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

Nayak, Prasanta K.; Subramaniam, Annapurni; Choudhury, Sagnik Ray; Indu, G.; Sagar, Ram

doi:10.1093/mnras/stw2043

Cited by 25 publications

(37 citation statements)

References 44 publications

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“…In general, we find our reddening map is in excellent agreement with the recent reddening studies in the optical region except that of the Nayak et al (2016). The histograms shown in Figure 10 also provide opportunity to examine the difference in the reddening estimates traced through different stellar populations.…”

Section: The Reddening E(v − I) Values In the Lmc Is Estimated Bysupporting

confidence: 89%

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

Joshi

Panchal

2019

A&A

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Context. The reddening maps of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) are constructed using the Cepheid Period-Luminosity (P-L) relations. Aims. We examine reddening distribution across the LMC and SMC through largest data on Classical Cepheids provided by the OGLE Phase IV survey. We also investigate the age and spatio-temporal distributions of Cepheids to understand the recent star formation history in the LMC and SMC. Methods. The V and I band photometric data of 2476 fundamental mode (FU) and 1775 first overtone mode (FO) Cepheids in the LMC and 2753 FU and 1793 FO Cepheids in the SMC are analyzed for their P-L relations. We convert period of FO Cepheids to corresponding period of FU Cepheids before combining the two modes of Cepheids. Both galaxies are divided into small segments and combined FU and FO P-L diagrams are drawn in two bands for each segment. The reddening analysis is performed on 133 segments covering a total area of about 154.6 deg 2 in the LMC and 136 segments covering a total area of about 31.3 deg 2 in the SMC. By comparing with well calibrated P-L relations of these two galaxies, we determine reddening E(V − I) in each segment and equivalent reddening E(B − V) assuming the normal extinction law. The period-age relations are used to derive the age of the Cepheids.Results. Using reddening values in different segments across the LMC and SMC, reddening maps are constructed. We find clumpy structures in the reddening distributions of the LMC and SMC. From the reddening map of the LMC, highest reddening of E(V − I) = 0.466 mag is traced in the region centered at α ∼ 85 o .13, δ ∼ −69 o .34 which is in close vicinity of the star forming HII region 30 Doradus. In the SMC, maximum reddening of E(V − I) = 0.189 mag is detected in the region centered at α ∼ 12 o .10, δ ∼ −73 o .07. The mean reddening values in the LMC and SMC are estimated as E(V − I) LMC = 0.113 ± 0.060 mag, E(B − V) LMC = 0.091 ± 0.050 mag, E(V − I) S MC = 0.049 ± 0.070 mag, and E(B − V) S MC = 0.038 ± 0.053 mag.Conclusions. The LMC reddening map displays heterogeneous distribution having small reddening in the central region and higher reddening towards eastern side of the LMC bar. The SMC have relatively small reddening in peripheral regions but larger reddening towards south-west region. In these galaxies, we see an evidence of a common enhanced Cepheid population at around 200 Myr ago which appears to have occurred due to close encounter between the two clouds.

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Section: The Reddening E(v − I) Values In the Lmc Is Estimated Bysupporting

confidence: 89%

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

Joshi

Panchal

2019

A&A

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“…Unfortunately, specific ages of individual clusters are not provided by Bica et al (2008). Nayak et al (2016) measured the ages of Bica et al (2008) clusters around the bar and showed that most of them are younger than < 250 Myr. If we exclude these younger clusters, the spatial correlation between the overdensity and the rest of Bica et al (2008) clusters becomes more clear.…”

Section: Stellar Overdensity In the Lmc Diskmentioning

confidence: 99%

“…The red dots are all star clusters from theBica et al (2008) catalog, ranging in age between a few Myr to 4 Gyr without specific ages for individual clusters. The blue dots are the clusters with ages available fromNayak et al (2016). Most of them are young (< 250 Myr) star clusters overlapping with the star-forming bar.…”

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confidence: 99%

SMASHing the LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk

Choi

Nidever

Olsen

et al. 2018

ApJ

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We explore the stellar structure of the Large Magellanic Cloud (LMC) disk using data from the Survey of the MAgellanic Stellar History (SMASH) and the Dark Energy Survey. We detect a ringlike stellar overdensity in the red clump star count map at a radius of ∼6 • (∼5.2 kpc at the LMC distance) that is continuous over ∼270 • in position angle and is only limited by the current data coverage. The overdensity shows an amplitude up to 2.5 times higher than that of the underlying smooth disk. This structure might be related to the multiple arms found by de Vaucouleurs. We find that the overdensity shows spatial correlation with intermediate-age star clusters, but not with young (< 1 Gyr) main-sequence stars, indicating the stellar populations associated with the overdensity are intermediate in age or older. Our findings on the LMC overdensity can be explained by either of two distinct formation mechanisms of a ring-like overdensity: (1) the overdensity formed out of an asymmetric one-armed spiral wrapping around the LMC main body, which is induced by repeated encounters with the Small Magellanic Cloud (SMC) over the last Gyr, or (2) the overdensity formed very recently as a tidal response to a direct collision with the SMC. Although the measured properties of the overdensity alone cannot distinguish between the two candidate scenarios, the consistency with both scenarios suggests that the ring-like overdensity is likely a product of tidal interaction with the SMC, but not with the Milky Way halo.

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“…The region of interest is a box where the density of stars is counted and compared to the local background density, which is estimated over a much larger box, whose size is not critical as long as it samples the local background density well. After accurate testing, we observed that the ideal size of the region-of-interest is approximately that of a cluster at the distance of the LMC (∼60 arcsec in diameter; Nayak et al 2016), since it minimizes the detection of false associations.…”

Section: Implementing the Detection Sequencementioning

confidence: 99%

“…Their data suggest a burst of cluster formation about 1 Gyr ago, with little evidence for the existence of similar activity afterwards. More recently, Nayak et al (2016) presented a semi-automated method to estimate age and reddening of 1072 star clusters in the LMC. They found at least one major cluster formation event 125 Myr ago.…”

Section: Introductionmentioning

confidence: 99%

A Novel Method to Automatically Detect and Measure the Ages of Star Clusters in Nearby Galaxies: Application to the Large Magellanic Cloud

Bitsakis¹,

Bonfini²,

González-Lópezlira

et al. 2017

ApJ

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We present our new, fully automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and MonteCarlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramírez-Siordia et al., estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multiband imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7 deg 2 we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring ∼310 Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1 Gyr.

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

Cited by 25 publications

References 44 publications

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

Reddening map and recent star formation in the Magellanic Clouds based on OGLE IV Cepheids

SMASHing the LMC: Mapping a Ring-like Stellar Overdensity in the LMC Disk

A Novel Method to Automatically Detect and Measure the Ages of Star Clusters in Nearby Galaxies: Application to the Large Magellanic Cloud

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