A new identity card for the bulge globular cluster NGC 6440 from resolved star counts

Abstract

We present a new identity card for the cluster NGC 6440 in the Galactic Bulge. We have used a combination of high-resolution Hubble Space Telescope images, wide-field ground-based observations performed with the ESO-FORS2, and the public survey catalog Pan-STARRS, to determine the gravitational center, projected density profile and structural parameters of this globular from resolved star counts. The new determination of the cluster center differs by ~ 2" (corresponding to 0.08 pc) from the previous estimate, which was based on the surface brightness peak. The star density profile, extending out to 700" from the center and suitably decontaminated from the Galactic field contribution, is best-fitted by a King model with significantly larger concentration ($c=1.86\pm 0.06$) and smaller core radius ($r_c=6.4"\pm 0.3"$) with respect to the literature values. By taking advantage of high-quality optical and near-infrared color-magnitude diagrams, we also estimated the cluster age, distance and reddening. The luminosity of the RGB-bump was also determined. This study indicates that the extinction coefficient in the bulge, in the direction of the cluster has a value ($R_V=2.7$) that is significantly smaller than that traditionally used for the Galaxy ($R_V=3.1$). The corresponding best-fit values of the age, distance and color excess of NGC 6440 are 13 Gyr, 8.3 kpc and $E(B-V)\sim 1.27$, respectively. These new determinations also allowed us to update the values of the central ($t_{rc}=2.510^7$ yr) and half-mass ($t_{rh}=10^9$ yr) relaxation times, suggesting that NGC 6440 is in a dynamically evolved stage.

Accepted for publication in The Astrophysical Journal; 19 pages, 9 figures and 2 tables

References in corpus (28)

• The Gaia mission
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The Dartmouth Stellar Evolution Database
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• Dynamical age differences among coeval star clusters as revealed by blue stragglers
• Surface Brightness Profiles of Galactic Globular Clusters from Hubble Space Telescope Images
• Ceci n'est pas a globular cluster: the metallicity distribution of the stellar system Terzan 5
• Extinction ratios in the inner Galaxy as revealed by the VVV survey
• The age of the young bulge-like population in the stellar system Terzan5: linking the Galactic bulge to the high-z Universe
• The surface density profile of NGC 6388: a good candidate for harboring an intermediate-mass black hole
• Investigating mass segregation process in globular clusters with Blue Straggler Stars: the impact of dark remnants
• A Panchromatic Study of the Globular Cluster NGC 1904. I: The Blue Straggler Population
• The Blue Straggler Population of the Globular Cluster M5
• High resolution infrared spectra of NGC 6440 and NGC 6441: two massive Bulge Globular Clusters
• A Deep View of a Fossil Relic in the Galactic Bulge: The Globular Cluster HP1
• A new class of fossil fragments from the hierarchical assembly of the Galactic bulge
• A panchromatic view of the bulge globular cluster NGC 6569
• Radio timing and optical photometry of the black widow system PSR J1518+0204C in the globular cluster M5
• Ultra-deep GEMINI near-infrared observations of the bulge globular cluster NGC 6624
• The "dynamical clock": dating the internal dynamical evolution of star clusters with Blue Straggler Stars
• Digging for relics of the past: the ancient and obscured bulge globular cluster NGC6256
• Star density profiles of six old star clusters in the Large Magellanic Cloud
• Discovery of a double Blue Straggler sequence in M15: new insight into the core-collapse process
• The VISCACHA survey -- II. Structure of star clusters in the Magellanic Clouds periphery
• The Optical Counterpart to the Accreting Millisecond X-ray Pulsar SAX J1748.9-2021 in the Globular Cluster NGC 6440
• Probing the Galactic Bulge with deep Adaptive Optics imaging: the age of NGC 6440
• A complete census of $H\alpha$ emitters in NGC 6397

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• Unveiling the nature of 12 new low-luminosity Galactic Globular Cluster Candidates
• Empirical measurement of the dynamical ages of three globular clusters and some considerations on the use of the dynamical clock
• Discoveries and Timing of Pulsars in NGC 6440
• Chrono-chemodynamical analysis of the globular cluster NGC 6355: Looking for the fundamental bricks of the Bulge
• Internal kinematics and structure of the bulge globular cluster NGC 6569
• The ESO-VLT MIKiS survey reloaded: exploring the internal kinematics of NGC 6440
• A Photometric in-depth look at the core-collapsed globular cluster NGC 6284
• The Bulge Cluster Origin (BulCO) survey at the ESO-VLT: probing the early history of the Milky Way assembling. Design and first results in Liller1
• On the manifest link between Terzan 5 and the Galactic bulge
• Revisited parameters for the twin bulge globular clusters NGC 6528 and NGC 6553
• The multi-age stellar populations of Terzan 5 as revealed by JWST
• Photo-chemo-dynamical analysis and the origin of the bulge globular cluster Palomar 6
• The ESO-VLT MIKiS survey reloaded: velocity dispersion profile and rotation curve of NGC 1904
• Revealing the stellar population of the ultra-obscured Galactic globular cluster Glimpse-C02