Ultra-Flat Galaxies Selected from RFGC Catalog. I. The Sample Properties

Abstract

We used the Revised Flat Galaxy Catalog (RFGC) to create a sample of ultra-flat galaxies (UFG) covering the whole northern and southern sky apart from the Milky Way zone. It contains 817 spiral galaxies seen edge-on, selected into the UFG sample according to their apparent axial ratios $(a/b{)}_B\ge 10.0$ and $(a/b{)}_R\ge 8.53$ in the blue and red bands, respectively. Within this basic sample we fixed an exemplary sample of 441 UFG galaxies having the radial velocities of $V_{LG}<10000$ km s${}^{-1}$, Galactic latitude of $\mid b\mid >10^{\circ }$ and the blue angular diameter of $a_B>1.0^{\prime }$. According to the Schmidt test the exemplary sample of 441 galaxies is characterized by about (80-90)% completeness, what is quite enough to study different properties of the ultra-flat galaxies. We found that more than 3/4 of UFGs have the morphological types within the narrow range of $T=7\pm 1$, i.e. the thinnest stellar disks occur among the Scd, Sd, and Sdm types. The average surface brightness of UFG galaxies tends to diminish towards the flattest bulge-less galaxies. Regularly shaped disks without signs of asymmetry make up about 2/3 both among all the RFGC galaxies, and the UFG sample objects. About 60% of ultra-flat galaxies can be referred to dynamically isolated objects, while 30% of them probably belong to the scattered associations (filaments, walls), and only about 10% of them are dynamically dominating galaxies with respect to their neighbours.

13 pages, 7 figures, 5 tables, 1 annex, published in Astrophysical Bulletin, 2016, 71, 1, 1-13

References in corpus (3)

• The Catalog of Edge-on Disk Galaxies from SDSS. Part I: the catalog and the Structural Parameters of Stellar Disks
• Catalog of Isolated Galaxies Selected from the 2MASS Survey
• Binary Galaxies in the Local Supercluster and Its Neighborhood

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