Unions with UNIONS: Using galaxy-galaxy lensing to probe galaxy mergers
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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Cheng, Isaac Elvin-Poole, Jack Hudson, Michael J. Barré, Ruxin Ellison, Sara L. Bickley, Robert W. de Boer, Thomas J. L. Fabbro, Sébastien Ferreira, Leonardo Guerrini, Sacha Hildebrandt, Hendrik Kilbinger, Martin McConnachie, Alan W. van Waerbeke, Ludovic Wittje, Anna |
| author_facet | Cheng, Isaac Elvin-Poole, Jack Hudson, Michael J. Barré, Ruxin Ellison, Sara L. Bickley, Robert W. de Boer, Thomas J. L. Fabbro, Sébastien Ferreira, Leonardo Guerrini, Sacha Hildebrandt, Hendrik Kilbinger, Martin McConnachie, Alan W. van Waerbeke, Ludovic Wittje, Anna |
| contents | We use galaxy-galaxy lensing to investigate how the dark matter (DM) haloes and stellar content of galaxies with $0.012 \leq z \leq 0.32$ and $10 \leq \log_{10}(M_\star/\mathrm{M}_\odot) \leq 12$ change as a result of the merger process. To this end, we construct two samples of galaxies obtained from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), comprising 1 623 post-mergers and $\sim$30 000 non-merging controls, that live in low-density environments to use as our lenses. These samples are weighted to share the same distributions of stellar mass, redshift, and geometric mean distance to a galaxy's three nearest neighbours to ensure differences in the lensing signal are due to the merger process itself. We do not detect a statistically significant difference in the excess surface density profile of post-mergers and non-merging controls with current data. Fitting haloes composed of a point-like stellar mass component and an extended DM structure described by a Navarro-Frenk-White profile to the lensing measurements yields, for both samples, halo masses of $M_\text{halo} \sim 4\times10^{12}\,\mathrm{M}_\odot$ and a moderately negative correlation between $M_\text{halo}$ and concentration $c$. This allows us to rule out, at the 95% confidence level, merger-induced starbursts in which more than 60% of the stellar mass is formed in the burst. The application of our methods to upcoming surveys that are able to provide samples $\sim$10$\times$ larger than our current catalogue are expected to detect the weak-lensing signatures of mergers and further constrain their properties. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_00584 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Unions with UNIONS: Using galaxy-galaxy lensing to probe galaxy mergers Cheng, Isaac Elvin-Poole, Jack Hudson, Michael J. Barré, Ruxin Ellison, Sara L. Bickley, Robert W. de Boer, Thomas J. L. Fabbro, Sébastien Ferreira, Leonardo Guerrini, Sacha Hildebrandt, Hendrik Kilbinger, Martin McConnachie, Alan W. van Waerbeke, Ludovic Wittje, Anna Astrophysics of Galaxies We use galaxy-galaxy lensing to investigate how the dark matter (DM) haloes and stellar content of galaxies with $0.012 \leq z \leq 0.32$ and $10 \leq \log_{10}(M_\star/\mathrm{M}_\odot) \leq 12$ change as a result of the merger process. To this end, we construct two samples of galaxies obtained from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS), comprising 1 623 post-mergers and $\sim$30 000 non-merging controls, that live in low-density environments to use as our lenses. These samples are weighted to share the same distributions of stellar mass, redshift, and geometric mean distance to a galaxy's three nearest neighbours to ensure differences in the lensing signal are due to the merger process itself. We do not detect a statistically significant difference in the excess surface density profile of post-mergers and non-merging controls with current data. Fitting haloes composed of a point-like stellar mass component and an extended DM structure described by a Navarro-Frenk-White profile to the lensing measurements yields, for both samples, halo masses of $M_\text{halo} \sim 4\times10^{12}\,\mathrm{M}_\odot$ and a moderately negative correlation between $M_\text{halo}$ and concentration $c$. This allows us to rule out, at the 95% confidence level, merger-induced starbursts in which more than 60% of the stellar mass is formed in the burst. The application of our methods to upcoming surveys that are able to provide samples $\sim$10$\times$ larger than our current catalogue are expected to detect the weak-lensing signatures of mergers and further constrain their properties. |
| title | Unions with UNIONS: Using galaxy-galaxy lensing to probe galaxy mergers |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2502.00584 |