For refcode 1997MNRAS.287..221G: Retrieve 26 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by Royal Astronomical Society.
1997MNRAS.287..221G
Some effects of galaxy structure and dynamics on the Fundamental Plane
Alister Graham and Matthew Colless
Accepted 1997 January 6. Received 1996 December 12; in original form 1996
September 16
ABSTRACT
We examine the effects on the Fundamental Plane (FP) of structural
departures from an R^1/4^ galaxy light profile. We also explore the use
of spatial (i.e., volumetric) as well as projected galaxy parameters. We
fit the Sersic R^1/n^ law to the Vband light profiles of 26 E/S0 Virgo
galaxies, where n is a shape parameter that allows for structural
differences amongst the profiles. The galaxy light profiles show a trend
of systematic departures from a de Vaucouleurs R^1/4^ law, in the sense
that n increases with increasing effective halflight radius R_e_. This
results in R_e_, and the associated mean surface brightness within this
radius, having systematic biases when constructed using an R^1/4^ law.
Adjustments to the measured velocity dispersion are also made, based upon
the theoretical velocity dispersion profile shapes of the different
R^1/4^ light profiles, constructed assuming spherical symmetry and
isotropic pressure support.
We construct the FP for the case when structural homology is assumed
(specifically, an R^1/4^ law is fitted to all galaxies) and central
velocity dispersions, {sigma}_0_, are used. The plane we obtain is
R_e_ is proportional to {sigma}_0_^1.33+/0.10^{SIGMA}_e_^0.79+/0.11^,
where {SIGMA}_e_ is the mean surface brightness within the projected
effective radius R_c_. This agrees with the FP obtained by others, and
departs from the virial theorem expectation R is proportional to
{sigma}^2^{SIGMA}^1^. We find that allowing for broken structural
homology through fitting R^1/n^ profiles (with n a free parameter), but
still using central velocity dispersions, actually increases the
departure of the observed FP from the virial plane  the increase in
effective radius with galaxy luminosity (and n) is overbalanced by an
associated decrease in the mean surface brightness.
In examining the use of spatial quantities and allowing for the
different velocity dispersion profiles corresponding to the observed
light profiles, we find that use of the spatial velocity dispersion at
the spatial halflight radius decreases the departure of the observed FP
from the virial plane. (Use of the spatial halflight radius and mean
surface brightness term has no effect on the FP, as they are constant
multiples of their projected values.) Through use of the Jeans
hydrodynamical equation, we convert the projected central aperture
velocity dispersion, {sigma}_0_ into the infinite aperture velocity
dispersion, {sigma}_tot,n_ (which is equal to onethird of the virial
velocity dispersion). Using both the R^1/n^ fit and {sigma}_tot,n_ we
obtain R_c,n_ is proportional to {sigma}_tot,n_^1.44+/
0.11^{SIGMA}_c,n_^0.93+/0.08^. Making the fullest allowance for broken
structural homology thus brings the observed FP closer to the virial
plane, with the exponent of the surface brightness term consistent with
the virial expectation.
Key words: galaxies: elliptical and lenticular, cD  galaxies:
fundamental parameters galaxies: kinematics and dynamics  galaxies:
structure  dark matter.
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