Examinando por Autor "Cresci, G."
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Ítem Properties of the interstellar medium in star-forming galaxies at redshifts 2lz >5 from the VANDELS survey(EDP Sciences, 2022-11-01) Calabrò, A.; Pentericci, L.; Talia, M.; Cresci, G.; Castellano, M.; Belfiori, D.; Mascia, S.; Zamorani, G.; Amorín, R.; Fynbo, J.P.U.; Ginolfi, M.; Guaita, L.; Hathi, N.P.; Koekemoer, A.; Llerena, M.; Mannucci, F.; Santini, P.; Saxena, A.; Schaerer, D.Gaseous flows inside and outside galaxies are key to understanding galaxy evolution, as they regulate their star formation activity and chemical enrichment across cosmic time. We study the interstellar medium (ISM) kinematics of a sample of 330 galaxies with Ca ¯III] or Hea ¯II emission using far-ultraviolet (far-UV) ISM absorption lines detected in the ultra deep spectra of the VANDELS survey. These galaxies span a broad range of stellar masses from 108 to 1011 M, and star formation rates (SFRs) from 1 to 500 M yrin the redshift range between 2 and 5. We find that the bulk ISM velocity along the line of sight (vIS) is globally in outflow, with a vIS of a60a ±a10 km sfor low-ionisation gas traced by Sia ¯IIλ1260 A, Ca ¯IIλ1334 A , Sia ¯IIλ1526 A , and Ala ¯IIλ1670 A absorption lines, and a vIS of a160a±a30 and a170a±a30 km sfor higher ionisation gas traced respectively by Ala ¯IIIλλ1854-1862 A and Sia ¯IVλλ1393-1402 A . Interestingly, we notice that BPASS models are able to better reproduce the stellar continuum around the Sia ¯IV doublet than other stellar population templates. For individual galaxies, 34% of the sample has a positive ISM velocity shift, almost double the fraction reported at lower redshifts. We additionally derive a maximum outflow velocity vmax for the average population, which is of the order of a14;aaa500 and a 14;aaa600 km sfor the lower and higher ionisation lines, respectively. Comparing vIS to the host galaxies properties, we find no significant correlations with stellar mass Mor SFR, and only a marginally significant dependence (at a 14;2Ï) on morphology-related parameters, with slightly higher velocities found in galaxies of smaller size (probed by the equivalent radius rT50), higher concentration (CT), and higher SFR surface density ΣSFR. From the spectral stacks, vmax shows a similarly weak dependence on physical properties (at 2Ï). Moreover, we do not find evidence of enhanced outflow velocities in visually identified mergers compared to isolated galaxies. From a physical point of view, the outflow properties are consistent with accelerating momentum-driven winds, with densities decreasing towards the outskirts. Our moderately lower ISM velocities compared to those found in similar studies at lower redshifts suggest that inflows and internal turbulence might play an increased role at za > 2 and weaken the outflow signatures. Finally, we estimate mass-outflow rates á out that are comparable to the SFRs of the galaxies (hence a mass-loading factor η of the order of unity), and an average escape velocity of 625 km sa1, suggesting that most of the ISM will remain bound to the galaxy halo. © 2022 EDP Sciences. All rights reserved.Ítem The environmental dependence of the stellar and gas-phase mass-metallicity relation at 2 < z < 4(EDP Sciences, 2022-08-01) Calabrò, A.; Guaita, L.; Pentericci, L.; Fontanot, F.; Castellano, M.; De Lucia, G.; Garofalo, T.; Santini, P.; Cullen, F.; Carnall, A.; Garilli, B.; Talia, M.; Cresci, G.; Franco, M.; Fynbo, J.P.U.; Hathi, N.P.; Hirschmann, M.; Koekemoer, A.; Llerena, M.; Xie, L.In the local universe, galaxies in clusters typically show different physical and chemical properties compared to more isolated systems. Understanding how this difference originates, and whether it is already in place at high redshift, is still a matter of debate. Thanks to uniquely deep optical spectra available from the VANDELS survey, we investigate environmental effects on the stellar mass- metallicity relation (MZR) for a sample of nearly 1000 star-forming galaxies in the redshift range 2 < z < 4. We complement our dataset with the MOSFIRE follow-up of 21 galaxies to study the environmental dependence of the gas-phase MZR. Robust stellar and gas-phase metallicities are derived from well-calibrated photospheric absorptions features, respectively at 1501 and 1719Å in the stacked spectra, and from optical emission lines ([OII]λ λ3726-3729, [OIII] λ5007, and Hβ) in individual systems.We characterize the environment through multiple criteria by using the local galaxy density maps derived in the VANDELS fields to identify overdense structures and protoclusters of varying sizes. We find that environmental effects are weak at redshifts 2 < z < 4, and they are more important around the densest overdensity structures and protoclusters, where galaxies have a lower stellar metallicity (by ∼0:2 dex) and a lower gas-phase metallicity (by 0.1 dex) compared to the field, with a significance of 1σ and 2σ, respectively. Crucially, this downward offset cannot be explained by a selection effect due to a higher star formation rate, a fainter UV continuum, or different dust attenuations and stellar ages for galaxies in overdense enviroments with respect to the field. In spite of the still low signal-to-noise ratio of our results, we consider possible explanations of this environmental dependence. We propose a combination of increased mergers and high-speed encounters, more efficient AGN feedback in dense cores, and cold gas inflows from the cosmic web as viable physical mechanisms diluting the metal content of the cold gas reservoirs of overdense galaxies or expelling their metals to the intergalactic medium, even though additional studies are needed to determine the most significant scenario. Finally, some tensions remain between observations and both semi-analytic models and hydrodynamical simulations, which predict no significant metallicity offset as a function of host halo mass, suggesting that an explicit implementation of environmental processes in dense protocluster cores is needed. © ESO 2022.Ítem The NIRVANDELS Survey: a robust detection of α-enhancement in star-forming galaxies at z 3.4(Oxford University Press, 2021-05) Cullen, F.; Shapley, A.; McLure, R.; Dunlop, J.S; Sanders, R.L; Topping, M.W; Reddy, N.A; Amorin, R.; Begley, R.; Bolzonella, M.; Calabro, A.; Carnall, A.C; Castellano, M.; Cimatti, A.; Cirasuolo, M.; Cresci, G.; Fontana, A.; Fontanot, F.; Garilli, B.; Guaita, L.; Hamadouche, M.; Hathi, N.P; Mannucci, F.; McLeod, D. J; Pentericci, L.; Saxena, A.; Talia, M.; Zamorani, G.We present results from the NIRVANDELS survey on the gas-phase metallicity (Zg, tracing O/H) and stellar metallicity (Z∗, tracing Fe/H) of 33 star-forming galaxies at redshifts 2.95 < z < 3.80. Based on a combined analysis of deep optical and near-IR spectra, tracing the rest-frame far-ultraviolet (FUV; 1200-2000 Å) and rest-frame optical (3400-5500 Å), respectively, we present the first simultaneous determination of the stellar and gas-phase mass-metallicity relationships (MZRs) at z ≃ 3.4. In both cases, we find that metallicity increases with increasing stellar mass (M∗) and that the power-law slope at M∗ ≤ 1010M⊙ of both MZRs scales as Z ∝ M∗0.3. Comparing the stellar and gas-phase MZRs, we present direct evidence for super-solar O/Fe ratios (i.e. α-enhancement) at z > 3, finding (O/Fe) = 2.54 ± 0.38 × (O/Fe)⊙, with no clear dependence on M∗. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.