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

Autor(es)

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]}

Afiliação do(s) autor(es)

^[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

• Tipo de documento: Artigo Científico
• Fonte: Monthly Notices of the Royal Astronomical Society; v. 484, n. 4, p. 5530-5550, APR 2019.
• Citações Web of Science: 4

Resumo

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)

• Processo FAPESP: 17/15893-1 - Órbitas de aglomerados globulares do bojo: formação e evolução da Via Láctea
• Beneficiário: Maria de Los Angeles Perez Villegas
• Linha de fomento: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 16/20566-7 - Diagramas cor-magnitude de aglomerados globulares com filtros ultravioleta do Telescópio Espacial Hubble
• Beneficiário: Stefano Oliveira de Souza
• Linha de fomento: Bolsas no Brasil - Iniciação Científica