Radio properties of a complete sample of nearby groups of galaxies Konstantinos Kolokythas Department of Physics University of Birmingham This dissertation is submitted for the degree of Doctor of Philosophy October 2014 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. My parents have always told me to aim high. Therefore i turned my head to the sky and since then, never wanted to take my eyes down. I would like to dedicate this Thesis to my loving parents and sister who supported me throughout the long trip of chasing my dream: Become an astrophysicist. Declaration I hereby declare that except where specific reference is made to the work of others, the contents of this dissertation are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other University. This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration, except where specifically indicated in the text. This dissertation contains less than 50,000 words including appendices, bibliography, footnotes, tables and equations and has less than 150 figures. Konstantinos Kolokythas October 2014 Paper publications 1. New insights into the evolution of the FR I radio galaxy 3C 270 (NGC 4261) from low frequency GMRT radio observations Konstantinos Kolokythas, Ewan O’Sullivan, Simona Giacintucci, Somak Raychaud- hury, C.H. Ishwara-Chandra, Diana M. Worrall and Mark Birkinshaw Material covered in Chapter 3. This paper is accepted for publication in the Monthly Notices of the Royal Astronomical Society (MNRAS). The citation for the article is: Monthly Notices of the Royal Astronomical Society 2015 450 (2): 1732-1744doi: 10.1093/mnras/stv665. In this work that involved the collaboration of many people I performed the analysis of the radio data, the calculations for the age, internal pressure and lobe energy es- timations and was the only author that wrote the entire material of the paper, which of course was subject to corrections and suggestions by the co-authors. Dr Ewan O’Sullivan performed the calculation of the inverse-Compton contribution from the X-rays (bottom of page 106) and contributed only in the writting of this paragraph. Fig. 3.11 was also done by Dr. Ewan O’Sullivan. The model fit of the spectral index distribution in the lobes (JP model) of Figs. 3.8 and 3.9, in order to calculate the age of the radio source in the lobes, was performed by Dr. Simona Giacintucci. The same model fit of the integrated spectrum (Fig. 3.4) was also performed by Dr.Simona Giacintucci. The inspiration for the paper was from Prof. Somak Raychaudhury who along with Prof. Mark Birkinshaw and Prof. Diana Worrall contributed in the cor- rection of the text. Finally Dr. Ishwara-Chandra helped in the demanding radio data analysis of this system. 2. Radio properties of nearby groups of galaxies Konstantinos Kolokythas, Ewan O’Sullivan, Somak Raychaudhury, C.H. Ishwara- Chandra, and Nimisha Kantharia Material covered in Chapter 4. This appeares in the proceedings of The Metrewave- length Sky (MWSKY) conference held at NCRA-TIFR, Pune, from 9-13 December viii Paper publications 2013 (arXiv:1402.5109). This is a conference proceeding paper I wrote where I briefly summarize the first ra- dio results of the CLoGS project and show some of the interesting systems and radio images. The X-ray characteristics of each system, the energy outputs and any X-ray results I refer to were calculated by Dr. Ewan O’Sullivan. 3. First Results from the Complete Local-Volume Groups Sample Ewan O’Sullivan, Konstantinos Kolokythas, Somak Raychaudhury, Jan M. Vrtilek and Nimisha Kantharia Material partially covered in Chapter 4. This appeares in the proceedings of The Me- trewavelength Sky (MWSKY) conference held at NCRA-TIFR, Pune, from 9-13 De- cember 2013 (arXiv:1402.4676). This proceeding was written entirely by Dr. Ewan O’Sullivan. 4. The radio properties of the central group galaxies in the Complete Local-Volume Groups Sample (CLoGS) Normal author list: Konstantinos Kolokythas, Ewan O’Sullivan, Somak Raychaud- hury, Nimisha Kantharia and Simona Giacintucci Paper in prep. This is the material covered in Chapter 4. 