De Vaucouleurs Atlas Type: (R1')SAB(rs)a
Telescope: Palomar 1.5-m
North right , East up
Field Dimensions: 5.2 x 3.9 arcminutes
RC3 Type: (R)SB(s)a
RSA Type: SBa or Sa
Surface Brightness Range Displayed: 17.0-26.0 mag per square arcsec
Absolute Blue Magnitude: -20.6
Elmegreen Spiral Arm Class: AC 6
De Vaucouleurs Atlas Description:
This is an excellent example of an early-type , weakly barred spiral with an OLR -type outer ring . Although classified as a true ring by de Vaucouleurs, it is actually a pseudoring made of two tightly wrapped diffuse spiral arms. The inner zone is a classic oval with only a trace of an inner pseudoring . The bar itself is a weak ansae type, and the oval is slightly pointy. The Gunn r-band image of the galaxy is shown because it reveals the ansae best and is deeper than the g-band image used for the color index map.
The g-r color index map reveals a dust ring around a blue nucleus, and perhaps one weak bar leading dust lane. There is little star formation around the rim of the oval.
NGC 5377 is a classic resonance ring barred spiral with a dimpled outer pseudoring characteristic of the OLR . We recognize the feature as type R1' , based on two arms that intersect after winding 180 degrees. The deprojected r-band image, based on ellipse fits to faint outer isophotes, indicates that the outer pseudoring is elongated nearly perpendicular to the bar, as is typical of such features.