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See detailLow-Density Structures in the Local Universe. II. Nearby Cosmic Voids
Elyiv, Andrii ULg; Karachentsev, I.D.; Karachentseva, V.E. et al

in Astrophysical Bulletin (2013), 68

We present the results of the search for spherical volumes containing no galaxies with luminosities brighter than the Magellanic Clouds in the Local Supercluster and its vicinity. Within a distance of 40 ... [more ▼]

We present the results of the search for spherical volumes containing no galaxies with luminosities brighter than the Magellanic Clouds in the Local Supercluster and its vicinity. Within a distance of 40 Mpc from us, 89 cosmic voids were discovered with the diameters of 24 to 12 Mpc, containing no galaxies with absolute magnitudes brighter than M_K < -18.4. A list of these voids and the sky distribution maps are given. It was found that 93% of spherical voids overlap, forming three more extended percolated voids (hypervoids). The largest of them, HV1, has 56 initial spherical cells and extends in a horseshoe shape, enveloping the Local Volume and the Virgo cluster. The Local Void (Tully, 1988) in the Hercules-Aquila region is the closest part of the HV1. Another hypervoid, HV2, contains 22 spherical voids in the Eridanus constellation, and the third compact hypervoid (HV3) comprises 6 spherical cells in the Bootes. The total volume of these voids incorporates about 30% of the Local Universe. Among 2906 dwarf galaxies excluded from the original sample (n = 10502) in the search for spherical volumes, only 68 are located in the voids we have discovered. They are characterized by late morphological types (85% are Ir, Im, BCD, Sm), absolute magnitudes M_B ranging from -13.0 to -16.7, moderate star formation rates (log SSFR ~ -10 M_sun/(yr*L_sun) and gas reserves per luminosity unit twice to three times larger than in the other dwarf galaxies located in normal environments. The dwarf population of the voids shows a certain tendency to sit shallow near the surfaces of cosmic voids. [less ▲]

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See detailLow density structures in the local universe. I. Diffuse agglomerates of galaxies
Karachentsev, I.D.; Karachentseva, V.E.; Melnyk, Olga et al

in Astrophysical Bulletin (2012), 67(4), 353-361

This paper is the first of a series considering the properties of distribution of nearby galaxies in the low density regions. Among 7596 galaxies with radial velocities V_{LG}<3500 km/s, absolute ... [more ▼]

This paper is the first of a series considering the properties of distribution of nearby galaxies in the low density regions. Among 7596 galaxies with radial velocities V_{LG}<3500 km/s, absolute magnitudes M_K<-18.4^m$, and Galactic latitudes |b| >15 degr there are 3168 field galaxies (i.e. 42%) that do not belong to pairs, groups or clusters in the Local universe. Applying to this sample the percolation method with a radius of r_0=2.8 Mpc, we found 226 diffuse agglomerates with n>=4 number of members. The structures of eight most populated objects among them (n>=25) are discussed. These non-virialized agglomerates are characterized by a median dispersion of radial velocities of about 170 km/s, the linear size of around 6 Mpc, integral K-band luminosity of 3*10^{11} L_sun, and a formal virial-mass-to-luminosity ratio of about 700 M_sun/L_sun. The mean density contrast for the considered agglomerates is only <Delta n/\bar{n}\gtrsim 5, and their crossing time is about 30-40 Gyr. [less ▲]

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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 ▲]

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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 ▲]

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