Optical and Infrared Photometric Study of Pre-Main Sequence Stars in Young Open Cluster NGC 7419
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Optical and Infrared Photometric Study of Pre-Main Sequence Stars in Young Open Cluster NGC 7419 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Philosophy in Physics by Vrinda Mukundan (Reg. No. 1235209) Under the Guidance of K T Paul Professor Department of Physics CHRIST UNIVERSITY BANGALORE, INDIA December 2013 Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. Approval of Dissertation Dissertation entitled Optical and Infrared Photometric Study of Pre-main Sequence Stars in Young Open Cluster NGC 7419 by Vrinda Mukundan, Reg. No. 1235209 is approved for the award of the degree of Master of Philosophy in Physics. Examiners: 1. 2. 3. Supervisor(s): Chairman: Date: ___________ Place: Bangalore Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. i Declaration I Vrinda Mukundan hereby declare that the dissertation, titled Optical and Infrared Photometric study of Pre-main Sequence Stars in Young Open Cluster NGC 7419 is a record of original research work undertaken by me for the award of the degree of Master of Philosophy in Physics. I have completed this study under the supervision of Dr K T Paul, Associate Professor, Department of Physics. I also declare that this dissertation has not been submitted for the award of any degree, diploma, associate ship, fellowship or other title. It has not been sent for any publication or presentation purpose. I hereby confirm the originality of the work and that there is no plagiarism in any part of the dissertation. Place: Bangalore Date: Vrinda Mukundan Reg No. 1235209 Department of Physics Christ University,Bangalore Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. ii Certificate This is to certify that the dissertation submitted by Vrinda Mukundan (Reg. No.1235209) titled ‘Optical and Infrared Photometric study of Pre-main Sequence Stars in Young Open Cluster NGC 7419’ is a record of research work done by her during the academic year 2012-2013 under my supervision in partial fulfilment for the award of Master of Philosophy in Physics. This dissertation has not been submitted for the award of any degree, diploma, associate ship, fellowship or other title. It has not been sent for any publication or presentation purpose. I hereby confirm the originality of the work and that there is no plagiarism in any part of the dissertation. Place:Bangalore Date: Dr K T Paul Associate Professor Department of Physics Christ University, Bangalore - 29 Dr George Thomas C Professor & Head Department of Physics Christ University, Bangalore - 29 Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. iii Acknowledgements It gives me great pleasure to express my sincere gratitude to my guide, Dr K T Paul, for the constant support and guidance that he has provided all along my work. This work would not have been possible without his active support. I am deeply indebted to Dr Annapurni Subramaniam (Indian Institute of Astrophysics) for the fruitful discussions, valuable suggestions and support that shehas provided for my work. I have been benefited by her constructive suggestions and inspirations. The support extended by Ms Aadara B (IISER,Trivandrum), for carrying out the study is gratefully acknowledged. I thank to Dr George Thomas C (Associate Dean & Head of the Department of Physics), Dr Bubbly S G (M.Phil Co-ordinator) and all other faculty members of the Department of Physics for help and encouragement for carrying out this work. I extend my heartfelt gratitude to my parents and my husband for being strong pillars of support all through my endeavours. This study makes use of data products 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. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. iv Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration This research has made use of the WEBDA database, operated at the Department of Theoretical Physics and Astrophysics of the Masaryk University Place: Bangalore Vrinda Mukundan Date: Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. v Abstract The embryonic stage of development of stars has been a field of astrophysics which still pose many unresolved queries. The problem is largely due to the solitary nature of embryonic stars. Even the largest optical telescopes were not able to reveal many details about such stars as they are formed deep inside molecular cloud thorough which optical wavelength cannot pass through. Forbidding distances to such stars is an added problem. However, recently, this field is slowly turning into observational science. Even though optical radiations fail to reach the destination, longer wavelength infrared (IR) radiations can penetrate through such dusty region. These infrared radiations have been known for decades. But it is only during very recent times that infrared telescopes that have very high sensitivity and resolution came in to scenario. So now the astronomers are able to observe these stellar embryos. Studies about this stage of star formation can help us to solve many questions like how the birth of a star takes place, how these stars accrete matter into it from surroundings, when will this accretion stops, why do some stars have planetary systems around them etc. Current study is an attempt to look for the presence of these embryonic stars in an open cluster using infrared data and to get more details on nature of those stellar embryos. We investigate the properties of young stars and their circumstellar disks in young open cluster NGC 7419. The pre-determined V magnitude and B magnitude of these stars are combined with infrared data from 2MASS J,H, K and 4 band WISE data. The color-color diagrams are made using these 9 bands to identify young stellar objects. The individual SED fitting is done for these identified stars and parameters like their age, mass, temperature, disk radius and disk mass are estimated. These are used to comment on the evolutionary stage of the pre-main sequence stars and their circumstellar disk. Dissertation has been divided into five chapters. Chapter 1 gives a general introduction to the work done. Literatures referred are explained in Chapter 2. Data used in the current study and methodology adopted is described in chapter 3. Current work done on the young stellar objects in cluster NGC 7419 and results obtained from the study are explained in Chapter 4 and Chapter 5 respectively. 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Use it for fair purpose.Give credit to the author by citing properly, if you are using it. vi Contents Approval of Dissertation i Declaration ii Certificate iii Acknowledgements iv Abstract vi List of Tables ix List of Figures x List of Abbreviations xi Chapter 1 : Introduction 1 1.2 Star formation …………………………………………………………................ 2 1.2 Circumstellar Disk ………………………………………………………............. 4 1.2.1 Transition Disk…………………………………………………………............... 5 1.3 Classification of Young Stellar Objects (YSOs)…………………………............ 6 1.4 Stellar Clusters……………………………………………………………............ 8 1.4.1 Globular Clusters………………………………………………………............... 8 1.4.2 Open Clusters…………………………………………………………................ 9 1.5 Photometry……………………………………………………………………...... 9 1.6 Thesis Objective……………………………………………………………......... 10 Chapter 2 : Literature Review 12 2.1 Previous Works………………………………………………………………....... 13 2.2 NGC 7419……………………………………………………………………....... 17 Chapter 3 : Data and Methodology 20 3.1 Infrared Data…………………………………………………………………....... 21 3.1.1 Two Micron All Sky Survey(2MASS)……………………………….................. 21 3.1.2 Wide Field Infrared Survey Explorer (WISE)………………………….............. 21 3.2 Optical Data…………………………………………………………………........ 22 Property of Christ University. Use it for fair purpose.Give credit to the author by citing properly, if you are using it. vii 3.3 Methodology…………………………………………………………………...... 22 3.3.1 Cross matching of Optical and Infrared Data………………………..................... 22 3.3.2 Color-Color Diagrams (CCDs)……………………………………...................... 24 3.3.3 Spectral Energy Distribution (SED)………………………….............................. 24 Chapter 4 : Results and Discussion 27 4.1 Classification based on WISE color-color diagram…………………………...... 28 4.2 Classification based on Spectral Energy Distribution………………………........ 31 4.3 Parameter Estimation using SED ……………………………………………...... 34 4.4 Parameter Plots………………………………………………………………....... 39 4.4.1 Age Vs Disk mass.................................................................................................. 39 4.4.2 Age Vs Disk accretion rate................................................................................... 40 4.4.3 Age Vs Mass of central source............................................................................