Ungku Ferwani Salwa Ungku Ibrahim

Dark Matter Study of NGC 5055

This paper is about rediscovering dark matter (DM) in galaxies before the year 1970. It is an Italy-Malaysia Astroproject (SISSA-Radio Cosmology Research group), introducing to the field of DM. Investigations about the rotation curve (RC) of NGC 5055 or the Sunflower Galaxy at that time showed that there was a distinct possibility that they had the knowledge and also the theory of gravitation to initiate the study of dark matter. NGC 5055 was chosen because of its good kinematical and photometric data. Information of the surface brightness of this spiral galaxy will determine the disk length scale, RD. Using this RD and by fitting the RC data of NGC 5055 with the velocity profile of the Freemans disk, we look at the results to conclude whether there are signs of dark matter in the Sunflower Galaxy.

Measuring the neutral hydrogen mass of galaxy cluster A262

The total neutral hydrogen mass of galaxy cluster, MHI is measured using spectra taken by a 7 meter single dish radio telescope at Jodrell Bank Observatory. This have been done by using a concept introduced by R. A. Bettye which is make use of small single radio telescope for findings MHI as a whole. MHI is calculated by using simple relationship involving parameter distance of the object from the observer, D and radiated flux of continuum radio source, S ν. A262 is chosen as our test subject since it is compatible with the capability of our instrument. It is a spiral rich galaxy cluster and a fragment of Pisces in the Perseus supercluster, located approximately at 62 – 77 Mpc. It is a part of Local Group Supercluster that is centered at giant elliptical galaxy, NGC 708, and it is also called ‘cluster dominant’ because of its strongly X-ray source concentrated. A262 is chosen as our candidate in this study because of its relatively low redshift, z = 0.0156, observed in 21 cm emission as their tracer. We calculate MHI of A262 according to some analysis from previous studies. Preliminary detection of A262 showed some degree of success.

NEUTRINO ENERGY LOSS AT MATTER-RADIATION DECOUPLING PHASE

Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be in equilibrium with radiation when the weak interaction rate becomes slower than the rate expansion of the universe. The ratio of the temperature of the photon to the temperature of the neutrino at this stage is Tγ/Tν = (11/4)1/3. We investigate the neutrino energy loss due to the oscillation of the electron neutrino into a different flavor in the charged-current interaction of νe-e- based on the work of Sulaksono and Simanjuntak. The energy loss from the neutrinos ΔEν during the decoupling of the neutrinos with the rest of the matter would be a gain in the energy of the electrons and can be obtained from the integration of stopping power equation ΔEν = (dEν/dT-1)dT-1 where Eν and T are the energy of the neutrinos and the temperature respectively. When the universe expands and matter-radiation decouples, an extra energy will be transferred to the photons via the annihilation of the electron-positron pairs, e++e-→γ+γ. This consequently will increase the temperature of the photons. The net effect to the lowest order is an increase in the ratio of the photon temperature to the neutrino temperature. The magnitude of energy loss of the neutrino is ∼10-4-10-5 MeV for the probability of conversion of νe → νi (i = μ,τ) between 0 to 1.0.