Photometric and kinematic study of the seyfert galaxy Mark 176

Leningrad State University. Translated from Astrofizika, Vol. 31, No. 1, pp. 49–62, July–August, 1989.     

Rotation Curves of Galaxies in Various Space Environments

A sample of giant Sb-Sc spiral galaxies for which there are highly accurate and extended rotation curves was considered. Having divided the galaxies into three groups as a function of the overall spatial density of luminosity (mass) within 0.5 Mpc ( _L ), we investigated the characteristics of the rotation curves as functions of _L . It turned out that for such massive galaxies, the shape of the rotation curve (the logarithmic gradient) and the Tully-Fisher relation do not depend on the overall space environment. The only difference is that the rotation curves of galaxies in regions with high _L can be traced out to smaller relative distances from the nucleus, on the average. This may be related to destruction of the outer regions of their gaseous disks in gravitational interaction with surrounding galaxies.     

Tidal structures of z ∼ 1 galaxies in the Hubble Deep Field

An analysis of the images of objects in the Northern Hubble Space Telescope Deep Field has revealed twelve galaxies with tidal tails at redshifts from 0.5 to 1.5. The integrated characteristics of the newly discovered tidal structures are found to be similar to those of the tails of local interacting galaxies. The space density of galaxies with tidal tails is found to depend on z as (1+z)^4±1(q ₀=0.05), according to the data on objects with z=0.5–1.0. The exponent decreases to 3.6 if barred galaxies are included. The change in the rate of close encounters between galaxies of comparable masses (i.e., those that produce extended tidal structures) is estimated. If the rate of galactic mergers is governed by the same process, our data are indicative of the rapid evolution of galaxy merger rate toward z ～ 1.     

The polar stellar ring and dark halo of NGC 5907

Numerical simulations of the disruption of a dwarf companion moving in the polar plane of a massive galaxy are presented. The constructed model is compared with observational data on the recently discovered low-surface-brightness stellar ring around the galaxy NGC 5907. Constraints on the ring lifetime (≤ 1.5 Gyr after the first approach of the galaxies), on the structure of the companion—the ring precursor, and on the mass of the dark halo of the main galaxy in whose gravitational field the companion moves are provided. The dark-halo mass within 50 kpc of the NGC 5907 center cannot exceed 3 or 4 “visible” masses.