5,192 research outputs found
A Morphological Method to Determine Co-Rotation Radii in Spiral Galaxies
Shock induced star formation in a stellar density wave scenario produces an
azimuthal gradient of ages across the spiral arms which has opposite signs on
either side of the corotation resonance (CR). We present a method based on the
Fourier analysis of azimuthal profiles, to locate the CR and determine the arm
character (trailing or leading) in spiral galaxies. Basically, we compare the
behavior of the phase angle of the two-armed spiral in blue and infrared colors
which pick out respectively young and older disk stellar population. We
illustrate the method using theoretical leading and trailing, spirals. We have
also applied the method to the spiral galaxies NGC 7479, for which we confirm
the reported leading arms, and NGC 1832. In these galaxies we find two and
three CRs respectively.Comment: 9 pages, accepted for publication in ApJL, figures 4 and 6 avaliables
at ftp://ftp.inaoep.mx/pub/salida/puerari, full paper also avaliable at
http://www.inaoep.mx/~puerar
Trends for Outer Disk Profiles
The surface-brightness profiles of galaxy disks fall into three main classes,
based on whether they are simple exponentials (Type I), bend down at large
radii (Type II, "truncations") or bend up at large radii (Type III,
"antitruncations"). Here, we discuss how the frequency of these different
profiles depends on Hubble type, environment, and the presence or absence of
bars; these trends may herald important new tests for disk formation models.Comment: LaTeX, 2 pages, 1 EPS figure, uses modified newpasp.sty (included).
To appear in Formation and Evlution of Galaxy Disks, eds. J.G. Funes and E.M.
Corsin
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