Active Galactic Nuclei among Polar-Ring Galaxies

Astronomy Letters - Based on SDSS data, we consider the fraction of active galactic nuclei among polar-ring galaxies. We have found evidence for an excess of Seyfert galaxies and LINERS among...     

Studying methane emission in the north of Western Siberia

Methane emitted into the atmosphere from sources located in the Urengoi natural gas field is estimated from direct methane concentration measurements in the atmospheric boundary layer and modeling. The results of direct profile measurements in the summer-fall season of 2003 are generalized versus the data from the previous field studies and background monitoring of greenhouse gases in the northern polar region. The use of models for calculating the intensity of emission from sources located in the field area together with a set of methane concentration measurements at three altitudes allowed the authors to develop a method of verification of emission from a specific source, a deposit. The method estimates the emission both from part of the field area and from the whole field with an irregular distribution of the intensity of sources across the deposit area.     

The milky way as a galaxy

On the basis of literature data, and assuming that the Milky Way satisfies the Tully-Fisher relationship, the main photometric and kinematic characteristics of the Galaxy are summarized. It is shown that, based on the aggregate of the large-scale properties, the Milky Way is a normal L* galaxy. The contribution of dark matter within the limits of the optical disk of the Milky Way evidently does not exceed 30%. Five spiral galaxies that are similar to the Milky Way in their characteristics are selected from among relatively nearby objects. Translated from Astrofizika, Vol. 43, No. 2, pp. 197–210, April–June, 2000.     

UGC 7388: A galaxy with two tidal loops

We present the results of our spectroscopic and morphological studies of the galaxy UGC 7388 with the 8.1-m Gemini North telescope. Judging by its observed characteristics, UGC 7388 is a giant late-type spiral galaxy seen nearly edge-on. The main body of the galaxy is surrounded by two faint (μ _B ～ 24 ^m /□″ and μ _B ～ 25 _· ^m 5/□″) extended (～ 20–30 kpc) loop-like structures. A large-scale rotation of the brighter loop about the main galaxy has been detected. We discuss the assumption that the tidal disruption of a relatively massive companion is observed in the case of UGC 7388. A detailed study and modeling of the observed structure of this unique galaxy can give important information about the influence of the absorption of massive companions on the galactic disks and about the structure of the dark halo around UGC 7388.     

Estimation of methane sources from concentration measurements in the area of gas production in the north of Western Siberia

Data on atmospheric methane concentrations, measured at different levels (20, 30, and 60 m) with a time step of 20 min at an observation point at a distance of 50 km from the Urengoi field, are presented. The NOAA HYSPLIT model was used to identify technogenic emissions, and method of nocturnal accumulation was used to evaluate emissions from wetlands. It is demonstrated that observed short-term increases in methane concentration can be caused by salvo gas emissions during technological operations in the gas field. Mean methane flux density is estimated for the wetland adjoining the observation point.     

The structure and evolution of M 51-type galaxies

We discuss the integrated kinematic parameters of 20 M 51-type binary galaxies. A comparison of the orbital masses of the galaxies with the sum of the individual masses suggests that moderately massive dark halos surround bright spiral galaxies. The relative velocities of the galaxies in binary systems were found to decrease with increasing relative luminosity of the satellite. We obtained evidence that the Tully-Fisher relation for binary members could be flatter than that for local field galaxies. An enhanced star formation rate in the binary members may be responsible for this effect. In most binary systems, the direction of the orbital motion of the satellite coincides with the direction of the rotation of the main galaxy. Seven candidates for distant M 51-type objects were found in the Northern and Southern Hubble Deep Fields. A comparison of this number with the statistics of nearby galaxies provides evidence for the rapid evolution of the space density of M 51-type galaxies with redshift z. We assume that M 51-type binary systems could be formed through the capture of a satellite by a massive spiral galaxy. It is also possible that the main galaxy and its satellite in some of the systems have a common cosmological origin.