Taking the Bull by the 'Horns'
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Taking the Bull by the ’Horns’ Modelling the structure and kinematics of star-forming regions using Gaia DR2 by Graham David FLEMING A thesis submitted in partial fulfilment for the requirements for the degree of Master of Science (by Research) in Astrophysics at the University of Central Lancashire Tuesday 8th December, 2020 University of Central Lancashire Master of Science (by Research) Thesis Taking the Bull by the ’Horns’ Modelling the structure and kinematics of star-forming regions using Gaia DR2 Author: Graham David FLEMING Supervisor: Dr. Jason KIRK Second Supervisor: Prof. Derek WARD-THOMPSON A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science (by Research) in Astrophysics in the Jeremiah Horrocks Institute School of Natural Sciences Tuesday 8th December, 2020 Declaration of Authorship Type of Award: Master of Science (by Research) in Astrophysics School: Jeremiah Horrocks Institute I, Graham David FLEMING, declare that this thesis titled, “Taking the Bull by the ’Horns’” and the work presented in it are my own and was completed wholly whilst in candidature for a research degree at the University of Central Lancashire. In addition: 1. Concurrent registration for two or more academic awards. I declare that while registered as a candidate for the research degree, I have not been a registered candidate or enrolled student for another award of the University or other academic or professional institution. 2. Material submitted for another award. I declare that no material contained in the thesis has been used in any other submission for an academic award and is solely my own work. 3. Previously published works. Some of the work presented in this thesis has been submitted for publication by the author (Fleming, Kirk, and Ward- Thompson, 2019). 4. Collaboration. Where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself. I have acknowledged all main sources of help. 5. Referencing previous works. Where I have consulted the published work of others, this is always clearly attributed. Also, where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work. 6. Use of a Proof-reader. No proof-reading service was used in the compilation of this thesis. Signed: Print Name: Graham David Fleming Date: Tuesday 8th December, 2020 i Supervisor’s Declaration I, Dr. Jason KIRK, as supervisor, hereby declare that this thesis titled, “Taking the Bull by the ’Horns’” written by Graham David FLEMING, is his own writing prepared under my supervision and that I supported his work with regular consultations. I confirm that to the best of my knowledge, Graham David FLEMING has carried out his research according to the University of Central Lancashire requirements for a Master’s degree. I also declare that, based on its professional merits, the thesis meets the formal and professional requirements of the University of Central Lancashire and those of the Jeremiah Horrocks Institute, I therefore support its submission. Signed: Print Name: Jason M. Kirk Date: Tuesday 8th December, 2020 ii Figure 1 Herschel’s infrared view of the Taurus Molecular Cloud. Image: http://sci.esa.int/jump.cfm?oid=59536. © ESA/Herschel/NASA/JPL-Caltech. “I’ve been studying the Taurus Molecular Cloud for decades, and I had no idea I was looking at two clouds, one behind the other – we’ve never before had a three-dimensional view of anything so distant.” Derek WARD-THOMPSON (June 2019) iii UNIVERSITY OF CENTRAL LANCASHIRE Abstract Jeremiah Horrocks Institute School of Natural Sciences Master of Science (by Research) in Astrophysics Taking the Bull by the ’Horns’ by Graham David FLEMING The Taurus Molecular Cloud (TMC) is a star forming region, containing all stages of pre-main sequence stellar types, lying at an accepted distance of approximately 140 parsecs from Earth, spread across the Taurus and Auriga constellations. This cloud has been extensively studied and is known to contain hundreds of young stellar objects in the form of deeply embedded protostars displaying disks and outflows, classical and weak-lined T Tauri stars, Herbig-Haro objects and low-mass brown dwarfs. By using data obtained from the European Space Agency’s Gaia space observatories second data release (DR2), an area of sky of 10◦x15◦, centred on right ascension (J2000.0)=68.5◦ and declination (J2000.0)=27.0◦ is studied, this being an area surrounding the Taurus molecular cloud. A preliminary investigation of a small sample of objects previously identified in the Spitzer catalogue found two main associations, hitherto unrecognised, centred at 130±6 pc and 160±4 pc at 1s which also have different proper motions, of 