NGC 7742 - SAB(r)ab

NGC 7742

De Vaucouleurs Atlas Type: SAB(r)ab

Filter: S(~B)

Telescope: HST 2.4-m
North lower left , East lower right
Field Dimensions: 1.4 x 1.0 arcminutes

RC3 Type: SA(r)b
RSA Type: Sa(r!)
Surface Brightness Range Displayed: 15.0-24.5 mag per square arcsec
Absolute Blue Magnitude: -19.4
Elmegreen Spiral Arm Class: AC n

De Vaucouleurs Atlas Description:

The ring in NGC 7742 is the dominant feature of its morphology. De Zeeuw et al. (2002) found that the ionized gas in the ring counter-rotates wuth respect to the stars inside the ring. Since the galaxy is nearly face-on, the near circular shape of the ring is its intrinsic shape. In the V-I color index map, the ring is very blue, indicating it is a region of very active star formation. Thin dust lanes can be seen winding nearly to the center inside the ring. The outer disk includes weak, patchy spiral features, part of the basis for the Sab classification. Pogge and Eskridge (1993) and Crocker, Baugus, and Buta (1996) showed that the ring is also strong in H-alpha flux and is lined with HII regions . The HST image also shows that the galaxy has a weak central oval (see also Wakamatsu et al. 1996); this feature is the basis for the SAB classification.