De Vaucouleurs Atlas Type: (R1)SAB(r)a
Telescope: KPNO 0.9-m
North left , East down
Field Dimensions: 4.6 x 3.4 arcminutes
RC3 Type: SAB(r)a:
RSA Type: SBb(s)II
Surface Brightness Range Displayed: 18.0-27.0 mag per square arcsec
Absolute Blue Magnitude: -21.4
Elmegreen Spiral Arm Class: AC 2
De Vaucouleurs Atlas Description:
The SB94 type of SBb(s) is failing to recognize the interesting nature of this system. If the prototype SBb(s) galaxy is NGC 1300 , then this galaxy cannot be SBb(s). Instead, NGC 5728 is a triple-ringed Seyfert 2 galaxy, each ring having distinctive characteristics. The bar is a conspicuous feature but is a little weaker-looking than a typical SB-type bar, hence the underline notation . The bar also shows two leading dust lanes , one more prominent than the other, and the presence of these lanes probably explains the SB94 type of SBb. Inside the bar there is a strong, nearly circular nuclear ring which is miscentered on the nucleus. The inner ring is a very good example that is lightly patchy and made mostly of two tightly wrapped spiral arms; it is clearly a zone of active star formation and is closed enough to merit the (r) classification. Beyond this ring is a bright, slightly dimpled R1 outer ring which is also a very good example of the type. The insert shows this feature more clearly.
The ionized gas kinematics of NGC 5728 has been studied by a number of authors, including Schommer et al. (1988), who found doubled line profiles in the nuclear ring. The galaxy also has a secondary bar which is discussed by Erwin (2004).