Millimeter-Wavelength Characterization of the CO Emission of Comets 174P/Echeclus, 29P/Schwassmann-Wachmann, and C/ 2016 R2 (Panstarrs)
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University of South Florida Scholar Commons Graduate Theses and Dissertations Graduate School November 2019 Millimeter-wavelength characterization of the CO emission of comets 174P/Echeclus, 29P/Schwassmann-Wachmann, and C/ 2016 R2 (PanSTARRS) Kacper Wierzchos University of South Florida Follow this and additional works at: https://scholarcommons.usf.edu/etd Part of the Astrophysics and Astronomy Commons, and the Physics Commons Scholar Commons Citation Wierzchos, Kacper, "Millimeter-wavelength characterization of the CO emission of comets 174P/Echeclus, 29P/Schwassmann-Wachmann, and C/2016 R2 (PanSTARRS)" (2019). Graduate Theses and Dissertations. https://scholarcommons.usf.edu/etd/8695 This Dissertation is brought to you for free and open access by the Graduate School at Scholar Commons. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Millimeter-wavelength characterization of the CO emission of comets 174P/Echeclus, 29P/Schwassmann-Wachmann, and C/2016 R2 (PanSTARRS) by Kacper Wierzchos A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Physics College of Art and Sciences University of South Florida Co-Major Professor: Maria Womack, Ph.D. Co-Major Professor: Andreas Muller, Ph.D. Myung K. Kim, Ph.D. Matthew Pasek, Ph.D. Zhimin Shi, Ph.D. Date of Approval: November 7, 2019 Keywords: Comets, Rotational spectroscopy, Radio astronomy Copyright c 2019, Kacper Wierzchos Dedication Dedicated to my parents, who ever since an early age, encouraged my curiosity and made of me the scientist that I am today. Acknowledgements There are many factors involved in the successful completion of a Ph.D program. I firmly believe that the most important is your Major Professor. This work could not have been possible without the guidance of Dr. Maria Womack who was the most knowledgeable and understanding advisor and Major Professor that I could have ever wished for. Thank you. As reflected in the dedication of this work, I’m infinitely thankful to my parents. They have both been amazing life coaches, always stimulating my curiosity and rational thinking. It goes without saying that I’m greatly indebted to my wife Sheila, who has been very sup- portive and accommodating throughout the course of my graduate studies and who always encourages me to follow my passion and my dreams. Babe, you know this could not have been possible without you. On a technical note, the help of the staff of the Arizona Radio Observatory 10m Sub- milimiter Telescope and the IRAM 30m antenna is greatly appreciated as well as the help provided by Yamil Nieves with the LaTex formatting of the current dissertation. I would also like to acknowledge the support from the NSF grants AST-1615917 and AST-1945950 and the University of South Florida Duckwall Summer Research Fellowship. Table of Contents List of Figures...................................... iii List of Tables ...................................... iv List of Abbreviations .................................v Abstract ..........................................v Chapter 1: Introduction .............................1 1.1 Investigating cometary volatiles: Radio Spectroscopy . .4 1.2 Excitation processes of linear molecules . .7 1.3 Calculation of column densities and production rates . .8 Chapter 2: Carbon monoxide in the distantly active Centaur (60558) 174P/Echeclus at 6 au........................... 16 2.1 Introduction . 16 2.2 Observations and Results . 20 2.2.1 ARO SMT 10-m . 21 2.2.2 IRAM 30-m . 23 2.3 Analysis and Discussion . 24 2.3.1 Spectral line profile . 24 2.3.2 Excitation and production rates . 25 2.3.3 CO production in Centaurs . 26 2.3.4 Outbursts, outgassing and fragmentation . 30 2.4 Conclusions . 31 Chapter 3: CO gas and dust outbursts of Centaur 29P/Schwassmann- Wachmann ......................................... 33 3.1 Introduction . 33 3.2 Observations . 37 3.2.1 Millimeter-wavelength spectra . 37 3.2.2 Visible magnitudes . 38 3.3 Results . 40 3.4 Discussion . 42 3.4.1 Quiescent activity of gas and dust . 42 i 3.4.2 CO outbursts . 44 3.4.3 Dust outbursts . 46 3.4.4 Causes of outbursts . 47 3.5 Summary and Conclusions . 52 Chapter 4: C/2016 R2 (PANSTARRS): A comet rich in CO and depleted in HCN..................................... 53 4.1 Introduction . 53 4.2 Observations and Results . 54 4.3 Analysis and Discussion . 56 4.3.1 CO outgassing velocities and spatial extent . 56 4.3.2 Production rates of CO and HCN . 59 4.3.3 High N2 Production Rates . 63 4.4 Conclusions . 64 Chapter 5: Case study: Evolution of the CO outgassing and observations of 13CO and HCN in C/2016 R2 (PanSTARRS) ...... 