183 research outputs found
One Plane for All: Massive Star-Forming and Quiescent Galaxies Lie on the Same Mass Fundamental Plane at z~0 and z~0.7
Scaling relations between galaxy structures and dynamics have been studied
extensively for early and late-type galaxies, both in the local universe and at
high redshifts. The abundant differences between the properties of disky and
elliptical, or star-forming and quiescent, galaxies seem to be characteristic
of the local Universe; such clear distinctions begin to disintegrate as
observations of massive galaxies probe higher redshifts. In this Paper, we
investigate the existence the mass fundamental plane of all massive galaxies
( 100 km/s). This work includes local galaxies (0.05<z<0.07)
from the SDSS, in addition to 31 star-forming and 72 quiescent massive galaxies
at intermediate redshift (z~0.7) with absorption line kinematics from deep
Keck-DEIMOS spectra and structural parameters from HST imaging. In two
parameter scaling relations, star-forming and quiescent galaxies differ
structurally and dynamically. However, we show that massive star-forming and
quiescent galaxies lie on nearly the same mass fundamental plane, or the
relationship between stellar mass surface density, stellar velocity dispersion,
and effective radius. The scatter in this relation (measured about
) is low: 0.072 dex (0.055 dex intrinsic) at z~0 and 0.10 dex (0.08
dex intrinsic) at z~0.7. This three dimensional surface is not unique: virial
relations, with or without a dependence on luminosity profile shapes, can
connect galaxy structures and stellar dynamics with similar scatter. This
result builds on the recent finding that mass fundamental plane has been stable
for early-type galaxies since z~2 (Bezanson et al. 2013). As we now find this
also holds for star-forming galaxies to z~0.7, this implies that these scaling
relations of galaxies will be minimally susceptible to progenitor biases due to
the evolving stellar populations, structures, and dynamics of galaxies through
cosmic time.Comment: 28 pages, 22 figures, resubmitted to ApJ after addressing referee
comment
Massive quenched galaxies at z~0.7 retain large molecular gas reservoirs
The physical mechanisms that quench star formation, turning blue star-forming
galaxies into red quiescent galaxies, remain unclear. In this Letter, we
investigate the role of gas supply in suppressing star formation by studying
the molecular gas content of post-starburst galaxies. Leveraging the wide area
of the SDSS, we identify a sample of massive intermediate-redshift galaxies
that have just ended their primary epoch of star formation. We present ALMA
CO(2-1) observations of two of these post-starburst galaxies at z~0.7 with M* ~
2x10^11 Msun. Their molecular gas reservoirs of (6.4 +/- 0.8) x 10^9 Msun and
(34.0 +/- 1.6) x 10^9 Msun are an order of magnitude larger than
comparable-mass galaxies in the local universe. Our observations suggest that
quenching does not require the total removal or depletion of molecular gas, as
many quenching models suggest. However, further observations are required both
to determine if these apparently quiescent objects host highly obscured star
formation and to investigate the intrinsic variation in the molecular gas
properties of post-starburst galaxies.Comment: Accepted for publication in ApJ Letters (6 pages, 5 figures
Discovery of a dark, massive, ALMA-only galaxy at z~5-6 in a tiny 3-millimeter survey
We report the serendipitous detection of two 3 mm continuum sources found in
deep ALMA Band 3 observations to study intermediate redshift galaxies in the
COSMOS field. One is near a foreground galaxy at 1.3", but is a previously
unknown dust-obscured star-forming galaxy (DSFG) at probable ,
illustrating the risk of misidentifying shorter wavelength counterparts. The
optical-to-mm spectral energy distribution (SED) favors a grey
attenuation curve and results in significantly larger stellar mass and SFR
compared to a Calzetti starburst law, suggesting caution when relating
progenitors and descendants based on these quantities. The other source is
missing from all previous optical/near-infrared/sub-mm/radio catalogs
("ALMA-only"), and remains undetected even in stacked ultradeep optical
( AB) and near-infrared ( AB) images. Using the ALMA position as
a prior reveals faint measurements in stacked IRAC 3.6+4.5,
ultradeep SCUBA2 850m, and VLA 3GHz, indicating the source is real. The
SED is robustly reproduced by a massive M and
M, highly obscured , star forming
Myr galaxy at redshift 1.1. The
ultrasmall 8 arcmin survey area implies a large yet uncertain
contribution to the cosmic star formation rate density CSFRD(z=5)
M yr Mpc, comparable to all
ultraviolet-selected galaxies combined. These results indicate the existence of
a prominent population of DSFGs at , below the typical detection limit of
bright galaxies found in single-dish sub-mm surveys, but with larger space
densities Mpc, higher duty cycles ,
contributing more to the CSFRD, and potentially dominating the high-mass galaxy
stellar mass function.Comment: Accepted for publication in ApJ. 2 galaxies, too many pages, 8
figures, 2 table
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