196,073 research outputs found
Studio per la trasformazione in residenza d’epoca di villa De Angelis a Sant'Enea (Pg)
No full textProgett
Re-assessment of the mid to late Quaternary glacial and environmental history of the Boco Plain, western Tasmania
No full textThe glacial geomorphology and drill core-based stratigraphy of the Boco Plain, western Tasmania, reveal a complex sequence of Quaternary glacial and non-glacial episodes. The upper part of the southern Boco Plain stratigraphy was previously dated by 14C and U-series on interbedded organics of MIS 1 to MIS 5 affinity. U-series dating of ferricretes associated with glacial diamictons from Boco Plain cores suggested that there were glacial advances broadly correlative with MIS 6, 8 and ≥10. However, terrestrial cosmogenic nuclide (10Be and 26Al) exposure ages for the moraine sequence preserved on the wider Boco Plain area indicate that moraines previously attributed to MIS 6 and 8 advances were deposited during MIS 10 or earlier cold stages. There is no evidence for MIS 2, 4 or 6 affinity glacial advances onto the Boco Plain with ice of this age restricted to the West Coast Range. New palynological records from the Boco Plain core 6690 confirmed the late Quaternary ages of the upper part of the sequence, whilst extinct palynomorphs indicate a pre-Quaternary age for the glacial diamictons at the base of core Boco 4 and 10. Consequently, the mid-Pleistocene glacial sequence preserved in the Boco Plain is significantly older than previously envisaged, with the post MIS 10 to 12 geomorphology of the plain dominated by fluvial deltaic, swamp peat and lacustrine environments
The impact of the FMR and starburst galaxies on the (low metallicity) cosmic star formation history
No full textsponsorship: We thank Karina Caputi and Jarle Brinchmann for helpful discussions. We thank the anonymous referee for their thoughtful comments that helped to improve this paper. MC and GN acknowledge support from the Netherlands Organisation for Scientific Research (NWO). ALandLBare supported by PRINMIUR 2017 prot. 20173ML3WW, `Opening the ALMA window on the cosmic evolution of gas, stars and supermassive black holes', and by the EU H2020-MSCA-ITN2019 Project 860744 'BiD4BESt: Big Data applications for black hole Evolution STudies.' (Netherlands Organisation for Scientific Research (NWO), PRINMIUR|20173ML3WW, EU H2020-MSCA-ITN2019|860744)status: Publishe
Gravitational waves throughout galaxy evolution: stellar BH mergers and heavy SMBH seeds.
No full textThe main goal of my thesis is to carefully characterize different astrophysical processes leading to gravitational wave (GW) emission, strongly relying on theoretical and observational astrophysical basis. From an observational point of view, current interferometers (Advanced Laser Interferometer Gravitational wave Observatory/Virgo (AdvLIGO/Virgo)) and future detectors (Einstein Telescope (ET), Cosmic Explorer (CE), Deci-hertz Interferometer Gravitational wave Observatory (DECIGO), Laser Interferometer Space Antenna (LISA)) will greatly enlarge the number of detected GW events. However, in order to extract meaningful information about various astrophysical phenomena and improve our knowledge on cosmology and fundamental physics from this large sample of observational data, a correct modelization of the impact of different astrophysical processes on GWs rates is necessary.
The marking feature of all the work is an accurate and deep study of the galactic environment, making use of classic theoretical arguments and recent observational results in the galaxy formation and evolution field. Galactic properties, such as star formation rate, gas and stellar density, metallicity, can have a profound impact on stellar and compact object evolution and on the ensuing GW emissions. In particular, throughout the thesis I focused on the study of 2 different channels of GW production: merging of isolated double compact object binaries of stellar origin (neutron stars and stellar black holes) and dynamical merging of stellar and, eventually, primordial black holes in the central regions of early-type galaxy progenitors.
