b) Narrow ring or wide annulus?
Polar rings appear to come in two flavors; 1) an annulus (i.e., a disk-like component with the central region cut out), and 2) a narrow ring which is not extended in radius. Figure 2 shows two galaxies which are examples of annular systems (NGC 4650A in the upper left and A0136-0801 in the lower left) and two galaxies which are examples of narrow ring systems (ESO 415-G26 in the upper right and AM 2020-504 in the lower right). In many cases the polar ring component is too edge-on to make this distinction obvious. Table 1 includes a summary of various characteristics for Category A and B galaxies from the PRC. Column 2 is a determination of what type of ring the galaxies have. In the 16 cases where a clear determination can be made, seven are annular rings while nine are narrow rings.
|
Figure 2. Examples of polar-ring galaxies with annular rings (NGC 4650A in the upper left and A0136-0801 in the lower left) and with narrow rings (ESO 415-G26 in the upper right and AM 2020-504 in the lower right). |
There are no obvious correlations between the width of the polar ring and other properties. For example, while ESO 415-G26 and NGC 2685 have narrow polar-rings and appear to be young systems with chaotic distributions of luminosity and HI, IC 1689 and AM 2020-504 also have narrow rings but appear to be very symmetric.
| Angle | Type of | Ring | Outer | |||
| PRC | Other ID | Type | (deg) | warp | symmetry | debris |
| Category A - KINEMATICALLY CONFIRMED | ||||||
| A-1, | A 0136-0801 | annulus(1) | 7 (1) | integral-inner (1) | 1 (1) | 1 (1) |
| A-2, | ESO 415-G26 | narrow (1) | 16 (1) | - | 2 (2) | 3 (1) |
| A-3, | NGC 2685 | narrow (1) | 7 (2) | - | 3 (1) | 3 (1) |
| A-4, | UGC 7576 | - | 12 (2) | banana (2) | 1 (2) | 1 (2) |
| A-5, | NGC 4650A | annulus(3) | 12 (2) | integral-outer (1) | 1 (2) | 2 (1) |
| A-6, | UGC 9796, IIZw73 | annulus(1) | 26 (2) | straight (2) | 2 (2) | 1 (2) |
| Category B - GOOD CANDIDATES | ||||||
| B-1, | IC 0051 | narrow (3) | 2 (2) | - | 2 (3) | 3 (2) |
| B-2, | A 0113-5442 | annulus(3) | 10 (3) | banana (2) | 2 (2) | - |
| B-3, | IC 1689 | narrow (2) | 2 (2) | - | 1 (2) | 1 (2) |
| B-4, | A 0336-4905 | - | 13 (2) | - | 1 (2) | 3 (2) |
| B-5, | A 0351-5458 | narrow (1) | 32 (2) | - | 2 (2) | - |
| B-6, | AM 0442-622 | - | 34 (2) | - | - | - |
| B-7, | Abell 548-17 | - | 7 (2) | banana (3) | 2 (3) | - |
| B-8, | AM 0623-371 | - | 4 (2) | - | 1 (2) | - |
| B-9, | UGC 5119 | - | 6 (2) | - | 2 (2) | - |
| B-10 | A 0950-2234 | - | 3 (2) | - | 2 (2) | - |
| B-11, | UGC 5600 | - | 3 (2) | - | - | 3 (1) |
| B-12, | ESO 503-G17 | - | 9 (1) | - | 1 (2) | - |
| B-13, | Abell 1631-14 | annulus(3) | 30 (3) | - | 3 (2) | - |
| B-14, | Abell 1644-105 | narrow (2) | 2 (3) | - | 1 (1) | 1 (2) |
| B-15, | A 1256-1710 | - | 7 (3) | - | - | - |
| B-16, | NGG 5122 | annulus (3) | 1 (1) | straight (2) | 1 (2) | - |
| B-17, | UGC 09562 | - | 18 (2) | straight (2) | 2 (2) | 2 (2) |
| B-18, | AM 1934-563 | annulus(3) | 30 (2) | integral-outer (1) | - | - |
| B-19, | AM 2020-504 | narrow (1) | 1 (1) | - | 1 (1) | 1 (1) |
| B-20, | A 2135-2132 | - | 3 (2) | - | 1 (2) | 2 (2) |
| B-21, | ESO 603-G21 | - | 1 (2) | integral-inner (2) | 2 (2) | 2 (2) |
| B-22, | A 2329-4102 | narrow (2) | 36 (2) | - | 2 (2) | - |
| B-23, | A 2330-3751 | - | 8 (2) | - | - | - |
| B-24, | A 2333-1637 | narrow (3) | 43 (3) | - | 2 (2) | - |
| B-25, | A 2349-3927 | - | 5 (2) | straight (2) | 3 (2) | 3 (2) |
| B-26, | AM 2350-4042 | - | 4 (2) | banana (2) | 2 (2) | - |
| B-27, | ESO 293-IG17 | - | 1 (2) | - | - | - |
| NOTES: Column 1: Name from PRC, other identification Column 2: type of ring (annulus means a disk with the central region cut out; narrow means the ring is not extended in radius) Column 3: angular distance away from perpendicularity of the disk and ring Column 4: type of warp (integral means the two sides bend in opposite directions [inner or outer refers to which part of the ring is more perpendicular to the disk], banana means the two sides bend in the same direction) Column 5: how symmetric the ring is with respect to the plane of the disk (1 = very symmetric to 3 = very asymmetric) Column 6: amount of material not associated with either the ring or disk (1 = no debris to 3 = extensive debris). Quality ratings are included in parenthesis (1 = very good to 3 = uncertain). | ||||||