Candels+3D-HST: compact SFGs at z ∼ 2-3, the progenitors of the first quiescent galaxies



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Pérez González, Pablo Guillermo (2014) Candels+3D-HST: compact SFGs at z ∼ 2-3, the progenitors of the first quiescent galaxies. Astrophysical journal, 791 (1). ISSN 0004-637X

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We analyze the star-forming and structural properties of 45 massive (log(M/M_) > 10) compact star-forming galaxies (SFGs) at 2 < z < 3 to explore whether they are progenitors of compact quiescent galaxies at z ∼ 2. The optical/NIR and far-IR Spitzer/Herschel colors indicate that most compact SFGs are heavily obscured. Nearly half (47%) host an X-ray-bright active galactic nucleus (AGN). In contrast, only about 10% of other massive galaxies at that time host AGNs. Compact SFGs have centrally concentrated light profiles and spheroidal morphologies similar to quiescent galaxies and are thus strikingly different from other SFGs, which typically are disk-like and sometimes clumpy or irregular.Most compact SFGs lie either within the star formation rate (SFR)–mass main sequence (65%) or below it (30%), on the expected evolutionary path toward quiescent galaxies. These results show conclusively that galaxies become more compact before they lose their gas and dust, quenching star formation. Using extensive HST photometry from CANDELS and grism spectroscopy from the 3D-HST survey, we model their stellar populations with either exponentially declining (τ ) star formation histories (SFHs) or physically motivated SFHs drawn from semianalytic models (SAMs). SAMs predict longer formation timescales and older ages ∼2 Gyr, which are nearly twice as old as the estimates of the τ models. Both models yield good spectral energy distribution fits, indicating that the systematic uncertainty in the age due to degeneracies in the SFH is of that order of magnitude. However, SAM SFHs better match the observed slope and zero point of the SFR–mass main sequence. Contrary to expectations, some low-mass compact SFGs (log(M/M_) = 10–10.6) have younger ages but lower specific SFRs than that of more massive galaxies, suggesting that the low-mass galaxies reach the red sequence faster. If the progenitors of compact SFGs are extended SFGs, state-of-the-art SAMs show that mergers and disk instabilities (DIs) are both able to shrink galaxies, but DIs are more frequent (60% versus 40%) and form more concentrated galaxies. We confirm this result via high-resolution hydrodynamic simulations.

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© 2014. The American Astronomical Society. We thank David Elbaz for very useful discussions. Support for Program number HST-GO-12060 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. G.B. acknowledges support from NSF grant AST-08-08133. P.G.P.-G. acknowledges support from grant AYA2012-31277-E. This work has made use of the Rainbow Cosmological Surveys Database, which is operated by the Universidad Complutense de Madrid (UCM), partnered with the University of California Observatories at Santa Cruz (UCO/Lick, UCSC). C.P. acknowledges the support by the KASIYonsei Joint Research Program for the Frontiers of Astronomy and Space Science funded by the Korea Astronomy and Space Science Institute. J.L. acknowledges the support by the National Research Foundation of Korea through the SRC grant to the Center for Galaxy Evolution Research and the Doyak grant (No. 20090078756).

Uncontrolled Keywords:Star-forming galaxies; Active galactic nuclei; Hubble-space-telescope; Ultra-deep-field; Lyman-break galaxies; Digital sky survey; Goods-south field; Greater-Than 1; Spectral energy-distribution; Stellar population synthesis.
Subjects:Sciences > Physics > Astrophysics
ID Code:29223
Deposited On:16 Mar 2015 11:19
Last Modified:10 Dec 2018 15:05

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