De Vaucouleurs Atlas Type: (R')SAB(r)ab pec
Telescope: Issac Newton 2.5-m\b
North up , East left
Field Dimensions: 9.8 x 9.2 arcminutes
RC3 Type: SAB(r)ab pec
RSA Type: Sb/SBb(r)II
Surface Brightness Range Displayed: 17.0-27.0 mag per square arcsec
Absolute Blue Magnitude: -20.8
Elmegreen Spiral Arm Class: AC 6
De Vaucouleurs Atlas Description:
This bright nearby galaxy has the largest inner ring (in terms of angular size) in the sky. The ring and the bar inside it are the dominant morphological features. The bar is broad and looks relatively weak. There is no star formation in the bulge region. Much of the galaxy's star formation is instead concentrated in the inner ring . The distribution of this star formation is interesting: it appears to concentrate in broad arcs around the ends of the bar. These arcs are brighter than the interbar sections of the ring. In a study of radial velocities of HII regions around the ring, Buta (1988) showed that models of an expanding circular ring, or an elliptical bar orbit, could equally well explain the variation of radial velocity with angle around the ring. Given the ``bunching up" of the HII regions around the bar major axis, it is most likely that the ring is intrinsically elliptical in shape.
Outside the relatively symmetric inner ring and bar region, a tightly wrapped one-armed spiral follows the ring closely before spiraling into the outer disk. The asymmetry is due to an interaction with the neighboring galaxy NGC 4747 (Haynes 1979).
The Sab classification is based on the large bulge, the general tightness of the spiral arms, and the light patchiness in the ring and inner arm regions.