5. Star formation and AGN in the Complete Local-Volume Groups Sample (CLoGS) from multiwavelength analysis Normal author list: Konstantinos Kolokythas, Ewan O’Sullivan, Somak Raychaud- hury and Nimisha Kantharia Paper in prep. This is the material covered in Chapter 5. Konstantinos Kolokythas October 2014 Acknowledgements During this period of my life that I was passing through the ‘doctorate’ path, I see many people whose help and support must be acknowledged. Friends, parents and colleagues, they made these few years much easier than they could have been. At the top of this list is my supervisor, Prof. Somak Raychaudhury. He is a wonderful person and a charismatic scientistic as well. He always had good advice and great insight, without which I wouldn’t be able to move on. I will be always grateful for being selected and trusted in order to accomplish the dificult task of this project. Especially grateful for all these trips toIndia, where I learned a new culture and interacted with new people (although I never liked curry and spicy food in general). He is, as we say in my country, my spiritual father. Special thanks and enormous gratitute to Dr. Ewan O’Sullivan, for all his help with every aspect of my phd. He was always there to support, help and guide in every step of my phd. His advice helped me get through some tough times. I really thank him for all the long telecons and discussions we had every time a problem came up or I wasn’t understanding something. Without his help, I could not have completed a huge part of my work. His support and help, especially for my first publication was invaluable. I would also like to thank two people specifically: Ishwara Chandra, who taught me everything about the radio data analysis and David Stops for the help with all these mysterious (to me) computer and software problems but also for his interesting discussions at the coffee lounge. What would I do without my friends? I wanted to thank Charlotte, Trevor, Chris, Mark, Rory, Nikos and Richard. They helped make the hard times easier, the happy times happier and all the other times in be- tween, enjoyable. I would like to extend thanks to Prof. Trevor Ponman, for many useful discussions applying his critical thinking in my Thesis and the invaluable help in organising it and for the job applications. None of this would have been possible without my mother Athina Siatira and my father, Athanasios Kolokythas, who encouraged me to go for research and to travel abroad to study. My parents and my sister Vana, have always supported me in all my endeavors, inspite of opposition from other quarters. I want to thank them for always believing in me. Last but not the least, I want to thank Maira Mitrou, for her unwavering support and encouragement x Paper publications and all the things she cheerfully put up with on a day to day basis as I raced to finish. This research has made extensive use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of NASA’s Astrophysics Data System Bibliographic Services. Abstract Much of the evolution of galaxies takes place in groups where feedback has the greatest impact on galaxy formation. By using an optically selected, statistically complete sam- ple of 53 nearby groups (CLoGS), observed at radio (GMRT) and X-ray (Chandra and XMM-Newton) frequencies, we aim to characterise the radio-AGN population in groups and examine their impact on the intra-group gas and member galaxies. In this dissertation, low-frequency GMRT radio images of the nearby (<80 Mpc) central brightest group ellip- ticals from the high richness CLoGS sub-sample are presented for the first time at 235 and 610 MHz. Using the sensitivity to older electron populations at 235 MHz and the resolution of 610 MHz as a key to identify past and current AGN activity, a detailed analysis of the radio properties for each of the central group radio sources is performed, with the results being in addition combined with findings from the X-ray observations. Using models of spectral ageing, we report an age of ∼29-36 Myr for the radio source 3C 270 in NGC 4261, concluding that the expansion of the radio jet underwent several outbursts during the lifetime of the source. From the entire sample, we find that 13/26 systems (50%) have a group-scale X-ray emission that reach beyond 65 kpc (X-ray bright), with 5/13 (39%) of these X-ray bright systems presenting radio emission in the form of small/large scale jet. Furthermore, 5/13 (39%) are radio point sources and 3/13 (22%) host diffuse radio emission with no particular orientation. The largest radio sources which are currently active or have been so in the recent past, lie in X-ray bright cool-core groups, while the systems that do not present radio emission at any frequency appear in the X-ray faint systems.