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Regulation of Star Formation Amidst Heating and Cooling in Galaxies and Galaxy Clusters

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Regulation of Star Formation Amidst Heating and Cooling in Galaxies and Galaxy Clusters Rochester Institute of Technology RIT Scholar Works Theses 8-2016 Regulation of Star Formation Amidst Heating and Cooling in Galaxies and Galaxy Clusters Sravani Vaddi [email protected] Follow this and additional works at: https://scholarworks.rit.edu/theses Recommended Citation Vaddi, Sravani, "Regulation of Star Formation Amidst Heating and Cooling in Galaxies and Galaxy Clusters" (2016). Thesis. Rochester Institute of Technology. Accessed from This Dissertation is brought to you for free and open access by RIT Scholar Works. It has been accepted for inclusion in Theses by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. Regulation of Star Formation amidst Heating and Cooling in Galaxies and Galaxy Clusters by Sravani Vaddi A dissertation submitted in partial fulfillment of the requirements for the degree of Ph.D. in Astrophysical Sciences and Technology in the College of Science, School of Physics and Astronomy Rochester Institute of Technology August, 2016 Approved by Dr. Andrew Robinson Date Director, Astrophysical Sciences and Technology Astrophysical Sciences and Technology College of Science Rochester Institute of Technology Rochester, New York, USA Certificate of Approval Ph.D. Degree Dissertation The Ph.D. Degree Dissertation of SRAVANI VADDI has been examined and approved by the dissertation committee as satisfactory for the dissertation requirement for the Ph.D. degree in Astrophysical Sciences and Technology. Dr. Chris O’Dea, Dissertation Advisor Date Dr. Stefi Baum, Dissertation Advisor Date Dr. Anthony Vodacek, Committee Chair Date Dr. Alice Quillen Date Dr. Andrew Robinson Date To all my teachers who believed in me and supported me all through my life. ABSTRACT Galaxy clusters are the largest gravitationally bound systems in the Uni- verse and often host the largest galaxies (known as the brightest cluster galaxies (BCG)) at its centers. These BCG’s are embedded in hot 1-10 keV X-ray gas. A subset of galaxy clusters known as cool-core clusters show sharply peaked X-ray emission and high central densities, demonstrating cooling of the surrounding halo gas in timescales much shorter than a Hub- ble time. These observations led to the development of a simple cooling flow model. In the absence of an external heating process, a cooling flow model predicts that the hot intracluster medium gas in these dense cores would hydrostatically cool, generating cooling flows in the center of the cluster. This cooled gas will eventually collapse to form stars and contribute to the bulk of galaxy mass. The rates of star formation actually observed in the clusters however are far less than predicted by the cooling flow model, sug- gesting a non-gravitational heating source. Active galactic nuclei (AGN), galaxies hosting a supermassive black hole that ejects outflows via accretion, is currently the leading heating mechanism (referred to as AGN feedback) explaining the observed deficit in the star formation rates. AGN feedback also offers an elegant explanation to the observed black hole and galaxy co- evolution. Much of the evidence for AGN feedback has been obtained from studies focussed on galaxy clusters and luminous massive systems with little evidence that it occurs in more typical systems in the local universe. Our re- search investigates this less explored area to address the importance of AGN heating in the regulation of star formation in typical early type galaxies in the local universe. We selected a sample of 200+ early type, low redshift galaxies and carried out a multiple wavelength study using archival observed in the UV, IR and radio. Our results suggest that early type galaxies in the i current epoch are rarely powerful AGN and AGN feedback is constrained to be low in our sample of low redshift, typical early type galaxies. Although heating from the AGN is powerful enough to suppress the cool- ing of the hot gas, it does not completely offset gas cooling at all times and substantial cooler gas exists in the cores of some galaxy clusters (cool-core clusters), the gas properties of which are not explained by AGN heating models alone. The second part of our research focusses on unravelling the mystery of the unknown heating source regulating star formation in galaxy clusters. We have obtained deep FUV spectroscopy using the HST cos- mic origins spectrograph of two cool-core clusters A2597 and Zw3146. FUV spectral lines provide the much needed diagnostics capable of discriminating between various heating models, which was difficult with the standard op- tical line diagnostics. We investigate several heating/ionization mechanisms namely stellar photoionization, AGN photoionization, and shock heating. We use pre-run Mappings III photoionization code results to model the ion- izing radiation field. In general, we notice that there is no one single model that provides a satisfactory explanation for the ionization