Detalles de publicación
PP 08023
Color Profiles of Spiral Galaxies: Clues on Outer-Disk Formation Scenarios
(1) Insituto de Astrofísica de Canarias (IAC)
(2) Cardiff University, School of Physics and Astronomy
We have explored radial color and stellar surface mass density profiles for a
sample of 85 late-type spiral galaxies with deep (down to ~ 27
mag/arcsec^2 SDSS g' and r' band surface brightness profiles. About 90%
of the light profiles have been classified as broken exponentials, exhibiting either truncations (Type II galaxies) or antitruncations (Type III galaxies). The color profiles of Type II galaxies show a ``U shape'' with a minimum of (g' - r') = 0.47 +- 0.02 mag at the break radius. Around the break
radius, Type III galaxies have a plateau region with a color of (g' - r') =
0.57 +- 0.02. Using the color to calculate the stellar surface mass density
profiles reveals a surprising result. The breaks, well established in the light
profiles of the truncated galaxies, are almost gone, and the mass profiles now
resemble those of the pure exponential (Type I) galaxies. This result
suggests that the origin of the break in Type II galaxies is more likely due to
a radial change in stellar population than being associated with an actual drop
in the distribution of mass. Type III galaxies, however, seem to preserve their
shape in the stellar mass density profiles. We find that the stellar surface
mass density at the break for truncated galaxies is 13.6 +- 1.6 M_sun/pc^2 and for the antitruncated ones is 9.9 +- 1.3 M_sun/pc^2 for the antitruncated ones. We estimate that the fraction of stellar mass outside the break radius is ~ 15% for truncated galaxies and ~ 9% for antitruncated galaxies.
sample of 85 late-type spiral galaxies with deep (down to ~ 27
mag/arcsec^2 SDSS g' and r' band surface brightness profiles. About 90%
of the light profiles have been classified as broken exponentials, exhibiting either truncations (Type II galaxies) or antitruncations (Type III galaxies). The color profiles of Type II galaxies show a ``U shape'' with a minimum of (g' - r') = 0.47 +- 0.02 mag at the break radius. Around the break
radius, Type III galaxies have a plateau region with a color of (g' - r') =
0.57 +- 0.02. Using the color to calculate the stellar surface mass density
profiles reveals a surprising result. The breaks, well established in the light
profiles of the truncated galaxies, are almost gone, and the mass profiles now
resemble those of the pure exponential (Type I) galaxies. This result
suggests that the origin of the break in Type II galaxies is more likely due to
a radial change in stellar population than being associated with an actual drop
in the distribution of mass. Type III galaxies, however, seem to preserve their
shape in the stellar mass density profiles. We find that the stellar surface
mass density at the break for truncated galaxies is 13.6 +- 1.6 M_sun/pc^2 and for the antitruncated ones is 9.9 +- 1.3 M_sun/pc^2 for the antitruncated ones. We estimate that the fraction of stellar mass outside the break radius is ~ 15% for truncated galaxies and ~ 9% for antitruncated galaxies.