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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

A deep view of a fossil relic in the Galactic bulge: the Globular Cluster HP1

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Kerber, L. O. [1, 2] ; Libralato, M. [3, 4, 5] ; Souza, S. O. [1] ; Oliveira, R. A. P. [1] ; Ortolani, S. [3, 4] ; Perez-Villegas, A. [1] ; Barbuy, B. [1] ; Dias, B. [6, 7] ; Bica, E. [8] ; Nardiello, D. [3, 4]
Total Authors: 10
[1] Univ Sao Paulo, IAG, Rua Matao 1226, BR-05508900 Sao Paulo - Brazil
[2] Univ Estadual Santa Cruz, Rodovia Jorge Amado Km 16, BR-45662000 Ilheus, BA - Brazil
[3] Univ Padua, Dipartimento Fis & Astron, I-35122 Padua - Italy
[4] INAF Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua - Italy
[5] Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 - USA
[6] European Southern Observ, Alonso Cordova 3107, Santiago - Chile
[7] Univ Andres Bello, Fac Ciencias Exactas, Dept Fis, Av Fernandez Concha 700, Santiago - Chile
[8] Univ Fed Rio Grande do Sul, Dept Astron, CP 15051, BR-91501970 Porto Alegre, RS - Brazil
Total Affiliations: 8
Document type: Journal article
Source: Monthly Notices of the Royal Astronomical Society; v. 484, n. 4, p. 5530-5550, APR 2019.
Web of Science Citations: 4

HP 1 is an alpha-enhanced and moderatelymetal-poor bulge globular cluster with a blue horizontal branch. These combined characteristics make it a probable relic of the early star formation in the innermost Galactic regions. Here, we present a detailed analysis of a deep near-infrared (NIR) photometry of HP 1 obtained with the NIR GSAOI + GeMS camera at the Gemini-South telescope. J and K-S images were collected with an exquisite spatial resolution (FWHM similar to 0.1 arcsec), reaching stars at two magnitudes below the MSTO. We combine our GSAOI data with archival F606W-filter HST ACS/WFC images to compute relative proper motions and select bona fide cluster members. Results from statistical isochrone fits in the NIR and optical-NIR colour-magnitude diagrams indicate an age of 12.8(-0.8)(+0.9) Gyr, confirming that HP 1 is one of the oldest clusters in the Milky Way. The same fits also provide apparent distance moduli in the K-S and V filters in very good agreement with the ones from 11 RR Lyrae stars. By subtracting the extinction in each filter, we recover a heliocentric distance of 6.59(-0.15)(+0.17) kpc. Furthermore, we refine the orbit of HP 1 using this accurate distance and update and accurate radial velocities (from high-resolution spectroscopy) and absolute proper motions (from Gaia DR2), reaching mean perigalactic and apogalactic distances of similar to 0.12 and similar to 3 kpc, respectively. (AU)

FAPESP's process: 16/20566-7 - Colour-magnitude diagrams of globular clusters with ultraviolet filters of the Hubble Space Telescope
Grantee:Stefano Oliveira de Souza
Support type: Scholarships in Brazil - Scientific Initiation
FAPESP's process: 17/15893-1 - Globular cluster orbits of bulge: the formation and evolution of the Milky Way
Grantee:Maria de Los Angeles Perez Villegas
Support type: Scholarships in Brazil - Post-Doctorate