66 5.1 Introduction . 66 5.2 Observations and Results . 68 5.3 Analysis and Discussion . 72 5.3.1 CO heliocentric evolution . 72 5.3.2 13CO J=2-1 emission . 78 5.3.3 Depleted HCN emission . 80 5.4 Conclusions . 81 Chapter 6: Summary of Results ........................ 82 References......................................... 87 Appendix A: Proof of copyright permissions ............... 107 Appendix B: Author’s Work ........................... 108 B.1 Refereed Publications . 108 B.2 Selected non-refereed publications . 110 B.3 Conference Presentations . 111 About the Author ................................... End Page ii List of Figures Figure 1: Solar system diagram...............................2 Figure 2: CO(2-1) spectrum of comet C/2016 R2 (PanSTARRS)...........3 Figure 3: Arizona Radio Observatory 10m Submillimiter Telescope..........5 Figure 4: CO(2-1) emission in comet 29P/Schwassmann-Wachmann.........6 Figure 5: Spectrum of the CO(2-1) emission of 174P/Echeclus............. 22 Figure 6: IRAM spectrum of 174P/Echeclus....................... 24 Figure 7: Specific production rates for distant comets and Centaurs......... 28 Figure 8: Spectrum of 29P/Schwassmann-Wachmann.................. 38 Figure 9: Lightcurves of 29P with CO gas curve..................... 41 Figure 10: First detection of CO(2-1) in comet C/2016 R2............... 56 Figure 11: Map of the CO(2-1) emission in comet C/2016 R2.............. 57 Figure 12: Last detection of CO(2-1) in C/2016 R2.................... 70 Figure 13: CO(1-0) spectrum of C/2016 R2........................ 72 Figure 14: CO(6-5) spectrum of C/2016 R2........................ 73 Figure 15: 13CO spectrum of C/2016 R2.......................... 74 Figure 16: HCN(3-2) spectrum of C/2016 R2....................... 75 Figure 17: Evolution of Q(CO) with heliocentric distance of C/2016 R2........ 76 iii List of Tables Table 1: Parameters needed to model production rates................9 Table 2: Values of hν/kTrot for the application of the Rayleigh-Jeans correction.. 14 Table 3: Constants used for the derivation of production rates............ 15 Table 4: Observations of CO J=2-1 line in 174P/Echeclus............... 21 Table 5: Typical visual magnitude observations of 29P/SW1............. 35 Table 6: Measured and derived properties of dust and gas in 29P/SW1 coma... 36 Table 7: CO(J=2-1) observations of 29P/SW1 using the ARO SMT 10-m telescope 39 Table 8: Observations of R2 with the ARO 10m SMT................. 55 Table 9: Compiled Q(CO)/Q(HCN) ratios in CO-rich and other comets...... 62 Table 10: Observations of Comet C/2016 R2....................... 71 iv List of Abbreviations IRAM........... 30m Telescope of the Institut de Radio Astronomie Millimetrique SMT................. Arizona Radio Observatory 10m Submillimiter Telescope au......................................... Astronomical unit ηc........................................... Beam efficiency Q(CO)............................. Carbon monoxide production rate FWHM................................. Full Width Half Maximum ∆........................................ Geocentric distance r........................................ Heliocentric distance Q(HCN)............................ Hydrogen cyanide production rate JD............................................. Julian date JFC...................................... Jupiter-family comet KBO....................................... Kuiper Belt object ∗ TAdv............................................ Line area δv.............................................. Line-shift mol s−1..................................... Molecules second −1 v Abstract Comets are fascinating minor solar system bodies. They contain some of the most pristine and unprocessed material found in the solar system. As a comet approaches the Sun it displays the characteristic cometary coma and tail. This is due to the release of volatile species through a variety of processes. In the present work I studied the carbon monoxide emission of three very unique comets; 174P/Echeclus, 29P/Schwassmann-Wachmann and C/2016 R2 (PanSTARRS) with different radio telescopes at millimeter wavelengths. After molecular hydrogen, carbon monoxide is the second most abundant molecule in the universe, and is also the most volatile of the species found in most comets. The study of its release mechanisms, content and distribution within the coma of a comet can constrain current models of cometary and solar system formation. Some of the most relevant results of this work include: Detection of carbon monoxide in comet/Centaur 174P/Echeclus -only the third Centaur in which CO has been detected-, evidence for non-correlation between the CO emission and dust production in comet 29P/Schwassmann-Wachmann, and the first detection of 13CO in a comet. The results