state of gas. How- ever, we show that stellar and AGN photoionization alone are not enough to ionize the nebula in A2597 and speculate that, shock heating is the likely ionizing source. ii ACKNOWLEDGEMENTS My journey would not have been made possible without help from my family, teachers, and friends. This is the journey of an engineer who dreamt of becoming an astronomer. As I am writing this, I look back to remember all the people who have helped me in making this dream come to true. I am immensely thankful to my advisors Dr. Chris O’Dea and Dr. Stefi Baum for their unending support and encouragement during these years. Even after moving to Manitoba, Dr. O’dea had provided me continual guidance and was readily available to answer questions. I am also grateful to my profes- sors Dr. Andrew Robinson, Dr. Michael Richmond, Dr. David Merritt, Dr. Joel Kastner from whom I have learnt so many things. A special mention to Dr. Michael Richmond for giving me hands-on experience with telescopes and also for providing outreach opportunities at the observatory. I thank Dr. Christine Jones and Dr. Bill Forman for constructing and sharing the galaxy sample with me which formed the basis for this project. This journey would not have been possible without my dear mentors Dr. Najam Hasan and Dr. Priya Hasan who welcomed my dream of becoming an astronomer and gave me an opportunity to work with them. I wish to thank my inspirational teachers Mr. Phani Bhushan and late Mr. Timma Reddy who believed in me and motivated me to reach for the stars. I thank my wonderful friends for making this a fun-filled and most mem- orable journey. The hikes we went to, and movie nights, festivals and dinners we enjoyed have enriched my life. I thank you for listening to me and the advice you all provided. Among them are Adnan Kashif, Davide Lena, Dave Principe, Preeti Vaidyanathan, Ashima Chhabra, Alexander Rasskavoz, Di- iii nalva Sales, Gabor Kupi, Marcus Freeman, Dmitry Vorobiev, Billy Vazquez, Prabath Peiris, Eugene Vasiliev, Christine Trombley, Vg Prasuna, yuanhao Zang, Yashar Seyed, Masoud Golshadi, Mustafa Koz, Kamal Jnawali, Jam Sadiq, Ekta Shah, Triana Almyeda, and Bipana Jnawali. Special thanks to my mentor Preeti Kharb for giving me training on AIPS, and for helping me view issues from different perspectives; Rupal Mittal and Grant Tremblay for insightful discussions on the project. I am deeply appreciative of Cari Hind- man, Cindy Drake, Sue Chan, Joyce French, and Dr. Michael Kotlarchyk, who have been working tirelessly behind the scenes helping the students. I can never thank my family enough for being my strength and respecting my pursuit of Astronomy. In particular, I thank my mother for giving me everything in life. Like a candle, you burnt yourself for lighting up my life. Thank you for all the sacrifices you have made. iv CONTENTS Abstracti Acknowledgements iii List of Tables ix List of Figures xxiii 1 Introduction1 1.1 Galaxy Formation and AGN Feedback.............2 1.1.1 Galaxy Luminosity Function..............4 1.1.2 Co-evolution of galaxy and black hole.........5 1.1.3 ICM heating in cool core galaxy clusters........8 1.1.4 AGN Feedback...................... 10 1.1.5 Quasar Mode....................... 11 1.1.6 Radio-Mode........................ 13 1.2 Galaxy Clusters.......................... 14 1.3 X-ray hot ICM.......................... 16 1.3.1 Physics of the X-ray hot ICM.............. 16 1.3.2 Physical properties of the ICM............. 17 1.4 Cooling Flow Model....................... 20 1.4.1 Problems with the Cooling Flow Model........ 23 1.4.2 Solutions to the CF Model................ 24 1.4.3 Residual Cooling..................... 27 v CONTENTS 1.5 Cool-core BCG Emission Line Nebulae............. 27 1.5.1 Properties of emission line nebulae........... 28 1.6 A review of previous studies................... 31 1.6.1 AGN feedback...................... 31 1.6.2 Ionization of emission line nebulae........... 32 1.7 Goals of the Thesis........................ 33 1.8 Road Map............................. 35 2 Sample and Data Analysis 37 2.1 Sample............................... 37 2.2 The Data............................. 38 2.2.1 IR data.......................... 39 2.2.2 Radio data........................ 40 2.2.3 UV data.......................... 41 2.2.4 Galactic Extinction Correction............. 42 2.3 Aperture Photometry...................... 42 2.4 Photometry comparisions.................... 45 2.4.1 Comparision with the 2MASS.............. 45 2.4.2 Comparison with WISE................. 45 2.4.3 Error Analysis...................... 51 3 Photometric Properties of the Sample 57 3.1 MIR-FUV Properties....................... 57 3.1.1 SFR estimation using FUV............... 61 3.1.2 Galaxy mass estimation................. 64 3.1.3 Specific SFR estimation................. 65 3.2 Radio properties......................... 68 3.3 Summary............................. 69 4 Results and Discussion 72 4.1 Relation between radio power and host galaxy properties... 72 4.1.1 Radio power and galaxy mass relation - Radio power from AGN is dependent on the galaxy mass.....
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