24.5±2.8 and 20.1±2.4 mas yr−1 respectively. These associations are here named the ‘Two Horns’ of Taurus. Applying the same procedures as those used in our preliminary study a sample of Gaia optical sources are investigated using quality filters identified in the literature. The existence of two populations at a mean distance of 139.7 pc centred on 130±3 pc and 159±12 pc at 1s standard deviation is confirmed. These ‘near’ and ‘far’ groups are found to have proper motions of 25.2±3.4 and 22.1±4.5 mas yr−1 respectively at 1s. Using data from Gaia DR2, two previously unidentified populations of Young Stellar Objects are identified in the Taurus Molecular Cloud. This study investigates the positions, classifications, ages and kinematics of these groups and 3-dimensional visualizations of these populations are presented. iv Publications and Conferences Paper Title: Revealing the Two ‘Horns’ of Taurus with Gaia DR2. Pre-print submitted to arXiv https://arxiv.org/abs/1904.06980. 16th April 2019. STARRY Final Conference: Gaia’s view of Pre-Main Sequence Evolution - Linking the T Tauri and Herbig Ae/Be stars. Weetwood Hall, Leeds, UK. 18th - 21st June 2019. Presentation Title: Revealing the Two ‘Horns’ of Taurus with Gaia DR2. A copy of the presentation can be found at https://starry- project.eu/final-conference/programme/. National Astronomy Meeting (NAM2019): Lancaster University, Lancaster, UK. 30th June - 4th July 2019. Poster presentation: Revealing the Two ‘Horns’ of Taurus with Gaia DR2. A copy of the poster can be found at https://lancaster.app.box.com/v/nam2019-posters/file/486068363251. v Acknowledgements I would like to express my sincere gratitude to my supervisor Doctor Jason Kirk for his sustained support throughout the course of my research. His patience and guidance have helped on numerous occasions. Also, to Professor Derek Ward-Thompson who has given me encouragement and advice during the completion of my studies. I would also like to acknowledge the invaluable collaborative support given by Dr. Kate Pattle in providing the underlying Python code used in the analysis of our data using Hartigans’ Dip Test (Section 3.2.1) and in her contribution to Section 3.4.3. I also express my gratitude to Dr. Nigel Hambly of the Royal Observatory, Edinburgh and member of the European Space Agency’s Gaia mission Data Processing and Analysis Consortium (DPAC) for his in-depth knowledge of the Gaia Archive and how to access it through the use of ADQL queries. This work has used the NASA Astrophysics Data System (ADS) Bibliographic Services1 as well as the VizieR catalogue access tool2 and SIMBAD astronomical database3, operated at CDS, Strasbourg, France. During the early stages of this study I was grateful to be able to use the online UVW Calculator4 created by David Rodriguez, UCLA (2010). Celestial coordinate conversions have been made using the online RA DEC flexible converter5 provided by Jan Skowron at the Warsaw University Observatory. Data products have been used from the European Space Agency (ESA) mission Gaia6, processed by the Gaia Data Processing and Analysis Consortium (DPAC)7. Funding for the DPAC is provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Use has also been made of data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Data from the Guoshoujing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope) has been used in Section 4.4.1. LAMOST is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has been provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences. 1http://ads.harvard.edu/ 2http://vizier.u-strasbg.fr/viz-bin/VizieR 3http://simbad.u-strasbg.fr/simbad/ 4http://www.astro.ucla.edu/ drodrigu/UVWCalc.html 5http://www.astrouw.edu.pl/ jskowron/ra-dec/ 6https://www.cosmos.esa.int/gaia 7https://www.cosmos.esa.int/web/gaia/dpac/consortium vi Contents Page Declaration of Authorshipi Supervisor’s Declaration ii Abstract iv Publications and Conferencesv Acknowledgements vi 1 INTRODUCTION1 1.1 The Taurus Molecular Cloud ....................... 1 1.1.1 Evidence for star formation in the TMC............. 2 1.1.2 Contextualising this study..................... 3 1.1.3 Contemporary studies....................... 5 2 GAIA 6 2.1 Gaia’s science payload .......................... 9 2.2 Data Processing and Presentation.................... 11 2.3 Data Release 2 (DR2) ........................... 12 2.3.1 Data Access............................. 12 3 COMPARATIVE SPITZER INFRARED STUDY 14 3.1 Identifying the study group........................ 16 3.2 Validation of Gaia DR2 distance data.................. 18 3.2.1 Statistical analysis of distance distribution........... 20 3.3 Proper Motion study...........................