Un'Unione europea finalmente democratica: chimera o realtà? Alcune riflessioni sull'implementazione del principio democratico nella costruzione europea a partire dalle "Consultazioni sul futuro dell'Europa"

La legittimità democratica dell'ordinamento comunitario è messa in discussione fin dagli albori della sua istituzione. Se, infatti, all’interno degli Stati nazionali che compongono l’Unione il concetto di governo del popolo è storicamente nato, e tradizionalmente si è evoluto, ancorandosi a istituti di democrazia rappresentativa e diretta, o anche mediata; il sistema comunitario ha finito col porsi su un binario differente, sia per la difficoltà di adattare i modelli che si sono sedimentati nel corso degli anni, sia per l’impossibilità di introiettare tout court i formati esistenti a livello statale

Dissecting the 3D structure of elliptical galaxies with gravitational lensing and stellar kinematics

The combination of strong gravitational lensing and stellar kinematics provides a powerful and robust method to investigate the mass and dynamical structure of early-type galaxies. We demonstrate this approach by analysing two massive ellipticals from the XLENS Survey for which both high-resolution HST imaging and X-Shooter spectroscopic observations are available. We adopt a flexible axisymmetric two-component mass model for the lens galaxies, consisting of a generalised NFW dark halo and a realistic self-gravitating stellar mass distribution. For both systems, we put constraints on the dark halo inner structure and flattening, and we find that they are dominated by the luminous component within one effective radius. By comparing the tight inferences on the stellar mass from the combined lensing and dynamics analysis with the values obtained from stellar population studies, we conclude that both galaxies are characterised by a Salpeter-like stellar initial mass function.Comment: Proceedings of the IAU Symposium 309, Contributed Talk, Vienna, July 2014; 4 pages, 2 figure

The non-universality of the low-mass end of the IMF is robust against the choice of SSP model

We perform a direct comparison of two state-of-the art single stellar population (SSP) models that have been used to demonstrate the non-universality of the low-mass end of the Initial Mass Function (IMF) slope. The two public versions of the SSP models are restricted to either solar abundance patterns or solar metallicity, too restrictive if one aims to disentangle elemental enhancements, metallicity changes and IMF variations in massive early-type galaxies (ETGs) with star formation histories different from the solar neighborhood. We define response functions (to metallicity and \alpha-abundance) to extend the parameter space of each set of models. We compare these extended models with a sample of Sloan Digital Sky Survey (SDSS) ETGs spectra with varying velocity dispersions. We measure equivalent widths of optical IMF-sensitive stellar features to examine the effect of the underlying model assumptions and ingredients, such as stellar libraries or isochrones, on the inference of the IMF slope down to ~0.1 solar masses. We demonstrate that the steepening of the low-mass end of the Initial Mass Function (IMF) based on a non-degenerate set of spectroscopic optical indicators is robust against the choice of the stellar population model. Although the models agree in a relative sense (i.e. both imply more bottom-heavy IMFs for more massive systems), we find non-negligible differences on the absolute values of the IMF slope inferred at each velocity dispersion by using the two different models. In particular, we find large inconsistency in the quantitative predictions of IMF slope variations and abundance patterns when sodium lines are used. We investigate the possible reasons for these inconsistencies.Comment: 16 pages, 9 figures, 2 tables, accepted for publication on Ap

(Sche)Dati. Il diritto alla protezione dei dati personali nella legislazione europea

Dal 25 maggio 2018 il Regolamento (EU) n. 2016/679 del 27 aprile 2016 (General Data Protection Regulation – GDPR) è entrato in vigore in tutti gli Stati membri dell’Unione europea. Riscostruendo il processo di acquisizione del diritto alla protezione dei dati personali nel quadro normativo europeo, il contributo affronta l’analisi degli interventi regolatori seguiti alla primigenia Direttiva 81/108/CE. In particolare, oggetto d’indagine è stato il nuovo Regolamento e i necessari standard di sicurezza introdotti per il trattamento dei dati personali

MUSE observations of M87: radial gradients for the stellar initial-mass function and the abundance of Sodium

Based on MUSE integral-field data we present evidence for a radial variation at the low-mass end of the stellar initial-mass function (IMF) in the central regions of the giant early-type galaxy NGC4486 (M87). We used state-of-the-art stellar population models and the observed strength of various IMF-sensitive absorption-line features to solve for the best low-mass tapered "bimodal" form of the IMF, while accounting also for radial variations in stellar metallicity, the overall $\alpha$-elements abundance, and the abundance of individual elements such as Ti, O, Na and Ca. Our analysis reveals a strong IMF gradient in M87, corresponding to an exceeding fraction of low-mass stars compared to the case of the Milky Way toward the center of M87 that drops to nearly Milky-way levels by 0.4 $R_e$. This IMF gradient is found to correlate well with both the radial profile for stellar metallicity and for $\alpha$-elements abundance but not with stellar velocity dispersion. Such IMF variations correspond to over a factor two increase in stellar mass-to-light M/L ratio compared to the case of a Milky-way like IMF, consistent with other investigations into IMF gradients in early-type galaxies, including recent dynamical constraints on M/L radial variations in M87 by Oldham & Auger. In addition to constraining the IMF in M87 we also looked into the abundance of Sodium, which turned up to be super-Solar over the entire radial range of our MUSE observations and to exhibit a considerable negative gradient. These findings suggest an additional role of metallicity in boosting the Na-yields in the central, metal-rich regions of M87 during its early and brief star-formation history. Our work adds the case of M87 to the few objects that as of today have radial constraints on their IMF or [Na/Fe] abundance, while also illustrating the accuracy that MUSE could bring to this kind of investigations.Comment: 17 pages, 13 figures, re-submitted for publication on MNRAS following the referee's comment

