Determining the Dark Matter Content of Dwarfs and Dwarfs
Spheroidal Galaxies in the Local Group Cluster using the CAS
Parameters
Ungku Ferwani Salwa Ungku Ibrahim
1,2,*
, Zamri Zainal Abidin
1
, Norsiah Hashim
1,2
, Mohd Shaiful Rizal Hassan
1
,
Zety Sharizat Hamidi
3
and Zainol Abidin Ibrahim
1
1
Department of Physics,
Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
2
Center for Foundation Studies in Science, University of Malaya,
50603 Kuala Lumpur, Malaysia
3
Faculty of Applied Sciences, Universiti Teknologi MARA,
UiTM S.Alam, Selangor, Malaysia
*uferwanis@um.edu.my
Abstract—In this paper, we will discuss the CAS parameters
(concentration, asymmetry and clumpiness) which are used to
determine the non-parametric structures of dwarf samples to
calculate the dark matter masses of dwarfs and dwarfs
spheroidal galaxies in the Local Group Cluster. Dwarf galaxies
are the most numerous galaxies in our Universe and the Milky
Way is surrounded by dozens of them. Measuring the dark
matter content of dwarf galaxies has mainly been carried out
using kinematic measures of individual stars in Local Group
systems. However, if the galaxy is perturbed by tides, the
assumption that it is in virial equilibrium will be incorrect. A
new method which was introduced by Samantha J. Penny et al.
(2008) for measuring the dark matter content of dwarf
Ellipticals in the Perseus Cluster is based on the radius of the
dwarf, the projected distance of the dwarf from the cluster
centre and the total mass of the cluster interior to it. We will
present this new method and use it to determine the dark
matter content of dwarfs and dwarfs spheroidal galaxies in the
Local Group. We will also describe our new method in
determining Dark Matter Halos content in Galaxy Clusters.
Keywords-Cosmology, Dark Matter, Radio Astronomy
INTRODUCTION
By introducing new parameter, known as CAS
parameter [1], one can determined the non-parametric
structures of dwarf galaxy sample. The CAS
parameters are useful for characterizing the structural
properties of galaxies using model-independent
measurements. We need to review how galaxy
structure correlates with physical properties of
galaxies in determining the galaxy morphology- redshift
relationship. Technically speaking, galaxy morphology
correlates with galaxy properties such as luminosities,
environment and mass-to-light ratio.
Some quantitative measurements of galaxy
structure correlates hardly with physical properties but it
is impossible to describe all. The light concentration
of an evolved stellar population was first to be
discovered relates with its luminosity, stellar mass and
scale. While the concentration of a galaxy’s light profile
correlates with its stellar mass, absolute magnitude and size,
in a sense revealing the past formation history of a galaxy,
there are several indicators in the structures of galaxies
ongoing galaxy formation. For instant, recently it has
been shown that the clumpiness of the galaxy’s light
distribution correlates with the amount and the
location of star formation. The clumpiness is
measured by quantifying the fraction of galaxy’s light in
the rest-frame B-band in high spatial frequency structures.
The ratio between the amount of light in these high spatial
frequency structures and total light gives a measure of
clumpiness, or star formation. There is also strong
relationship between the dynamical state of a galaxy
and the presence of a merger. Generally, merging galaxies
are asymmetric, while non-mergers are not. This has been
shown in numerous ways, including empirical methods and
the correlation of internal HI dynamics and asymmetries of
stellar distributions.
The study of hydrogen line spectral in the 21 cm
background is becoming one of the most exciting fields in
astrophysics and vast quantity of high profile instruments are
being built and designed at present day. Most of these
instruments general purpose and are designed to detect
neutral hydrogen (HI) in galaxies at around redshifts of 1
or 4 from the epoch of reionization out to redshifts of 10
and beyond. However, the understanding of neutral
hydrogen at low redshifts is also of interest and the project
we propose will contribute to this area and allow us to
build up experience for future studies using these more
powerful instruments. Computing the mass (and accurate
redshifts) of low redshift galaxy clusters is the main
objective of the proposed instrument and this will
provide a useful resource for the wider- community
especially in Malaysia since it will be the first research-
based radio astronomical instrument ever to be built in the
country.
Onset of the epoch of reionization might be possible
to detect using redshifted 2l cm emission. It has been noted
also that the spin-temperature prior to reionization can be
observed in Cosmic Microwave Background (CMB) at very
low frequencies (~ 30-50 MHz) enabling accurate
determination of important cosmological parameters. The
motivation of this work is however takes a different
approach. Mapping of the large-scale structure, after the
Proceeding of the 2011 IEEE International Conference on Space Science and Communication (IconSpace)
12-13 July 2011, Penang, Malaysia
978-1-4577-0564-9/11/$26.00 ©2011 IEEE 182