Open AccessResponse of the integrals in the Tremaine–Weinberg method to multiple pattern speeds: a counter‐rotating inner bar in NGC 2950?
Author(s) -
Maciejewski Witold
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10679.x
Subject(s) - physics , galaxy , bar (unit) , astrophysics , extension (predicate logic) , barred spiral galaxy , hubble sequence , disc galaxy , galaxy formation and evolution , meteorology , computer science , programming language
When integrals in the standard Tremaine–Weinberg method are evaluated for the case of a realistic model of a doubly barred galaxy, their modifications introduced by the second rotating pattern are in accord with what can be derived from a simple extension of that method, based on separation of tracer's density. This extension yields a qualitative argument that discriminates between prograde and retrograde inner bars. However, the estimate of the value of inner bar's pattern speed requires further assumptions. When this extension of the Tremaine–Weinberg method is applied to the recent observation of the doubly barred galaxy NGC 2950, it indicates that the inner bar there is counter‐rotating, possibly with the pattern speed of −140 ± 50 km s −1 arcsec −1 . The occurrence of counter‐rotating inner bars can constrain theories of galaxy formation.