Examinando por Autor "Kunder, Andrea"

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    Impact of Distance Determinations on Galactic Structure. II. Old Tracers
    (Springer Netherlands, 2018-08) Kunder, Andrea; Valenti, Elena; Dall’Ora, Massimo; Pietrukowicz, Pawel; Sneden, Chris; Bono, Giuseppe; Braga, Vittorio F.; Ferraro, Iván; Fiorentino, Giuliana; Iannicola, Giacinto; Marconi, Marcella; Martínez-Vázquez, Clara E.; Monelli, Matteo; Musella, Ilaria; Ripepi, Vincenzo; Salaris, Maurizio; Stetson, Peter B.
    Here we review the efforts of a number of recent results that use old tracers to understand the build up of the Galaxy. Details that lead directly to using these old tracers to measure distances are discussed. We concentrate on the following: (1) the structure and evolution of the Galactic bulge and inner Galaxy constrained from the dynamics of individual stars residing therein; (2) the spatial structure of the old Galactic bulge through photometric observations of RR Lyrae-type stars; (3) the three-dimensional structure, stellar density, mass, chemical composition, and age of the Milky Way bulge as traced by its old stellar populations; (4) an overview of RR Lyrae stars known in the ultra-faint dwarfs and their relation to the Galactic halo; and (5) different approaches for estimating absolute and relative cluster ages. © 2018, Springer Nature B.V.
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    Interstellar extinction curve variations towards the inner Milky Way: A challenge to observational cosmology
    (Oxford University Press, 2016-03) Nataf, David M.; Gonzalez, Oscar A.; Casagrande, Luca; Zasowski, Gail; Wegg, Christopher; Wolf, Christian; Kunder, Andrea; Alonso-Garcia, Javier; Minniti, Dante; Rejkuba, Marina; Saito, Roberto K.; Valenti, Elena; Zoccali, Manuela; Poleski, Radosław; Pietrzyński, Grzegorz; Skowron, Jan; Soszyński, Igor; Szymański, Michał K.; Udalski, Andrzej; Ulaczyk, Krzyszto; Wyrzykowski, Łukasz
    We investigate interstellar extinction curve variations towards ∼4 deg2 of the inner Milky Way in VIJKs photometry from the OGLE-III (third phase of the Optical Gravitational Lensing Experiment) and VVV (VISTA Variables in the Via Lactea) surveys, with supporting evidence from diffuse interstellar bands and F435W, F625W photometry. We obtain independent mea surements towards ∼2000 sightlines of AI, E(V − I), E(I − J) and E(J − Ks), with median precision and accuracy of 2 per cent. We find that the variations in the extinction ratios AI/E(V − I), E(I − J)/E(V − I) and E(J − Ks)/E(V − I) are large (exceeding 20 per cent), signifi cant and positively correlated, as expected. However, both the mean values and the trends in these extinction ratios are drastically shifted from the predictions of Cardelli and Fitzpatrick, regardless of how RV is varied. Furthermore, we demonstrate that variations in the shape of the extinction curve have at least two degrees of freedom, and not one (e.g. RV), which we confirm with a principal component analysis. We derive a median value of AV/AKs = 13.44, which is ∼60 per cent higher than the ‘standard’ value. We show that the Wesenheit magnitude WI = I − 1.61(I − J) is relatively impervious to extinction curve variations. Given that these extinction curves are linchpins of observational cosmology, and that it is generally assumed that RV variations correctly capture variations in the extinction curve, we argue that systematic errors in the distance ladder from studies of Type Ia supernovae and Cepheids may have been underestimated. Moreover, the reddening maps from the Planck experiment are shown to systematically overestimate dust extinction by ∼100 per cent and lack sensitivity to extinction curve variations.