Issue |
A&A
Volume 386, Number 1, April IV 2002
|
|
---|---|---|
Page(s) | 149 - 168 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20020248 | |
Published online | 15 April 2002 |
Weak homology of elliptical galaxies
1
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
2
Università degli Studi di Milano, Dipartimento di Fisica, via Celoria 16, 20133 Milano, Italy e-mail: Giuseppe.Bertin@unimi.it
3
Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: ciotti@bo.astro.it
4
Università degli Studi dell'Aquila, Dipartimento di Fisica, via Vetoio Località Coppito, 67100 L'Aquila, Italy e-mail: milena@terri1.te.astro.it
Corresponding author: M. Del Principe, milena@terri.te.astro.it
Received:
22
November
2001
Accepted:
8
February
2002
Studies of the Fundamental Plane of early–type galaxies,
from small to intermediate redshifts, are generally carried out under
the guiding principle that the Fundamental Plane reflects the
existence of an underlying mass–luminosity relation for such
galaxies, in a scenario where galaxies are homologous systems in
dynamical equilibrium. In this paper we re-examine the question of
whether a systematic non–homology could be partly responsible for the
correlations that define the Fundamental Plane. We start by studying
a small set of objects characterized by photometric profiles that have
been pointed out to deviate significantly from the standard
law. For these objects we confirm that a generic
law, with n
a free parameter, can provide superior fits (the best-fit value of n
can be lower than 2.5 or higher than 10), better than those that can
be obtained by a pure
law, by an
+ exponential model, and
by other dynamically justified self–consistent models. Therefore,
strictly speaking, elliptical galaxies should not be considered
homologous dynamical systems. Still, a case for weak homology,
useful for the interpretation of the Fundamental Plane, could be made
if the best-fit parameter n, as often reported, correlates with
galaxy luminosity L, provided the underlying dynamical
structure also follows a systematic trend with luminosity. We
demonstrate that this statement may be true even in the presence
of significant scatter in the correlation
. Preliminary
indications provided by a set of “data points" associated with a
sample of 14 galaxies suggest that neither the strict homology nor the
constant stellar mass–to–light solution are a satisfactory
explanation of the observed Fundamental Plane. These conclusions await
further extensions and clarifications, because the class of
low–luminosity early–type galaxies, which contribute significantly
to the Fundamental Plane, falls outside the simple dynamical framework
considered here and because dynamical considerations should be
supplemented with other important constraints derived from the
evolution of stellar populations.
Key words: galaxies: elliptical and lenticular, cD / galaxies: fundamental parameters / galaxies: kinematics and dynamics / galaxies: photometry
© ESO, 2002
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