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  • 1
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    Geochemical evidence for and characterization of CO2 rich gas sources in the epicentral area of the Abruzzo 2009 earthquakes (2011)
    Elsevier
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    Publication Date: 2017-04-04
    Description: We describe the results of a detailed hydrogeochemical campaign on the groundwater circulating in two regional aquifers located in the area of the Abruzzo 2009 earthquakes. The influx of deeply derived CO2 rich gases into the two aquifers is highlighted by the 13C isotopic composition of dissolved carbon species. The source of the gas is roughly localised beneath the epicentral area of the earthquakes where the presence of sources of fluids under high pressure is suggested by seismological investigations. The carbon isotopic-mass balance of the aquifers indicates that the amount of the deep CO2 dissolved and transported by the groundwaters is ~530 t/day. The chemical and isotopic composition of the gas entering the aquifers, named Abruzzo gas, has been derived by comparing the data measured in the springs with the results of a gas–water– rock reaction model, that simulates the evolution of the chemical and isotopic composition of groundwater affected by the input of a deeply-derived CO2 rich gas phase. The composition of Abruzzo gas is compared to that of 40 large gas emissions located in central Italy. The gas becomes progressively richer in radiogenic elements (4He and 40Ar) and in N2, from the volcanic complexes in the west to the Apennines in the east. The Abruzzo gas, in agreement with its location, well matches the composition of the gases emitted in the pre- Apennine region. These geochemical features, consistent with the structural setting of the region, indicate increasing residence times of the gas in the crust moving from west to east. In particular we suggest that the strong increase in radiogenic crustal gases reflects the occurrence of deep traps where the gas is stored at high pressures for a long time and that such high pressure gas pockets play a major role in the generation of Apennine earthquakes.
    Description: Published
    Description: 389–398
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: 4.5. Studi sul degassamento naturale e sui gas petroliferi
    Description: JCR Journal
    Description: reserved
    Keywords: carbon dioxide ; Abruzzo earthquakes ; carbon isotopes ; helium isotopes ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Colour gradients of high-redshift early-type galaxies from hydrodynamical monolithic models (2013)
    Oxford University Press
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    Publication Date: 2013-09-17
    Description: We analyse the evolution of colour gradients predicted by the hydrodynamical models of early-type galaxies (ETGs) in Pipino et al., which reproduce fairly well the chemical abundance pattern and the metallicity gradients of local ETGs. We convert the star formation (SF) and metal content into colours by means of stellar population synthetic model and investigate the role of different physical ingredients, as the initial gas distribution and content, and SF , i.e. the normalization of SF rate. From the comparison with high-redshift data, a full agreement with optical rest-frame observations at z   1 is found, for models with low SF , whereas some discrepancies emerge at 1 〈  z  〈 2, despite our models reproduce quite well the data scatter at these redshifts. To reconcile the prediction of these high SF systems with the shallower colour gradients observed at lower z we suggest intervention of one to two dry mergers. We suggest that future studies should explore the impact of wet galaxy merging, interactions with environment, dust content and a variation of the initial mass function from the galactic centres to the peripheries.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 3
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    The two regimes of the cosmic sSFR evolution are due to spheroids and discs (2013)
    Oxford University Press
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    Publication Date: 2013-06-09
    Description: This paper aims at explaining the two phases in the observed specific star formation rate (sSFR), namely the high (〉3/Gyr) values at z  〉 2 and the smooth decrease since z  = 2. In order to do this, we compare to observations the sSFR evolution predicted by well-calibrated models of chemical evolution for elliptical and spiral galaxies, using the additional constraints on the mean stellar ages of these galaxies (at a given mass). We can conclude that the two phases of the sSFR evolution across cosmic time are due to different populations of galaxies. At z  〉 2, the contribution comes from spheroids: the progenitors of present-day massive ellipticals (which feature the highest sSFR) as well as haloes and bulges in spirals (which contribute with average and lower-than-average sSFR). In each single galaxy, the sSFR decreases rapidly and the star formation stops in 〈1 Gyr. However, the combination of different generations of ellipticals in formation might result in an apparent lack of strong evolution of the sSFR (averaged over a population) at high redshift. The z  〈 2 decrease is due to the slow evolution of the gas fraction in discs, modulated by the gas accretion history and regulated by the Schmidt law. The Milky Way makes no exception to this behaviour.
