DARK MATTER DENSITY PROFILE IN THE INNER RADIUS OF MASSIVE DWARFÂ GALAXIES

• Main Author: Muhammad Al Farisy, Fahmi
• Format: Final Project
• Language: Indonesia
• Subjects: Astronomi
• Online Access: https://digilib.itb.ac.id/gdl/view/73568
• Institution: Institut Teknologi Bandung

The presence and distribution of dark matter on galactic scales can be studied through rotation curves. Dwarf galaxies generally have a larger fraction of dark matter compared to more massive galaxies. The cold dark matter (CDM) model is the standard model for dark matter and is supported by observational evidence. However, this model has issues, one of which is the core-cusp problem, which refers to the discrepancy between the observed and simulated dark matter density profiles in the inner regions of dwarf galaxies using the CDM model. Typically, the dark matter density profiles in normal galaxies match the cuspy profiles, such as the Navarro-Frenk-White (NFW) profile, while dwarf galaxies tend to match profiles that are cored, with a flatter inner region. In this Final Project, the density profiles of dark matter in massive dwarf galaxies (with masses between dwarf and normal galaxies) are studied to determine whether they tend to be cored or cuspy. By selecting data from the SPARC catalogue, which includes observations using HI, H?, and CO tracers, eight galaxies (109.2 ? M(M?) < 109.7) were obtained. Rotation curve decompositions were performed using various dark matter halo models through the Markov Chain Monte Carlo (MCMC) method. Most galaxies are better fit by cored profiles rather than NFW, both overall and at the inner radii, except for NGC 4214 and UGC 8490, which are dark matter-dominated, have small effective radii, and match the NFW model. The parameters obtained from the MCMC analysis were used to construct dark matter density profiles and calculate the parameter (??) that quantifies the degree of coredness or cuspiness behavior. The value of ?? = 0.699+0.759 ?0.767 is consistent with the literature, indicating that the inner density profiles of massive dwarf galaxies tend to be shallower than the NFW profile but have a tendency to be more cuspy than low-mass dwarf galaxies. The rotation curves based on different tracers (HI, H?, and CO) were also studied, and it was found that, in general, the rotation curves from all three tracers are consistent. However, there may be offsets caused by non-gravitational processes such as star formation, as observed in NGC24. Combining data from multiple tracers provides a better understanding of the mass distribution of galaxies, including dark matter.