In the context of double compact object merging binaries, given the relevance of gas-phase metallicity for all the stellar and binary evolution processes, the main effort of my work is in the characterization of a metallicity dependent cosmic star formation rate density. I compute this term in various ways, highlighting the impact of different galactic prescriptions, such as galaxy statistics and metallicity scaling relations. In particular I focus on the gas-phase metallicity, showing that the two main empirical scaling relations present in literature, the Mass Metallicity Relation and the Fundamental Metallicity Relation, hold substantially different results at high redshift ( > 2), with the Fundamental Metallicity Relation featuring relatively high metallicitites ∼ 0.4 − 0.5 Z⊙ and the Mass Metallicity Relation predicting a significant metallicity drop below 0.1 Z⊙. I discuss the reasons and possible biases originating this discrepancy, arguing in favor of the Fundamental Metallicity Relation or of a slowly declining Mass Metallicity Relation. I also present a chemical evolution model to deal with metallicity from a theoretical point of view and I find a pleasant agreement between the model and the Fundamental Metallicity Relation. Finally, I show the impact of these different astrophysical prescriptions on the merging rates and on the properties of compact objects binaries, such as their chirp mass or time delay distribution. I complete the work forecasting the ensuing GW detection rates with present and future detectors, as well as the expected lensed event rates and the stochastic GW background.
As for the dynamical merging channel, recent observations of the extremely star-forming and gas-dense environments in the central regions of early-type galaxy progenitors at z bigger than 1, inspired the idea for the proposal of a new mechanism for the growth of supermassive black hole seeds. This envisages the migration and merging of compact objects via gaseous dynamical friction toward the galactic center where a central black hole accumulates mass thanks to these continuous merging events. I show that, under reasonable assumptions, the process can build up central BH masses of order 10^4 − 10^5 M⊙ within some 10^7 yr, so effectively providing heavy seeds before standard (Eddington-like) disk accretion takes over to become the dominant process for further BH growth. Remarkably, such a mechanism may provide an explanation, alternative or complementary to other processes, for the buildup of billion solar masses black holes in quasar hosts at z bigger than 7, when the age of the Universe less than 0.8 Gyr constitutes a demanding constraint. This process naturally present a possibility to be tested via detections of the gravitational waves produced by mergers between the migrating compact objects and the growing central black hole. I also make predictions for the produced stochastic GW background which extends over a wide range of frequencies [10^(−6) Hz, 10 Hz], very different from the typical range originated by mergers of isolated binaries. I show that both the single events and the background could be revealed by future ground- and space-based interferometers as ET, DECIGO and LISA
Modelling the host galaxies of binary compact object mergers with observational scaling relations
No full textThe merger rate density evolution of binary compact objects and the
properties of their host galaxies carry crucial information to understand the
sources of gravitational waves. Here, we present galaxyRate, a new code that
estimates the merger rate density of binary compact objects and the properties
of their host galaxies, based on observational scaling relations. We generate
our synthetic galaxies according to the galaxy stellar mass function. We
estimate the metallicity according to both the mass-metallicity relation (MZR)
and the fundamental metallicity relation (FMR). Also, we take into account
galaxy-galaxy mergers and the evolution of the galaxy properties from the
formation to the merger of the binary compact object. We find that the merger
rate density changes dramatically depending on the choice of the star-forming
galaxy main sequence, especially in the case of binary black holes (BBHs) and
black hole neutron star systems (BHNSs). The slope of the merger rate density
of BBHs and BHNSs is steeper if we assume the MZR with respect to the FMR,
because the latter predicts a shallower decrease of metallicity with redshift.
