The infant Milky Way

We investigate the physical properties of the progenitors of today living Milky Way-like galaxies that are visible as Damped Lya Absorption systems and Lya Emitters at higher redshifts (z ~ 2.3,5.7). To this aim we use a statistical merger-tree approach that follows the formation of the Galaxy and its dwarf satellites in a cosmological context, tracing the chemical evolution and stellar population history of the progenitor halos. The model accounts for the properties of the most metal-poor stars and local dwarf galaxies, providing insights on the early cosmic star-formation. Fruitful links between Galactic Archaeology and more distant galaxies are presented.Comment: 6 pages, 6 figures; to appear in the proceedings of the Subaru conference on Galactic Archaeology, Shuzenji, Japan (Nov. 1-4 2011); Astronomical Society of the Pacific Conference Series 201

The surge of souverainism in radical right populism. The Italian case of the League

https://www.ester.ee/record=b5407013*es

High redshift Lya emitters: clues on the Milky Way infancy

With the aim of determining if Milky Way (MW) progenitors could be identified as high redshift Lyman Alpha Emitters (LAEs) we have derived the intrinsic properties of z ~ 5.7 MW progenitors, which are then used to compute their observed Lyman-alpha luminosity, L_alpha, and equivalent width, EW. MW progenitors visible as LAEs are selected according to the canonical observational criterion, L_alpha > 10^42 erg/s and EW > 20 A. Progenitors of MW-like galaxies have L_alpha = 10^(39-43.25) erg/s, making some of them visible as LAEs. In any single MW merger tree realization, typically only 1 (out of ~ 50) progenitor meets the LAE selection criterion, but the probability to have at least one LAE is very high, P = 68%. The identified LAE stars have ages, t_* ~ 150-400 Myr at z ~ 5.7 with the exception of five small progenitors with t_* 10% of the halo very metal-poor stars [Fe/H] < -2, thus establishing a potentially fruitful link between high-z galaxies and the Local Universe.Comment: Accepted for publication in MNRAS lette

The faintest galaxies

We investigate the nature of Ultra Faint dwarf spheroidal galaxies (UF dSphs) in a general cosmological context, simultaneously accounting for various "classical" dSphs and Milky Way (MW) properties, including their Metallicity Distribution Function (MDF). The model successfully reproduces both the observed [Fe/H]-Luminosity relation and the mean MDF of UFs. According to our results UFs are the living fossils of H2-cooling minihaloes formed at z>8.5, i.e. before the end of reionization. They are the oldest and the most dark matter-dominated (M/L > 100) dSphs in the MW system, with a total mass of M = 10^(7-8) Msun. The model allows to interpret the different shape of UFs and classical dSphs MDF, along with the frequency of extremely metal-poor stars in these objects. We discuss the "missing satellites problem" by comparing the UF star formation efficiencies with those derived for minihaloes in the Via Lactea simulation.Comment: To appear in the conference proceeding: "First Stars and Galaxies: Challenges in the Next Decade" . Publisher: American Institute of Physics. Editors: V. Bromm, D. Whalen, N. Yoshid

Book Reviews

Book Review 1Book Title: BoiardoBook Authors: Jo Ann Cavallo &amp; Corrado Confalonieri Milano: Unicopli, 2018.Reviewed by: Andrea PriviteraBook Review 2Book Title: All’ombra della memoria. Saggi su Paolo Volponi, 2° ed. riveduta e ampliataBook Author: Salvatore RitrovatoPesaro: Metauro, 2017Reviewed by: Diego SalvadoriBook Review 3Book Title: Francesca Turini Bufalini e la “letteratura di genere”Book Author: John ButlerCon una premessa di Antonio Lanza. Città di Castello, PG: Nuova Prhomos, 2018Reviewed by: Giulia Tonell

PROGETTAZIONE E SVILUPPO DI UN FRAMEWORK PER LA DEFINIZIONE E L'UTILIZZO DI METAFORE DI INTERAZIONE PER AMBIENTI VIRTUALI

Il progetto di tesi consiste nella progettazione e nella realizzazione di un framework per semplificare l’implementazione dell’interazione utente in applicazioni tridimensionali interattive e di realtà virtuale. Il framework è stato sviluppato in XVR, un ambiente integrato per la realizzazione di applicazioni di realtà virtuale, sviluppato presso il laboratorio PERCRO della Scuola Superiore Sant’Anna di Pisa. Esso definisce un insieme di metafore di interazione già pronte all’uso, e fornisce al programmatore gli strumenti necessari per crearne di nuove. Le metafore presenti sono state scelte tra quelle più usate nell’ambito applicativo della fruizione di contenuti culturali e supportano funzionalità quali collision detection e terrain following della camera. A tal fine è stata definita una libreria contenente gli algoritmi e le strutture dati necessarie all’esecuzione di alcuni tipi di test di intersezione tra primitive geometriche. Uno degli obiettivi principali che il framework si propone è quello di rendere le metafore e le altre funzionalità offerte indipendenti dal tipo di dispositivo usato. Inoltre l’architettura adottata consente di uniformare e semplificare la gestione dell’input rispetto a quanto avviene nei programmi XVR tradizionali. Allo stato attuale i dispositivi di input supportati sono il mouse, la tastiera ed il touchscreen. In via sperimentale è presente anche il supporto al Microsoft Kinect, quale esempio di dispositivo di tracking. Viene comunque data la possibilità aggiungere il supporto ad ulteriori dispositivi, anche di natura diversa. Infine è stata definita una libreria minimale per la realizzazione di semplici interfacce grafiche bidimensionali. La libreria è progettata in modo da poter essere impiegata con dispositivi di diversa natura

