15 research outputs found
The rest-frame optical sizes of massive galaxies with suppressed star formation at
We present the rest-frame optical sizes of massive quiescent galaxies (QGs)
at measured at -band with the Infrared Camera and Spectrograph
(IRCS) and AO188 on the Subaru telescope. Based on a deep multi-wavelength
catalog in the Subaru XMM-Newton Deep Survey Field (SXDS), covering a wide
wavelength range from the -band to the IRAC over 0.7 deg, we
evaluate photometric redshift to identify massive ($M_{\star}\sim10^{11}\
M_\odot\rm \AAz\sim4K'K_{AB,total}=22.5\sim23.4z\sim4r_{eff}=0.21.8r_{eff}=0.7\rm\ kpcz\sim4\sim0.2z\sim4\log(r_e/{\rm kpc})= -0.44+1.77
\log(t/\rm Gyr)$. Their size growth is proportional to the square of stellar
mass, indicating the size-stellar mass growth driven by minor dry mergers.Comment: 15 pages, 11 figures, ApJ accepte
An exquisitely deep view of quenching galaxies through the gravitational lens: Stellar population, morphology, and ionized gas
This work presents an in-depth analysis of four gravitationally lensed red
galaxies at z = 1.6-3.2. The sources are magnified by factors of 2.7-30 by
foreground clusters, enabling spectral and morphological measurements that are
otherwise challenging. Our sample extends below the characteristic mass of the
stellar mass function and is thus more representative of the quiescent galaxy
population at z > 1 than previous spectroscopic studies. We analyze deep
VLT/X-SHOOTER spectra and multi-band Hubble Space Telescope photometry that
cover the rest-frame UV-to-optical regime. The entire sample resembles stellar
disks as inferred from lensing-reconstructed images. Through stellar population
synthesis analysis we infer that the targets are young (median age = 0.1-1.2
Gyr) and formed 80% of their stellar masses within 0.07-0.47 Gyr. Mg II
absorption is detected across the sample.
Blue-shifted absorption and/or redshifted emission of Mg II is found in the two
youngest sources, indicative of a galactic-scale outflow of warm (
K) gas. The [O III] luminosity is higher for the two young
sources (median age less than 0.4 Gyr) than the two older ones, perhaps
suggesting a decline in nuclear activity as quenching proceeds. Despite
high-velocity ( km s) galactic-scale outflows seen in the
most recently quenched galaxies, warm gas is still present to some extent long
after quenching. Altogether our results indicate that star formation quenching
at high redshift must have been a rapid process (< 1 Gyr) that does not
synchronize with bulge formation or complete gas removal. Substantial bulge
growth is required if they are to evolve into the metal-rich cores of
present-day slow-rotators.Comment: Accepted for publication in the Astrophysical Journal. 37 pages, 20
figures, 10 table
Stellar Velocity Dispersion of a Massive Quenching Galaxy at z = 4.01
We present the first stellar velocity dispersion measurement of a massive quenching galaxy at z = 4. The galaxy is first identified as a massive z ≥ 4 galaxy with suppressed star formation from photometric redshifts based on deep multiband data. A follow-up spectroscopic observation with MOSFIRE on Keck revealed strong multiple absorption features, which are identified as Balmer lines, giving a secure redshift of z = 4.01. This is the most distant quiescent galaxy known to date. Thanks to the high S/N of the spectrum, we are able to estimate the stellar velocity dispersion, σ=268±59 km s⁻¹, making a significant leap from the previous highest redshift measurement at z = 2.8. Interestingly, we find that the velocity dispersion is consistent with that of massive galaxies today, implying no significant evolution in velocity dispersion over the last 12 Gyr. Based on a stringent upper limit on its physical size from deep optical images (r_(eff) < 1.3 kpc), we find that its dynamical mass is consistent with the stellar mass inferred from photometry. Furthermore, the galaxy is located on the mass fundamental plane extrapolated from lower redshift galaxies. The observed no strong evolution in σ suggests that the mass in the core of massive galaxies does not evolve significantly, while most of the mass growth occurs in the outskirts of the galaxies, which also increases the size. This picture is consistent with a two-phase formation scenario in which mass and size growth is due to accretion in the outskirts of galaxies via mergers. Our results imply that the first phase may be completed as early as z ~ 4
Stellar Velocity Dispersion of a Massive Quenching Galaxy at z = 4.01
We present the first stellar velocity dispersion measurement of a massive quenching galaxy at z = 4. The galaxy is first identified as a massive z ≥ 4 galaxy with suppressed star formation from photometric redshifts based on deep multiband data. A follow-up spectroscopic observation with MOSFIRE on Keck revealed strong multiple absorption features, which are identified as Balmer lines, giving a secure redshift of z = 4.01. This is the most distant quiescent galaxy known to date. Thanks to the high S/N of the spectrum, we are able to estimate the stellar velocity dispersion, σ=268±59 km s⁻¹, making a significant leap from the previous highest redshift measurement at z = 2.8. Interestingly, we find that the velocity dispersion is consistent with that of massive galaxies today, implying no significant evolution in velocity dispersion over the last 12 Gyr. Based on a stringent upper limit on its physical size from deep optical images (r_(eff) < 1.3 kpc), we find that its dynamical mass is consistent with the stellar mass inferred from photometry. Furthermore, the galaxy is located on the mass fundamental plane extrapolated from lower redshift galaxies. The observed no strong evolution in σ suggests that the mass in the core of massive galaxies does not evolve significantly, while most of the mass growth occurs in the outskirts of the galaxies, which also increases the size. This picture is consistent with a two-phase formation scenario in which mass and size growth is due to accretion in the outskirts of galaxies via mergers. Our results imply that the first phase may be completed as early as z ~ 4
