Weighing Galaxies Inside-Out: Small-Scale Lensing and the Stellar Mass Problem
Abstract
Small-scale galaxy-galaxy weak lensing provides an independent way to probe the stellar initial mass function by constraining the matter distribution within galaxies. We forecast the potential of upcoming \textit{Euclid} observations using realistic mock catalogues designed for a DESI-like Bright Galaxy Survey, which is expected to cover approximately 9000 deg2 of the \textit{Euclid} wide survey area. We assess the impact of foreground lens light, which introduces significant scale-dependent biases in source detection, photometry, and shape measurements. Subtracting the lens light with \textsc{Galfit} reduces these biases by nearly an order of magnitude at scales down to four times the half-light radius. We model the predicted lensing signal around central galaxies with stellar masses between 9.5 ≤ log(M*/h−2M⊙) ≤ 11.5 over projected separations of $10$ to 100 h−1kpc. The resulting signal-to-noise ratios reach ∼ 150 for intermediate-mass galaxies. Assuming an NFW profile for the dark matter contribution, we constrain the stellar mismatch parameter α to a precision of approximately $8.5$ percent for the full sample and $8.6$ percent for massive galaxies. These results highlight the potential of small-scale galaxy--galaxy weak lensing as a robust probe of the IMF and the connection between stellar and dark matter in galaxies using upcoming \textit{Euclid} data.
Related
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BibTeX
@misc{rana2026weighing,
title = {{Weighing Galaxies Inside-Out: Small-Scale Lensing and the Stellar Mass Problem}},
author = {Divya Rana and Henk Hoekstra and Konrad Kuijken and Alessandro Sonnenfeld and Maryam Tajalli},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01541},
eprint = {2610.01541},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01541},
}
RIS
TY - UNPB
TI - Weighing Galaxies Inside-Out: Small-Scale Lensing and the Stellar Mass Problem
AU - Divya Rana
AU - Henk Hoekstra
AU - Konrad Kuijken
AU - Alessandro Sonnenfeld
AU - Maryam Tajalli
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.01541
UR - https://arxiv.org/abs/2610.01541
AB - Small-scale galaxy-galaxy weak lensing provides an independent way to probe the stellar initial mass function by constraining the matter distribution within galaxies. We forecast the potential of upcoming \textit{Euclid} observations using realistic mock catalogues designed for a DESI-like Bright Galaxy Survey, which is expected to cover approximately 9000 deg^2 of the \textit{Euclid} wide survey area. We assess the impact of foreground lens light, which introduces significant scale-dependent biases in source detection, photometry, and shape measurements. Subtracting the lens light with \textsc{Galfit} reduces these biases by nearly an order of magnitude at scales down to four times the half-light radius. We model the predicted lensing signal around central galaxies with stellar masses between 9.5 ≤ log(M_*/h^−2M_⊙) ≤ 11.5 over projected separations of $10$ to 100 h^−1kpc. The resulting signal-to-noise ratios reach ∼ 150 for intermediate-mass galaxies. Assuming an NFW profile for the dark matter contribution, we constrain the stellar mismatch parameter α to a precision of approximately $8.5$ percent for the full sample and $8.6$ percent for massive galaxies. These results highlight the potential of small-scale galaxy--galaxy weak lensing as a robust probe of the IMF and the connection between stellar and dark matter in galaxies using upcoming \textit{Euclid} data.
ER -