Identifying star clusters in a field: A comparison of different algorithms

Schmeja, S.

doi:10.1002/asna.201011484

Cited by 69 publications

(77 citation statements)

References 97 publications

(121 reference statements)

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“…As described in Schmeja (2011), large values of S det will be able to detect real overdensities only in low background density regions. On the other hand, low S det values may be able to extract clusters in high background density regions (e.g., the LMC bar), at the cost of detecting many false associations (results of random projections) in the lower density regions, such as the outskirts of the galaxy.…”

Section: Implementing the Detection Sequencementioning

confidence: 96%

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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Section: Implementing the Detection Sequencementioning

confidence: 96%

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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“…Initially, we adopt the star count method outlined in Schmeja (2011). The entire field is subdivided into rectilinear grids of overlapping squares.…”

Section: Revisiting the Cluster Associated With Iras 20286+4105mentioning

confidence: 99%

“…Each square grid acts as a single point for producing the surface density map. The square grids with star counts greater than some significant threshold (∼ 2 -5σ) above the background are regions of density enhancements and hence are considered as potential cluster locations (Schmeja 2011). In our case, the mode (0.019 stars arcsec −2 or 312 stars pc −2 ) of the grids is considered to be the background and the noise/fluctuation in them defines σ which is estimated to be 0.005 stars arcsec −2 or 82 stars pc −2 .…”

Section: Revisiting the Cluster Associated With Iras 20286+4105mentioning

confidence: 99%

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Radio and infrared study of the star-forming region IRAS 20286+4105

Ramachandran

Das

Tej

et al. 2016

Mon. Not. R. Astron. Soc.

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A multi-wavelength investigation of the star forming complex IRAS 20286+4105, located in the Cygnus-X region, is presented here. Near-infrared K-band data is used to revisit the cluster / stellar group identified in previous studies. The radio continuum observations, at 610 and 1280 MHz show the presence of a HII region possibly powered by a star of spectral type B0 -B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model where the likely association with a nearby supernova remnant is also explored. A compact radio knot with non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus-X region show the presence of six Class I YSOs inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be ∼ 175 M and 30 M . The mass-radius relation and the surface density of the clumps do not qualify them as massive star forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediate-mass, Class I sources located toward the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature.

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“…Casertano & Hut 1985;Schmeja, Kumar & Ferreira 2008;Schmeja 2011). We have performed 20NN surface density analysis because Monte Carlo simulations show that 20NN is adequate to detect cluster with 10 to 1500 YSOs (Schmeja, Kumar & Ferreira 2008).…”

Section: Surface Density Of Ysosmentioning

confidence: 99%

Sh2-138: physical environment around a small cluster of massive stars

Baug

Ojha

Dewangan

et al. 2015

Mon. Not. R. Astron. Soc.

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We present a multi-wavelength study of the Sh2-138, a Galactic compact H II region. The data comprise of optical and near-infrared (NIR) photometric and spectroscopic observations from the 2-m Himalayan Chandra Telescope, radio observations from the Giant Metrewave Radio Telescope (GMRT), and archival data covering radio through NIR wavelengths. A total of 10 Class I and 54 Class II young stellar objects (YSOs) are identified in a 4.′ 6×4. ′ 6 area of the Sh2-138 region. Five compact ionized clumps, with four lacking of any optical or NIR counterparts, are identified using the 1280 MHz radio map, and correspond to sources with spectral type earlier than B0.5. Free-free emission spectral energy distribution fitting of the central compact H II region yields an electron density of ∼2250±400 cm −3 . With the aid of a wide range of spectra, from 0.5-15 µm, the central brightest source -previously hypothesised to be the main ionizing source -is characterized as a Herbig Be type star. At large scale (15′ ), the Herschel images (70-500 µm) and the nearest neighbour analysis of YSOs suggest the formation of an isolated cluster at the junction of filaments. Furthermore, using a greybody fit to the dust spectrum, the cluster is found to be associated with the highest column density (∼3×10 22 cm −2 ) and high temperature (∼35 K) regime, as well as with the radio continuum emission. The mass of the central clump seen in the column density map is estimated to be ∼3770 M ⊙ .

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Identifying star clusters in a field: A comparison of different algorithms

Cited by 69 publications

References 97 publications

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

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

Radio and infrared study of the star-forming region IRAS 20286+4105

Sh2-138: physical environment around a small cluster of massive stars

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