The Ionized Intergalactic Medium and Its Influence on Galaxies And
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The Ionized Intergalactic Medium and its Influence on Galaxies and Galaxy Clusters A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Mohammad Mehdi Lame'e IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Advisor: Lawrence Rudnick June, 2017 c Mohammad Mehdi Lame'e 2017 ALL RIGHTS RESERVED Acknowledgements First of all, I would like to express my special appreciation and thanks to my advisor Prof. Lawrence Rudnick. Without his support, guidance, suggestions, feedbacks and critics this thesis would not have been possible. He thought me to be a critical thinker and question even the most obvious assumptions. Under his supervision, I learned how to properly use the so-called scientific methodology and perform high quality research with only and only one intention in mind: doing science. He has used my mistakes to empower and teach me to learn from failed attempts and use them to improve my research. He, unconsciously, has thought me how to not give up when facing, seemingly, unsolvable obstacles and problems and instead, start thinking about out-of-the-box solutions. It has been such a great honor to work with him. I want to thank my co-advisor Dr. Claudia Scarlata. She gave me the opportu- nity to gain invaluable experience and expertise working with data of some of the most impressive optical telescopes. Her motivation and passion for research was contagious and definitely has played a crucial role in shaping the second chapter of this thesis. I wish to express my sincere gratitude to my committee members Prof. Thomas Jones and Prof. Vuk Mandic for their insightful comments in improving this thesis. I have had many important discussions and conversations with Prof. Jones about the underlying Physics of some of the most interesting findings of this thesis, espe- cially the discovery of a few radio relics and filaments in the intracluster medium of the Abell 2255 merging system. His ideas and suggestions have provided vital i insights in this thesis. A very special acknowledgment goes out to all my collaborators and colleagues, especially Prof. Frazer Owen, Dr. Peter Capak and Dr. Walter Brisken who helped me overcome technical challenges of reducing radio interferometry as well as optical imaging data obtained by world-class radio interferometer antennas such as the Very Large Array and ground based optical telescopes such as Subaru and Palomar. During several years of my PhD study, I have been so lucky to have the chance to work with some amazing people. I would like to express my thankfulness to all my labmates, in particular, Micaela Bagley who helped me run my first onsite observation, Dr. Michael Rutkowski who provided detailed comments on the second chapter of this thesis and Vihang Mehta who helped incorporating the SPLASH project data in the section 2.6 of this thesis. Moreover, I am lucky to have some amazing friends who helped maintain positive attitude and overcome very hard challenges of PhD lifestyle. I am grate- ful to Pedram Baldari, Noushin Hakim, Pejman Roohani, Farnaz Forootaninia, Soroush Sotoudeh, Armin Zare, Samira Bahrami, Maziar Sanjabi, Pardees Azo- danloo, Morteza Mardani, Karen Khatamifard, Sepideh Moghaddam, Meisam Razaviyayn, Nazila Haratipour, Mehrdad Hairani, Zohreh Ebadi, Ellie Ziaie, Roushanak Navab, Mojtaba Kadkhodaie, Mohammadreza Nasiri, Ameer Kian, Sahar Kian, Fateme Sheikholeslami, Karlen Shahinian, Stou Sandalski, Kyle Dolan and Sepehr Salehi who helped me in proofreading parts of this thesis. Last but not the least, I would like to thank my family. My parents, Zahra and Ali, my dear sister, Mahdieh, my lovely brother, Mahan and my beloved wife Behnaz Forootaninia who supported me in all these years with pure unconditional love and absolutely no expectation. I would not be able to complete my journey without them. This research is partially supported by National Science Foundation, NSF, under grant AST-1211595 and National Aeronautics and Space Administration, NASA. ii Dedication To my lovely wife Behnaz and my dear parents for their unconditional love and support. iii Abstract In this thesis, we studied physical and evolutionary aspects of the intergalactic medium throughout the universe. We used the archived Subaru telescope data and measured the ionization ra- diation escape fraction of 207 Lyα emitting galaxies at z ' 3:3 in the SXDS field which does not contain any known overdensity region. Our stacking analy- sis enabled us to put strong limits on the IGM-absorption-corrected UV{to{LyC flux ratio > 13:8 (3σ). The average ionizing radiation relative escape fraction is LyC fesc;rel < 20% (3σ), assuming an intrinsic FUV=FLyC = 3. These limits indicate that the cluster and field populations