Dwarf satellites of high-z Lyman Break Galaxies: a free lunch for JWST

We show that the James Webb Space Telescope will be able to detect dwarf satellites of high-$z$ Lyman Break Galaxies (LBGs). To this aim, we use cosmological simulations following the evolution of a typical $M_\star\simeq10^{10}\rm M_\odot$ LBG up to $z\simeq6$, and analyse the observational properties of its five satellite dwarf galaxies ($10^7{\rm M_\odot}<M_\star<10^9{\rm M_\odot}$). Modelling their stellar emission and dust attenuation, we reconstruct their rest-frame UV-optical spectra for $6<z<6.5$. JWST/NIRCam synthetic images show that the satellites can be spatially resolved from their host, and their emission is detectable by planned deep surveys. Moreover, we build synthetic spectral energy distributions and colour-magnitude diagrams for the satellites. We conclude that the color $\rm F200W-F356W$ is a powerful diagnostic tool for understanding their physical properties once they have been identified. For example, $\rm F200W-F356W~\lesssim-0.25$ can be used to identify star-bursting ($\rm SFR\sim5~M_\odot yr^{-1}$), low-mass ($M_\star\lesssim5\times 10^8\rm M_\odot$) systems, with $\sim80\%$ of their stars being young and metal-poor ($\log(Z_\star/Z_\odot) < -0.5$).Comment: 8 pages, 3 figures, accepted for publication in ApJ

Quiescent low-mass galaxies observed by JWST in the Epoch of Reionization

The surprising JWST discovery of a quiescent, low-mass ($M_\star=10^{8.7} \rm M_\odot$) galaxy at redshift $z=7.3$ (JADES-GS-z7-01-QU) represents a unique opportunity to study the imprint of feedback processes on early galaxy evolution. We build a sample of 130 low-mass ($M_\star\lesssim 10^{9.5} \rm M_\odot$) galaxies from the SERRA cosmological zoom-in simulations, which show a feedback-regulated, bursty star formation history (SFH). The fraction of time spent in an active phase increases with the stellar mass from $f_{duty}\approx 0.6$ at $M_\star\approx 10^{7.5} \rm M_\odot$ to $\approx 0.99$ at $M_\star\geq 10^{9} \rm M_\odot$, and it is in agreement with the value $f_{duty}\approx 0.75$ estimated for JADES-GS-z7-01-QU. On average, 30% of the galaxies are quiescent in the range $6 < z < 8.4$; they become the dominant population at $M_\star\lesssim 10^{8.3} \rm M_\odot$. However, none of these quiescent systems matches the Spectral Energy Distribution of JADES-GS-z7-01-QU, unless their SFH is artificially truncated a few Myr after the main star formation peak. As supernova feedback can only act on a longer timescale ($\gtrsim 30 \rm \, Myr$), this implies that the observed abrupt quenching must be caused by a faster physical mechanism, such as radiation-driven winds.Comment: submitted to ApJ Letters, 5 pages, 4 figure

First stars in Damped Lyman Alpha systems

In order to characterize Damped Lyman Alpha systems (DLAs) potentially hosting first stars, we present a novel approach to investigate DLAs in the context of Milky Way (MW) formation, along with their connection with the most metal-poor stars and local dwarf spheroidal (dSph) galaxies. The merger tree method previously developed is extended to include inhomogeneous reionization and metal mixing, and it is validated by matching both the Metallicity Distribution Function of Galactic halo stars and the Fe-Luminosity relation of dSph galaxies. The model explains the observed NHI-Fe relation of DLAs along with the chemical abundances of [Fe/H] < -2 systems. In this picture, the recently discovered z_abs ~ 2.34 C-enhanced DLA (Cooke et al. 2011a), pertains to a new class of absorbers hosting first stars along with second-generation long-living low-mass stars. These "PopIII DLAs" are the descendants of H2-cooling minihalos with Mh ~ 10^7 Msun, that virialize at z > 8 in neutral, primordial regions of the MW environment and passively evolve after a short initial period of star formation. The gas in these systems is warm Tg \sim (40-1000) K, and strongly C-enriched by long-living, extremely metal-poor stars of total mass M* \sim 10^{2-4} Msun.Comment: 5 pages, 4 figures, accepted for publication in MNRAS lette