Bibcode
del Rio, M. S.; Cepa, J.
Bibliographical reference
Astronomy and Astrophysics, v.340, p.1-20 (1998)
Advertised on:
12
1998
Journal
Citations
14
Refereed citations
13
Description
In this paper we analyse the structure of a small sample of galaxies
using a set of CCD images in standard photometric bands presented in a
previous paper (del Rio & Cepa 1998a, hereafter cite{p2}). The
galaxies are NGC 157, 753, 895, 4321, 6764, 6814, 6951, 7479 and 7723,
and the selected bands were B and I. Seven galaxies are grand design,
i.e. they have two long and symmetric arms, second in the classification
of cite{ee87} (1987), and are the best laboratories for testing the
predictions of the spiral density wave (SDW) theory. Two of the galaxies
have intermediate arms, i.e., they are not so well defined. They are
selected to compare the results with those found in the grand design
spirals. Using the method of analyse the azimuthal flux profiles
presented by cite{c88} (1988) and Beckman & Cepa (1990) (hereafter
cite{bc90}) and assuming that star formation is triggered by a spiral
density wave, we look for evidence of the existence of a corotation
radius, as predicted by the SDW theory. We have determined the
corotation radius in all but two grand design galaxies, and,
tentatively, in the other four. Galaxies with very weak arms (such as
NGC 753 and NGC 6951) or arms which are not well defined (such as NGC
6764 and NGC 7723) present difficulties when employing the azimuthal
profile method, but even in these cases, the method is powerful enough
to give a good estimate of the value of corotation, which must then be
confirmed (or discarded) by other independent methods (del Rio &
Cepa 1998b, hereafter cite{p4}).