In contrast, binary neutron stars (BNSs) are only mildly affected by both the
galaxy main sequence and metallicity relation. Overall, BBHs and BHNSs tend to
form in low-mass metal-poor galaxies and merge in high-mass metal-rich
galaxies, while BNSs form and merge in massive galaxies. We predict that
passive galaxies host at least ~5-10%, ~15-25%, and ~15-35% of all BNS, BHNS
and BBH mergers in the local Universe.Comment: 21 pages, 22 figures (including appendices), 3 tables, published in
MNRA
Exploring galaxies-gravitational waves cross-correlations as an astrophysical probe
No full textGravitational waves astronomy has opened a new opportunity to study the Universe. Full exploitation of this window can especially be provided by combining data coming from gravitational waves experiments with luminous tracers of the Large Scale Structure, like galaxies. In this work we investigate the cross-correlation signal between gravitational waves resolved events, as detected by the Einstein Telescope, and actively star-forming galaxies. The galaxies distribution is computed through their UV and IR luminosity functions and the gravitational waves events, assumed to be of stellar origin, are self-consistently computed from the aforementioned galaxies distribution. We provide a state-of-the-art treatment both on the astrophysical side, {taking} into account the impact of the star formation and chemical evolution histories of galaxies, and in computing the cross-correlation signal, for which we include lensing and relativistic effects. {We find that the measured cross-correlation signal can be sufficiently strong to overcome the noise and provide a clear signal. As a possible application of this methodology, we consider a proof-of-concept case in which we aim at discriminating a metallicity dependence on the compact objects merger efficiency against a reference case with no metallicity dependence.} When considering galaxies with a Star Formation Rate ψ > 10 Mo ̇/yr, a Signal-to-Noise ratio around a value of 2-4 is gained after a decade of observation time, depending on the observed fraction of the sky. This formalism can be exploited as an astrophysical probe and could potentially allow to test and compare different astrophysical scenarios
Constraining the Initial Mass Function in the Epoch of Reionization from Astrophysical and Cosmological Data
No full textWe aim to constrain the stellar initial mass function (IMF) during the epoch of reionization. To this purpose, we build up a semi-empirical model for the reionization history of the Universe based on various ingredients: the latest determination of the UV galaxy luminosity function from JWST out to redshift z≲12; data-inferred and simulation-driven assumptions on the redshift-dependent escape fraction of ionizing photons from primordial galaxies; a simple yet flexible parameterization of the IMF ϕ(m⋆)∼m⋆ξe−m⋆,c/m⋆ in terms of a high-mass end slope ξ0 and a characteristic mass m⋆,c, below which a flattening or a bending sets in (allowing description of a variety of IMF shapes from the classic Salpeter to top-heavy ones); the PARSEC stellar evolution code to compute the UV and ionizing emission from different stars’ masses as a function of age and metallicity; and a few physical constraints related to stellar and galaxy formation in faint galaxies at the reionization redshifts. We then compare our model outcomes with the reionization observables from different astrophysical and cosmological probes and perform Bayesian inference on the IMF parameters via a standard MCMC technique. We find that the IMF slope ξ is within the range from −2.8 to −2.3, consistent with direct determination from star counts in the Milky Way, while appreciably flatter slopes are excluded at great significance. However, the bestfit value of the IMF characteristic mass m⋆,c∼a few M⊙ implies a suppression in the formation of small stellar masses at variance with the IMF in the local Universe. This may be induced by the thermal background of ∼20–30 K provided by CMB photons at the reionization redshifts. We check that our results are robust against different parameterizations for the redshift evolution of the escape fraction. Finally, we investigate the implications of our reconstructed IMF for the recent JWST detections of massive galaxies at and beyond the reionization epoch, showing that any putative tension with the standard cosmological framework is substantially alleviated
The effects of the initial mass function on Galactic chemical enrichment
