Abstract
HP 1 is an α-enhanced and moderately metal-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 1/40.1 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 +0.9-0.8 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 +0.17-0.15 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 1/40.12 and 1/43 kpc, respectively.
| Original language | English |
|---|---|
| Pages (from-to) | 5530-5550 |
| Number of pages | 21 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 484 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 21 Apr 2019 |
| Externally published | Yes |
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Keywords
- Galaxy: bulge
- globular clusters: individual: HP 1
- infrared: stars
- instrumentation: adaptive optics
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
Cite this
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A deep view of a fossil relic in the Galactic bulge : The Globular Cluster HP 1. / Kerber, L. O.; Libralato, M.; Souza, S. O.; Oliveira, R. A.P.; Ortolani, S.; Pérez-Villegas, A.; Barbuy, B.; Dias, B.; Bica, E.; Nardiello, D.
In: Monthly Notices of the Royal Astronomical Society, Vol. 484, No. 4, 21.04.2019, p. 5530-5550.Research output: Contribution to journal › Article
TY - JOUR
T1 - A deep view of a fossil relic in the Galactic bulge
T2 - The Globular Cluster HP 1
AU - Kerber, L. O.
AU - Libralato, M.
AU - Souza, S. O.
AU - Oliveira, R. A.P.
AU - Ortolani, S.
AU - Pérez-Villegas, A.
AU - Barbuy, B.
AU - Dias, B.
AU - Bica, E.
AU - Nardiello, D.
PY - 2019/4/21
Y1 - 2019/4/21
N2 - HP 1 is an α-enhanced and moderately metal-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 1/40.1 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 +0.9-0.8 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 +0.17-0.15 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 1/40.12 and 1/43 kpc, respectively.
AB - HP 1 is an α-enhanced and moderately metal-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 1/40.1 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 +0.9-0.8 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 +0.17-0.15 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 1/40.12 and 1/43 kpc, respectively.
KW - Galaxy: bulge
KW - globular clusters: individual: HP 1
KW - infrared: stars
KW - instrumentation: adaptive optics
UR - http://www.scopus.com/inward/record.url?scp=85062278147&partnerID=8YFLogxK
U2 - 10.1093/mnras/stz003
DO - 10.1093/mnras/stz003
M3 - Article
VL - 484
SP - 5530
EP - 5550
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -