The Quenching of Cluster Galaxies by Cory R. Wagner A thesis submitted to the Department of Physics, Engineering Physics & Astronomy in conformity with the requirements for the degree of Doctor of Philosophy Queen’s University Kingston, Ontario, Canada September 2018 Copyright c Cory R. Wagner, 2018 Abstract In this thesis we present two projects investigating the evolution and quenching of cluster galaxy star formation (SF) activity. Leveraging a sample of 36 galaxy clusters, we measure the level of member SF activity. Over the 7.5 billion years spanned by our clusters, from z = 1.5 to z = 0.15, the SF activity of cluster galaxies decreases by a factor of 11. This is much larger than the three-fold decline experienced by star-forming galaxies (SFGs), or the factor of four drop for quiescent galaxies, which have SF activity more than an order of magnitude lower than SFGs. The overall evolution of cluster member SF activity is driven not by the decline of either subset, but instead by the transitioning of galaxies from star-forming to quiescence. Indeed, from z = 1.5 to z = 0.15, the fraction of quiescent galaxies rises from 28% to 88%. To investigate the impact of strangulation, a long timescale quenching mechanism, we determine whether 58 members of the nearby galaxy cluster Abell 1795 possess hot halos. Markov chain Monte Carlo sampling is used to fit surface brightness profiles (SBPs) of stacked X-ray images with models that account for the dominant X-ray emission in and around cluster members. Hot gas halos around outer Abell 1795 members are detected, in a statistical sense. Inner cluster hot halos, however, remain undetected, with a luminosity upper limit six times lower than the hot halo luminosity in the outer cluster. This suggests that Abell 1795’s intracluster medium i is likely stripping the hot gas halos of infalling members. To further test our modeling technique we apply it to five additional clusters. Combining their data, we generate profiles and retrieve a good fit to the inner cluster SBP. Due to a relative lack of data in the clusters’ outskirts, we are unable to provide much constraint on hot halo presence. We propose stacking a greater number of outer cluster members, which would necessitate acquiring additional X-ray data, likely through a more targeted search of the Chandra Data Archive. ii Statement of Co-Authorship The research presented in this thesis was completed under the supervision of Stéphane Courteau (Queen’s University). Unless explicitly stated otherwise, the author (Cory R. Wagner) performed all the analysis, wrote the manuscripts, and created all figures and tables. All observations and data reductions were done by others. Chapter2 of this thesis contains a version of a paper published in The Astrophys- ical Journal, entitled “The Evolution of Star Formation Activity in Cluster Galaxies Over 0.15 < z < 1.5” by Cory R. Wagner, Stéphane Courteau, Mark Brodwin, S. A. Stanford, Gregory F. Snyder, and Daniel Stern. This work made use of proprietary IRAC Shallow Cluster Survey data provided by M. Brodwin, and an unpublished membership list for the cluster Abell 611 provided by D. Lemze. All other data products used for this project were publicly available at the time they were acquired. Chapter3 contains a version of a paper submitted for publication to The Astro- physical Journal, titled “Stripping of the Hot Gas Halos in Member Galaxies of Abell 1795” by Cory R. Wagner, Michael McDonald, and Stéphane Courteau. All data products used for this project were publicly available at the time they were acquired. Chapter4 contains an ongoing project whose publication is planned for a future date. All data products in use for this project were publicly available at the time they were acquired. iii Acknowledgments The results reported in this thesis are based in part on: data obtained from the Chandra Data Archive; observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA; data from the SDSS. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. The research contained herein made use of: Astropy (Astropy Collaboration et al. 2013); NumPy;1 SciPy;2 NASA’s Astrophysics Data System; Ned Wright’s online cos- mology calculator (Wright 2006); Eric O. Lebigot’s Uncertainties: a Python package for calculations with uncertainties; topcat (Taylor 2005); and Montage.3 In addition to my co-authors on Wagner et al.(2017), I am grateful to D. Lemze for providing his spectroscopic membership list for Abell 611, and to the CLASH collaboration for making their data publicly available. I would like to thank M. Balogh, D. Marchesini, and M. McDonald for constructive discussions, P. Eisenhardt for a helpful review of the paper, and A. Karunakaran for compiling a thorough list 1http://www.numpy.org 2https://www.scipy.org/index.html 3http://montage.ipac.caltech.edu iv of cluster velocity dispersions. I appreciate the helpful suggestions by the anonymous referees for both Wagner et al.(2017) and Wagner et al.(2018). I am grateful for the generous support I received during my time as a PhD student: a Duncan and Urlla Carmichael Fellowship, an R. Samuel McLaughlin Fellowship, and an Ontario Graduate Scholarship. Thank you to Loanne Meldrum, for her incredible helpfulness with the multitude of questions I had and forms I had to fill out. I would like to acknowledge my advisor, Stéphane Courteau, for his continued support and mentorship throughout the many challenges and triumphs over the course of my time at Queen’s. A special thank you goes out to Michael McDonald, who had the clever idea to fit stacked surface brightness profiles of Abell 1795 members. Without his close collaboration and guidance, through countless emails, numerous Skype calls, and three trips to MIT, the stacking project would not have been possible. Thanks to Colin, James, Majd, and Nathalie, for your friendship over the years and making my time at Queen’s enjoyable. Thank you to my good friends: Matt, who kept me sane for nearly five years (I promise I still am) as the best officemate a squash-playing orangutan could ever ask for; and Ananthan, who was often more excited about my new plots than I was, and was always up for tech talk and hitting tiny rubber balls against hard walls. To Tasha, my wife and friend forever meow meow kitty kitty meow meow I love you. v Table of Contents Abstracti Statement of Co-Authorship iii Acknowledgments iv Table of Contents vi List of Tables ix List of Figuresx List of Abbreviations and Symbols xiii Chapter 1: Introduction.......................... 1 1.1 Galaxies in Clusters............................ 3 1.2 Quenching Cluster Galaxies ....................... 5 Chapter 2: The Evolution and Quenching of Cluster Galaxy Star Formation............................ 11 2.1 Abstract.................................. 12 2.2 Introduction................................ 13 vi 2.3 Cluster Samples.............................. 15 2.4 Galaxy Data and Sample Selection ................... 22 2.5 Results and Discussion.......................... 36 2.6 Summary ................................. 50 2.7 Appendix: Comparison of CIGALE-derived Star Formation Rates and Stellar Masses............................... 52 Chapter 3: Stripping of the Hot Gas Halos in Member Galaxies of Abell 1795 ........................... 55 3.1 Abstract.................................. 56 3.2 Introduction................................ 57 3.3 Data and Sample Selection........................ 59 3.4 Modeling the X-ray Emission From Member Galaxies in Abell 1795 . 67 3.5 Discussion................................. 86 3.6 Summary ................................. 96 Chapter 4: Extending the Search for Hot Gas Halos Around Cluster Galaxies............................. 98 4.1 Introduction................................ 98 4.2 Data and Sample Selection........................ 99 4.3 Modeling the Extended Sample Surface Brightness Profiles . 101 4.4 Potential Future Work .......................... 105 Chapter 5: Summary............................107 vii Appendix A: Measuring and Analyzing Surface Brightness Profiles of Cluster Galaxies .....................130 A.1 Chandra Data Files and Initial Processing . 131 A.2 Determining Chandra Coverage ..................... 131 A.3 Creating and Stacking Chandra Cutouts . 132 A.4 Simulating the Chandra Point-Spread Function . 136 A.5 Fitting X-ray Surface Brightness Profiles . 139 viii List of Tables 2.1 CLASH and ISCS Cluster Samples ................... 16 2.2 M200 Evolutionary Track Parameters .................. 19 2.3 CIGALE Input Parameters........................ 31 2.4 MAD of ∆ log (SF R) ........................... 54 3.1 0.5–1.5 keV Luminosities......................... 85 4.1 Extended Sample Properties....................... 99 4.2 Number of Model Parameters and emcee Settings . 102 A.1 emcee Runtimes for X-ray SBP Models Tested in Chapter3 . 142 ix List of Figures 1.1 Image of the galaxy cluster Abell 1795.................. 2 1.2 Qualitative representation of different quenching mechanisms..... 6 1.3 A galaxy with stripped material harboring regions of star formation.. 7 2.1 Cluster M200 versus redshift for 31 CLASH and ISCS clusters. 18 2.2 Mass evolution for selected CLASH and ISCS clusters. 20 2.3 Redshift histograms of CLASH members................. 25 2.4 Examples of visually classified ETGs and LTGs............. 27 2.5 CIGALE-derived SFR versus stellar mass for cluster members. 33 2.6 SFR-M? plane for SFGs and quiescent galaxies. ............ 35 2.7 SFR versus M? for cluster SFGs and a comparison of best-fit SFR-M? parameters. ................................ 37 2.8 Fraction of quiescent cluster galaxies as a function of stellar mass. Specific SFR versus stellar mass for cluster SFGs and quiescent galaxies. 40 2.9 Specific SFR versus redshift for cluster galaxies. Fraction of quiescent cluster galaxies versus redshift. ..................... 44 x 2.10 Fraction of quiescent cluster galaxies versus redshift, separated by mor- phology.