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PhD Thesis: Exploring Star Formation in Cluster Galaxies

Abstract : Galaxy clusters are the most dense virialized environments in the known Universe. Hence they are the best locations to study the effect of the high-density environment on the evolution of galaxies. The intracluster medium (ICM) plays an important role in galaxy evolution. The goal of this dissertation is to study the effect of the ICM on galaxy evolution using star formation. A sample of 10 galaxy clusters were observed through the $r$-band and redshifted $H\alpha$ narrow-band filters using the Mayall 4-m telescope at the Kitt Peak National Observatory. Continuum image subtraction was used to measure H$\alpha$ flux to quantify star formation. Cluster galaxies were selected using the red-sequence method. The radial dependence ($0.0\leq (r/r_{200})\leq 1.0$) of the star formation rate (SFR), equivalent width (EW), and specific star formation rate (SSFR) were measured for the cluster galaxy sample. Evidence for quenching of star formation towards the cluster center was found at all radii using the SFR, EW, and SSFR to estimate star formation activity. Results suggest that both galaxy harassment and ram pressure stripping help to quench star formation in the low-density cluster outskirts, while ram pressure stripping plays a more important role towards the high-density cluster center. The cluster galaxy sample was divided into giant (high-mass) and dwarf (low-mass) galaxies. It was found that dwarfs are more susceptible to ram pressure stripping than the giant systems. The effect of the cluster environment on different morphological types, such as elliptical and spiral galaxies, was studied and it was determined that ram pressure and galaxy harassment have similar effects on the SFR for both morphological types.

Peer reviewed journals

1. “Star formation in low-redshift cluster dwarf galaxies. Cody M. Rude, MR Sultanova, GL Gamage, WA Barkhouse, Sandanuwan P. Kalawila Vithanage, Monthly Notices of the Royal Astronomical Society, Volume 493, Issue 4, April 2020, Pages 5625–5635, https://doi.org/10.1093/mnras/staa697
2. “Globular cluster population of the HST frontier fields galaxy J07173724+3744224”, Nathan L. Carlson, Madina R. Sultanova, Sandanuwan P. Kalawila Vithanage, Wayne A. Barkhouse , Gihan L. Ipita Kaduwa Gamage, Cody M. Rude , Omar Lopez-Cruz, Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 2, October 2018, Pages 1956–1972, https://doi.org/10.1093/mnras/sty1979 .

Major conference presentations

• H-alpha Imaging survey of Low redshift Cluster Dwarf Galaxies, W Barkhouse, Sandanuwan Kalawila, M Sutanova, C Rude , HN Archer, G Foote, American Astronomical Society Meeting Abstracts, 2016.
• The Nature of Red sequence Spiral Galaxies ,Lane Kashur, Wayne Barkhouse, Madina Sultanova, Sandanuwa Kalawila Vithanage, Haylee Archer, Gregory Foote, Elijah Mathew, Cody Rude, Omar Lopez-Cruz, American Astronomical Society Meeting Abstracts, 2017.
• Exploring Star Formation in Cluster Galaxies, Sandanuwan Kalawila, Madina Sultanova, Technical conference, University of North Dakota, Grand Forks, ND, 2018