Examinando por Autor "Stefanon, M."

Mostrando 1 - 2 de 2

Acceso Abierto
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
(The Institute of Physics (IOP), 2020-10-30) Forrest, B.; Cemile Marsan, Z.; Annunziatella, M.; Wilson, G.; Muzzin, A.; Marchesini, D.; Cooper, M. C.; Chan, J. C. C.; McConachie, I.; Gómez, P.; Kado Fong, E.; La Barbera, F.; Lange Vagle, Daniel J.; Nantais, J.; Nonino, M.; Saracco, P.; Stefanon, M.; Van der Burg, F. J.; National Aeronautics and Space Administration (NASA); Istituto Nazionale di Astrofisica (INAF); National Science Foundation (NSF); Faculty Research Fund (FRF); Forrest, B. [0000-0001-6003-0541]; Cemile Marsan, Z. [0000-0002-7248-1566]; Wilson, G. [0000-0002-6572-7089]; Muzzin, A. [0000-0002-9330-9108]; Marchesini, D. [0000-0001-9002-3502]; Cooper, M. C. [0000-0003-1371-6019]; Chan, J. C. C. [0000-0001-6251-3125]; Gómez, P. [0000-0003-0408-9850]; Kado Fong, E. [0000-0002-0332-177X]; La Barbera, F. [0000-0003-1181-6841]; Nantais, J. [0000-0002-7356-0629]; Nonino, M. [0000-0001-6342-9662]; Saracco, P. [0000-0003-3959-2595]; Stefanon, M. [0000-0001-7768-5309]; Van der Burg, R. F. J. [0000-0003-1535-2327]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present near-infrared spectroscopic confirmations of a sample of 16 photometrically selected galaxies with stellar masses log(M-*/M-circle dot) > 11 at redshift z > 3 from the XMM-VIDEO and COSMOS-UltraVISTA fields using Keck/MOSFIRE as part of the Massive Ancient Galaxies At z > 3 NEar-infrared (MAGAZ3NE) survey. Eight 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 D-n(4000) and EW0(H delta). 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 K-s=21.7, raising the intriguing possibility that even (fainter) older quiescent UMGs could exist at this epoch.
Acceso Abierto
The Rapid Buildup of Massive Early-type Galaxies: Supersolar Metallicity, High Velocity Dispersion, and Young Age for an Early-type Galaxy at z = 3.35
(The Institute of Physics (IOP), 2020-12-10) Saracco, P.; Marchesini, D.; La Barbera, F.; Gargiulo, A.; Annunziatella, M.; Forrest, B.; Lange Vagle, D. J.; Cemile Marsan, Z.; Muzzin, A.; Stefanon, M.; Wilson, G.; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Fondation Raoul Follereau (FRF); Agencia Estatal de Investigación (AEI); Saracco, P. [0000-0003-3959-2595]; Marchesini, D. [0000-0001-9002-3502]; Forrest, B. [0000-0001-6003-0541]; Cemile Marsan, Z. [0000-0002-7248-1566]; Muzzin, A. [0000-0002-9330-9108]; Stefanon, M. [0000-0001-7768-5309]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
How massive early-type galaxies (ETGs) assembled their mass, on which timescales the star formation quenched, and when their supersolar metallicity has been established are still open and debated issues. Thanks to very deep spectroscopic observations carried out at the Large Binocular Telescope, we simultaneously measured stellar age, metallicity, and velocity dispersion for C1-23152, an ETG at redshift z = 3.352, corresponding to an epoch when the universe was ~1.8 Gyr old. The analysis of its spectrum shows that this galaxy, hosting an active galactic nucleus (AGN), formed and assembled ~2 × 1011 M⊙, shaping its morphology within the ~600 Myr preceding the observations, since z ~ 4.6. The stellar population has a mean mass-weighted age of ${400}_{-70}^{+30}$ Myr, and it is formed between ~600 and ~150 Myr before the observed epoch, the latter being the time since quenching. Its high stellar velocity dispersion, σe = 409 ± 60 km s−1, confirms the high mass (Mdyn = 2.2 (±0.4) × 1011 M⊙) and the high mass density (${{\rm{\Sigma }}}_{e}^{{M}^{* }}$ = Σ1kpc = 3.2 (±0.7) × 1010 M⊙ kpc−2), suggesting a fast dissipative process at its origin. The analysis points toward a supersolar metallicity, [Z/H] = 0.25${}_{-0.10}^{+0.006}$, in agreement with the above picture, suggesting a star formation efficiency much higher than the replenishment time. However, subsolar-metallicity values cannot be firmly ruled out by our analysis. Quenching must have been extremely efficient to reduce the star formation to SFR < 6.5 M⊙ yr−1 in less than 150 Myr. This could be explained by the presence of the AGN, even if a causal relation cannot be established from the data. C1-23152 has the same stellar and physical properties of the densest ETGs in the local universe of comparable mass, suggesting that they are C1-23152-like galaxies that evolved to z = 0 unperturbed.