De Vaucouleurs Atlas Type: (R1')SAB(rs)ab
Telescope: Perkins 1.8-m
North up , East left
Field Dimensions: 3.4 x 2.5 arcminutes
RC3 Type: (R)SAB(s)ab
RSA Type: Sb(s)/SBb(s)I-II
Surface Brightness Range Displayed: 16.5-26.0 mag per square arcsec
Absolute Blue Magnitude: -20.4
Elmegreen Spiral Arm Class: AC 8
De Vaucouleurs Atlas Description:
NGC 3504 is not as face-on as it looks. Peterson (1982) showed that the galaxy is inclined approximately around the bar axis. Thus, the prominent outer pseudoring could be slightly elongated perpendicular to the bar. The Sab classification is based on the patchiness of the inner ring , and the relative smoothness of the two outer arms.
NGC 3504 is very much a resonance ring galaxy in the mold of NGC 1433 , only in this case the inner and nuclear rings are not as well-defined. De Vaucouleurs adopted a classification of (R)SAB(s)ab because he viewed the entire inner zone as the bar. The image, however, shows a clear bar with leading dust lanes inside the oval pseudoring zone. We use the underline notation to show that the bar almost merits an SB classification but is relatively weak. The inner pseudoring is ill-defined but definitely real and should be so recognized.
The outer ring of NGC 3504 is very well-defined but, being a pseudoring made of two outer arms, it is not recognized at all in the Carnegie and Hubble Atlas classifications. The ring is an excellent example of an undimpled R1' outer pseudoring .
In the center of NGC 3504 , a partial nuclear ring/spiral is found. This area has considerable H-alpha emission and is dominated by a starburst (Knapen, P\'erez-Ram\'irez, and Laine 2002).