedly at z > 1.3, the median specific SFRs of the disks and spheroids detected by MIPS are very similar, ranging from 0.1 to 1 Gyr^−1 (SFR = 10–200 M_☉ yr^−1). We estimate that massive spheroid-like galaxies may have doubled (at the most) their stellar mass from star-forming events at z < 2: less than 20% mass increase at 1.7 < z < 2.0, up to 40% more at 1.1 < z < 1.7, and less than 20% additional increase at z < 1. Disklike galaxies may have tripled (at the most) their stellar mass at z < 2 from star formation alone: up to ~40% mass increase at 1.7 < z < 2.0, and less than 180% additional increase below z = 1.7 occurred at a steady rate.

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© 2008. The American Astronomical Society. We thank an anonymous referee for her/his very constructive comments. We acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA 2006-02358 and AYA 2006- 15698- C02-02. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, Caltech under NASA contract 1407. P. G. P.-G. and I. T. acknowledge support from the Ramón y Cajal Program financed by the Spanish Government and the European Union.

Uncontrolled Keywords:Active galactic nuclei; Star-formation rate; Goods-music sample; Spectral energy-distributions; Hubble-space-telescope; Extended groth strip; Digital sky survey; Deep field-south; High-redshift; Stellar mass
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:34177
Deposited On:10 Nov 2015 13:15
Last Modified:10 Dec 2018 15:05

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