ACTIVE GALACTIC NUCLEI: THE PERIODICITY OF BLAZAR MARKARIAN 501 by Angelia Yvonne Royston A senior thesis submitted to the faculty of Brigham Young University - Idaho in partial fulfillment of the requirements for the degree of Bachelor of Science Department of Physics Brigham Young University - Idaho April 2017 Copyright c 2017 Angelia Yvonne Royston All Rights Reserved BRIGHAM YOUNG UNIVERSITY - IDAHO DEPARTMENT APPROVAL of a senior thesis submitted by Angelia Yvonne Royston This thesis has been reviewed by the research committee, senior thesis coor- dinator, and department chair and has been found to be satisfactory. Date Stephen McNeil, Advisor and Department Chair Date Todd Lines, Senior Thesis Coordinator Date Brian Tonks, Committee Member Date Brian Pyper, Committee Member ABSTRACT ACTIVE GALACTIC NUCLEI: THE PERIODICITY OF BLAZAR MARKARIAN 501 Angelia Yvonne Royston Department of Physics Bachelor of Science The Remote Observatory for Variable Object Research (ROVOR), built by Brigham Young University, is operated by faculty and undergraduate students. A sampling of ROVOR's accumulated data for the target blazar Markarian 501 was collected for analysis in hopes of witnessing a sinusoidal variation in its apparent magnitude. This sample consisted of 18 days worth of imaging, taken between June 23, 2009 and September 26, 2009, through the Johnson V filter. Data reduction was done through software provided by the National Optical Astronomy Observatory called Image Reduction and Analysis Facility (IRAF). Final photometric analysis was accomplished through the use of an online tool, VPhot, made accessible by the American Association of Variable Star Observers (AAVSO). Photometric analysis, using Mathematica, shows a period of ∼80 days. This result supports either a multiperiodic nature of active galactic nuclei (AGN), or multiple orbiting black holes at the nucleus of such galaxies. Analysis of data samples covering a longer time period is recommended. ACKNOWLEDGMENTS I would like to thank my advisor, Professor Stephen McNeil, for his guid- ance throughout this research and as I wrote my thesis. I would also like to thank him for his mentorship and support during my years at Brigham Young University Idaho. In addition to my advisor I would like to thank my the- sis committee members: Professor Brian Pyper, Professor Brian Tonks, and Professor Todd Lines for their time, and advice. This work would not have been complete without Patricia Hall and Kelli Melville, my peers. I thank them for their assistance in the error analysis portion of this project. I would also like to thank Professor Joseph W. Moody and the ROVOR research team for allowing me to take part in their research, and their help with writing this thesis. I would also like to thank the National Science Foundation for funding this research. Finally, I would like to thank my peers and the fac- ulty in the BYU-Idaho Physics Department for their friendship, support, and encouragement. Contents Table of Contents xi List of Figures xiii 1 Introduction1 1.1 Blazar Model...............................4 1.2 Markarian 501...............................5 1.3 Previous Work..............................8 1.4 Goals....................................9 2 Methodology 11 2.1 Instrumentation.............................. 11 2.1.1 ROVOR.............................. 12 2.1.2 Johnson Filters.......................... 15 2.2 Data Collection.............................. 17 2.3 Reduction................................. 18 2.4 Photometry................................ 19 2.4.1 IRAF Error............................ 20 2.4.2 VPhot Correction......................... 21 3 Results 23 3.1 Grid-Search Method........................... 25 3.2 Parabolic Expansion Method....................... 28 4 Conclusion 31 4.1 Future Work................................ 31 Bibliography 33 A Data List 37 B Mathematica Code 39 xi List of Figures 1.1 Image of the universal Active Galactic Nuclei (AGN) model [6]....3 1.2 Distribution of radiation from AGN and their associated source of emis- sion [19]...................................4 1.3 Subclasses of AGN based on observational orientation [2]........5 1.4 Colored captured image of Markarian 501 provided by Astronomerica [12].....................................6 1.5 Raw image of Markarian 501 taken by ROVOR [9]...........7 2.1 Image of the Remote Observatory for Variable Object Research (ROVOR). Seen is the larger building (the \doghouse") with the Lifferth Dome in motion, and the smaller building (the \outhouse") [13]......... 13 2.2 Image of the telescope enclosed under the dome............. 14 2.3 Image of the Lifferth Dome. The mechanism pivots to the west [13].. 15 2.4 Bessell approximations to UBVRI filters/passbands. Transmission axis is in percentage, and wavelength axis in A[˚ 16]............. 16 3.1 (Left) Graph of Markarian 501's apparent magnitude (m) vs the Julian Date (JD). (Right) Graph of manipulated sine curve plotted over the data points after parameters were found using the grid-search method. 