Examinando por Autor "Fynbo, J.P.U."
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Ítem A blast from the infant universe: the very high- z GRB 210905A(EDP Sciences, 2022-09) Rossi, A.; Frederiks, D.D.; Kann, D.A.; De Pasquale, M.; Pian, E.; Lamb, G.; D'Avanzo, P.; Izzo, L.; Levan, A.J.; Malesani, D.B.; Melandri, A.; Nicuesa Guelbenzu, A.; Schulze, S.; Strausbaugh, R.; Tanvir, N.R.; Amati, L.; Campana, S.; Cucchiara, A.; Ghirlanda, G.; Della Valle, M.; Klose, S.; Salvaterra, R.; Starling, R.L.C.; Stratta, G.; Tsvetkova, A.E.; Vergani, S.D.; D'Aì, A.; Burgarella, D.; Covino, S.; D'Elia, V.; Postigo, A. De Ugarte; Fausey, H.; Fynbo, J.P.U.; Frontera, F.; Guidorzi, C.; Heintz, K.E.; Masetti, N.; Maiorano, E.; Mundell, C.G.; Oates, S.R.; Page, M.J.; Palazzi, E.; Palmerio, J.; Pugliese, G.; Rau, A.; Saccardi, A.; Sbarufatti, B.; Svinkin, D.S.; Tagliaferri, G.; Van Der Horst, A.J.; Watson, D.J.; Ulanov, M.V.; Wiersema, K.; Xu, D.; Zhang, J.We present a detailed follow-up of the very energetic GRB 210905A at a high redshift of z = 6.312 and its luminous X-ray and optical afterglow. Following the detection by Swift and Konus-Wind, we obtained a photometric and spectroscopic follow-up in the optical and near-infrared (NIR), covering both the prompt and afterglow emission from a few minutes up to 20 Ms after burst. With an isotropic gamma-ray energy release of Eiso = 1.27−0.19+0.20 × 1054 erg, GRB 210905A lies in the top ∼7% of gamma-ray bursts (GRBs) in the Konus-Wind catalogue in terms of energy released. Its afterglow is among the most luminous ever observed, and, in particular, it is one of the most luminous in the optical at t ≳ 0.5 d in the rest frame. The afterglow starts with a shallow evolution that can be explained by energy injection, and it is followed by a steeper decay, while the spectral energy distribution is in agreement with slow cooling in a constant-density environment within the standard fireball theory. A jet break at ∼46.2 ± 16.3 d (6.3 ± 2.2 d rest-frame) has been observed in the X-ray light curve; however, it is hidden in the H band due to a constant contribution from the host galaxy and potentially from a foreground intervening galaxy. In particular, the host galaxy is only the fourth GRB host at z > 6 known to date. By assuming a number density n = 1 cm−3 and an efficiency η = 0.2, we derived a half-opening angle of 8.4 ° ±1.0°, which is the highest ever measured for a z ≳ 6 burst, but within the range covered by closer events. The resulting collimation-corrected gamma-ray energy release of ≃1 × 1052 erg is also among the highest ever measured. The moderately large half-opening angle argues against recent claims of an inverse dependence of the half-opening angle on the redshift. The total jet energy is likely too large to be sustained by a standard magnetar, and it suggests that the central engine of this burst was a newly formed black hole. Despite the outstanding energetics and luminosity of both GRB 210905A and its afterglow, we demonstrate that they are consistent within 2σ with those of less distant bursts, indicating that the powering mechanisms and progenitors do not evolve significantly with redshift.Ítem GRB 171010A/SN 2017htp: A Grb-Sn at z = 0.33(Oxford University Press, 2019-12) Melandri, A.; Malesani, D.B.; Izzo, L.; Japelj, J.; Vergani, S.D.; Schady, P.; Sagués Carracedo, A.; de Ugarte Postigo, A.; Anderson, J.P.; Barbarino, C.; Bolmer, J.; Breeveld, A.; Calissendorff, P.; Campana, S.; Cano, Z.; Carini, R.; Covino, S.; D'Avanzo, P.; D'Elia, V.; della Valle, M.; de Pasquale, M.; Fynbo, J.P.U.; Gromadzki, M.; Hammer, F.; Hartmann, D.H.; Heintz, K.E.; Inserra, C.; Jakobsson, P.; Kann, D.A.; Kotilainen, J.; Maguire, K.; Masetti, N.; Nicholl, M.; Olivares, F.E.; Pugliese, G.; Rossi, A.; Salvaterra, R.; Sollerman, J.; Stone, M.B.; Tagliaferri, G.; Tomasella, L.; Thöne, C.C.; Xu, D.; Young, D.R.The number of supernovae known to be connected with long-duration gamma-ray bursts (GRBs) is increasing and the link between these events is no longer exclusively found at low redshift (z ≲ 0.3) but is well established also at larger distances. We present a new case of such a liaison at z = 0.33 between GRB 171010A and SN 2017htp. It is the second closest GRB with an associated supernova of only three events detected by Fermi-LAT. The supernova is one of the few higher redshift cases where spectroscopic observations were possible and shows spectral similarities with the well-studied SN 1998bw, having produced a similar Ni mass (MNi=0.33±0.02 M⊙ ) with slightly lower ejected mass (Mej=4.1±0.7 M⊙ ) and kinetic energy (EK=8.1±2.5×1051 erg ). The host-galaxy is bigger in size than typical GRB host galaxies, but the analysis of the region hosting the GRB revealed spectral properties typically observed in GRB hosts and showed that the progenitor of this event was located in a very bright H II region of its face-on host galaxy, at a projected distance of ∼ 10 kpc from its galactic centre. The star-formation rate (SFRGRB ∼ 0.2 M⊙ yr−1) and metallicity (12 + log(O/H) ∼8.15 ± 0.10) of the GRB star-forming region are consistent with those of the host galaxies of previously studied GRB–SN systems.