of Lyα emitters show different properties in their ionizing emissivity. In chapter3, we study the influence of the intervening IGM on depolarizing the synchrotron radiation of radio galaxies. We combined observations of the NVSS at 1.4 GHz and the S-PASS at 2.3 GHz for 533 extragalactic radio sources with total intensity I2:3 > 420 mJy. We found that fractional polarization, π, depends on the source magnetic field disorder, spectral index, size and depolarization. The relationship between the latter three shows that depolarization occurs primarily in the source vicinity. The intrinsic magnetic field disorder is the dominant mech- anism responsible for the low π of radio sources at high frequencies. Objects with π1:4 ≈ π2:3 ≥ 4% typically have simple Faraday structures and therefore, are most useful for studying foreground Faraday screens. At the end, we present deep and high-resolution L-band VLA observations of diffuse radio relics and filaments in the ICM of Abell-2255 merging galaxy cluster. We discovered three thin filaments close to the X-ray center of the cluster and at the tip of the tails of two radio galaxies. The spectral analysis of two filaments suggest that the responsible seed electrons belong to the tail of the same galaxy and have experienced an adiabatic compression due to a passing weak shock with iv Mach number M ∼ 1:1. We discovered two substructures and a new relic in the southern part and west of the NE relic. In addition, the alignment of three sources, C1, C2 and the Bridge suggests they might be remnants of a giant radio galaxy. v Contents Acknowledgementsi Dedication iii Abstract iv List of Tablesx List of Figures xiii 1 Introduction1 1.1 Diffuse intergalactic medium.....................1 1.2 Ionization history of the IGM....................3 1.2.1 First stars and start of reionization era...........4 1.2.2 First galaxies and their available ionizing budget......4 1.2.3 Completion of the IGM reionization.............6 1.2.4 Ionization bubbles and HII regions.............8 1.2.5 Photoionization and recombination equilibrium...... 10 1.2.6 Stromgren radius....................... 12 1.3 Influence of IGM on polarization of background radio galaxies.. 14 1.3.1 Spectrum of synchrotron radiation............. 15 1.3.2 Polarization of synchrotron radiation............ 18 1.3.3 Stokes parameters....................... 19 vi 1.3.4 Faraday screens and rotation of the polarization angle.. 21 1.3.5 Depolarization of synchrotron radiation........... 23 1.4 The intracluster medium in merging systems............ 25 1.4.1 The ICM weather and its synchrotron features....... 26 1.4.2 Lifetime of ultra relativistic Cosmic ray electrons..... 29 1.4.3 Merger shocks and Re-acceleration of electrons....... 30 1.4.4 Seed electrons......................... 31 2 Ionizing emissivity from galaxies at z ∼ 3: differences in field versus cluster galaxy populations 33 2.1 Introduction.............................. 33 2.2 Overall strategy............................ 36 2.2.1 Observations and data reduction.............. 37 2.2.2 Flux measurement...................... 41 2.3 Selection of Lyα{emitters...................... 42 2.4 Results................................. 47 2.4.1 Number density of Lyα emitters in SXDS......... 47 2.4.2 Observed ionizing emissivity................. 49 2.5 Escape fraction of ionizing radiation................. 50 2.6 Stellar mass distribution....................... 52 2.7 Discussion and Conclusions..................... 53 3 Magnetic field disorder and Faraday effects on the polarization of extragalactic radio sources 68 3.1 Introduction.............................. 69 3.2 Observations.............................. 72 3.2.1 The 2.3 GHz Data...................... 72 3.2.2 The 1.4 GHz Data...................... 73 3.3 Creating the new sample....................... 74 3.3.1 Cross-matching and selection criteria............ 74 3.3.2 Derived quantities...................... 75 vii 3.3.3 Selection Bias......................... 82 3.3.4 Statistical tests........................ 83 3.4 Results................................. 84 3.4.1 Rotation measures...................... 87 3.4.2 Distribution of fractional polarization and depolarization. 87 3.4.3 Total intensity and fractional polarization......... 91 3.4.4 Correlation between RRM, ∆RM, π and D ......... 92 3.4.5 Polarization, depolarization and the object angular extent 93 3.4.6 Spatial distribution of depolarization in the sky...... 94 3.4.7 WISE colors and polarization................ 110 3.4.8 Redshift Dependence..................... 111 3.4.9 Summary of major results.................. 113 3.5 Discussion............................... 115 3.5.1 Radio source field disorder.................. 115 3.5.2 Prospects for high frequency surveys............ 116 3.5.3 Prospects for RM grid