AGE DETERMINATION OF SIX INTERMEDIATE-AGE SMALL MAGELLANIC CLOUD STAR CLUSTERS WITH HST/ACS

By K. Glatt, E. Grebel, E. Sabbi, J. S. Gallagher, A. Nota, M. Sirianni, Gisella Clementini, M. Tosi, D. Harbeck, Andreas Koch and 2 more. 2008

173 citations recorded by the source corpus.

We present a photometric analysis of the star clusters Lindsay 1, Kron 3, NGC 339, NGC 416, Lindsay 38, and NGC 419 in the Small Magellanic Cloud (SMC), observed with the Hubble Space Telescope Advanced Camera for Surveys (ACS) in the F555W and F814W filters. Our color-magnitude diagrams (CMDs) extend ∼3.5 mag deeper than the main-sequence turnoff points, deeper than any previous data. Cluster ages were derived using three different isochrone models: Padova, Teramo, and Dartmouth, which are all available in the ACS photometric system. Fitting observed ridgelines for each cluster, we provide a homogeneous and unique set of low-metallicity, single-age fiducial isochrones. The cluster CMDs are best approximated by the Dartmouth isochrones for all clusters, except for NGC 419 where the Padova isochrones provided the best fit. Using Dartmouth isochrones we derive ages of 7.5 ± 0.5 Gyr (Lindsay 1), 6.5 ± 0.5 Gyr (Kron 3), 6 ± 0.5 Gyr (NGC 339), 6 ± 0.5 Gyr (NGC 416), and 6.5 ± 0.5 Gyr (Lindsay 38). The CMD of NGC 419 shows several main-sequence turnoffs, which belong to the cluster and to the SMC field. We thus derive an age range of 1.2–1.6 Gyr for NGC 419. We confirm that the SMC contains several intermediate-age populous star clusters with ages unlike those of the Large Magellanic Cloud and the Milky Way. Interestingly, our intermediate-age star clusters have a metallicity spread of ∼0.6 dex, which demonstrates that the SMC does not have a smooth, monotonic age-metallicity relation. We find an indication for centrally-concentrated blue straggler star candidates in NGC 416, while these are not present for the other clusters. Using the red clump magnitudes, we find that the closest cluster, NGC 419 (∼50 kpc), and the farthest cluster, Lindsay 38 (∼67 kpc), have a relative distance of ∼17 kpc, which confirms the large depth of the SMC. The three oldest SMC clusters (NGC 121, Lindsay 1, and Kron 3) lie in the northwestern part of the SMC, while the youngest (NGC 419) is located near the SMC main body.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3f040e588df0288072f673be4201a5640f4a4935

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In Astronomy and Astrophysics

1. Jay Anderson
2. Aaron Dotter
3. G. Piotto
4. A. Milone
5. L. Bedin
6. S. Majewski
7. A. Sarajedini
8. A. Aparicio

In Instrumentation

1. Jay Anderson
2. Aaron Dotter
3. S. Majewski
4. G. Piotto
5. L. Bedin
6. A. Milone
7. E. Carretta
8. A. Bragaglia

Citations in the corpus

• NEW OPTICAL REDDENING MAPS OF THE LARGE AND SMALL MAGELLANIC CLOUDS (2011, methodology): “The metallicities of the intermediate age populations show a considerable spread at any given age (Glatt et al. 2008a).”
• Multiple populations in globular clusters (2012, background): “However, the first clear indications of multiple population in Magellanic Cloud globular clusters came again from HST photometry, see e.g., Mackey & Broby Nielsen (2007); Milone et al. (2008); Glatt et al. (2008); and Goudfrooij et al. (2011).”
• THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. IX. HORIZONTAL BRANCH MORPHOLOGY AND THE SECOND PARAMETER PHENOMENON (2009, background): “…the present study is focused on the Galactic GCs, including some of those associated with the Sagittarius dwarf, there is ample evidence to suggest that metal-poor GCs with red HBs are also found in the Magellanic Clouds (Johnson et al. 1999; Glatt et al. 2008) and Fornax (Buonanno et al. 1999).”
• Multiple stellar populations in Magellanic Cloud clusters - I. An ordinary feature for intermediate age globulars in the LMC? (2008, methodology): “…electronic form at http://www.aanda.org and NGC 6388 (Piotto 2008), also in some intermediate-age Large Magellanic Cloud (LMC) clusters (Bertelli et al. 2003; Mackey & Broby Nielsen 2007 [M07]; Mackey et al. 2008 [M08]) and in the Small Magellanic Cloud (SMC) cluster NGC 419 (Glatt et al. 2008a).”
• Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud (2019, unknown): “In the SMC, the revised cluster ages by Glatt et al. (2008) indicate that the youngest such cluster is the ∼1.5-Gyr old NGC 419, with its impressive population of 10 C-stars.”
• Accreted versus in situ Milky Way globular clusters (2010, methodology): “7 SMC open and globular clusters from the ACS study by Glatt et al. (2008).”
• CLUSTERING OF LOCAL GROUP DISTANCES: PUBLICATION BIAS OR CORRELATED MEASUREMENTS? III. THE SMALL MAGELLANIC CLOUD (2014, methodology): “…out by these authors, the distances based on the Schlegel et al. (1998) extinction estimates are systematically shorter; a comparison between the Glatt et al. (2008c) distances and the Crowl et al. (2001) values using Burstein & Heiles (1982) extinction estimates shows that the Crowl et al.…”
• A NEW GENERATION OF PARSEC-COLIBRI STELLAR ISOCHRONES INCLUDING THE TP-AGB PHASE (2017, background): “The most prominent features in these diagrams, in addition to the tip of the RGB (TRGB) at −6.5, are: • the well-populated and diagonal sequence of O-rich AGB stars extending from the TRGB up to MKs and at J−Ks < 1.3, which is well matched by the isochrones with t > 1 Gyr; • an upward, less-populate”
• The bifurcated age–metallicity relation of Milky Way globular clusters and its implications for the accretion history of the galaxy (2013, background): “…mass of ∼ 5×107M , has only one old GC, while the LMC and SMC, and particularly Sagittarius are known to have extended cluster AMRs of 3 Gyrs or more (Glatt et al. 2008; Law & Majewski 2010; 10 The notable exception is Ruprecht 106 at [Fe/H]= −1.78 and 10.75 Gyr in this plot, however as discussed…”
• The Effect of Stellar Rotation on Colour-Magnitude Diagrams: On the apparent presence of multiple populations in intermediate age stellar clusters (2009, background): “Of particular interest has been the discovery that intermediate age (1-2 Gyr) clusters in the Magellanic Clouds often have bi- or multi-modal distributions in their main-sequence turn-off (Mackey & Broby Nielsen 2007; Mackey et al. 2008; Glatt et al. 2008; Milone et al. 2009).”
• GLOBULAR CLUSTERS IN THE OUTER GALACTIC HALO: NEW HUBBLE SPACE TELESCOPE/ADVANCED CAMERA FOR SURVEYS IMAGING OF SIX GLOBULAR CLUSTERS AND THE GALACTIC GLOBULAR CLUSTER AGE–METALLICITY RELATION (2011, background): “Turn the clock back ∼ 2 Gyr and the HB morphology-metallicity diagram would have been populated only on the red side—as, for example, in the SMC (Glatt et al. 2008).”