Evolution And Distributions Of Planetary Systems In Different Galactic Environments And Stellar Evolution Stages

It has been a quarter century since the discovery of the first exoplanet 51 Peg b.To date,over 4,000 exoplanets have been identified and thousands of candidates are to be confirmed,which are distributed over a wide range of distance(order of kpc)in our Milky Way Galaxy.Now some kinematic parameters(such as parallax,proper motion and radial velocities)and physical properties(such as mass,effective temperature,and evolutionary stage)of planet host stars have been measeared thanks to the photometry,astrometry,and spectroscopy observation.The large quantities of observational data provide a good opportunity to statistically study the correlations between planetary system properties and stellar kinematic characteristics/stages.Therefore,in this paper,based on previous studies,we main focus on effects of galactic environment(spatial location,composition and age)and stellar evolution stages on the evolution and distributions of planetary systems,which will provide insights on the exoploration of the ubiquitous and diverse exoplanets and deepen our understanding of planet formation and evolution.In Chapter 1,we briefly review the history of exoplanet detection and introduce the planet formation theory.We then outline the statistical characteristics of the exoplanets so far,including planet size,occurrence rate,orbital architecture and their correlations with the physical properties of stars.These observational characteristics pose many challenges and constraints to the theory of planet formation and evolution.Next,we focus on what are the differences in the properties of planetary systems at different position/components in the Galaxy with different ages?The basis for studying these topics is to determine the kinematic properties of the stars(galactic position,velocity,composition)and ages.To do this,the basic step is to accurately characterize the planet host stars.In Chapter 2,we revisit the kinematic method to classify the Galactic components and extend its applicable range from?100 pc to?1,500 pc from the sun in order to cover most known planet hosts.Besides,we revisit the Age-Velocity dispersion Relation(AVR)and improve the precisons of parameters,which allows us to derive kinematic age with a typical uncertainty of 10-20%for an ensemble of stars.In Chapter 3 and Chapter 4,applying the above revised methods,we characterize the kinematic properties(e.g.,Galactic orbit,velocities and Galactic components)for the 2,174 planet host stars(2,872 planets)and 35,864 LAMOST-Gaia-Kepler stars.The revised kinematic method and AVR as well as the stellar catalog of kinematic properties and ages lay foundation for future studies on exoplanets in the Galactic context.Based on the foregoing kinemtaic methods and catalogs,we exoplore the evolution of stellar magnetic activity/rotation with kinematic ages and find that as stars aging,they spin down and become less active.We also explored the differences in kinematic propertie between the Kepler planet host stars and filed stars(stars without planets).we find that with the increasing of the transiting planet multiplicity(Np=0,1,2 and 3+),the fraction of thin(thick)disk stars increases(decreases)and the kinematic age decreases,which could be a consequence of the dynamical evolution of planetary architecture with age,i.e,the long term dynamical evolution can pump up orbital eccentricity/inclination of planets or even cause planet merge/ejection,which reduces the observed transiting planet multiplicity.In Chapter 5,we study the age distributions and evolution of hot Jupiters(Jupitermass planets with orbitial periods less than 10 days)with the above kinematic methods and star catalogs.We find that hot Jupiters favors younger stars comparing to warm/cold Jupiters(Jupiters with periods longer than 10 days).We also find that the fraction(occurrence rate)of hot Jupiters decreases with the age of the host star,while the fraction(occurrence rate)of cold Jupiters is nearly indepent with age.This phenomenon is consistent with what is expected by tidal theory,i,e,hot Jupiters lose angular momentum due to tidal interaction and the semi-major axisdecreases.Part of hot Jupiters enter the Roche limit of the host star and are swallowed up by the host star,resulting in the observed decay of the occurrence rate of hot Jupiters with age.It is also the first statistical evidence of orbital decay in a large sample of hot Jupiters.If the observed decay results from tidal dissipation,the modified stellar tidal quality factor for solarlike star is constraint as Q*'?105-106 and the best match is?3 × 105.Besides,the observed continuous-decrease also expects that the bulk of hot Jupiters form/arrive before?0.7 Gyr since the formation of stars.Furthermore,in Chapter 6,we study the remanent planetary systems around white dwarfs.Planetary systems can survive stellar evolution,as is evidenced from the atmospheric metal pollution and circumstellar dusty disks.By analysing a sample of metal-polluted white dwarfs from the Spitzer Space Telescope(Spitzer)and the Sloan Digital Sky Survey(SDSS),we find that the mass accretion rate onto the white dwarf generally follows a broken power-law decay.Combined with numerical simulation and theoretical derivation,we propose an evolution scenario of the atmospheric metal pollution and circumstellar dusty disks.The success of this scenario also implies that the configuration of an asteroid belt with an outer gas giant might be common around stars of several solar masses.In Chapter 7,we summarize the main conclusions of this paper.