Grown up with the VO(a VO-powered PhD thesis)
Ivan Zolotukhin (SAI MSU)
iz@sai.msu.ru
The Virtual Observatory has reached sufficient maturity for its routine scientificexploitation by astronomers. To prove this statement, here we present a complete
VO-powered PhD thesis successfully defended on Oct 1, 2009, comprising 4
science cases covering several aspects of Galactic and extragalactic research.
These includes: (1) homogeneous search and measurement of main physicalparameters of Galactic open star clusters in huge multi-band photometricsurveys; (2) interpretation of optical-to-NIR colors of nearby galaxies using a large
homogeneous dataset including spectroscopy and photometry from SDSS andUKIDSS; (3) study of faint low-mass x-ray binaries population in modern
observational archives, imposing physical constraints on this poorly-studied typeof objects; (4) search for optical counterparts of unidentified x-ray objects withlarge positional uncertainties in the Galactic Plane. All these studies make heavy
use of VO technologies and tools and would not be achievable without them. So
refereed papers published in the frame of this thesis can undoubtedly be added tothe growing list of VO-based research works.

1. SAI Open Clusters Catalog
We developed an automated method to search for open
clusters in large multi-band surveys. It finds star density
peaks and tests their color-magnitude diagrams fitting an
isochrone there (see example on the upper right). If fit
converges we consider peak to be a real cluster and at thesame time get an estimate of the age, distance, color excessfor it. We applied this method to the 2MASS data in the stripe|b| < 24 degrees along Galactic Plane and found 168 new
open clusters (see their distribution by the age and on asphere at the bottom left and right correspondingly) which is~25% increase of the information about this importantsubsystem of the Galaxy. The results of the undergoingstudy, SAI Open Clusters Catalog, are presented in a VOready form at dedicated web-site http://ocl.sai.msu.ru .

2. Optical-to-NIR colors of nearby galaxies
We cross-identified a spectral sample of SDSS DR7 galaxies lying at 0.03 < z < 0.6 withUKIDSS DR5 data, and fitted their spectra with simple stellar population models thus
constructing a catalog of 200k galaxies with ugriz and YJHK photometry measurements,redshifts, spectra, ages and metallicities. This allowed us to determine an analytical
approximation of k-corrections having great practical value for extragalactic research.

Analytical approximations of k-corrections inSDSS filter g as a function of observed colorg-r (color-coded) and redshift (upper panel)anddifferences
betweenanalytical
approximation and direct estimation of kcorrections from the spectra (bottom panel).

Color-magnitude diagram MH vs. g-r (kcorrected) for nearby galaxies. Ages from 1
to 12 Gyr are color-coded from violet to red. 3
mag bright tail of the red sequence galaxies
indicates that they cannot be formed from themerging of a blue cloud objects.

3. Optical/IR LMXB identification

Fields of three low mass x-ray binaries
4U1323-619, IGR J17254-3257 and SLX
1735-269 (see pictures clockwise) identified
in archival data (ESO, Chandra, XMM
archives used). In the case of 4U1323-619
there was a wrong identification based onEinstein
x-rayobservations
withunderestimated error radius.

4. X-ray sources in the Galactic Plane
With the help of IPHAS (INT Photometric H-alphaSurvey) we identified an x-ray source AXJ194939+2631 from ASCA Galactic Plane Surveythat initially had 1 arcmin positional uncertainty.
Upper right: color-color diagram of IPHAS
detections in 1 arcmin field around ASCA
coordinates of the source; three measurementsof the potential counterpart demonstrating Halpha emission excess are shown in squares.
Bottom right: direct H-alpha image from IPHAS,
the candidate marked with an arrow. Lower left:
optical spectrum of the source obtained at 3.5m
Calar Alto telescope, time granted in DDT quota
on a basis of the input from the VO shown on thispage. Source Is appeared to be a cataclysmic
variable.