Browsing by Author "Beccari, G."

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    Mass accretion rates from multiband photometry in the Carina Nebula : The case of Trumpler 14
    (2015) Beccari, G.; De Marchi, G.; Panagia, N.; Valenti, E.; Carraro, G.; Romaniello, M.; Zoccali, Manuela; Weidner, Carsten
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    NEW DENSITY PROFILE AND STRUCTURAL PARAMETERS OF THE COMPLEX STELLAR SYSTEM TERZAN 5
    (2010) Lanzoni, B.; Ferraro, F. R.; Dalessandro, E.; Mucciarelli, A.; Beccari, G.; Miocchi, P.; Bellazzini, M.; Rich, R. M.; Origlia, L.; Valenti, E.; Rood, R. T.; Ransom, S. M.
    Terzan 5 is a globular cluster-like stellar system in the Galactic bulge which has been recently found to harbor two stellar populations with different iron content and probably different ages. This discovery suggests that Terzan 5 may be the relic of a primordial building block that contributed to the formation of the Galactic bulge. Here we present a re-determination of the structural parameters (center of gravity, density and surface brightness profiles, total luminosity, and mass) of Terzan 5, as obtained from the combination of high-resolution (ESO-MAD and Hubble Space Telescope ACS-WFC) and wide-field (ESO-WFI) observations. We find that Terzan 5 is significantly less concentrated and more massive than previously thought. Still it has the largest collision rate of any stellar aggregate in the Galaxy. We discuss the impact of these findings on the exceptional population of millisecond pulsars harbored in this stellar system.
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    The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge
    (2009) Ferraro, F. R.; Dalessandro, E.; Mucciarelli, A.; Beccari, G.; Rich, R. M.; Origlia, L.; Lanzoni, B.; Rood, R. T.; Valenti, E.; Bellazzini, M.; Ransom, S. M.; Cocozza, G.
    Globular star clusters are compact and massive stellar systems old enough to have witnessed the entire history of our Galaxy, the Milky Way. Although recent results(1-3) suggest that their formation may have been more complex than previously thought, they still are the best approximation to a stellar population formed over a relatively short timescale (less than 1 Gyr) and with virtually no dispersion in the iron content. Indeed, only one cluster-like system (omega Centauri) in the Galactic halo is known to have multiple stellar populations with a significant spread in iron abundance and age(4,5). Similar findings in the Galactic bulge have been hampered by the obscuration arising from thick and varying layers of interstellar dust. Here we report that Terzan 5, a globular-cluster-like system in the Galactic bulge, has two stellar populations with different iron contents and ages. Terzan 5 could be the surviving remnant of one of the primordial building blocks that are thought to merge and form galaxy bulges.
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    The extended structure of the dwarf irregular galaxies Sextans A and Sextans B Signatures of tidal distortion in the outskirts of the Local Group
    (2014) Bellazzini, M.; Beccari, G.; Fraternali, F.; Oosterloo, T. A.; Sollima, A.; Testa, V.; Galleti, S.; Perina Pala, Sibilla; Faccini, M.; Cusano, F.
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    The extended structure of the dwarf irregular galaxy Sagittarius
    (2014) Beccari, G.; Bellazzini, M.; Fraternali, F.; Battaglia, G.; Perina, S.; Sollima, A.; Oosterloo, T. A.; Testa, V.; Galleti, S.
    We present a detailed study of the stellar and H I structure of the dwarf irregular galaxy Sagittarius. We use new deep and wide field photometry to trace the surface brightness profile of the galaxy out to similar or equal to 5.0' (corresponding to similar or equal to 1600 pc) and down to mu V similar or equal to 30.0 mag/arcsec(2), thus showing that the stellar body of the galaxy is much more extended than previously believed, and it is similarly (or more) extended than the overall H i distribution. The whole major-axis profile is consistent with a pure exponential, with a scale radius of similar or equal to 340 pc. The surface density maps reveal that the distribution of old and intermediate-age stars is smooth and remarkably flattened out to its edges, while the associated H I has a much rounder shape, is off-centred and presents multiple density maxima and a significant hole. No clear sign of systemic rotation is detectable in the complex H i velocity field. No metallicity gradient is detected in the old and intermediate age population of the galaxy, and we confirm that this population has a much more extended distribution than young stars (age less than or similar to 1 Gyr).