Examinando por Autor "Gomez, Percy"
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Ítem An Extremely Massive Quiescent Galaxy at z = 3.493: Evidence of Insufficiently Rapid Quenching Mechanisms in Theoretical Models(Institute of Physics Publishing, 2020-02) Forrest, Ben; Annunziatella, Marianna; Wilson, Gillian; Marchesini, Danilo; Muzzin, Adam; Cooper, M.C; Marsan, Cemile; McConachie, Ian; C. C. Chan, Jeffrey; Gomez, Percy; Kado-Fong, Erin; La Barbera, Francesco; Labbé, Ivo; Daniel, Langle -Vagle; Julie, Nantais; Nonino, Mario; Peña, Theodore; Saracco, Paolo; Mauro, Stefanon; Remco van der Burg, F.JWe present spectra of the most massive quiescent galaxy yet spectroscopically confirmed at z > 3, verified via the detection of Balmer absorption features in the H- A nd K-bands of Keck/MOSFIRE. The spectra confirm a galaxy with no significant ongoing star formation, consistent with the lack of rest-frame UV flux and overall photometric spectral energy distribution. With a stellar mass of 3.1-0.2-+0.1× 10-11\,M at z = 3.493, this galaxy is nearly three times more massive than the highest redshift spectroscopically confirmed absorption-line-identified galaxy known. The star formation history of this quiescent galaxy implies that it formed >1000 M o yr-1 for almost 0.5 Gyr beginning at z ∼ 7.2, strongly suggestive that it is the descendant of massive dusty star-forming galaxies at 5 < z < 7 recently observed with ALMA. While galaxies with similarly extreme stellar masses are reproduced in some simulations at early times, such a lack of ongoing star formation is not seen there. This suggests the need for a quenching process that either starts earlier or is more rapid than that currently prescribed, challenging our current understanding of how ultra-massive galaxies form and evolve in the early universe. © 2020. The American Astronomical Society. All rights reserved.Ítem MAGAZ3NE: High Stellar Velocity Dispersions for Ultramassive Quiescent Galaxies at z ≳ 3* * The spectra presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.(Institute of Physics, 2022-10-01) Forrest, Ben; Wilson, Gillian; Muzzin, Adam; Marchesini, Danilo; Cooper, M.C.; Cemile Marsan, Z.; Annunziatella, Marianna; McConachie, Ian; Zaidi, Kumail; Gomez, Percy; Urbano Stawinski, Stephanie M.; Chang, Wenjun; Lucia, Gabriella de; Barbera, Francesco La; Lubin, Lori; Nantais, Julie; Peña, Theodore; Saracco, Paolo; Surace, Jason; Stefanon, MauroIn this work, we publish stellar velocity dispersions, sizes, and dynamical masses for eight ultramassive galaxies (UMGs; log ( M * / M ⊙ ) > 11), z ≳ 3) from the Massive Ancient Galaxies At z > 3 NEar-infrared (MAGAZ3NE) Survey, more than doubling the number of such galaxies with velocity dispersion measurements at this epoch. Using the deep Keck/MOSFIRE and Keck/NIRES spectroscopy of these objects in the H and K bandpasses, we obtain large velocity dispersions of ∼400 km s−1 for most of the objects, which are some of the highest stellar velocity dispersions measured and ∼40% larger than those measured for galaxies of similar mass at z ∼ 1.7. The sizes of these objects are also smaller by a factor of 1.5-3 compared to this same z ∼ 1.7 sample. We combine these large velocity dispersions and small sizes to obtain dynamical masses. The dynamical masses are similar to the stellar masses of these galaxies, consistent with a Chabrier initial mass function (IMF). Considered alongside previous studies of massive quiescent galaxies across 0.2 < z < 4.0, there is evidence for an evolution in the relation between the dynamical mass-stellar mass ratio and velocity dispersion as a function of redshift. This implies an IMF with fewer low-mass stars (e.g., Chabrier IMF) for massive quiescent galaxies at higher redshifts in conflict with the bottom-heavy IMF (e.g., Salpeter IMF) found in their likely z ∼ 0 descendants, though a number of alternative explanations such as a different dynamical structure or significant rotation are not ruled out. Similar to data at lower redshifts, we see evidence for an increase of IMF normalization with velocity dispersion, though the z ≳ 3 trend is steeper than that for z ∼ 0.2 early-type galaxies and offset to lower dynamical-to-stellar mass ratios. © 2022. The Author(s). Published by the American Astronomical Society.Ítem The Massive Ancient Galaxies at z > 3 NEar-infrared (MAGAZ3NE) Survey: Confirmation of Extremely Rapid Star Formation and Quenching Timescales for Massive Galaxies in the Early Universe(IOP Publishing Ltd, 2020-11-01) Forrest, Ben; Cemile Marsan Z.; Annunziatella, Marianna; Wilson, Gillian; Muzzin, Adam; Marchesini, Danilo; Cooper M.C.; Chan, Jeffrey C.C.; McConachie, Ian; Gomez, Percy; Kado-Fong, Erin; Barbera, Francesco La; Lange-Vagle, Daniel; Nantais, Julie; Nonino, Mario; Saracco, Paolo; Stefanon, Mauro; van der Burg, Remco F.J.We present near-infrared spectroscopic confirmations of a sample of 16 photometrically selected galaxies with stellar Keck/MOSFIRE masses log(as M*part M*of ) > the 11 Massive at redshift Ancient z > 3 Galaxies from the At XMM-VIDEO z > 3 NEar-infrared and COSMOS-UltraVISTA (MAGAZ3NE) survey. fields Eight using of the ultramassive galaxies (UMGs) have specific star formation rates (sSFR) < 0.03 Gyr−1, with negligible emission lines. Another seven UMGs show emission lines consistent with active galactic nuclei and/or star formation, while only one UMG has sSFR > 1 Gyr−1. Model star formation histories of these galaxies describe systems that formed the majority of their stars in vigorous bursts of several hundred megayear duration around 4 < z < 6 during which hundreds to thousands of solar masses were formed per year. These formation ages of <1 Gyr prior to observation are consistent with ages derived from measurements of Dn(4000) and EW0(Hδ). Rapid quenching followed these bursty star-forming periods, generally occurring less than 350 Myr before observation, resulting in post-starburst SEDs and spectra for half the sample. The rapid formation timescales are consistent with the extreme star formation rates observed in 4 < z < 7 dusty starbursts observed with ALMA, suggesting that such dusty galaxies are progenitors of these UMGs. While such formation histories have been suggested in previous studies, the large sample introduced here presents the most compelling evidence yet that vigorous star formation followed by rapid quenching is almost certainly the norm for high-mass galaxies in the early universe. The UMGs presented here were selected to be brighter than Ks = 21.7, raising the intriguing possibility that even (fainter) older quiescent UMGs could exist at this epoch.