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    First detection of weak lensing around spectroscopically confirmed low-mass galaxies

    Chun-Hao To1,2,3,*, Chihway Chang1,2,3, Dhayaa Anbajagane1,2,3, Risa H. Wechsler4,5,6, Alex Drlica-Wagner1,2,3,7, M. Adamów8,9, A. Alarcon10, M. R. Becker11, J. A. Carballo-Bello12 et al. (DELVE Collaboration)

    J. A. Carballo-Bello12, R. Cawthon13, N. Chicoine1,14, C. Doux15, J. H. Esteves16, P. S. Ferguson17,18, M. Gatti2, D. Gruen19, R. A. Gruendl20,8,9, K. Herron21, David J. James22,23, C. E. Martínez-Vázquez24, S. Mau4,25, J. McCullough26, G. E. Medina27,28, B. Mutlu-Pakdil21, A. Navarro-Alsina29, N. E. D. Noël30, A. B. Pace31, M. Raveri32, A. H. Riley33,34, D. J. Sand35, L. F. Secco2, T. Shin36, G. S. Stringfellow37, D. Suson38, C. Y. Tan39,2, R. Teixeira1,40, A. Zenteno41, and Z. Zhang1,4,6 (DELVE Collaboration)

    • 1Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637, USA
    • 2Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637, USA
    • 3NSF-Simons AI Institute for the Sky (SkAI),172 E. Chestnut Street, Chicago, Illinois 60611, USA
    • 4Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, USA
    • 5Kavli Institute for Particle Astrophysics and Cosmology, P. O. Box 2450, Stanford University, Stanford, California 94305, USA
    • 6SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
    • 7Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510, USA
    • 8Center for Astrophysical Surveys, National Center for Supercomputing Applications, 1205 West Clark Street, Urbana, Illinois 61801, USA
    • 9Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green Street, Urbana, Illinois 61801, USA
    • 10Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, s/n, 08193 Barcelona, Spain
    • 11Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, USA
    • 12Instituto de Alta Investigacion, Universidad de Tarapaca, Casilla 7D, Arica, Chile
    • 13Oxford College of Emory University, Oxford, Georgia 30054, USA
    • 14Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, Pennsylvania 15260
    • 15Université Grenoble Alpes, CNRS, LPSC-IN2P3, 38000 Grenoble, France
    • 16Department of Physics, Harvard University, 17 Oxford Street, Cambridge, Massachusetts, USA
    • 17DiRAC Institute, Department of Astronomy, University of Washington, 3910 15th Avenue NE, Seattle, Washington 98195, USA
    • 18DIRAC Institute, Department of Astronomy, University of Washington, 3910 15th Avenue NE, Seattle, Washington 98195, USA
    • 19University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstrasse 1, 81679 Munich, Germany; Excellence Cluster ORIGINS, Boltzmannstrasse 2, 85748 Garching, Germany
    • 20Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green Street, Urbana, Illinois 61801, USA
    • 21Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA
    • 22ASTRAVEO LLC, PO Box 1668, Gloucester, Massachusetts 01931, USA
    • 23Applied Materials Inc., 35 Dory Road, Gloucester, Massachusetts 01930, USA
    • 24NSF NOIRLab, 670 N. A’ohoku Place, Hilo, Hawai’i, 96720, USA
    • 25Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 2450, Stanford University, Stanford, California 94305, USA
    • 26Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, New Jersey 08544, USA
    • 27David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, Ontario M5S 3H4, Canada
    • 28Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada
    • 29Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-859, Campinas, SP, Brazil
    • 30Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom
    • 31Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, Virginia 22904, USA
    • 32Department of Physics and INFN, University of Genova, Via Dodecaneso 33, 16146, Italy
    • 33Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE, United Kingdom
    • 34Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, SE-221 00 Lund, Sweden
    • 35Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721-0065, USA
    • 36Department of Physics and Astronomy, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
    • 37University of Colorado Boulder, Boulder, Colorado 80309, USA
    • 38Department of Chemistry and Physics, Purdue University Northwest 2200, 169th Avenue, Hammond, Indiana 46323
    • 39Department of Physics, University of Chicago, Chicago, Illinois 60637, USA
    • 40Department of Physics, Duke University Durham, North Carolina 27708, USA
    • 41Cerro Tololo Inter-American Observatory/NSF NOIRLab, Casilla 603, La Serena, Chile

    • *Contact author: chto@uchicago.edu

    Phys. Rev. D 114, 023040 – Published 22 July, 2026

    DOI: https://doi.org/10.1103/sqkx-dhd4

    Abstract

    We present the first detection of weak gravitational lensing around spectroscopically confirmed dwarf galaxies, using the large overlap between DESI DR1 spectroscopic data and DECADE/DES weak lensing catalogs. A clean dwarf galaxy sample with well-defined redshift and stellar mass cuts enables excess surface mass density measurements in two stellar mass bins (logM*=[8.2,9.2]M⊙ and logM*=[9.2,10.2]M⊙), with signal-to-noise ratios of 5.6 and 12.4 respectively. This signal-to-noise drops to 4.5 and 9.2 respectively for measurements without applying individual inverse probability (IIP) weights, which mitigates fiber incompleteness from DESI’s targeting. The measurements are robust against variations in stellar mass estimates, photometric shredding, and lensing calibration systematics. Using a simulation-based modeling framework with stellar mass function priors, we constrain the stellar mass-halo mass relation and find a satellite fraction of ≃0.3, which is higher than previous photometric studies and somewhat lower than the value predicted by the same Λ cold dark matter (ΛCDM)-based forward model given the inferred stellar mass-halo mass relation. We find that IIP weights have a significant impact on lensing measurements and can change the inferred fsat by a factor of two, highlighting the need for accurate fiber incompleteness corrections for dwarf galaxy samples. Our results open a new observational window into the galaxy-halo connection at low masses, showing that future massively multiplexed spectroscopic observations and weak lensing data will enable stringent tests of galaxy formation models and ΛCDM predictions.

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