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    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    Erratum: Europium production: neutron star mergers versus core-collapse supernovae (2014)
    Oxford University Press
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    Publication Date: 2014-12-17
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 5
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    Galactic and cosmic Type Ia supernova (SNIa) rates: is it possible to impose constraints on SNIa progenitors? (2013)
    Oxford University Press
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    Publication Date: 2013-10-08
    Description: We compute the Type Ia supernova (SNIa) rates in typical elliptical galaxies by varying the progenitor models for SNeIa. To do that a formalism which takes into account the delay distribution function of the explosion times and a given star formation history is adopted. Then the chemical evolution for ellipticals with baryonic initial masses 10 10 , 10 11 and 10 12 M is computed, and the mass of Fe produced by each galaxy is precisely estimated. We also compute the expected Fe mass ejected by ellipticals in typical galaxy clusters (e.g. Coma and Virgo), under different assumptions about SNIa progenitors. As a last step, we compute the cosmic SNIa rate in a unitary volume of the Universe by adopting several cosmic star formation rates and compare it with the available and recent observational data. Unfortunately, no firm conclusions can be derived only from the cosmic SNIa rate, neither on SNIa progenitors nor on the cosmic star formation rate. Finally, by analysing all our results together, and by taking into account previous chemical evolution results, we try to constrain the best Type Ia progenitor model. We conclude that the best progenitor models for SNeIa are still the single degenerate model, the double degenerate wide model and the empirical bimodal model. All these models require the existence of prompt SNeIa, exploding in the first 100 Myr since the beginning of star formation, although their fraction should not exceed 15–20 per cent in order to fit chemical abundances in galaxies.
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    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    Abundance gradients in spiral discs: is the gradient inversion at high redshift real? (2013)
    Oxford University Press
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    Publication Date: 2013-10-12
    Description: We compute the abundance gradients along the disc of the Milky Way by means of the two-infall model: in particular, the gradients of oxygen and iron and their temporal evolution. First, we explore the effects of several physical processes which influence the formation and evolution of abundance gradients. They are (i) the inside-out formation of the disc, (ii) a threshold in the gas density for star formation, (iii) a variable star formation efficiency along the disc, (iv) radial flows and their speed and (v) different total surface mass density (gas plus stars) distributions for the halo. We are able to reproduce at best the present day gradients of oxygen and iron if we assume an inside-out formation, no threshold gas density, a constant efficiency of star formation along the disc and radial gas flows. It is particularly important the choice of the velocity pattern for radial flows and the combination of this velocity pattern with the surface mass density distribution in the halo. Having selected the best model, we then explore the evolution of abundance gradients in time and find that the gradients in general steepen in time and that at redshift z  ~ 3 there is a gradient inversion in the inner regions of the disc, in the sense that at early epochs the oxygen abundance decreases towards the Galactic Centre. This effect, which has been observed, is naturally produced by our models if an inside-out formation of the disc and a constant star formation efficiency are assumed. The inversion is due to the fact that in the inside-out formation a strong infall of primordial gas, contrasting chemical enrichment, is present in the innermost disc regions at early times. The gradient inversion remains also in the presence of radial flows, either with constant or variable speed in time, and this is a new result.
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    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Chemical evolution models: GRB host identification and cosmic dust predictions (2014)
    Oxford University Press
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    Publication Date: 2014-08-29
    Description: The nature of some GRB host galaxies has been investigated by means of chemical evolution models of galaxies of different morphological types following the evolution of the abundances of H, He, C, N, O, α-elements, Ni, Fe, Zn, and including also the evolution of dust. By comparing predictions with abundance data, we were able to constrain nature and age of GRB hosts. We also computed a theoretical cosmic dust rate, including stellar dust production, accretion and destruction, under the hypotheses of pure luminosity evolution and strong number density evolution of galaxies. We suggest that one of the three GRB hosts is a massive protospheroid caught during its formation, while for the other two the situation is more uncertain, although one could perhaps be a spheroid and the other a spiral galaxy. We estimated the chemical ages of the host galaxies which vary from 15 to 320 Myr. Concerning the cosmic effective dust production rate in a unitary volume of the Universe, our results show that in the case of pure luminosity evolution there is a first peak between redshift z = 8 and 9 and another at z ~ 5, whereas in the case of strong number density evolution, it increases slightly from z = 10 to z ~ 2 and then it decreases down to z = 0. Finally, we found that the total cosmic dust mass density at the present time is dust ~ 3.5 10 –5 in the case of pure luminosity evolution, and dust ~ 7 10 –5 in the case of number density evolution.
