References of "Melnyk, Olga"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailClassification and environmental properties of X-ray selected point-like sources in the XMM-LSS field
Melnyk, Olga ULg; Plionis, M.; Elyiv, Andrii ULg et al

in Astronomy and Astrophysics (2013), 557(A81),

Detailed reference viewed: 26 (7 ULg)
Full Text
Peer Reviewed
See detailThe XMM-LSS catalogue: X-ray sources and associated multiwavelength data. Version II
Chiappetti, L.; Clerc, N.; Pacaud, F. et al

in Monthly Notices of the Royal Astronomical Society (2013), 429

We present the final release of the multi-wavelength XMM-LSS data set,covering the full survey area of 11.1 square degrees, with X-ray data processed with the latest XMM-LSS pipeline version. The present ... [more ▼]

We present the final release of the multi-wavelength XMM-LSS data set,covering the full survey area of 11.1 square degrees, with X-ray data processed with the latest XMM-LSS pipeline version. The present publication supersedes the Pierre et al.(2007) catalogue pertaining to the initial 5 square degrees. We provide X-ray source lists in the customary energy bands (0.5-2 and 2-10 keV) for a total of 6721 objects in the deep full-exposure catalogue and 5572 in the 10ks-limited one, above a detection likelihood of 15 in at least one band. We also provide a multiwavelength catalogue, cross-correlating our list with IR, NIR, optical and UV catalogues. Customary data products (X-ray FITS images, CFHTLS and SWIRE thumbnail images) are made available together with our interactively queriable database in Milan, while a static snapshot of the catalogues will be supplied to CDS, as soon as final acceptance is completed. [less ▲]

Detailed reference viewed: 27 (20 ULg)
Full Text
See detailTheoretical incidence of gravitational lensing effects (AGN) in the XXL field
Finet, François ULg; Elyiv, Andrii ULg; Melnyk, Olga ULg et al

in Proceedings of the XXL Consortium meeting in the Castle of the Meudon observatory, from 9 to 13 July, 2012 (2012, July 09)

Detailed reference viewed: 30 (5 ULg)
Full Text
See detailClassification, photo-z and environment of X-ray selected sources in the XMM-LSS field
Melnyk, Olga ULg; Plionis, M; Elyiv, Andrii ULg et al

in Proceedings of the XXL Consortium meeting in the Castle of the Meudon observatory, from 9 to 13 July, 2012 (2012, July 09)

Detailed reference viewed: 29 (1 ULg)
Full Text
See detailVisual and automatic search for lens candidates in the XMM-LSS and XXL fields
Elyiv, Andrii ULg; Melnyk, Olga ULg; Finet, François ULg et al

in Proceedings of the XXL Consortium meeting in the Castle of the Meudon observatory, from 9 to 13 July, 2012 (2012, July 09)

Detailed reference viewed: 21 (2 ULg)
Full Text
Peer Reviewed
See detailAngular correlation functions of X-ray point-like sources in the full exposure XMM-LSS field
Elyiv, Andrii ULg; Clerc, N.; Plionis, M. et al

in Astronomy and Astrophysics (2012), 537

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and ... [more ▼]

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and 2500 X-ray point-like sources over the 11 sq. deg. XMM-LSS field in the soft (0.5-2 keV) and hard (2-10 keV) bands. For the conversion from the angular to the spatial correlation function we used the Limber integral equation and the luminosity-dependent density evolution model of the AGN X-ray luminosity function. <BR /> Results: We have found significant angular correlations with the power-law parameters γ = 1.81 ± 0.02, θ[SUB]0[/SUB] = 1.3'' ± 0.2'' for the soft, and γ = 2.00 ± 0.04, θ[SUB]0[/SUB] = 7.3'' ± 1.0'' for the hard bands. The amplitude of the correlation function w(θ) is higher in the hard than in the soft band for f[SUB]x[/SUB] ≲ 10[SUP]-14[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] and lower above this flux limit. We confirm that the clustering strength θ[SUB]0[/SUB] grows with the flux limit of the sample, a trend which is also present in the amplitude of the spatial correlation function, but only for the soft band. In the hard band, it remains almost constant with r[SUB]0[/SUB] ≃ 10h[SUP]-1[/SUP] Mpc, irrespective of the flux limit. Our analysis of AGN subsamples with different hardness ratios shows that the sources with a hard-spectrum are more clustered than soft-spectrum ones. This result may be a hint that the two main types of AGN populate different environments. Finally, we find that our clustering results correspond to an X-ray selected AGN bias factor of 2.5 for the soft band sources (at a median <inline-formula>bar{z} ≃ 1.1) and 3.3 for the hard band sources (at a median <inline-formula>bar{z} ≃ 1), which translates into a host dark matter halo mass of 10[SUP]13[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] and 10[SUP]13.7[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] for the soft and hard bands, respectively. This paper is dedicated to the memory of Olivier Garcet who has initiated the present work just before his sudden death. [less ▲]

Detailed reference viewed: 16 (6 ULg)
Full Text
Peer Reviewed
See detailFaint companions of isolated 2MIG galaxies
Karachentseva, V. E.; Karachentsev, I. D.; Melnyk, Olga ULg

in Astrophysical Bulletin (2011), 66

We present the results of a search for companions around the isolated galaxies from the 2MIG catalog. Among 3227 2MIG galaxies we detected 125 objects with a total of 214 neighbors having radial velocity ... [more ▼]