26 3.2 The same graphs in respective order as those in Fig. 3.1, but found after averaging the data points over each night............. 27 xiii Chapter 1 Introduction Astronomical objects that are billions of light years away are being observed in the state they were in billions of years ago. This is due to the finite speed in which light travels through space and time. As observers look further and further away they are looking further back in time, towards the youthful beginning of our universe. This distance, and associated age, by which objects are measured and observed is characterized by a cosmological redshift (z). The larger the redshift the further away the object is, and therefore, the younger the universe is from that observer's viewpoint. In the 1950s a large collection of radio sources without accompanying visible ob- jects were observed and recorded by astronomers. In 1963 Allan Sandage and Thomas A. Matthews published the first findings of a radio source with a visible object. Ap- pearing first as a faint blue star, confusion emerged as these astronomers studied the spectrum of this object and found many strange emission lines that they had never encountered before. Due to the unique nature of these objects, they began being referred to as quasi-stellar radio sources - later shortened to quasars. Since further understanding of these objects showed that not all quasars are radio-loud sources they also became commonly referred to as just called QSOs (quasi-stellar objects). A 1 2 Chapter 1 Introduction much more detailed account of the history of quasar observation, and what quasars are, can be found at Shields [18]. \The most distant quasars are seen at a time when the universe was one tenth its present age, roughly a billion years after the Big Bang" [20]. They are the most distant directly detected objects due to their incredible brightness. A discussion of the source of this brightness is given later in this chapter. Quasar research expanded and became a subclass of galaxies known as active galactic nuclei (AGN) - or just active galaxies. These galaxies have \extraordinarily luminous cores powered by black holes containing millions or even billions of times more material than our Sun. As gas is trapped by a monster black hole's gravity, it settles into an accretion disk and starts to spiral down... Before the gas crosses the black hole's outer boundary (the event horizon) the material generates a vast outpouring of electromagnetic radiation. In the most luminous AGN, the visible light exceeds the combined output of an entire galaxy's worth of stars, even though the light-emitting area is only about the size of our solar system" [5]. The activity of these AGN are normally seen at high redshifts. This is because AGN are thought to have formed during the early universe when collisions were very common. As time has progressed, and objects have drifted apart, AGN do not form as often and some AGN are probably no longer active in their current state. They just appear active to observers because the light being viewed is billions of years old. Since collisions happened a lot in the chaotic nature of the early universe about 10% of all galaxies are considered active [6]. 3 Figure 1.1 Image of the universal Active Galactic Nuclei (AGN) model [6]. One of the most interesting characteristics of AGN is that the major source of radiation from these objects is nonthermal. Fig. 1.1 shows the basic model for AGNs and shows where the nonthermal radiation is coming from. Relativistic jets of radiation shoot out from the magnetic poles of these galaxies (most likely due to synchrotron radiation - radiation emitted from charged particles accelerating radially within a magnetic field [1]). Fig. 1.2 shows the distribution of types of radiation emitted from AGN. Active galactic nuclei capture the attention of astronomers and physicists because of their extreme nature. They are the brightest objects in the universe. Observation of these AGN can lead to a deeper understanding of relativistic physics and galaxy 4 Chapter 1 Introduction evolution. Figure 1.2 Distribution of radiation from AGN and their associated source of emission [19]. 1.1 Blazar Model When observing astronomical objects the viewer's orientation can cause a difference in perspective, and consequently a difference in observed phenomena. This concept holds true when observing active galactic nuclei (AGN). Subclasses of AGN are based on two characteristics: 1) how much radio source is detected and 2) the objects orientation. Fig. 1.3 shows the different subclasses of AGN based on how the observer is viewing the object. The most luminous AGN are classified as blazars. Blazars are oriented such that one of the jets of radiation is pointed towards the Earth. This 1.2 Markarian 501 5 allows an observer to essentially look down the barrel of the gun. These objects are of great interest to study because they are so powerful, so bright, and so chaotic. Figure 1.3 Subclasses of AGN based on observational orientation [2].