Structural Parameters of Seven Small Magellanic Cloud Intermediate-Age and Old Star Clusters

Glatt, K.; Grebel, Eva K.; Gallagher, John S.; Nota, A.; Sabbi, E.; Sirianni, M.; Clementini, G.; Costa, G. S. Da; Tosi, M.; Harbeck, D.; Koch, Andreas; Kayser, Andrea

doi:10.1088/0004-6256/138/5/1403

Cited by 61 publications

(67 citation statements)

References 73 publications

(167 reference statements)

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“…The cluster disruption time for the SMC and the LMC derived in the literature is on the order of 8 × 10 9 Myr (e.g., Boutloukos & Lamers 2003;Parmentier & de Grijs 2008). We have shown (Glatt et al 2009) that clusters with ages older than 1 Gyr have a trend to larger core radii with increasing age. This trend was first found by Mackey & Gilmore (2003a) and is also visible for LMC, Fornax, and Sagittarius clusters (Mackey & Gilmore 2003b,c).…”

Section: Dissolution Effectsmentioning

confidence: 59%

Ages and luminosities of young SMC/LMC star clusters and the recent star formation history of the Clouds

Glatt

Grebel

Koch

2010

A&A

166

213

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Aims. In this paper we discuss the age and spatial distribution of young (age < 1 Gyr) Small Magellanic Cloud (SMC) and Large Magellanic Cloud (LMC) clusters using data from the Magellanic Cloud Photometric Surveys. Luminosities are calculated for all age-dated clusters. Methods. The ages of 324 and 1193 populous star clusters in the SMC and the LMC were determined fitting Padova and Geneva isochrone models to their resolved color-magnitude diagrams. The clusters cover an age range between 10 Myr and 1 Gyr in each galaxy. For the SMC, a constant distance modulus of (m − M) 0 = 18.90 and a metallicity of Z = 0.004 were adopted. For the LMC, we used a constant distance modulus of (m − M) 0 = 18.50 and a metallicity of Z = 0.008. For both galaxies, we used a variable color excess to derive the cluster ages. Results. We find two periods of enhanced cluster formation in both galaxies at 160 Myr and 630 Myr (SMC) and at 125 Myr and 800 Myr (LMC). We present the spatially resolved recent star formation history of both Clouds based on young star clusters. The first peak may have been triggered by a close encounter between the SMC and the LMC. In both galaxies, the youngest clusters reside in the supergiant shells, giant shells, the intershell regions, and toward regions with a high Hα content, suggesting that their formation is related to expansion and shell-shell interaction. Most of the clusters are older than the dynamical age of the supergiant shells. No evidence of cluster dissolution was found. Computed V band luminosities show a trend toward fainter magnitudes with increasing age, as well as a trend toward brighter magnitudes with increasing apparent cluster radii.

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Section: Dissolution Effectsmentioning

confidence: 59%

Ages and luminosities of young SMC/LMC star clusters and the recent star formation history of the Clouds

Glatt

Grebel

Koch

2010

A&A

166

213

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“…However, given the relatively weak tidal fields in the LMC/SMC, and the fact the intermediate age (and older) clusters do not appear to be tidally limited (e.g., Glatt et al 2009), it is more likely that the intermediate age clusters have not undergone strong mass loss, hence their current masses and escape velocities are similar to their initial values. In this interpretation, we see that there is no relation between the mass or escape velocity of clusters that do or do not display the extended MSTO feature (i.e.…”

Section: Comparison With the Intermediate Age Clustersmentioning

confidence: 99%

No evidence for significant age spreads in young massive LMC clusters

Niederhofer

Hilker

Bastian

et al. 2015

A&A

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Recent discoveries have put the picture of stellar clusters being simple stellar populations into question. In particular, the colormagnitude diagrams of intermediate age (1-2 Gyr) massive clusters in the Large Magellanic Cloud (LMC) show features that could be interpreted as age spreads of 100-500 Myr. If multiple generations of stars are present in these clusters then, as a consequence, young (<1 Gyr) clusters with similar properties should have age spreads of the same order. In this paper we use archival Hubble Space Telescope (HST) data of eight young massive LMC clusters (NGC 1831, NGC 1847, NGC 1850, NGC 2004, NGC 2100, NGC 2136, NGC 2157 and NGC 2249 to test this hypothesis. We analyzed the color-magnitude diagrams of these clusters and fitted their star formation history to derive upper limits of potential age spreads. We find that none of the clusters analyzed in this work shows evidence for an extended star formation history that would be consistent with the age spreads proposed for intermediate age LMC clusters. Tests with artificial single age clusters show that the fitted age dispersion of the youngest clusters is consistent with spreads that are purely induced by photometric errors. As an additional result we determined a new age of NGC 1850 of ∼100 Myr, significantly higher than the commonly used value of about 30 Myr, although consistent with early HST estimates.

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“…Our rc estimate is in good agreement with the value of rc = 15. 26 found by Glatt et al (2009) by fitting a King profile to the number density profiles. Our estimate for the tidal radius is however significantly smaller than the value published in Glatt et al (2009), rt = 165 .…”

Section: Structural Profilesmentioning

confidence: 99%

“…26 found by Glatt et al (2009) by fitting a King profile to the number density profiles. Our estimate for the tidal radius is however significantly smaller than the value published in Glatt et al (2009), rt = 165 . This discrepancy is not surprising given that the size of the cluster exceeds the observed field.…”

Section: Structural Profilesmentioning

confidence: 99%

The search for multiple populations in Magellanic Cloud clusters – I. Two stellar populations in the Small Magellanic Cloud globular cluster NGC 121

Niederhofer¹,

Bastian²,

Kozhurina-Platais³

et al. 2016

Mon. Not. R. Astron. Soc.

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We started a photometric survey using the WFC3/UVIS instrument onboard the Hubble Space Telescope to search for multiple populations within Magellanic Cloud star clusters at various ages. In this paper, we introduce this survey. As first results of this programme, we also present multi-band photometric observations of NGC 121 in different filters taken with the WFC3/UVIS and ACS/WFC instruments. We analyze the colour-magnitude diagram (CMD) of NGC 121, which is the only "classical" globular cluster within the Small Magellanic Cloud. Thereby, we use the pseudo-colour C F 336W,F 438W,F 343N = (F 336W − F 438W ) − (F 438W − F 343N ) to separate populations with different C and N abundances. We show that the red giant branch splits up in two distinct populations when using this colour combination. NGC 121 thus appears to be similar to Galactic globular clusters in hosting multiple populations. The fraction of enriched stars (N rich, C poor) in NGC 121 is about 32%±3%, which is lower than the median fraction found in Milky Way globular clusters. The enriched population seems to be more centrally concentrated compared to the primordial one. These results are consistent with the recent results by Dalessandro et al. (2016). The morphology of the Horizontal Branch in a CMD using the optical filters F 555W and F 814W is best produced by a population with a spread in Helium of ∆Y =0.025±0.005.

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Structural Parameters of Seven Small Magellanic Cloud Intermediate-Age and Old Star Clusters

Cited by 61 publications

References 73 publications

Ages and luminosities of young SMC/LMC star clusters and the recent star formation history of the Clouds

Ages and luminosities of young SMC/LMC star clusters and the recent star formation history of the Clouds

No evidence for significant age spreads in young massive LMC clusters

The search for multiple populations in Magellanic Cloud clusters – I. Two stellar populations in the Small Magellanic Cloud globular cluster NGC 121

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