Searching for strong lensing by late-type galaxies in UNIONS
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arXiv
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| Autori principali: | , , , , , , , , , , |
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| Natura: | Preprint |
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2025
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| author | Barroso, J. A. Acevedo Clément, B. Courbin, F. Gavazzi, R. Lemon, C. Rojas, K. Scott, D. Gwyn, S. Hammer, F. Hudson, M. J. Magnier, E. A. |
| author_facet | Barroso, J. A. Acevedo Clément, B. Courbin, F. Gavazzi, R. Lemon, C. Rojas, K. Scott, D. Gwyn, S. Hammer, F. Hudson, M. J. Magnier, E. A. |
| contents | Recent wide-field galaxy surveys have led to an explosion in the number of galaxy-scale strong gravitational lens candidates. However, the vast majority of them feature massive luminous red galaxies as the main deflectors, with late-type galaxies being vastly under-represented. This work presents a dedicated search for lensing by edge-on late-type galaxies in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS). The search covers $3600$ deg$^2$ of $r$-band observations taken from the Canada-France-Hawaii Telescope. We considered all sources with magnitudes in the range $17 < r < 20.5$, without any colour pre-selection, yielding a parent sample of seven million sources. We characterised our parent sample via the visual inspection of $120\,000$ sources selected at random. From it, we estimate, with a 68% confidence interval, that 1 in every $30\,000$ sources is an edge-on lens candidate, with at least eight high-quality candidates in the parent sample. Our search relied on a convolutional neural network (CNN) to select a reduced sample of candidates, which we followed with a visual inspection to curate the final sample. The CNN was trained from scratch using simulated $r$-band observations of edge-on lenses, and real observations of non-lenses. We found 61 good edge-on lens candidates using the CNN. Moreover, combining the CNN candidates with those found serendipitously and those identified while characterising the parent sample, we discovered 4 grade A, 20 grade B, and 58 grade C edge-on lens candidates, effectively doubling the known sample of these systems. We also discovered 16 grade A, 16 grade B, and 18 grade C lens candidates of other types. Finally, based on the characterisation of the parent sample, we estimate that our search found around 60% of the bright grade A and B edge-on lens candidates within the parent sample. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_10610 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Searching for strong lensing by late-type galaxies in UNIONS Barroso, J. A. Acevedo Clément, B. Courbin, F. Gavazzi, R. Lemon, C. Rojas, K. Scott, D. Gwyn, S. Hammer, F. Hudson, M. J. Magnier, E. A. Astrophysics of Galaxies Recent wide-field galaxy surveys have led to an explosion in the number of galaxy-scale strong gravitational lens candidates. However, the vast majority of them feature massive luminous red galaxies as the main deflectors, with late-type galaxies being vastly under-represented. This work presents a dedicated search for lensing by edge-on late-type galaxies in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS). The search covers $3600$ deg$^2$ of $r$-band observations taken from the Canada-France-Hawaii Telescope. We considered all sources with magnitudes in the range $17 < r < 20.5$, without any colour pre-selection, yielding a parent sample of seven million sources. We characterised our parent sample via the visual inspection of $120\,000$ sources selected at random. From it, we estimate, with a 68% confidence interval, that 1 in every $30\,000$ sources is an edge-on lens candidate, with at least eight high-quality candidates in the parent sample. Our search relied on a convolutional neural network (CNN) to select a reduced sample of candidates, which we followed with a visual inspection to curate the final sample. The CNN was trained from scratch using simulated $r$-band observations of edge-on lenses, and real observations of non-lenses. We found 61 good edge-on lens candidates using the CNN. Moreover, combining the CNN candidates with those found serendipitously and those identified while characterising the parent sample, we discovered 4 grade A, 20 grade B, and 58 grade C edge-on lens candidates, effectively doubling the known sample of these systems. We also discovered 16 grade A, 16 grade B, and 18 grade C lens candidates of other types. Finally, based on the characterisation of the parent sample, we estimate that our search found around 60% of the bright grade A and B edge-on lens candidates within the parent sample. |
| title | Searching for strong lensing by late-type galaxies in UNIONS |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.10610 |