On the Light-Profiles of Spiral Galaxy Bulges and the Hubble Sequence for Spirals

Graham, Alister W.; Prieto, Mercedes
Bibliographical reference

Astrophysics and Space Science, v. 269/270, p. 653-654 (1999).

Advertised on:
12
1999
Number of authors
2
IAC number of authors
0
Citations
1
Refereed citations
1
Description
Recent studies have claimed that the Hubble sequence of late-type spirals, and spirals in general, is scale-free. Within the photometric data used in these works, a trend exists between morphological type and bulge profile shape such that late-type spiral bulges are described by an exponential luminosity profile, where-as the early-type spiral bulges are better described by an r^1/2 or r^1/4 law. The universal application of an exponential light-profile to the disk and bulge of all spiral galaxies is not justified. Taking structural parameters from exponential disk models and the best-fitting r^1/n bulge models (with n = 1, 2 or 4), the mean effective-bulge-radius to disk scale-length ratio (r_e/h) increases at the 3σ significance level. Additionally, the early-type spiral galaxies are shown to have a larger r_e/h ratio than the late-type spirals in all passbands.