La morte della Regina riapre il dibattito sulla monarchia, mentre si riaccendono tensioni nei rapporti centro-periferia e il Québec è travolto dallo “Tsunami Caquiste"

In Canada, il quadrimestre settembre-dicembre 2022 è stato segnato dal riaccendersi di tensioni nei rapporti tra la Federazione e alcune Province (Québec, Alberta e Saskatchewan), alimentate dall'instaurazione di precedenti di adozione di emendamenti alla Costituzione unilaterali e di altri atti manifestamente illegittimi, perseguita in modo attivo, consapevole e persino entusiastico dagli organi di indirizzo provinciali, e potenzialmente in grado di aprire una grave crisi costituzionale. Anche il dibattito sul futuro della monarchia, innescato dalla morte della Regina Elisabetta II, è stato condizionato dal cleavage politico-istituzionale che storicamente, in Canada, attraversa il versante dei rapporti tra centro e periferia

Planetary nebulae as tracers of stellar population properties: unlocking their potential with integral-field spectroscopy

Planetary nebulae (PNe) are essential tracers of the kinematics of the diffuse halo and intracluster light where stellar spectroscopy is unfeasible, due to their strong emission lines. However, that is not all they can reveal about the underlying stellar population. In recent years, it has also been found that PNe in the metal-poor halos of galaxies have different properties (specific frequency, luminosity function), than PNe in the more metal-rich galaxy centers. A more quantitative understanding of the role of age and metallicity in these relations would turn PNe into valuable stellar-population tracers. In order to do that, a full characterization of PNe in regions where the stellar light can also be analysed in detail is necessary. In this work, we make use of integral-field spectroscopic data covering the central regions of galaxies, which allow us to measure both stellar ages and metallicities as well as to detect PNe. This analysis is fundamental to calibrate PNe as stellar population tracers and to push our understanding of galaxy properties at unprecedented galactocentric distances.Comment: Submitted to the Proceedings of IAU Symposium 384: Planetary Nebulae: a Universal Toolbox in the Era of Precision Astrophysics. Eds: O. De Marco, A. Zijlstra, R. Szczerb

Ages, metallicity, and alpha-enhancement of the globular cluster populations in NGC 3311

Aims. We aim to investigate the stellar population properties, ages, and metal content of the globular clusters (GCs) in NGC 3311, the central galaxy of the Hydra I cluster, to better constrain its evolution history. Methods. We used integral-field spectroscopic data from the Multi-Unit Spectroscopic Explorer (MUSE) to identify 680 sources in the central region of NGC 3311 and extract their 1D spectra. An analysis of these sources in terms of morphologies, radial velocities, and emission lines allowed us to narrow down our selection to 49 bona fide GC candidates. We split these candidates into two groups depending on their projected distance to the galaxy center (R), namely inner (R20arcsec) GCs. We stacked the extracted 1D spectra of the inner and outer GC populations to increase the signal-to-noise ratios (S/Ns) of the resulting spectra and hence allow full-spectrum fitting. In addition, we also created a stacked spectrum of all GCs in NGC 3311 and one of the two most central GC candidates. Using the code pPXF, we performed a stellar population analysis on the four stacked 1D spectra, obtaining mass-weighted integrated ages, metallicities, and [$\alpha$/Fe] abundances. Results. All GCs are old, with ages >13.5 Gyr, and they have super-solar metallicities. Looking at the color distribution, we find that the inner ones tend to be redder and more metal rich than the outer ones. This is consistent with the two-phase formation scenario. Looking at the full-spectral fitting results, at face value the outer GCs have a larger [$\alpha$/Fe] ratio, which is in line with what is found for the stars that dominate the surface brightness profile at the same radii. However, the values for outer and inner GCs are consistent within the uncertainties.Comment: Accepted for publication by A&A on November 15th 202

Searching for strong gravitational lenses

Strong gravitational lenses provide unique laboratories for cosmological and astrophysical investigations, but they must first be discovered - a task that can be met with significant contamination by other astrophysical objects and asterisms. Here we review strong lens searches, covering various sources (quasars, galaxies, supernovae, FRBs, GRBs, and GWs), lenses (early- and late-type galaxies, groups, and clusters), datasets (imaging, spectra, and lightcurves), and wavelengths. We first present the physical characteristics of the lens and source populations, highlighting relevant details for constructing targeted searches. Search techniques are described based on the main lensing feature that is required for the technique to work, namely one of: (i) an associated magnification, (ii) multiple spatially-resolved images, (iii) multiple redshifts, or (iv) a non-zero time delay between images. To use the current lens samples for science, and for the design of future searches, we list several selection biases that exist due to these discovery techniques. We conclude by discussing the future of lens searches in upcoming surveys and the new population of lenses that will be discovered.Comment: 54 pages, 15 figures, submitted to Space Science Reviews, Topical Collection "Strong Gravitational Lensing", eds. J. Wambsganss et a