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Molecular Jets and Outflows from Young Stellar Objects in Cygnus-X, Auriga, and Cassiopeia

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Molecular Jets and Outflows from Young Stellar Objects in Cygnus-X, Auriga, and Cassiopeia Kent Academic Repository Full text document (pdf) Citation for published version Makin, Sally Victoria (2019) Molecular jets and outflows from young stellar objects in Cygnus-X, Auriga, and Cassiopeia. Doctor of Philosophy (PhD) thesis, University of Kent,. DOI Link to record in KAR https://kar.kent.ac.uk/72857/ Document Version UNSPECIFIED Copyright & reuse Content in the Kent Academic Repository is made available for research purposes. Unless otherwise stated all content is protected by copyright and in the absence of an open licence (eg Creative Commons), permissions for further reuse of content should be sought from the publisher, author or other copyright holder. Versions of research The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record. Enquiries For any further enquiries regarding the licence status of this document, please contact: [email protected] If you believe this document infringes copyright then please contact the KAR admin team with the take-down information provided at http://kar.kent.ac.uk/contact.html UNIVERSITY OF KENT DOCTORAL THESIS Molecular jets and outflows from young stellar objects in Cygnus-X, Auriga, and Cassiopeia Author: Supervisor: Sally Victoria MAKIN Dr. Dirk FROEBRICH A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in the Centre for Astrophysics and Planetary Science School of Physical Sciences January 30, 2019 Declaration of Authorship I, Sally Victoria MAKIN, declare that this thesis titled, “Molecular jets and outflows from young stellar objects in Cygnus-X, Auriga, and Cassiopeia” and the work presented in it are my own. I confirm that: This work was done wholly or mainly while in candidature for a research degree at this • University. Where any part of this thesis has previously been submitted for a degree or any other quali- • fication at this University or any other institution, this has been clearly stated. Where I have consulted the published work of others, this is always clearly attributed. • 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. I have acknowledged all main sources of help. • 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. Signed: Date: i UNIVERSITY OF KENT Abstract Faculty of Science School of Physical Sciences Doctor of Philosophy Molecular jets and outflows from young stellar objects in Cygnus-X, Auriga, and Cassiopeia by Sally Victoria MAKIN An unbiased, systematic survey for jets and outflows from young stars has been performed in two distinct and different regions in the Galactic plane. It utilised the 1 – 0 S(1) near-infrared line of molecular hydrogen (H2) to trace shock-excited emission, using data from the UKIRT Widefield Infrared Survey for H2 (UWISH2) survey. A total of 572 outflows were found in the high-mass star forming complex of Cygnus-X, and 98 in the low-mass regions of Auriga and Cassiopeia. Of these outflows found, 84 % are entirely new discoveries, and now 40 % of all the currently known H2 outflows are a result of the UWISH2 survey. The properties of the outflows were consistently measured and a large statistical sample has been built. Similarities and differences between the outflow populations in the two regions were explored in order to discover which properties are universal and which depend on local factors. In both regions, most outflows are located in isolated (60 %) and not clustered environments, but those from clusters are longer and more luminous. Almost fifty new infrared cluster candidates have also been discovered as a result of this work, and the typical cluster is around 0.5 pc in diameter. About 10 % of outflows form crossing pairs of outflows, and 40 % of these show signs of precession compared to 20 % in the general population. The outflow position angles are in agreement with a homogeneous distribution. Most of the outflows are driven by protostars (Class 0/I) rather than the more evolved young stellar objects (Class II), as determined using their mid-infrared magnitudes. The typical outflow has a length of < 0.4 pc, and is slightly asymmetric with one lobe around 30 % longer than the other. The length distribution follows an exponential behaviour and there appears to be a maximum length. −3 The typical outflow luminosity is faint (1 10 L⊙) and most of the outflows are driven by low × or intermediate-luminosity protostars. The lobe luminosity ratios (the faint lobe over the bright lobe) are highly asymmetric in H2. There is a correlation between the length and luminosity of an outflow, and these do not depend on the evolutionary stage of the driving source. There is also a correlation between the luminosity of the driving source and the outflow luminosity, but the length distribution does not follow their