AM 1934-563: a giant spiral polar-ring galaxy in a triplet

Abstract

We have observed the emission-line kinematics and photometry of a southern triplet of galaxies. The triplet contains a giant spiral galaxy AM 1934-563 whose optical structure resembles a polar-ring galaxy: a distorted spiral disk, seen almost edge-on, and a faint large-scale (45 kpc in diameter) warped structure, inclined by 60• -70• with respect to the disk major axis. The triplet shows a relatively small velocity dispersion (69 km s −1 ) and a large crossing time (0.17 in units of the Hubble time). The disk of AM 1934-563 demonstrates optical colors typical of early-type spirals, a strong radial color gradient, and almost exponential surface brightness distribution with an exponential scalelength value of 3.1 kpc (R passband). The galaxy shows a maximum rotation velocity of about 200 km s −1 and it lies close to the Tully-Fisher relation for spiral galaxies. The suspected polar ring is faint (µ(B) ≥ 24) and strongly warped. Its total luminosity comprises 10−15% of the total luminosity of AM 1934-563. We model this system using numerical simulations, and study its possible formation mechanisms. We find that the most robust model that reproduces the observed characteristics of the ring and the host galaxy is the tidal transfer of mass from a massive gas-rich donor galaxy to the polar ring. The physical properties of the triplet of galaxies are in agreement with this scenario.

The polar ring galaxy AM1934-563 revisited

“…Deriving the rotation curves shown in Figs 7 and 8 we found that the systemic radial velocity of AM1934−563 is 11663 ± 3 km s −1 , formally higher by some 14 km s −1 than the value given by Reshetnikov et al (2006) in their table 3 but consistent with their value within the quoted uncertainties. This offset might be the result of a slightly different definition of the systemic velocity; we chose the value for which the NW branch of the rotation curve matched best that for the SE branch and by this procedure also found the rotation centre of the galaxy.…”

“…In this paper we analyse new observations of the PRG AM1934−563, a PRG with an optical redshift of 11649 ± 10 km s −1 located at l = 341.02, b =−28.73, also identified as PRC B‐18 in Whitmore et al (1990). The object was recently studied by Reshetnikov et al (2006), who showed that this is a giant galaxy in a compact triplet, together with PGC 400092 (classified Sd/Irr) and PGC 399718 (classified SBc) at approximately the same redshift. The authors used the 1.6‐m telescope of the Pico dos Dias Observatory in Brazil for imaging in B , V , R , I , the Cerro Tololo Inter‐American Observatory (CTIO) 1.5‐m telescope to collect spectral observations and included data from IRAS and 21‐cm line observations.…”

Stochastic “Beads on a String” in the Accretion Tail of Arp 285

“…Our simulation somewhat resembles models of polar ring formation via accretion from a companion (Reshetnikov et al 2006), however, the two model galaxies merge before this polar ring proceeds very far in its development (see later time steps in the Appendix). The star clusters formed in the pile-up region will eventually be carried with the companion halo into the merger with the primary.…”

Astrophysics in 2006

“…Other cases, including the classic Cartwheel, have been claimed as mere disk instabilities (Griv 2005). And a third category consists of galaxies with rings formed by late, slow gas in-drizzle (Iodice et al 2006) either from another galaxy or along a filament of the large scale structure (Reshetnikov et al 2006). About half of them are really polar disks anyway (Theis et al 2006).…”