Examinando por Autor "Garilli, B."
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Ítem Insights into the reionization epoch from cosmic-noon-Civ emitters in the VANDELS survey(EDP Sciences, 2023-05) Mascia, S.; Pentericci, L.; Saxena, A.; Belfiori, D.; Calabrò, A.; Castellano, M.; Saldana-Lopez, A.; Talia, M.; Amorín, R.; Cullen, F.; Garilli, B.; Guaita, L.; Llerena, M.; McLure, R.J.; Moresco, M.; Santini, P.; Schaerer, D.Recently, intense emission from nebular CaIII] and CIV emission lines have been observed in galaxies in the epoch of reionization (z > 6) and have been proposed as the prime way of measuring their redshift and studying their stellar populations. These galaxies might represent the best examples of cosmic reionizers, as suggested by recent low-z observations of Lyman continuum emitting galaxies, but it is hard to directly study the production and escape of ionizing photons at such high redshifts. The ESO spectroscopic public survey VANDELS offers the unique opportunity to find rare examples of such galaxies at cosmic noon (z∼ 3), thanks to the ultra deep observations available. We have selected a sample of 39 galaxies showing CIV emission, whose origin (after a careful comparison to photoionization models) can be ascribed to star formation and not to active galactic nuclei. By using a multiwavelength approach, we determined their physical properties including metallicity and the ionization parameter and compared them to the properties of the parent population to understand what the ingredients are that could characterize the analogs of the cosmic reionizers. We find that CIV emitters are galaxies with high photon production efficiency and there are strong indications that they might also have a large escape fraction: given the visibility of CIV in the epoch of reionization, this could become the best tool to pinpoint the cosmic reioinzers. © The Authors 2023.Ítem Metal content of the circumgalactic medium around star-forming galaxies at z ~ 2.6 as revealed by the VIMOS Ultra-Deep Survey(EDP Sciences, 2022-10-01) Méndez Hernández, H.; Cassata, P.; Ibar, E.; Amorín, R.; Aravena, M.; Bardelli, S.; Cucciati, O.; Garilli, B.; Giavalisco, M.; Guaita, L.; Hathi, N.; Koekemoer, A.; Le Brun, V.; Lemaux, B.C.; MacCagni, D.; Ribeiro, B.; Tasca, L.; Tejos, N.; Thomas, R.; Tresse, L.; Vergani, D.; Zamorani, G.; Zucca, E.Context. The circumgalactic medium (CGM) is the location where the interplay between large-scale outflows and accretion onto galaxies occurs. Metals in different ionization states flowing between the circumgalactic and intergalactic mediums are affected by large galactic outflows and low-ionization state inflowing gas. Observational studies on their spatial distribution and their relation with galaxy properties may provide important constraints on models of galaxy formation and evolution. Aims. The main goal of this paper is to provide new insights into the spatial distribution of the circumgalactic of star-forming galaxies at 1.5 < z < 4.5 (z ~2.6) in the peak epoch of cosmic star formation activity in the Universe. We also look for possible correlations between the strength of the low- and high-ionization absorption features (LIS and HIS) and stellar mass, star formation rate, effective radius, and azimuthal angle φ that defines the location of the absorbing gas relative to the galaxy disc plane. Methods. The CGM has been primarily detected via the absorption features that it produces on the continuum spectrum of bright background sources. We selected a sample of 238 close pairs from the VIMOS Ultra Deep Survey to examine the spatial distribution of the gas located around star-forming galaxies and generate composite spectra by co-adding spectra of background galaxies that provide different sight-lines across the CGM of star-forming galaxies. Results. We detect LIS (CII and SiII) and HIS (SiIV, CIV) up to separations b = 172 kpc and 146 kpc. Beyond this separation, we do not detect any significant signal of CGM absorption in the background composite spectra. Our Lyα, LIS, and HIS rest-frame equivalent width (W0) radial profiles are at the upper envelope of the W0 measurements at lower redshifts, suggesting a potential redshift evolution for the CGM gas content producing these absorptions. We find a correlation between CII and CIV with star formation rate and stellar mass, as well as trends with galaxy size estimated by the effective radius and azimuthal angle. Galaxies with high star formation rate (log[SFR/(M⊙ yr-1)] > 1.5) and stellar mass (log[M∗/M⊙] > 10.2) show stronger CIV absorptions compared with those low SFR (log[SFR/(M⊙ yr-1)] < 0.9) and low stellar mass (log[M∗/M⊙] < 9.26). The latter population instead shows stronger CII absorption than their more massive or more star-forming counterparts. We compute the CII/CIVW0 line ratio that confirms the CII and CIV correlations with impact parameter, stellar mass, and star formation rate. We do not find any correlation with φ in agreement with other high-redshift studies and in contradiction to what is observed at low redshift where large-scale outflows along the minor axis forming bipolar outflows are detected. Conclusions. We find that the stronger CIV line absorptions in the outer regions of these star-forming galaxies could be explained by stronger outflows in galaxies with higher star formation rates and stellar masses that are capable of projecting the ionized gas up to large distances and/or by stronger UV ionizing radiation in these galaxies that is able to ionize the gas even at large distances. On the other hand, low-mass galaxies show stronger CII absorptions, suggesting larger reservoirs of cold gas that could be explained by a softer radiation field unable to ionize high-ionization state lines or by the galactic fountain scenario where metal-rich gas ejected from previous star formation episodes falls back to the galaxy. These large reservoirs of cold neutral gas around low-mass galaxies could be funnelled into the galaxies and eventually provide the necessary fuel to sustain star formation activity. © 2022 Authors.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.Ítem The VANDELS ESO public spectroscopic survey: The spectroscopic measurements catalogue(EDP Sciences, 2023-10-01) Talia, M.; Schreiber, C.; Garilli, B.; Pentericci, L.; Pozzetti, L.; Zamorani, G.; Cullen, F.; Moresco, M.; Calabrò, A.; Castellano, M.; Fynbo, J.P.U.; Guaita, L.VANDELS is a deep spectroscopic survey, performed with the VIMOS instrument at VLT, aimed at studying in detail the physical properties of high-redshift galaxies. VANDELS targeted 2100 sources at 1 < z < 6.5 in the CANDELS Chandra Deep-Field South (CDFS) and Ultra-Deep Survey (UDS) fields. In this paper, we present the public release of the spectroscopic measurement catalogues from this survey, featuring emission and absorption line centroids, fluxes, and rest-frame equivalent widths obtained through a Gaussian fit, as well as a number of atomic and molecular indices (e.g. Lick) and continuum breaks (e.g. D4000), and including a correction to be applied to the error spectra. We describe the measurement methods and the validation of the codes that were used. © 2023 Authors. All rights reserved.