CRASH3: cosmological radiative transfer through metals

Here we introduce CRASH3, the latest release of the 3D radiative transfer code CRASH. In its current implementation CRASH3 integrates into the reference algorithm the code Cloudy to evaluate the ionisation states of metals, self-consistently with the radiative transfer through H and He. The feedback of the heavy elements on the calculation of the gas temperature is also taken into account, making of CRASH3 the first 3D code for cosmological applications which treats self-consistently the radiative transfer through an inhomogeneous distribution of metal enriched gas with an arbitrary number of point sources and/or a background radiation. The code has been tested in idealized configurations, as well as in a more realistic case of multiple sources embedded in a polluted cosmic web. Through these validation tests the new method has been proven to be numerically stable and convergent. We have studied the dependence of the results on a number of physical quantities such as the source characteristics (spectral range and shape, intensity), the metal composition, the gas number density and metallicity.Comment: accepted for publication in MNRA

UV background fluctuations traced by metal ions at z≈3z\approx3

Here we investigate how LyC-opaque systems present in the intergalactic medium at $z\approx3$ can distort the spectral shape of a uniform UV background (UVB) through radiative transfer (RT) effects. With this aim in mind, we perform a multi-frequency RT simulation through a cosmic volume of $10h^{-1}$~cMpc scale polluted by metals, and self-consistently derive the ions of all the species. The UVB spatial fluctuations are traced by the ratio of He$\, \rm \scriptstyle II\$ and H$\, \rm \scriptstyle I\$ column density, $\eta$, and the ratio of C$\,{\rm {\scriptstyle IV\ }}$ and Si$\,{\rm {\scriptstyle IV\ }}$ optical depths, $\zeta$. We find that: (i) $\eta$ spatially fluctuates through over-dense systems ($\Delta$) with statistically significant deviations $\delta\eta >25$\% in 18\% of the volume ; (ii) same fluctuations in $\zeta$ are also present in $34$\% of the enriched domain (only 8\% of the total volume) and derive from a combination of RT induced effects and in-homogeneous metal enrichment, both effective in systems with $\Delta > 1.5$.Comment: Accepted for pub. in MNRAS after very minor re

Enabling Radiative Transfer on AMR grids in CRASH

We introduce CRASH-AMR, a new version of the cosmological Radiative Transfer (RT) code CRASH, enabled to use refined grids. This new feature allows us to attain higher resolution in our RT simulations and thus to describe more accurately ionisation and temperature patterns in high density regions. We have tested CRASH-AMR by simulating the evolution of an ionised region produced by a single source embedded in gas at constant density, as well as by a more realistic configuration of multiple sources in an inhomogeneous density field. While we find an excellent agreement with the previous version of CRASH when the AMR feature is disabled, showing that no numerical artifact has been introduced in CRASH-AMR, when additional refinement levels are used the code can simulate more accurately the physics of ionised gas in high density regions. This result has been attained at no computational loss, as RT simulations on AMR grids with maximum resolution equivalent to that of a uniform cartesian grid can be run with a gain of up to 60% in computational time.Comment: 19 pages, 17 figures. MNRAS, in pres

Galaxy formation with radiative and chemical feedback

Here we introduce GAMESH, a novel pipeline which implements self-consistent radiative and chemical feedback in a computational model of galaxy formation. By combining the cosmological chemical-evolution model GAMETE with the radiative transfer code CRASH, GAMESH can post process realistic outputs of a N-body simulation describing the redshift evolution of the forming galaxy. After introducing the GAMESH implementation and its features, we apply the code to a low-resolution N-body simulation of the Milky Way formation and we investigate the combined effects of self-consistent radiative and chemical feedback. Many physical properties, which can be directly compared with observations in the Galaxy and its surrounding satellites, are predicted by the code along the merger-tree assembly. The resulting redshift evolution of the Local Group star formation rates, reionisation and metal enrichment along with the predicted Metallicity Distribution Function of halo stars are critically compared with observations. We discuss the merits and limitations of the first release of GAMESH, also opening new directions to a full implementation of feedback processes in galaxy formation models by combining semi-analytic and numerical methods.Comment: This version has coloured figures not present in the printed version. Submitted to MNRAS, minor revision

Where does galactic dust come from?

