A photometric in-depth look at the core-collapsed globular cluster NGC 6284

Deras, Dan; Cadelano, Mario; Lanzoni, Barbara; Ferraro, Francesco R.; Pallanca, Cristina; Dalessandro, Emanuele; Mucciarelli, Alessio

doi:10.1051/0004-6361/202347547

Cited by 4 publications

(1 citation statement)

References 103 publications

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“…We have performed the data reduction using the software DAOPHOT II (Stetson 1987), following the recipes described in detail in Cadelano et al (2020b,c); Deras et al (2023Deras et al ( , 2024. We selected about 200 bright, well-distributed, and isolated stars in order to model a spatially varying point spread function (PSF) for each image.…”

Section: Data Set and Data Reductionmentioning

confidence: 99%

An Ongoing Tidal Capture in the Large Magellanic Cloud: The Low-mass Star Cluster KMK 88-10 Captured by the Massive Globular Cluster NGC 1835?*

Giusti,

Cadelano,

Ferraro

et al. 2023

ApJ

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In the context of a project aimed at characterizing the dynamical evolution of old globular clusters in the Large Magellanic Cloud, we have secured deep HST/WFC3 images of the massive cluster NGC 1835. In the field of view of the acquired images, at a projected angular separation of approximately 2′ from the cluster, we detected the small stellar system KMK 88-10. The observations provided the deepest color–magnitude diagram ever obtained for this cluster, revealing that it hosts a young stellar population with an age of 600–1000 Myr. The cluster surface brightness profile is nicely reproduced by a King model with a core radius r c = 4″ (0.97 pc), a half-mass radius r hm = 12″ (2.9 pc), and a concentration parameter c ∼ 1.3 corresponding to a truncation radius r t ∼ 81″ (19.5 pc). We also derived its integrated absolute magnitude (M V = −0.71) and total mass (M ∼ 80–160 M ⊙). The most intriguing feature emerging from this analysis is that KMK 88-10 presents a structure elongated in the direction of NGC 1835, with an intracluster overdensity that suggests the presence of a tidal bridge between the two systems. If confirmed, this would be the first evidence of a tidal capture of a small star cluster by a massive globular.

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Section: Data Set and Data Reductionmentioning

confidence: 99%

An Ongoing Tidal Capture in the Large Magellanic Cloud: The Low-mass Star Cluster KMK 88-10 Captured by the Massive Globular Cluster NGC 1835?*

Giusti,

Cadelano,

Ferraro

et al. 2023

ApJ

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Discovery of an extended horizontal branch in the Large Magellanic Cloud globular cluster NGC 1835

Giusti,

Cadelano,

Ferraro

et al. 2024

A&A

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We present a high-angular-resolution multi-wavelength study of the massive globular cluster NGC 1835 in the Large Magellanic Cloud. Thanks to a combination of optical and near-ultraviolet images acquired with the WFC3 on board the HST, we performed a detailed inspection of the stellar population in this stellar system, adopting a `UV-guided search' to optimize the detection of relatively hot stars. This allowed us to discover a remarkably extended horizontal branch (HB): it spans more than 4.5 magnitudes in both the optical and the near-ultraviolet bands, and its colour (temperature) ranges from the region redder than the instability strip up to effective temperatures of 30,000 K. This is the first time that such a feature has been detected in an extragalactic cluster, demonstrating that the physical conditions responsible for the formation of extended HBs are ubiquitous. The HB of NGC 1835 includes a remarkably large population of RR Lyrae (67 confirmed variables and 52 new candidates). The acquired dataset was also used to redetermine the cluster distance modulus, reddening, and absolute age: $(m-M)_0=18.58$, $E(B-V)=0.08$, and $t=12.5$ Gyr.

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Determining the dynamical age of the LMC globular cluster NGC 1835 using the ‘dynamical clock’

Giusti,

Cadelano,

Ferraro

et al. 2024

A&A

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In the context of the study of the size--age relationship observed in star clusters in the Large Magellanic Cloud (LMC) and the investigation of its origin, we present the determination of the structural parameters and the dynamical age of the massive cluster NGC 1835. We used the powerful combination of optical and near-ultraviolet images acquired with the WFC3 on board the HST to construct the star density profile from resolved star counts, determining the values of the core, half-mass, and tidal radii through comparison with the King model family. The same data also allowed us to evaluate the dynamical age of the cluster by using the `dynamical clock'. This is an empirical method that quantifies the level of the central segregation of blue stragglers stars (BSSs) within the cluster half-mass radius by means of the $A^+_ rh $ parameter, which is defined as the area enclosed between the cumulative radial distribution of BSSs and that of a reference (lighter) population. The results confirm that NGC 1835 is a very compact cluster with a core radius of only 0.84 pc. The estimated value of $A^+_ rh 0.04$) is the largest measured so far in the LMC clusters, providing evidence of a highly dynamically evolved stellar system. NGC 1835 fits nicely into the correlation between rh $ and the central relaxation time and in the anti-correlation between $A^+_ rh $ and the core radius defined by the Galactic and Magellanic Cloud clusters investigated to date.

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A photometric in-depth look at the core-collapsed globular cluster NGC 6284

Cited by 4 publications

References 103 publications

An Ongoing Tidal Capture in the Large Magellanic Cloud: The Low-mass Star Cluster KMK 88-10 Captured by the Massive Globular Cluster NGC 1835?*

An Ongoing Tidal Capture in the Large Magellanic Cloud: The Low-mass Star Cluster KMK 88-10 Captured by the Massive Globular Cluster NGC 1835?*

Discovery of an extended horizontal branch in the Large Magellanic Cloud globular cluster NGC 1835

Determining the dynamical age of the LMC globular cluster NGC 1835 using the ‘dynamical clock’

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