Papers › The mass profiles of dwarf galaxies from Dark Energy Survey lensing

The mass profiles of dwarf galaxies from Dark Energy Survey lensing

24 Nov 2023arXiv:2311.14659links table onlyarchive 2025-07-28

Joseph Thornton, Alexandra Amon, Risa H. Wechsler, Susmita Adhikari, Yao-Yuan Mao, Justin Myles, Marla Geha, Nitya Kallivayalil, Erik Tollerud, Benjamin Weiner

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We present a novel approach to extracting dwarf galaxies from photometric data to measure their average halo mass profile with weak lensing. We characterise their stellar mass and redshift distributions with a spectroscopic calibration sample. Using the ∼5000deg² multi-band photometry from Dark Energy Survey and redshifts from the Satellites Around Galactic Analogs (SAGA) survey with an unsupervised machine learning method, we select a low-mass galaxy sample spanning redshifts z<0.3 and divide it into three mass bins. From low to high median mass, the bins contain [146 420, 330 146, 275 028] galaxies and have median stellar masses of log₁₀(M_*/M_⊙)= [8.52^(+0.57)_(-0.76), 9.02^(+0.50)_(-0.64), 9.49^(+0.50)_(-0.58)]. We measure the stacked excess surface mass density profiles, ΔΣ(R), of these galaxies using galaxy--galaxy lensing with a signal-to-noise of [14, 23, 28]. Through a simulation-based forward-modelling approach, we fit the measurements to constrain the stellar-to-halo mass relation and find the median halo mass of these samples to be log₁₀(Mₕₐₗₒ/M_⊙) = [10.67+0.2 -0.4, 11.01+0.14 -0.27,11.40+0.08 -0.15]. The CDM profiles are consistent with NFW profiles over scales ≲0.15 h⁻¹Mpc. We find that ∼20 per cent of the dwarf galaxy sample are satellites. This is the first measurement of the halo profiles and masses of such a comprehensive, low-mass galaxy sample. The techniques presented here pave the way for extracting and analysing even lower-mass dwarf galaxies and for more finely splitting galaxies by their properties with future photometric and spectroscopic survey data.

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