Here we investigate the origin of the dust mass (Mdust) observed in the Milky Way (MW) and of dust scaling relations found in a sample of local galaxies from the DGS and KINGFISH surveys. To this aim, we model dust production from Asymptotic Giant Branch (AGB) stars and supernovae (SNe) in simulated galaxies forming along the assembly of aMW-like halo in a well-resolved cosmic volume of 4 cMpc using the GAMESH pipeline. We explore the impact of different sets of metallicity and mass-dependent AGB and SN dust yields on the predicted Mdust. Our results show that models accounting for grain destruction by the SN reverse shock predict a total dust mass in the MW, that is a factor of ~4 less than observed, and cannot reproduce the observed galaxy-scale relations between dust and stellar masses, and dust-togas ratios and metallicity, with a smaller discrepancy in galaxies with low metallicity (12 + log(O/H) < 7.5) and low stellar masses (Mstar < 107 M⊙). In agreement with previous studies, we suggest that competing processes in the interstellar medium must be at play to explain the observed trends. Our result reinforces this conclusion by showing that it holds independently of the adopted AGB and SN dust yields

Tsunami: alla scoperta dei maremoti

Tsunami è una parola giapponese che significa “onda (nami) nel porto (tsu)”, in quanto anticamente si osservava che alcune onde diventavano devastanti avvicinandosi alla costa. Il termine italiano usato per definire uno tsunami è maremoto, cioè una serie di onde che, superando l'abituale linea costiera, provocano danni all'interno dei porti, ma anche lungo tutta la costa e a volte nell’entroterra

A new version of the European tsunami catalogue: updating and revision

A new version of the European catalogue of tsunamis is presented here. It differs from the latest release of the catalogue that was produced in 1998 and is known as GITEC tsunami catalogue in some important aspects. In the first place, it is a database built on the Visual FoxPro 6.0 DBMS that can be used and maintained under the PC operating systems currently available. Conversely, the GITEC catalogue was compatible only with Windows 95 and older PC platforms. In the second place, it is enriched by new facilities and a new type of data, such as a database of pictures that can be accessed easily from the main screen of the catalogue. Thirdly, it has been updated by including the newly published references. Minute and painstaking search for new data has been undertaken to re-evaluate cases that were not included in the GITEC catalogue, though they were mentioned in previous catalogues; the exclusion was motivated by a lack of data. This last work has focused so far on Italian cases of the last two centuries. The result is that at least two events have been found which deserve inclusion in the new catalogue: one occurred in 1809 in the Gulf of La Spezia, and the other occurred in 1940 in the Gulf of Palermo. Two further events are presently under investigation

A revision of the 1783?1784 Calabrian (southern Italy) tsunamis

International audienceSouthern Italy is one of the most tsunamigenic areas in the Mediterranean basin, having experienced during centuries a large number of tsunamis, some of which very destructive. In particular, the most exposed zone here is the Messina Straits separating the coasts of Calabria and Sicily that was the theatre of the strongest Italian events. In 1783?1785 Calabria was shaken by the most violent and persistent seismic crisis occurred in the last 2000 years. Five very strong earthquakes, followed by tsunamis, occurred in a short interval of time (February?March 1783), causing destruction and a lot of victims in a vast region embracing the whole southern Calabria and the Messina area, Sicily. In this study we re-examined these events by taking into account all available historical sources. In particular, we focussed on the 5 and 6 February 1783 tsunamis, that were the most destructive. As regards the 5 February event, we found that it was underestimated and erroneously considered a minor event. On the contrary, the analysis of the sources revealed that in some localities the tsunami effects were quite strong. The 6 February tsunami, the strongest one of the sequence, was due to a huge earthquake-induced rockfall and killed more than 1500 people in the Calabrian village of Scilla. For this event the inundated area and the runup values distribution were estimated. Further, the analysis of the historical sources allowed us to find three new tsunamis that passed previously unnoticed and that occurred during this seismic period. The first one occurred a few hours before the large earthquake of 5 February 1783. The second was generated by a rockfall on 24 March 1783. Finally, the third occurred on 9 January 1784, probably due to a submarine earthquake

INTEGRATED PHOTOGRAMMETRIC SURVEY AND BIM MODELLING FOR THE PROTECTION OF SCHOOL HERITAGE, APPLICATIONS ON A CASE STUDY

The contribution, considering the use of low-cost photogrammetric detection methodologies and the use of asset Historical-BIM, has as its aim the theme of knowledge and the adaptation of safety in school buildings, a topic brought to attention by the many situations of seismic risk that have interested the central Apennines in Italy. The specific investigation is referred to the Abruzzo region, hit by the recent earthquakes of 2016 and 2009 that have highlighted the vulnerability of the building structures involved in a large seismic crater covering large areas of the territory. The need to consider in advance the performance standards of building components, especially concerning the strategic ways of the functions contained in them, starts here. In this sense, the school buildings have emerged among the types on which to pay attention, a study theme to be promptly considered, considering the functions performed within them and the possible criticality of such constructions, often dated, enlarged or readjusted without appropriate seismic adaptation plans. From here derives the purpose of the research that is directed towards a systematic recognition of the scholastic heritage, deriving from objective and rapid surveys at low cost, taking into consideration the as-built and the different formal and structural aspects that define the architectural organisms to analyse and manage through three-dimensional models that can be interrogated using HBIM connected to databases containing information of a structural and functional nature. In summary, through the implementation of information in the BIM model, it will be possible to query and obtain in real time all the necessary information to optimize, in terms of efficiency, costs, and future maintenance operations