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    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Chemical evolution of the bulge of M31: predictions about abundance ratios (2014)
    Oxford University Press
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    Publication Date: 2014-12-21
    Description: We aim to reproduce the chemical evolution of the bulge of M31 using a detailed chemical evolution model, including radial gas flows coming from the disc. We study the impact of the initial mass function, the star formation rate and the time-scale for bulge formation on the metallicity distribution function of stars. We compute several models of chemical evolution using the metallicity distribution of dwarf stars as an observational constraint for the bulge of M31. Then, using the model that best reproduces the metallicity distribution function, we predict the [X/Fe]versus [Fe/H] relations for several chemical elements (O, Mg, Si, Ca, C, N). Our best model for the bulge of M31 is obtained by using a robust statistical method and assumes a Salpeter initial mass function, a Schmidt–Kennicutt law for star formation with an exponent k  = 1.5, an efficiency of star formation of ~15 ± 0.27 Gyr –1 and an infall time-scale of ~0.10 ± 0.03 Gyr. Our results suggest that the bulge of M31 formed very quickly as a result of an intense star formation rate and an initial mass function flatter than in the solar vicinity but similar to that inferred for the Milky Way bulge. The [α/Fe] ratios in the stars of the bulge of M31 should be high for most of the [Fe/H] range, as observed in the Milky Way bulge. These predictions await future data to be proven.
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    Topics: Physics
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  • 9
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    The dust content of QSO hosts at high redshift (2014)
    Oxford University Press
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    Publication Date: 2014-02-20
    Description: Infrared observations of high- z quasar (QSO) hosts indicate the presence of large masses of dust in the early Universe. When combined with other observables, such as neutral gas masses and star formation rates, the dust content of z  ~ 6 QSO hosts may help constraining their star formation history. We have collected a data base of 58 sources from the literature discovered by various surveys and observed in the far-infrared. We have interpreted the available data by means of chemical evolution models for forming protospheroids, investigating the role of the major parameters regulating star formation and dust production. For a few systems, given the derived small dynamical masses, the observed dust content can be explained only by assuming a top-heavy initial mass function, an enhanced star formation efficiency and an increased rate of dust accretion. However, the possibility that, for some systems, the dynamical mass has been underestimated cannot be excluded. If this were the case, the dust mass can be accounted for by standard model assumptions. We provide predictions regarding the abundance of the descendants of QSO hosts; albeit rare, such systems should be present and detectable by future deep surveys such as Euclid already at z  〉 4.
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    Topics: Physics
    Published by Oxford University Press
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  • 10
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    The galactic habitable zone of the Milky Way and M31 from chemical evolution models with gas radial flows (2014)
    Oxford University Press
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    Publication Date: 2014-04-10
    Description: The galactic habitable zone is defined as the region with sufficient abundance of heavy elements to form planetary systems in which Earth-like planets could be born and might be capable of sustaining life, after surviving to close supernova explosion events. Galactic chemical evolution models can be useful for studying the galactic habitable zones in different systems. We apply detailed chemical evolution models including radial gas flows to study the galactic habitable zones in our Galaxy and M31. We compare the results to the relative galactic habitable zones found with ‘classical’ (independent ring) models, where no gas inflows were included. For both the Milky Way and Andromeda, the main effect of the gas radial inflows is to enhance the number of stars hosting a habitable planet with respect to the ‘classical’ model results, in the region of maximum probability for this occurrence, relative to the classical model results. These results are obtained by taking into account the supernova destruction processes. In particular, we find that in the Milky Way the maximum number of stars hosting habitable planets is at 8 kpc from the Galactic Centre, and the model with radial flows predicts a number which is 38 per cent larger than what was predicted by the classical model. For Andromeda we find that the maximum number of stars with habitable planets is at 16 kpc from the centre and that in the case of radial flows this number is larger by 10 per cent relative to the stars predicted by the classical model.
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    Topics: Physics
    Published by Oxford University Press
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