X-shooter Spectroscopy and HST Imaging of 15 Massive Quiescent Galaxies at z ≳ 2
We present a detailed analysis of a large sample of spectroscopically confirmed massive quiescent galaxies (MQGs; log(M*/M ⊙) ~ 11.5) at z ≳ 2. This sample comprises 15 galaxies selected in the COSMOS and UDS fields by their bright K-band magnitudes and followed up with Very Large Telescope (VLT) X-shooter spectroscopy and Hubble Space Telescope (HST)/WFC3 H_(F160W) imaging. These observations allow us to unambiguously confirm their redshifts, ascertain their quiescent nature and stellar ages, and reliably assess their internal kinematics and effective radii. We find that these galaxies are compact, consistent with the high-mass end of the stellar mass–size relation for quiescent galaxies at z = 2. Moreover, the distribution of the measured stellar velocity dispersions of the sample is consistent with the most massive local early-type galaxies from the MASSIVE Survey, showing that evolution in these galaxies is dominated by changes in size. The HST images reveal, as surprisingly high, that 40% of the sample has tidal features suggestive of mergers and companions in close proximity, including three galaxies experiencing ongoing major mergers. The absence of velocity dispersion evolution from z = 2 to 0, coupled with a doubling of the stellar mass, with a factor of 4 size increase and the observed disturbed stellar morphologies, supports dry minor mergers as the primary drivers of the evolution of the MQGs over the last 10 billion yr
A massive, dead disk galaxy in the early Universe
International audienceAt redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation. It is believed that they were formed in intense nuclear starbursts and that they ultimately grew into the most massive local elliptical galaxies seen today, through mergers with minor companions, but validating this picture requires higher-resolution observations of their centres than is currently possible. Magnification from gravitational lensing offers an opportunity to resolve the inner regions of galaxies. Here we report an analysis of the stellar populations and kinematics of a lensed z = 2.1478 compact galaxy, which—surprisingly—turns out to be a fast-spinning, rotationally supported disk galaxy. Its stars must have formed in a disk, rather than in a merger-driven nuclear starburst. The galaxy was probably fed by streams of cold gas, which were able to penetrate the hot halo gas until they were cut off by shock heating from the dark matter halo. This result confirms previous indirect indications that the first galaxies to cease star formation must have gone through major changes not just in their structure, but also in their kinematics, to evolve into present-day elliptical galaxies
Erratum: “Stellar Velocity Dispersion of a Massive Quenching Galaxy at z = 4.01” (2019, ApJL, 885, L34)
International audienc
Stellar Velocity Dispersion of a Massive Quenching Galaxy at z=4.01
We present the first stellar velocity dispersion measurement of a massive
quenching galaxy at z=4.01. The galaxy is first identified as a massive z>~4
galaxy with suppressed star formation from photometric redshifts based on deep
multi-band data in the UKIDSS Ultra Deep Survey field. A follow-up
spectroscopic observation with MOSFIRE on Keck revealed strong multiple
absorption features, which are identified as Balmer absorption lines, giving a
secure redshift of z=4.01. Thanks to the high S/N of the spectrum, we are able
to estimate the stellar velocity dispersion, sigma=268+/-59 km/s. This velocity
dispersion is consistent with that of massive galaxies today, implying no
significant evolution in stellar velocity dispersion over the last 12 Gyr.
Based on an upper limit on its physical size from deep optical images
(r_eff<1.3 kpc), we find that its dynamical mass is consistent with the stellar
mass inferred from photometry. Furthermore, the galaxy is located on the mass
fundamental plane extrapolated from lower redshift galaxies. Combining all
these results, we find that the velocity dispersion does not significantly
evolve with redshift, although the size and mass of massive quenched galaxies
do. This suggests that the mass in the core of massive galaxies does not evolve
significantly, while most of the mass growth occurs in the outskirts of the
galaxies, which also increases the size. This picture is consistent with a
two-phase formation scenario in which mass and size growth is due to accretion
in the outskirts of galaxies via mergers.Comment: Published in the Astrophysical Journal letters. Fixed an error in
dynamical mas