Search

Aims. We aim to locate previously unknown stellar clusters using the VISTA variables in the Vía Láctea Survey (VVV) catalogue data. Methods. The method fits a mixture model of Gaussian densities and background noise and uses the expectation maximization algorithm to pre-filtered near-infrared survey stellar catalogue data; it was developed by the authors for the UKIDSS Galactic Plane Survey (GPS). Results. The search located 88 previously unknown candidates, most of which are embedded stellar cluster candidates, and 39 previously unknown sites of star formation in the 562 deg2 covered by VVV in the Galactic bulge and the southern disk. [ABSTRACT FROM AUTHOR]

Context. Data mining techniques must be developed and applied to analyse the large public data bases containing hundreds to thousands of millions entries. Aims. We develop methods for locating previously unknown stellar clusters from the UKIDSS Galactic Plane Survey (GPS) catalogue data. Methods. The cluster candidates are computationally searched from pre-filtered catalogue data using a method that fits a mixture mo Jel of Gaussian densities and background noise using the expectation maximization algorithm. The catalogue data contains a significant number of false sources clustered around bright stars. A large fraction of these artefacts were automatically filtered out before or during the cluster search. The UKIDSS data reduction pipeline tends to classify marginally resolved stellar pairs and objects seen against variable surface brightness as extended objects (or "galaxies" in the archive parlance). 10% or 66 x 106 of the aources in the IJKIDSS GPS catalogue brighter than 17m in the K band are classified as "galaxies". Young embedded clusters create variable NTR surface brightness because the gas/dust clouds in which they were formed scatters the light from the cluster members. Such clusters appear therefore an clusters of "galaxies" in the catalogue and can be found using only a subset of the catalogue data. The detected "galaxy clusters" were finally screened visually to eliminate the remaining false detections due to dala artefacts. Besides the embedded clusters the search also located locations of non clustered embedded star formation. Results. The search covered an area of 1302 deg2 and 137 previously unknown cluster candidates and 30 previously unknown sites of star formation were found. [ABSTRACT FROM AUTHOR]