De Vaucouleurs Atlas Type: SAB(rs)cd
Telescope: Pal 1.5-m
North up , East right
Field Dimensions: 12.6 x 11.3 arcminutes
RC3 Type: SAB(rs)cd
RSA Type: Sc(s)II
Surface Brightness Range Displayed: 19.0-26.0 mag per square arcsec
Absolute Blue Magnitude: -20.9
Elmegreen Spiral Arm Class: AC 9
De Vaucouleurs Atlas Description:
NGC 6946 is a prototype of de Vaucouleurs classification SAB(rs)cd. NGC 6946 's spiral structure is complex, multi-armed, and dominated by star formation. There is a small core region, from which an open, two-armed dust pattern emerges. The straightness of the spiral arm extending northward from the nucleus highlights one of the leading dust lanes in the bar. The opposing dust lane is also visible but does not have a ridge of star-formation to highlight it. The bar is best seen in the R-band image, where it appears to be elongated in a northeast-southwest direction. The inner pseudoring is of the wrapped arm type. At least three clear arms break from this region, with several more diffuse and ill-defined features further out.
The g-r color index map (calibrated approximately as B-V) shows finely detailed complex dust structure dominating the whole region of the inner pseudoring and bar, and lining the inner edges of the main outer arms.
NGC 6946 has been the subject of many detailed studies. Like other nearby, late-type spirals, it has a nuclear starburst (Turner and Ho 1983) and interesting nuclear structure, including a nuclear bar (Elmegreen, Chromey, and Santos 1998).