Kavli Affiliate: Risa H. Wechsler
| First 5 Authors: Helena Treiber, Helena Treiber, , ,
| Summary:
We present the most precise and lowest-mass weak lensing measurements of
dwarf galaxies to date, enabled by spectroscopic lenses from the Dark Energy
Spectroscopic Instrument (DESI) and photometric lenses from the Dark Energy
Survey (DES) calibrated with DESI redshifts. Using DESI spectroscopy from the
first data release, we construct clean samples of galaxies with median stellar
masses $log_10(M_*/M_odot)=8.3-10.1$ and measure their weak lensing
signals with sources from DES, KiDS, and SDSS, achieving detections with $S/N$
up to 14 for dwarf galaxies ($log_10(M_*/M_odot)<$9.25) — opening up a
new regime for lensing measurements of low-mass systems. Leveraging DES
photometry calibrated with DESI, we extend to a photometric dwarf sample of
over 700,000 galaxies, enabling robust lensing detections of dwarf galaxies
with combined $S/N=38$ and a significant measurement down to
$log_10(M_*/M_odot)=8.0$. We show that the one-halo regime (scales
$lesssim 0.15h^-1rm Mpc$) is insensitive to various systematic and sample
selection effects, providing robust halo mass estimates, while the signal in
the two-halo regime depends on galaxy color and environment. These results
demonstrate that DESI already enables precise dwarf lensing measurements, and
that calibrated photometric samples extend this capability. Together, they pave
the way for novel constraints on dwarf galaxy formation and dark matter physics
with upcoming surveys like the Vera C. Rubin Observatory’s LSST.
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