Compact elliptical galaxies form a rare class of stellar system (~30 presently known) characterized by high stellar densities and small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenito
rs, until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for nonisolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, which is in agreement with numerical simulations. Hence, isolated compact elliptical and isolated quiescent dwarf galaxies are tidally stripped systems that ran away from their hosts.
We report on the archival near-infrared and mid-infrared observations of 7 persistent X-ray sources situated in the Galactic bulge using data from the UKIRT Infrared Deep Sky Survey (UKIDSS), Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraord
inaire (GLIMPSE) and the Wide-field Infrared Survey Explorer (WISE) all-sky survey. We were able to successfully identify, or provide upper flux limits for the systems SAX J1747.0-2853, IGR J17464-2811, AX J1754.2-2754, IGR J17597-2201, IGR J18134-1636, IGR J18256-1035, Ser X-1 and constrain the nature of these systems. In the case of IGR J17597-2201 we present arguments that the source accretes matter from the stellar wind rather than via Roche lobe overflow of the secondary. We suggest that, at its X-ray luminosity of $10^{34-35}$ erg s$^{-1}$, we are probing the poorly known class of wind-fed low-mass X-ray binaries (LMXBs).
Although the optical colour-magnitude diagram of galaxies allows one to select red sequence objects, neither can it be used for galaxy classification without additional observational data such as spectra or high-resolution images, nor to identify blu
e galaxies at unknown redshifts. We show that adding the near ultraviolet colour to the optical CMD reveals a tight relation in the three-dimensional colour-colour-magnitude space smoothly continuing from the blue cloud to the red sequence. We found that 98 per cent of 225,000 low-redshift (Z<0.27) galaxies follow a smooth surface g-r=F(M,NUV-r) with a standard deviation of 0.03-0.07 mag making it the tightest known galaxy photometric relation. There is a strong correlation between morphological types and integrated NUV-r colours. Rare galaxy classes such as E+A or tidally stripped systems become outliers that occupy distinct regions in the 3D parameter space. Using stellar population models for galaxies with different SFHs, we show that (a) the (NUV-r, g-r) distribution is formed by objects having constant and exponentially declining SFR with different characteristic timescales; (b) colour evolution for exponentially declining models goes along the relation suggesting its weak evolution up-to a redshift of 0.9; (c) galaxies with truncated SFHs have very short transition phase offset from the relation thus explaining the rareness of E+A galaxies. This relation can be used as a powerful galaxy classification tool when morphology remains unresolved. Its mathematical consequence is the photometric redshift estimates from 3 broad-band photometric points. This approach works better than most existing photometric redshift techniques applied to multi-colour datasets. Therefore, the relation can be used as an efficient selection technique for galaxies at intermediate redshifts (0.3<Z<0.8) using optical imaging surveys.
We discuss what hampers the rate of scientific progress in our exponentially growing world. The rapid increase in technologies leaves the growth of research result metrics far behind. The reason for this lies in the education of astronomers lacking b
asic computer science aspects crucially important in the data intensive science era.
We report the discovery of a new cataclysmic variable (CV) among unidentified objects from the ASCA Galactic Plane Survey made using the Virtual Observatory data mining. First, we identified AX J194939+2631 with IPHAS J194938.39+263149.2, the only pr
ominent H-alpha emitter among 400 sources in a 1 arcmin field of the IPHAS survey, then secured as a single faint X-ray source found in an archival Chandra dataset. Spectroscopic follow-up with the 3.5-m Calar Alto telescope confirmed its classification as a CV, possibly of magnetic nature. Our analysis suggests that AX J194939+2631 is a medium distance system (d ~ 0.6 kpc) containing a late-K or early-M type dwarf as a secondary component and a partially disrupted accretion disc revealed by the double-peaked H-alpha line. However, additional deep observations are needed to confirm our tentative classification of this object as an intermediate polar.
We report on the archival optical and near-infrared observations of 6 low mass X-ray binaries situated in the Galactic bulge. We processed several recent Chandra and XMM-Newton as well as Einstein datasets of a binary systems suspected to be ultracom
pact, which gave us arcsec-scale positional uncertainty estimates. We then undertook comprehensive search in existing archives and other Virtual Observatory resources in order to discover unpublished optical/NIR data on these objects. We found and analysed data from ESO Archive and UKIRT Infrared Deep Sky Survey (UKIDSS) on SLX 1735-269, 3A 1742-294, SLX 1744-299, SLX 1744-300, GX 3+1, IGR J17505-2644 systems and publish their finding charts and optical flux constraints in this paper, as well as simple estimates of the physical parameters of these objects.
The Virtual Observatory has reached sufficient maturity for its routine scientific exploitation by astronomers. To prove this statement, here I present a brief description of the complete VO-powered PhD thesis entitled Galactic and extragalactic rese
arch with modern surveys and the Virtual Observatory comprising 4 science cases covering various aspects of astrophysical research. These comprize: (1) homogeneous search and measurement of main physical parameters of Galactic open star clusters in huge multi-band photometric surveys; (2) study of optical-to-NIR galaxy colors using a large homogeneous dataset including spectroscopy and photometry from SDSS and UKIDSS; (3) study of faint low-mass X-ray binary population in modern observational archives; (4) search for optical counterparts of unidentified X-ray objects with large positional uncertainties in the Galactic Plane. All these projects make heavy use of the 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 to the growing list of VO-based research works.
We re-examine the infrared counterpart of the dipping low-mass x-ray binary 4U1323-619. New X-ray data available from the XMM and Chandra observatories combined with archival IR observations from the ESO 3.6m New Technology Telescope allow us to defi
ne a new possible counterpart. We present here its photometric properties and compare them with a simple analytical model of an accretion disc illuminated by the hot central corona known to be present in the binary system.
