Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation
Eclipse mapping is a technique for inferring 2D brightness maps of transiting exoplanets from the shape of an eclipse light curve. With JWST’s unmatched precision, eclipse mapping is now possible for a large number of exoplanets. However, eclipse mapping has only been applied to two planets, and the...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astronomical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-3881/ad0366 |
| _version_ | 1797625571452125184 |
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| author | Ryan C. Challener Luis Welbanks Peter McGill |
| author_facet | Ryan C. Challener Luis Welbanks Peter McGill |
| author_sort | Ryan C. Challener |
| collection | DOAJ |
| description | Eclipse mapping is a technique for inferring 2D brightness maps of transiting exoplanets from the shape of an eclipse light curve. With JWST’s unmatched precision, eclipse mapping is now possible for a large number of exoplanets. However, eclipse mapping has only been applied to two planets, and the nuances of fitting eclipse maps are not yet fully understood. Here, we use Leave-one-out Cross Validation (LOO-CV) to investigate eclipse mapping, with application to a JWST NIRISS/SOSS observation of the ultrahot Jupiter WASP-18b. LOO-CV is a technique that provides insight into the out-of-sample predictive power of models on a data-point-by-data-point basis. We show that constraints on planetary brightness patterns behave as expected, with large-scale variations driven by the phase-curve variation in the light curve and smaller-scale structures constrained by the eclipse ingress and egress. For WASP-18b we show that the need for higher model complexity (smaller-scale features) is driven exclusively by the shape of the eclipse ingress and egress. We use LOO-CV to investigate the relationship between planetary brightness map components when mapping under a positive-flux constraint to better understand the need for complex models. Finally, we use LOO-CV to understand the degeneracy between the competing “hot spot” and “plateau” brightness map models of WASP-18b, showing that the plateau model is driven by the ingress shape and the hot spot model is driven by the egress shape, but preference for neither model is due to outliers or unmodeled signals. Based on this analysis, we make recommendations for the use of LOO-CV in future eclipse-mapping studies. |
| first_indexed | 2024-03-11T09:58:15Z |
| format | Article |
| id | doaj.art-cc21526af4754952b2ffbd9fff62b5fb |
| institution | Directory Open Access Journal |
| issn | 1538-3881 |
| language | English |
| last_indexed | 2024-03-11T09:58:15Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astronomical Journal |
| spelling | doaj.art-cc21526af4754952b2ffbd9fff62b5fb2023-11-16T15:37:50ZengIOP PublishingThe Astronomical Journal1538-38812023-01-01166625110.3847/1538-3881/ad0366Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross ValidationRyan C. Challener0https://orcid.org/0000-0002-8211-6538Luis Welbanks1https://orcid.org/0000-0003-0156-4564Peter McGill2https://orcid.org/0000-0002-1052-6749Department of Astronomy, University of Michigan , 1085 S. University Avenue, Ann Arbor, MI 48109, USA; Department of Astronomy, Cornell University , 122 Sciences Drive, Ithaca, NY 14853, USASchool of Earth and Space Exploration, Arizona State University , Tempe, AZ, 85257, USADepartment of Astronomy and Astrophysics, University of California , Santa Cruz, CA 93105, USA; Lawrence Livermore National Laboratory , 7000 East Avenue, Livermore, CA, USAEclipse mapping is a technique for inferring 2D brightness maps of transiting exoplanets from the shape of an eclipse light curve. With JWST’s unmatched precision, eclipse mapping is now possible for a large number of exoplanets. However, eclipse mapping has only been applied to two planets, and the nuances of fitting eclipse maps are not yet fully understood. Here, we use Leave-one-out Cross Validation (LOO-CV) to investigate eclipse mapping, with application to a JWST NIRISS/SOSS observation of the ultrahot Jupiter WASP-18b. LOO-CV is a technique that provides insight into the out-of-sample predictive power of models on a data-point-by-data-point basis. We show that constraints on planetary brightness patterns behave as expected, with large-scale variations driven by the phase-curve variation in the light curve and smaller-scale structures constrained by the eclipse ingress and egress. For WASP-18b we show that the need for higher model complexity (smaller-scale features) is driven exclusively by the shape of the eclipse ingress and egress. We use LOO-CV to investigate the relationship between planetary brightness map components when mapping under a positive-flux constraint to better understand the need for complex models. Finally, we use LOO-CV to understand the degeneracy between the competing “hot spot” and “plateau” brightness map models of WASP-18b, showing that the plateau model is driven by the ingress shape and the hot spot model is driven by the egress shape, but preference for neither model is due to outliers or unmodeled signals. Based on this analysis, we make recommendations for the use of LOO-CV in future eclipse-mapping studies.https://doi.org/10.3847/1538-3881/ad0366Exoplanet astronomyExoplanet atmospheresExoplanet atmospheric structureExoplanetsExtrasolar gaseous planetsHot Jupiters |
| spellingShingle | Ryan C. Challener Luis Welbanks Peter McGill Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation The Astronomical Journal Exoplanet astronomy Exoplanet atmospheres Exoplanet atmospheric structure Exoplanets Extrasolar gaseous planets Hot Jupiters |
| title | Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation |
| title_full | Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation |
| title_fullStr | Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation |
| title_full_unstemmed | Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation |
| title_short | Bringing 2D Eclipse Mapping out of the Shadows with Leave-one-out Cross Validation |
| title_sort | bringing 2d eclipse mapping out of the shadows with leave one out cross validation |
| topic | Exoplanet astronomy Exoplanet atmospheres Exoplanet atmospheric structure Exoplanets Extrasolar gaseous planets Hot Jupiters |
| url | https://doi.org/10.3847/1538-3881/ad0366 |
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