De Vaucouleurs Atlas Type: SB(r)0/a
Telescope: NOT 2.5-m
North left , East down
Field Dimensions: 4.0 x 3.0 arcminutes
RC3 Type: SB(r)0/a
RSA Type: SBa(s)
Surface Brightness Range Displayed: 17.5-27.0 mag per square arcsec
Absolute Blue Magnitude: -17.9
De Vaucouleurs Atlas Description:
This galaxy is a beautiful example of a system having a bar, an inner ring , and a nuclear ring, but no trace of an outer ring . If the rings are resonance features, and the pattern speed of the bar is low enough to allow a nuclear ring to exist, then the absence of an outer ring either means the OLR does not exist, or that there is no gas near that resonance to allow the ring to be seen.
All of the features in the galaxy are well-defined. The nuclear ring is a closed, patchy ellipse in projection, and in the B-V color index map is lined by blue associations. The regular shape of this ring is exceptional. Weak leading dust lanes are seen in the bar, but otherwise this region is uncomplicated compared to the bar regions in many other galaxies. The inner ring is very similar to that seen in NGC 1433 , that is, it appears to be made of four tightly wrapped spiral segments. This ring is also lined by blue associations, which are concentrated mainly in arcs around the bar axis, as in other galaxies where the inner ring is intrinsically elongated along the bar (Crocker, Baugus, and Buta 1996). The tight spiral character and patchiness of the inner ring are the basis for the type S0/a.
The deprojected image shows that the inner ring is indeed elongated parallel to the bar with a significant ellipticity. The axis ratio is ~0.8, typical of the average SB inner ring (Buta 1995). The nuclear ring deprojects into a nearly circular shape. The image also shows that NGC 4245 has only a small bulge compared to the typical S0/a galaxy.