Two Talks!

Speaker 1:  Antonija Oklopčić, CalTech

Probing Exoplanet Atmospheres with Raman Scattering (speaker: Antonija Oklopčić, CalTech)

Abstract: Rayleigh scattering is an important source of opacity in the atmospheres of exoplanets at short optical and near-UV wavelengths. Raman scattering on molecules is an inelastic process related to Rayleigh scattering which leaves specific spectral signatures imprinted in the reflected light and the geometric albedo spectrum of the planet. These spectral features can be used to probe the atmospheres of exoplanets. The intensity of Raman features depends on the column of the atmosphere that the radiation passes through before being scattered into our line of sight and hence can provide information on the presence and altitude of clouds, even in atmospheres composed of heavy molecular species. The so-called Raman ghost lines could be used to spectroscopically identify the main scatterer in the atmosphere, even molecules like hydrogen or nitrogen, which do not show prominent spectral signatures in the optical wavelength range. If detected, these ghost lines could also provide information about the temperature of the atmosphere. In this talk I will present a feasibility analysis for detecting Raman spectral features in nearby exoplanets using the next-generation observational facilities. I will also discuss which stellar types are the most promising candidates for hosting exoplanets with strong Raman features in their albedo spectra.

Speaker 2: Ana Mosquera

Applications of Lensed Quasars’ Variability

Flux variability of lensed quasars can be used as a fun and fancy way to study the structure of galaxies and quasar accretion disks. These fluctuations are a combination of the intrinsic variability of the quasar, from which it is possible to measure time delays and determine the dark matter halo structure of the lens galaxy, and microlensing variability induced by the stars and compact objects in the lensing galaxy, from which we can measure accretion disk sizes,the mean mass of the stars in the lens galaxy, and the dark matter mass fraction near thelensed images. In my talk I will discuss where these cool measurements are leading us, and the current status of our target selection and follow up. As a treat, at the end of my talk I will advertise BINGO experiment (BAOs from Integrated Neutral Gas Observations), a project to build a novel radio telescope to map redshifted neutral hydrogen emission between z = 0.13 and 0.48.