Examinando por Autor "Amorín, R."
Mostrando 1 - 4 de 4
Resultados por página
Opciones de ordenación
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 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 VANDELS survey: the ionizing properties of star-forming galaxies at 3 ≤ z ≤ 5 using deep rest-frame ultraviolet spectroscopy(Oxford University Press, 2023-07-01) Saldana-Lopez, A.; Schaerer, D.; Chisholm, J.; Calabrò, A.; Pentericci, L.; Cullen, F.; Saxena, A.; Amorín, R.; Carnall, A.C.; Fontanot, F.; Fynbo, J.P.U.; Guaita, L.; Hathi, N.P.; Hibon, P.; Ji, Z.; McLeod, D.J.; Pompei, E.; Zamorani, G.The physical properties of Epoch of Reionization (EoR) galaxies are still poorly constrained by observations. To better understand the ionizing properties of galaxies in the EoR, we investigate deep, rest-frame ultraviolet (UV) spectra of ≃500 star-forming galaxies at 3 ≤ z ≤ 5 selected from the public ESO-VANDELS spectroscopic survey. The absolute ionizing photon escape fraction (fescabs, i.e. the ratio of leaking against produced ionizing photons) is derived by combining absorption line measurements with estimates of the UV attenuation. The ionizing production efficiency (ξion, i.e. the number of ionizing photons produced per non-ionizing UV luminosity) is calculated by fitting the far-UV (FUV) stellar continuum of the VANDELS galaxies. We find that the fescabs and ξion parameters increase towards low-mass, blue UV-continuum slopes and strong Ly α emitting galaxies, and both are slightly higher-than-average for the UV-faintest galaxies in the sample. Potential Lyman Continuum Emitters (LCEs, fescabs ≥ 5 per cent) and selected Lyman Alpha Emitters (LAEs, WLyα ≤ −20 Å) show systematically higher ξion (log ξion(Hz erg−1) ≈ 25.38, 25.41) than non-LCEs and non-LAEs (log ξion(Hz erg−1) ≈ 25.18, 25.14) at similar UV magnitudes. This indicates very young underlying stellar populations (≈10 Myr) at relatively low metallicities (≈0.2 Z⊙). The FUV non-ionizing spectra of potential LCEs is characterized by blue UV slopes (≤−2), enhanced Ly α emission (≤−25 Å), strong UV nebular lines (e.g. high C IV1550/C III1908 ≥0.75 ratios), and weak absorption lines (≤1 Å). The latter suggests the existence of low gas-column-density channels in the interstellar medium, which enables the escape of ionizing photons. By comparing our VANDELS results against other surveys in the literature, our findings imply that the ionizing budget in the EoR was likely dominated by UV-faint, low-mass, and dustless galaxies. © The Author(s) 2023. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.