No full textContext. We have been seeing mounting evidence that the stellar initial mass function (IMF) might extend far beyond the canonical Mi ∼ 100 M⊙ limit, but the impact of such a hypothesis on the chemical enrichment of galaxies is yet to be clarified. Aims. We aim to address this question by analysing the observed abundances of thin- and thick-disc stars in the Milky Way with chemical evolution models that account for the contribution of very massive stars dying as pair instability supernovae. Methods. We built new sets of chemical yields from massive and very massive stars up to Mi ∼ 350 M⊙ by combining the wind ejecta extracted from our hydrostatic stellar evolution models with explosion ejecta from the literature. Using a simple chemical evolution code, we analysed the effects of adopting different yield tables by comparing predictions against observations of stars in the solar vicinity. Results. After several tests, we set our focus on the [O/Fe] ratio that best separates the chemical patterns of the two Milky Way components. We find that with a standard IMF, truncated at Mi ∼ 100 M⊙, we can reproduce various observational constraints for thin-disc stars; however, the same IMF fails to account for the [O/Fe] ratios of thick-disc stars. The best results are obtained by extending the IMF up to Mi = 350 M⊙, while including the chemical ejecta of very massive stars in the form of winds and pair instability supernova (PISN) explosions. Conclusions. Our study indicates that PISN may have played a significant role in shaping the chemical evolution of the thick disc of the Milky Way. Including their chemical yields makes it easier to reproduce not only the level of the α-enhancement, but also the observed slope of thick-disc stars in the [O/Fe] vs. [Fe/H] diagram. The bottom line is that the contribution of very massive stars to the chemical enrichment of galaxies is potentially quite important and should not be neglected in models of chemical evolution
Application of additive light increases leafy cutting rooting and survival in hazelnut (Corylus avellana L.).
No full textCorylusavellana is a hard-to-root species, thus hazelnut cultivar propagation by stem cuttings is considered difficult.The rooting of cuttings is influenced by many exogenous and endogenous factors such as hormones, cutting quality, and environmental conditions. In particular, rooting success of soft wood cuttings could be enhanced by the application of additive light during rooting due to the possible increase of photosynthetic activity of the cutting leaf and of the consequent increase of the carbohydrate content of the cutting. The aim of the present work was to evaluate the effect of additive light during the rooting process on cutting physiology and rooting success. Results showed that additive light (PAR ~300 μmol m-2 s-1), applied in 2014 on cuttings of Tonda di Giffoni, increased cutting leaf photosynthesis and increased cutting non-structural carbohydrate content. Such increase resulted in a consistent increase of the percentage of rooted cuttings and an increase of the quality of the roots that developed. Furthermore, plants obtained from rooting under the additive light condition suffered a reduced amount of mortality in comparison with control plants. The experiment was repeatedin 2015 on a pre-commercial scale using Tonda di Giffoni and Tonda Romana cuttings. Results confirmed the observation of the previous year. In conclusion, additive light during leafy cutting rooting is a technique able to increase cutting propagation success in hazelnut
Gravitational waves × HI intensity mapping: Cosmological and astrophysical applications
No full textTwo of the most rapidly growing observables in cosmology and astrophysics are gravitational waves (GW) and the neutral hydrogen (HI) distribution. In this work, we investigate the cross-correlation between resolved gravitational wave detections and HI signal from intensity mapping (IM) experiments. By using a tomographic approach with angular power spectra, including all projection effects, we explore possible applications of the combination of the Einstein Telescope and the SKAO intensity mapping surveys. We focus on three main topics: (i) statistical inference of the observed redshift distribution of GWs; (ii) constraints on dynamical dark energy models as an example of cosmological studies; (iii) determination of the nature of the progenitors of merging binary black holes, distinguishing between primordial and astrophysical origin. Our results show that: (i) the GW redshift distribution can be calibrated with good accuracy at low redshifts, without any assumptions on cosmology or astrophysics, potentially providing a way to probe astrophysical and cosmological models; (ii) the constrains on the dynamical dark energy parameters are competitive with IM-only experiments, in a complementary way and potentially with less systematics; (iii) it will be possible to detect a relatively small abundance of primordial black holes within the gravitational waves from resolved mergers. Our results extend towards GW × IM the promising field of multi-tracing cosmology and astrophysics, which has the major advantage of allowing scientific investigations in ways that would not be possible by looking at single observables separately
- …
