Raman scattering by molecular hydrogen and nitrogen in exoplanetary atmospheres

Oklopčić, Antonija; Hirata, Christopher M.; Heng, Kevin (2016). Raman scattering by molecular hydrogen and nitrogen in exoplanetary atmospheres. Astrophysical journal, 832(1), p. 30. Institute of Physics Publishing IOP 10.3847/0004-637X/832/1/30

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An important source of opacity in exoplanet atmospheres at short visible and near-UV wavelengths is Rayleigh scattering of light on molecules. It is accompanied by a related, albeit weaker process—Raman scattering. We analyze the signatures of Raman scattering imprinted in the reflected light and the geometric albedo of exoplanets, which could provide information about atmospheric properties. Raman scattering affects the geometric albedo spectra of planets in the following ways. First, it causes filling-in of strong absorption lines in the incident radiation, thus producing sharp peaks in the albedo. Second, it shifts the wavelengths of spectral features in the reflected light causing the so-called Raman ghost lines. Raman scattering can also cause a broadband reduction of the albedo due to wavelength shifting of a stellar spectrum with red spectral index. Observing the Raman peaks in the albedo could be used to measure the column density of gas, thus providing constraints on the presence of clouds in the atmosphere. Observing the Raman ghost lines could be used to spectroscopically identify the main scatterer in the atmosphere, even molecules like H2 or N2, which do not have prominent spectral signatures in the optical wavelength range. If detected, ghost lines could also provide information about the temperature of the atmosphere. In this paper, we investigate the effects of Raman scattering in hydrogen- and nitrogen-dominated atmospheres. We analyze the feasibility of detecting the signatures of Raman scattering with the existing and future observational facilities, and of using these signatures as probes of exoplanetary atmospheres.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Heng, Kevin

Subjects:

500 Science > 520 Astronomy
500 Science
500 Science > 530 Physics

ISSN:

0004-637X

Publisher:

Institute of Physics Publishing IOP

Language:

English

Submitter:

Janine Jungo

Date Deposited:

19 Jul 2017 07:59

Last Modified:

11 Oct 2017 06:33

Publisher DOI:

10.3847/0004-637X/832/1/30

BORIS DOI:

10.7892/boris.97256

URI:

https://boris.unibe.ch/id/eprint/97256

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