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Testing the performance of cross-correlation techniques to search for molecular features in JWST NIRSpec G395H observations of transiting exoplanets

Year: 2025
Type: preprint
Abstract: Cross-correlations techniques offer an alternative method to search for molecular species in JWST observations of exoplanet atmospheres. In a previous article, we applied cross-correlation functions for the first time to JWST NIRSpec/G395H observations of exoplanet atmospheres, resulting in a detection of CO in the transmission spectrum of WASP-39b and a tentative detection of CO isotopologues. Here we present an improved version of our cross-correlation technique and an investigation into how efficient the technique is when searching for other molecules in JWST NIRSpec/G395H data. Our search results in the detection of more molecules via cross-correlations in the atmosphere of WASP-39b, including $\rm H_{2}O$ and $\rm CO_{2}$, and confirms the CO detection. This result proves that cross-correlations are a robust and computationally cheap alternative method to search for molecular species in transmission spectra observed with JWST. We also searched for other molecules ($\rm CH_{4}$, $\rm NH_{3}$, $\rm SO_{2}$, $\rm N_{2}O$, $\rm H_{2}S$, $\rm PH_{3}$, $\rm O_{3}$ and $\rm C_{2}H_{2}$) that were not detected, for which we provide the definition of their cross-correlation baselines for future searches of those molecules in other targets. We find that that the cross-correlation search of each molecule is more efficient over limited wavelength regions of the spectrum, where the signal for that molecule dominates over other molecules, than over broad wavelength ranges. In general we also find that Gaussian normalization is the most efficient normalization mode for the generation of the molecular templates.
Authors: Esparza-Borges, Emma, López-Morales, Mercedes, Pallé, Enric, Makhnev, Vladimir, Gordon, Iouli, Hargreaves, Robert, Kirk, James, Cáceres, Claudio, Crossfield, Ian J. M., Crouzet, Nicolas, Decin, Leen, Désert, Jean-Michel, Flagg, Laura, Muñoz, Antonio García, Harrington, Joseph, Molaverdikhani, Karan, Morello, Giuseppe, Nikolov, Nikolay, Solmaz, Arif, Rackham, Benjamin V., Redfield, Seth
Institutions: Universidad de La Laguna, Instituto de Astrofísica de Canarias, Space Telescope Science Institute, Center for Astrophysics Harvard & Smithsonian, Imperial College London, Universidad Andrés Bello, University of Kansas, University of Groningen, KU Leuven, University of Amsterdam, Johns Hopkins University, Centre National de la Recherche Scientifique, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Astrophysique, Instrumentation et Modélisation, CEA Paris-Saclay, University of Central Florida, Ludwig-Maximilians-Universität München, Osservatorio Astronomico di Palermo, Instituto de Astrofísica de Andalucía, Istanbul Health and Technology University, Massachusetts Institute of Technology, Wesleyan University
Language: English
Open Access status: green
Funders: National Aeronautics and Space Administration, Space Telescope Science Institute, Imperial College London, European Commission, Deutsche Forschungsgemeinschaft, KU Leuven, Ministerio de Ciencia e Innovación, Agencia Nacional de Investigación y Desarrollo, Science Mission Directorate, Agencia Estatal de Investigación
Awards: G103270039, G1338664626, G1381791653, G1814045685, G1855990336, G1897041155, G2262748287, G2309174360, G2329447088, G2428672771, G256731684, G2601397997, G300979063, G3311989135, G3480869486, G3518538256, G3681454997, G3696727022, G3741235667, G4042783231, G4066435496, G4245300941, G425668148, G430777504, EXC 2094: ORIGINS: Vom Ursprung des Universums bis zu den ersten Bausteinen des Lebens, G463062595, G490073602, G5080475149, G5159467736, G5222444068, G5421974903, G5568641063, G5840133879, G5881647929, G5894067328, G5972664074, G6686480456, G6827456243, G7053437819, G7719629023, G7782773376, G7937275146, G7964634422, CENTRO DE ASTROFISICA Y TECNOLOGIAS AFINES (CATA)
OpenAlex ID: W7084626251
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