Examinando por Autor "Ripepi, V."

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    Ítem
    Inspection of 19 globular cluster candidates in the Galactic bulge with the VVV survey
    (EDP Sciences, 2022-02) Garro, E. R.; Minniti, D.; Gómez, M.; J. Alonso-García; Ripepi, V.; . Fernández-Trincado, J. G; Vivanco Cádiz, F.
    Abstract Context. The census of the globular clusters (GCs) in the Milky Way is still a work in progress. The advent of new deep surveys has made it possible to discover many new star clusters both in the Galactic disk and bulge, but many of these new candidates have not yet been studied in detail, leaving a veil on their true physical nature. Aims. We explore the nature of 19 new GC candidates in the Galactic bulge by analysing their colour-magnitude diagrams (CMDs) in the near-infrared (NIR) using the VISTA Variables in the Via Láctea Survey (VVV) database. We estimate their main astrophysical parameters: reddening and extinction, distance, total luminosity, mean cluster proper motions (PMs), metallicity, and age. Methods. We obtain the cluster catalogues including the likely cluster members by applying a decontamination procedure on the observed CMDs based on the vector PM diagrams from VIRAC2. We adopt NIR reddening maps in order to calculate the reddening and extinction for each cluster, and then estimate the distance moduli and heliocentric distances. Metallicities and ages are evaluated by fitting theoretical stellar isochrones. We also calculate their luminosities in comparison with known Galactic GCs. Results. We estimate a wide reddening range of 0.25 ≤ E(J - Ks)≤2.0 mag and extinction 0.11 ≤ AKs ≤ 0.86 mag for the sample clusters, as expected in the bulge regions. The range of heliocentric distances is 6.8 ≤ D ≤ 11.4 kpc. This allows us to place these clusters between 0.56 and 3.25 kpc from the Galactic centre, assuming R⊙ = 8.2 kpc. Also, their PMs are kinematically similar to the typical motion of the Galactic bulge, apart from VVV-CL160, which shows different PMs. We also derive their metallicities and ages, finding -1.40≤ [Fe/H] ≤ 0.0 dex and t ≈ 8 - 13 Gyr respectively. The luminosities are calculated both in Ks- and V-bands, recovering -3.4 ≤ MV ≤ -7.5. We also examine the possible RR Lyrae members found in the cluster fields. Conclusions. Based on their positions, kinematics, metallicities, and ages, and comparing our results with the literature, we conclude that nine candidates are real GCs, seven need more observations to be fully confirmed as GCs, and three candidates are discarded as GCs and appear to be younger open clusters. © ESO 2022.
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    Ítem
    Unveiling the nature of 12 new low-luminosity Galactic globular cluster candidates
    (EDP Sciences, 2022-03-01) Garro, E.R.; Minniti, D.; Alessi, B.; Patchick, D.; Kronberger, M.; Alonso-García, J.; Fernández-Trincado, J.G.; Gómez, M.; Hempel, M.; Pullen, J.B.; Saito, R.K.; Ripepi, V.; Zelada Bacigalupo, R.
    Context. The Galactic globular cluster system is incompletely known, especially in the low-latitude regions of the Galactic bulge and disk. We report the physical characterisation of 12 star clusters in the Milky Way, most of which are explored here for the first time. Aims. Our primary aim is determining their main physical parameters, such as reddening, extinction, metallicity, age, total luminosity, mean cluster proper motions (PMs), and distances, in order to reveal the physical nature of these clusters. Methods. We study the clusters using optical and near-infrared (NIR) datasets. In particular, we use the Gaia Early Data Release 3 (EDR3) PMs in order to perform a PM decontamination procedure and build final catalogues with probable members. We match the Gaia EDR3 with the VISTA Variables in the Vía Láctea extended (VVVX) survey and the Two Micron All-Sky survey (2MASS) in the NIR, in order to construct complete NIR and optical colour-magnitude diagrams (CMDs) and investigate the clusters properties. Results. The extinctions are evaluated using existing reddening maps. We find ranges spanning 0:09. AKs. 0:86 mag and 0:89. AG. 4:72 mag in the NIR and optical, respectively. Adopting standard intrinsic red clump (RC) magnitudes and extinction values, we first obtain the distance modulus for each cluster and thereafter their heliocentric distances, which range from about 4 to 20 kpc. Therefore, we are able to place these clusters at 3. RG. 14 kpc from the Galactic centre. The best PARSEC isochrone fit yields a metallicity range of-1:8 < [Fe/H] < +0:3 and an approximate age range of 2 < age < 14 Gyr. Finally, we find that all clusters have low luminosities, with-6:9 < MV <-3:5 mag. Conclusions. Based on our photometric analysis, we find both open clusters (OCs) and globular clusters (GCs) in our sample. In particular, we confirm the OC nature for Kronberger 100, while we classify Patchick 125 as a metal-poor GC, Ferrero 54 as a metalrich GC, and ESO 92-18 as a possible old OC or young GC. The classification as GC candidates is also suggested for Kronberger 99, Patchick 122, Patchick 126, Riddle 15, FSR 190, and Gaia 2. We also conclude that Kronberger 119 and Kronberger 143 might be either old OCs or young GCs. © ESO 2022.