The VMC survey – XVI. Spatial variation of the cluster formation activity in the innermost regions of the Large Magellanic Cloud

Abstract

We present results based on Y JK s photometry of star clusters in the Large Magellanic Cloud (LMC), distributed throughout the central part of the galaxy's bar and the 30 Doradus region. We analysed the field-star decontaminated colour-magnitude diagrams of 313 clusters to estimate their reddening values and ages. The clusters are affected by a mean reddening of E(B − V ) ∈ [0.2, 0.3] mag, where the average internal LMC reddening amounts to ∼ 0.1-0.2 mag. The region covering 30 Doradus includes clusters with reddening values in excess of E(B − V ) = 0.4 mag. Our cluster sample spans the age range 7.0 log(t yr −1 ) < 9.0, represents an increase of 30 per cent in terms of the number of clusters with robust age estimates and comprises a statistically complete sample in the LMC regions of interest here. The resulting cluster frequencies suggest that the outermost regions of the LMC bar first experienced enhanced cluster formation -log(t yr −1 ) ∈ [8.5, 9.0] -before the activity proceeded, although in a patchy manner, to the innermost regions, for log(t yr −1 ) < 7.7. Cluster frequencies in the 30 Doradus region show that the area is dominated by very recent cluster formation. The derived star-formation frequencies suggest that the cluster and field-star populations do not seem to have fully evolved as fully coupled systems during the last ∼ 100 Myr.

Three candidate double clusters in the LMC: truth or dare?

“…The position of these stars and the extension of the main sequence can be nicely fit by models with t = 240 ± 15 Myr. This estimate is compatible with that obtained by Piatti et al (2015). SL387 appears to be older than SL385.…”

“…Isochrones nicely reproduce the main sequence shape as well as the MSTO and blue-loop star luminosity, which represents a stringent constraint to the overall fit. These ages are larger than what obtained by Dieball et al (2000) who find t = 550 ± 110 Myr for both systems based on very shallow CMDs that do not reach the cluster MSTOs, and by Piatti et al (2015) who estimates t = 500 for SL349 by using VISTA near-IR observations. On the contrary, they are broadly compatible with results obtained by Bica et al (1996), who classified both clusters in category V, i.e.…”

Star clusters in the Magellanic Clouds – I. Parametrization and classification of 1072 clusters in the LMC

“…On the other hand, Piatti et al ( , 2015 used near-IR data from the VMC survey and hence a direct comparison is difficult. Piatti et al ( , 2015 used the metallicity Z=0.006 and isochrones from Bressan et al (2012). They also mention that the ages are not sensitive to the adopted metallicity.…”

“…The plots show the comparison of estimated age with previous age estimation. The previous studies used to compare our age estimation are that of G10 (Fig.a),PU00 (Fig.b), Piatti et al ( , 2015 (Fig.c) and Palma et al (2016) (Fig.4). Different point types are used for different group of clusters as mention in the Fig.a.…”

Astrophysical properties of star clusters in the Magellanic Clouds homogeneously estimated by ASteCA

“…The large number of cataloged clusters, ∼4000 are listed in the Bica et al (2008) catalog, makes them an invaluable resource for investigating the properties of the two most massive galaxies that orbit the Milky Way. The reddening that affects the MCs is relatively small, except for a few regions, such as 30 Doradus in the LMC, where E B−V can reach values above 0.4 mag (Piatti et al 2015a). The overall low levels of reddening simplifies the research of the clusters in these two galaxies.…”