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Models of Regular Galaxies DISSERTATIONEN ASTRO N OMI AE UNIVERSITATIS TAKTUENSIS 6 MODELS OF REGULAR GALAXIES b y PEETER TENJES TARTU 1993 DISSERTATIONEN ASTRONOMIAE UNIVERSITATIS TARTUEN 6 MODELS OF REGULAR GALAXIES by PEETER TENJES Supervisors: Prof. J. Einasto, Dr. Sei. M. Jõeveer, C&nd. Sei. Offieiöi opponents: В. Sundelius, Ph. D. (Göteborg) A. Chernin, Dr. Sei (Moscow) E. Saar, Dr. Sei. (T&rtv,) The Thesis will be defended on February 1993 at in the Council Hall of Ты-tu University, Ülikooli 18, EE2400 Tartu, Estonia. Secretary of the Council Ü. Uus The author was boro in 1956 in Türi, Estonia. In 1978 he graduated from the University of Tartu as a theoretical physicist and started work at the Chair of General Physics of the same University. In 1980 he started work at Tfextu Aetrophysical Observatory in the work group of extragalactic studies. Address of the author*. Institute of Astrophysics and Atmospheric Physics, ЕЁ2444 Tõravere, Estonia CONTENTS C H A P T E R I INTRODUCTION AND SUMMARY .................. 6 1 The structure of galaxies ............................................. .................. 3 2 Summary ...................... ....................................................................... 9 CHAPTER 3 THE ANDROMEDA GALAXY MSI ................ 15 1 Introduction . , .............. ..................................................................... 15 2 Analysis of observational data ........................................................ 16 3 Subsystems in M31 ................................................................. .......... 19 4 Best-approximation process ........................................................... 24 4.1 General parameter* of the approximation process ............. 24 4.2 Description of the fitting process ......................... ................. 25 4.3 Coupling of parameters...................... .............................. 28 4 3.1 Spheroidal components ......................... ............. .......... 29 4.3.2 Disk like components and the massive corona ........... 20 5 Results .......................... .................................................................... 32 6 Discussion ............................................................... ........................... 36 Appendix A: model construction...................................... 38 Appendix B: normalizing parameters............................................. 40 Appendix C: tbe 3-component m odel........................... 41 C H A P T E R 3 S T A R F O R M A T IO N IN M S I ................................. 4S 1 Introduction с.............................................................— ................ 48 2 An analysis of observational data ............................................... 49 3 Results ............................................................................. ......... ... 51 4 Discussion ........................................................................................... 53 C H A P T E R 4 THE ELLIPTICAL GALAXY M87 .................... 56 1 Introduction ..... .......... .................... .......... .................. .................56 2 Analysis of observational d a t a ......................................................... 57 3 Model construction .................................. ........................................ ...60 4 Subsystems in M87 ....... ....................................................................61 4.1 The nucleus ....... .........................................................................62 4.2 The k l o ...................... ........... ......................................................64 4.3 The bulge ................................................................................... ..66 4.4 The massive corona .................. .............................................66 5 Best-approximation model .................................................................68 в Discussion ......................................... ........................ ..........................69 CHAPTER 5 THE GALAXY M81 .................... ........................... T5 1 Introduction ......................................................................... ......... 75 2 Observations and data reduction............. ........................................75 3 An analysis of observational d ata.......................................................78 4 Subsystems in MSI ............. ............................... ............................. ...80 5 Description of the fitting process ................................... ..................84 6 Results and discussion ...................... .............................................. ...88 CHAPTER 6 REVIEW OF CONSTRUCTED MODELS ....... »2 1 Introduction ........................................................................................ .. 92 2 Overview of the model components . ............................................ 92 3 Description of the modelling ............................... .................... ......... 94 4 Results ..................................................................................................95 CHAPTER 7 PHYSICAL PROPERTIES OF GALACTIC P O P U L A T IO N S ......................................................................... 101 1 Introduction ...................................................................................... 101 2 The mass-to-light ratios for spheroidal and disk subsystems ... 101 3 The mean mass-to-light ratio of visible matter ........................... 103 CHAPTER 8 INTRINSIC SHAPE OF ELLIPTICAL G ALAXIES ...................................................................... 107 1 Introduction ....................................................................................... 107 2 Meihod ............................................................................................... 103 3 Results ................................................................................................. 14 4 Conclusions ........................................................................................ 120 S U M M A R Y (IN ESTO N IAN ) ............................................................... 124 LIST OF PUBLICATIONS ................................ .................................. 128 C H A P T E R 1 INTRODUCTION AND SUMMARY 1 The structure of galaxies One of the outstanding problems in modem astronomy is the investigation of the disfributior of mase in galaxies, the decomposing of the galaxy into subsys­ tems of ordinary and dark matter, and a study of their relationship. The struc­ ture of visible populations and the distribution of dark matter with respect to the visible one allows us to choose between various galaxy formation scenarios artd to clarify the nature o f dark matter in more detail. Simple one-component models, baeed on the radial light profiles, have not so far provided a strong test of theories of galaxy formation, since several evolution scenarios can be proposed that yield equally good fits to these observations (Gott 1977). Better results can be obtained by multiple-component models which incorporate the presence of physically different populations in galaxies. A useful diagnostic of galactic structure and evolution, at. least for spheroidal systems, is provided by the structure of isophot.es and the metaffidty gradients that are often obeerved in elliptical galaxies and spiral bulgee (Kormendy & Djorgovski 1Я89). The importance of the measurement of colours in galaxies is that they supply infor­ mation on the link between the chemical and dynamical evolution of galaxies end yield dues about how chemical evolution proceeded as stars formed in the history of a galaxy. Models of galaxy formation involving dissipative or dissi- pationless collapse or mergers (Larson 1990) predict relations between colour distribution and stellar density. Also, scenarios of galaxy formation, in which mergers play an important role, predict core-haio colour differences аз opposed to smooth continous gradients. During the collapse of the protogalaxy and the continuing star formation morphology' of galaxies was established. The form of a galaxy depends on dynamical properties of the collapsing matter and on the star formation process. The star formation products in different eras differ from each other physically, having different spatial distribution, chemical composition, as well as different kinematic properties that maintain the spatial distributions. Therefore, while studying the structure of stellar populations in galaxies it is possible to obtain quantitative information to understand the formation and evolution processes. The most effective tool for the analysis of the structure of stellar systems is construction of models. Ar appropriate empirical model of the galaxy should represent distribution of various structural constituents (globular clusters, gas, etc.), kinematical data, changes in chemical composition etc. 6 Decomposition of ft galaxy into subsystems on the basis of observations is complicated. Due to the large number of free parameters there may not be a unique solution to the problem. But when comparing the values of the parameters during the modelling also with the structure of other galaxies and with the models of chemical evolution (Tinsley 1980, Traat 1990), it is possible to avoid obviously nonphysical solutions. The modelling techniques of spiril galaxies have been well elaborated, The problem of the mass distribution in external galaxies was first formulated and solved by Öpik (1922) and Babcock (1938,
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