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 Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger(Nature Publishing Group, 2017-11) Pian, E.; D'Avanzo, P.; Benetti, S.; Branchesi, M.; Brocato, Campana S.; Cappellaro, E.; Covino, S.; D'Elia, V.; Fynbo, J.P.U.; Getman, F.; Ghirlanda, G.; Ghisellini, G.; Grado, A.; Greco, G.; Hjorth, J.; Kouveliotou, C.; Levan, A.; Limatola, L.; Malesani, D.; Mazzali, P.A.; Melandri, A.; Møller, P.; Nicastro, L.; Palazzi, E.; Piranomonte, S.; Rossi, A.; Salafia, O.S.; Selsing, J.; Stratta, G.; Tanaka, M.; Tanvir, N.R.; Tomasella, L.; Watson, D.; Yang, S.; Amati, L.; Antonelli, L.A.; Ascenzi, S.; Bernardini, M.G.; Boër, M.; Bufano, F.; Bulgarelli, A.; Capaccioli, M.; Casella, P.; Castro-Tirado, A.J.; Chassande-Mottin, E.; Ciolfi, R.; Copperwheat, C.M.; Dadina, M.; De Cesare, G.; Di Paola, A.; Fan, Y.Z.; Gendre, B.; Giuffrida, G.; Giunta, A.; Hunt, L.K.; Israel, G.L.; Jin, Z.-P.; Kasliwal, M.M.; Klose, S.; Lisi, M.; Longo, F.; Maiorano, E.; Mapelli, M.; Masetti, N.; Nava, L.; Patricelli, B.; Perley, D.; Pescalli, A.; Piran, T.; Possenti, A.; Pulone, L.; Razzano, M.; Salvaterra, R.; Schipani, P.; Spera, M.; Stamerra, A.; Stella, L.; Tagliaferri, G.; Testa, V.; Troja, E.; Turatto, M.; Vergani, S.D.; Vergani, D.The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical-near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process)1-3. Such transients, named 'macronovae' or 'kilonovae'4-7, are believed to be centres of production of rare elements such as gold and platinum8. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst9,10 at redshift z = 0.356, although findings indicating bluer events have been reported11. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source12 GW170817 and γ-ray burst13,14 GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models15,16. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides. © 2017 Macmillan Publishers Limited, part of Springer Nature.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 optical/NIR afterglow of GRB 111209A: Complex yet not unprecedented(EDP Sciences, 2018-09) Kann, D.A.; Schady, P.; Olivares, E.F.; Klose, S.; Rossi, A.; Perley, D.A.; Zhang, B.; Krühler, T.; Greiner, J.; Nicuesa Guelbenzu, A.; Elliott, J.; Knust, F.; Cano, Z.; Filgas, R.; Pian, E.; Mazzali, P.; Fynbo, J.P.U.; Leloudas, G.; Afonso, P.M.J.; Delvaux, C.; Graham, J.F.; Rau, A.; Schmidl, S.; Schulze, S.; Tanga, M.; Updike, A.C.; Varela, K.Context. Afterglows of gamma-ray bursts (GRBs) are simple in the most basic model, but can show many complex features. The ultra-long duration GRB 111209A, one of the longest GRBs ever detected, also has the best-monitored afterglow in this rare class of GRBs. Aims. We want to address the question whether GRB 111209A was a special event beyond its extreme duration alone, and whether it is a classical GRB or another kind of high-energy transient. The afterglow may yield significant clues. Methods. We present afterglow photometry obtained in seven bands with the GROND imager as well as in further seven bands with the Ultraviolet/Optical Telescope (UVOT) on-board the Neil Gehrels Swift Observatory. The light curve is analysed by multi-band modelling and joint fitting with power-laws and broken power-laws, and we use the contemporaneous GROND data to study the evolution of the spectral energy distribution. We compare the optical afterglow to a large ensemble we have analysed in earlier works, and especially to that of another ultra-long event, GRB 130925A. We furthermore undertake a photometric study of the host galaxy. Results. We find a strong, chromatic rebrightening event at 0.8 days after the GRB, during which the spectral slope becomes redder. After this, the light curve decays achromatically, with evidence for a break at about 9 days after the trigger. The afterglow luminosity is found to not be exceptional. We find that a double-jet model is able to explain the chromatic rebrightening. The afterglow features have been detected in other events and are not unique. Conclusions. The duration aside, the GRB prompt emission and afterglow parameters of GRB 111209A are in agreement with the known distributions for these parameters. While the central engine of this event may differ from that of classical GRBs, there are multiple lines of evidence pointing to GRB 111209A resulting from the core-collapse of a massive star with a stripped envelope. © 2018 ESO.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.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.