Star Cluster searches
Detecting new star clusters in the contemporary
era
Methods to detect star clusters
● Usually utilized in conjunction
● Visual → searching for stellar overdensities or ‘seeds’
● Star-counting (dividing the sky into bins and searching for
enhancements in star count)
● Radial number density profiles (RDPs)
● Parallaxes (distances), proper motions, radial velocities
● Color-magnitude diagrams comparisons
● Survey data products exploitations (catalogues of extended
sources, surface brightness maps, stellar count maps, etc.)
Infrared searches
● Current OC catalogues largely incomplete at d > 2 kpc
● Near IR: 2MASS searches → more than 1000 new OC
candidates, all-sky but shallow magnitude limit
● UKIRT Infrared Deep Sky Survey (UKIDSS), VISTA
Variables in the Via Lactea Survey (VVV) → deeper
but limited coverage, several hundred new Ocs
● Mid IR: Spitzer searches → very low extinction but only
limited coverage, Wide-Field Infrared Survey Explorer
(WISE) → all-sky but lower resolution
OCs toward the inner Galaxy
Credit: Ryu & Lee (2018)
‘Seeds’
● Massive stars or massive star formation indications
(YSOs, masers, etc.) → all or almost all massive
stars form in star clusters (beware of the wording!)
● Various type of nebulae (HII regions, mid-infrared
nebulae, supernova remnants?)
● Catalogue ‘seeds’ → catalogued compact extended
sources from older and/or lower resolution surveys
(2MASS, WISE), possible misclassified galaxies in
the Galactic plane
M103 (credit: APOD)
??
Cas A
Barba+ (2015)
Radial density profiles
Piatti (2017)
Parallax & Proper motions
Radial velocities
Bravi+ (2018)
Clustering
Which one is the most appropriate algorithm?
Cantat-Gaudin+ (2018)
Gaia 1 (star-counting)
Koposov+ (2017)
Color-magnitude diagram analysis
Navarrete+ (2017)
Gaia 2
Koposov+ (2017)
Survey exploitation
ra207.9981 (preliminary)
Froebrich (2017)
Ryu & Lee (2018)