CAUGHT IN THE ACT: GAS AND STELLAR VELOCITY DISPERSIONS IN A FAST QUENCHING COMPACT STAR-FORMING GALAXY AT z ∼ 1.7

• Published in: The Astrophysical journal 2016-04, Vol.820 (2), p.120-120
• Main Authors: Barro, Guillermo, Faber, Sandra M., Dekel, Avishai, Pacifici, Camilla, Pérez-González, Pablo G., Toloba, Elisa, Koo, David C., Trump, Jonathan R., Inoue, Shigeki, Guo, Yicheng, Liu, Fengshan, Primack, Joel R., Koekemoer, Anton M., Brammer, Gabriel, Cava, Antonio, Cardiel, Nicolas, Ceverino, Daniel, Eliche, Carmen, Fang, Jerome J., Finkelstein, Steven L., Kocevski, Dale D., Livermore, Rachael C., McGrath, Elizabeth
• Format: Article
• Language: English
• Subjects: ABSORPTION; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Compact galaxies; COMPUTERIZED SIMULATION; DISPERSIONS; EMISSION; FORECASTING; GALAXIES; galaxies: high-redshift; galaxies: photometry; INCLINATION; PHOTOMETRY; Progenitors (astrophysics); QUENCHING; RED SHIFT; ROTATION; SPECTRA; SPECTROSCOPY; STAR EVOLUTION; Star formation; STARS; Stellar age; VELOCITY
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/0004-637X/820/2/120

ABSTRACT We present Keck I MOSFIRE spectroscopy in the Y and H bands of GDN-8231, a massive, compact, star-forming galaxy at a redshift of z ∼ 1.7. Its spectrum reveals both H and [N ii] emission lines and strong Balmer absorption lines. The H and Spitzer MIPS 24 m fluxes are both weak, thus indicating a low star-formation rate of SFR yr−1. This, added to a relatively young age of ∼700 Myr measured from the absorption lines, provides the first direct evidence for a distant galaxy being caught in the act of rapidly shutting down its star formation. Such quenching allows GDN-8231 to become a compact, quiescent galaxy, similar to three other galaxies in our sample, by z ∼ 1.5. Moreover, the color profile of GDN-8231 shows a bluer center, consistent with the predictions of recent simulations for an early phase of inside-out quenching. Its line-of-sight velocity dispersion for the gas, = 127 32 km s−1, is nearly 40% smaller than that of its stars, = 215 35 km s−1. High-resolution hydro-simulations of galaxies explain such apparently colder gas kinematics of up to a factor of ∼1.5 with rotating disks being viewed at different inclinations and/or centrally concentrated star-forming regions. A clear prediction is that their compact, quiescent descendants preserve some remnant rotation from their star-forming progenitors.