We present the results of a search for companions around the isolated galaxies from the 2MIG catalog. Among 3227 2MIG galaxies we detected 125 objects with a total of 214 neighbors having radial velocity differences of Δ V < 500 km/s and projected separations of Rp < 500 kpc relative to the 2MIG galaxies. The median luminosity of the companions is 1/25 of the luminosity of catalog galaxies, which has little effect on the dynamic isolation of the latter. The median ratio of the orbital mass to the K-luminosity determined from 60 companions of E and S0 2MIG galaxies, 63 Msolar/Lsolar, is significantly greater than that found from the spiral galaxy companions (17 Msolar/Lsolar). We note that a fraction of 2MIG galaxies with companions may be a part of low-contrast diffuse structures: clouds and filaments. [less ▲]

Detailed reference viewed: 5 (0 ULg)
Full Text
Peer Reviewed
See detailCatalog of nearby isolated galaxies in the volume z < 0.01
Karachentsev, I. D.; Makarov, D. I.; Karachentseva, V. E. et al

in Astrophysical Bulletin (2011), 66

We present a catalog of 520 most isolated nearby galaxies with angular velocities V_LG < 3500 km/s, covering the entire sky. This population of "space orphans" makes up 4.8% among 10 900 galaxies with ... [more ▼]

We present a catalog of 520 most isolated nearby galaxies with angular velocities V_LG < 3500 km/s, covering the entire sky. This population of "space orphans" makes up 4.8% among 10 900 galaxies with measured radial velocities. We describe the isolation criterion used to select our sample, called the "Local Orphan Galaxies"(LOG), and discuss their basic optical and HI properties. A half of the LOG catalog is occupied by the Sdm, Im and Ir morphological type galaxies without a bulge. The median ratio Mgas/ Mstar in the LOG galaxies exceeds 1. The distribution of the catalog galaxies on the sky looks uniform with some signatures of a weak clustering on the scale of about 0.5 Mpc. The LOG galaxies are located in the regions where the mean local density of matter is approximately 50 times lower than the mean global density. We indicate a number of LOG galaxies with distorted structures, which may be the consequence of interaction of isolated galaxies with massive dark objects. [less ▲]

Detailed reference viewed: 10 (3 ULg)
Full Text
Peer Reviewed
See detailMorphological properties of isolated galaxies vs. isolation criteria
Vavilova, I. B.; Melnyk, Olga ULg; Elyiv, Andrii ULg

in Astronomische Nachrichten (2009), 330

We studied the morphological properties of isolated galaxies samples in dependence on the isolation parameter and properties of primary catalogs. With this aim we identified the samples of single and ... [more ▼]

We studied the morphological properties of isolated galaxies samples in dependence on the isolation parameter and properties of primary catalogs. With this aim we identified the samples of single and isolated galaxies from SDSS DR5 (Single and QIsol) with the 3D Voronoi tessellation method (Elyiv et al. 2009). We found that in comparison with other samples of isolated galaxies, the QIsol sample contains an excess of late-type galaxies, especially with a low luminosity and BCG/Im/Irr morphology. We also showed that the fractions of early type galaxies in QIsol SDSS DR5 sample and samples 2MIG (Karachentseva et al. 2010) and CIG (Karachentseva et al. 1973; Hernandez-Toledo et al. 2008) are in a good agreement (16-19 %), but Allam's (Allam et al. 2005) and Prada's (Prada et al. 2003) SDSS DR1 samples show a higher excess of the early type galaxies that can be explained by the selection criteria and morphology definition method. We found a weak relation between isolation parameter and color index for the Single sample that may indicate that even in the low dense environment the morphology density relation is observed. We conclude that morphological properties of the resulting sample of isolated galaxies are highly dependent on the primary catalogue from which the galaxies were selected. Moreover, the selection criterion is also important but plays a secondary role in the resulting morphological content, color indices distribution and other parameters of the isolated galaxy samples. Only four galaxies are common in the 2MIG, QIsol, and CIG samples, namely UGC5184, UGC6121, UGC8495, and UGC9598, that allows to consider them as really most isolated galaxies. [less ▲]

Detailed reference viewed: 3 (1 ULg)
Full Text
Peer Reviewed
See detailHigh-order 3D Voronoi tessellation for identifying isolated galaxies, pairs and triplets
Elyiv, Andrii ULg; Melnyk, Olga ULg; Vavilova, I.

in Monthly Notices of the Royal Astronomical Society (2009), 394

A geometric method based on the high-order 3D Voronoi tessellation is proposed for identifying single galaxies, pairs and triplets. This approach allows us to select small galaxy groups and isolated ... [more ▼]

A geometric method based on the high-order 3D Voronoi tessellation is proposed for identifying single galaxies, pairs and triplets. This approach allows us to select small galaxy groups and isolated galaxies in different environments and to find the isolated systems. The volume-limited sample of galaxies from the Sloan Digital Sky Survey Data Release 5 spectroscopic survey was used. We conclude that in such small groups as pairs and triplets, segregation by luminosity is clearly observed: galaxies in isolated pairs and triplets are on average two times more luminous than isolated galaxies. We consider the dark matter content in different systems. The median values of mass-to-luminosity ratio are 12M[SUB]solar[/SUB]/L[SUB]solar[/SUB] for the isolated pairs and 44M[SUB]solar[/SUB]/L[SUB]solar[/SUB] for the isolated triplets, and 7 (8) M[SUB]solar[/SUB]/L[SUB]solar[/SUB] for the most compact pairs (triplets). We also found that systems in denser environments have greater rms velocity and mass-to-luminosity ratio. [less ▲]

Detailed reference viewed: 3 (0 ULg)