behaviour. Therefore, the outflow lengths must also, to some extent, be governed by the density distribution of the local environment. ii Acknowledgements First and foremost, I would like to thank Dirk Froebrich. Working on this project has been a true pleasure thanks to his limitless patience, generosity, professionalism and dry humour. I hope one day to be as positive an influence on someone as he has been on me. I would also like to acknowledge the Sciences Technologies Research Council (STFC) whose funding made the project possible (scholarship #1482158). The United Kingdom Infra-Red Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the UK. The data were obtained as part of the UKIRT Service Program. Heartfelt thanks also go to CAPS for hosting me while I did this work. Each member of the group has given me helpful advice, spirited discussion, friendly words and sanity checks when I needed them. I would especially like to acknowledge Justin Donohoe, who in the early days of this project taught me how to Linux. His good humour, friendship and support while I was finding my feet were invaluable. Similarly, I would like to thank Tim Kinnear for his peerless technical support during an endless parade of machine-related mishaps. They are both an inspiration in their willingness to help others, and I will continue to pay it forward. Not to mention, of course, the Beacon Observatory gang; Justin, Ricky, Justyn and Sam, who helped me feel like less of an imposter. And to Netflix, for all those nights when coffee just wasn’t enough to keep me awake. The Applied Optics Group (AOG) deserve special thanks, for not just putting up with me, but for adopting me as an honorary member of the group. The banter and jokes are always top quality, and the willingness to share cake is one I very much appreciate. To the Adrians (Pod and Bradu), Prof, Ramona, Radu, Sophie, Magalie and Felix, Hisham (my taxi hero), Mikey, Mike, George, Andy and Adrian F: thank you for being my surrogate support network, for helping when I’ve been stuck, and for sharing in my successes. Thanks also to the Griffith Observatory, who provided the final inspirational straw to this camel’s back; and to my dear friends Shawn Harrison and Salvatore Finamore, who never stopped believing in me. On a more personal note, I also need to thank my wonderful family; my parents, my sisters, and brother-in-law, who have kept me going despite some painful times over the last few years. You haven’t always understood what I’m doing, but you loved and supported me while I did it. This work has been a labour of love, and I dedicate it to those we have lost and those we have gained. I hope I have done you proud. To Manuel’s family: from the very start, you have warmly welcomed me as one of your own. Obrigada. Last but definitely not least, Manuel. My Sun and stars. The order to my chaos. This Thesis could not have been finished without you. iii Contents Declaration of Authorship i Abstract ii Acknowledgements iii Contents iv List of Figures viii List of Tables x 1 Introduction 1 1.1 Structure of this Thesis ............................... 2 1.2 Publications ..................................... 4 2 Theoretical background 5 2.1 The interstellar medium ............................... 5 2.2 Molecular hydrogen transitions ........................... 7 2.3 Star formation .................................... 9 2.4 Classification of young stars ............................ 12 2.5 High-mass stars ................................... 13 2.6 Outflows ....................................... 15 2.6.1 Formation of outflows ........................... 16 2.6.2 Morphology ................................ 19 2.6.3 Accretion and mass loss .......................... 22 2.7 Previous outflow surveys in H2 ........................... 24 2.8 MHOs ........................................ 25 2.9 The Milky Way ................................... 26 2.10 Summary of the UWISH2 survey .......................... 28 2.11 Aims of this Thesis ................................. 31 3 Methodology 33 3.1 Part I: The search for extended H2 emission .................... 33 3.1.1 Continuum subtraction ........................... 33 3.1.2 Using images to identify features ..................... 34 3.1.2.1 JHK ............................... 34 iv 3.1.2.2 JHH2 ............................... 35 3.1.2.3 JKH2 ............................... 36 3.1.3 Automated detection of H2 features .................... 37 3.1.4 Feature verification ............................. 38 3.1.5 Image artefact removal ........................... 40 3.1.6 Results ................................... 42 3.2 Part II: Identifying outflows and their driving sources . 44 3.2.1 Groups of emission features ........................ 44 3.2.2 Setting up the images ............................ 44 3.2.3 Point-source catalogues .......................... 45 3.2.4 Sorting emission-line objects into outflows .
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