On constraining nontrivial properties of exoplanets and other topics in astrophysics.

摘要

Part I. At the present epoch, a significant fraction of the baryonic matter in the universe is in a hot, X--ray emitting intragroup medium of small galaxy groups; but at higher redshift the nature of the intergalactic medium of such groups is unconstrained. I examine the X--ray luminosity of 21 galaxy groups in the CNOC2 Field Galaxy Redshift Survey, at redshifts 0.1 z 0.6, and find that not one was visible in over 100 ksec of observation with XMM-Newton, therefore providing tentative evidence that groups at intermediate redshift are underluminous relative to their local cousins.; Part II. As the emerging field of astrobiology pursues the quest to learn if there is life on planets around other nearby stars, there are various properties of planets that it will be important to constrain yet difficult to measure. I address how to constrain three nontrivial properties of extrasolar planets: (i) the composition, and (ii) the rotation rate and atmospheric dynamics of hot Jupiters; and (iii) the habitability of terrestrial planets.; (i) When a giant planet in the source plane of a gravitational microlensing event crosses the fold-caustic of a foreground binary lens, the planet-star brightness ratio is greatly enhanced, which in a favorable situation could allow for a crude optical spectrum of the planet.; (ii) As a giant, tidally locked planet transits across the face of its star, the rotation of the planet's atmosphere will impose a Doppler shift on absorption features arising from the planet's atmosphere relative to where the features would be on a non-rotating planet. With future telescopes that have larger collecting areas, we will be able to place constraints on the rotation rate of nearby transiting hot Jupiters.; (iii) Finally, I revisit the habitability of terrestrial planets around sun-like stars: Using a 1-dimensional energy balance model, I investigate how the temperature distribution is likely to depend on many factors, including the covering fraction of ocean, the rotation rate, the obliquity, and more.