First Result for Dark Matter Search by WINERED

TL;DR

This paper reports the first results from using the WINERED spectrograph to search for dark matter decay signals in dwarf galaxies, setting stringent limits on dark matter particles around 2 eV.

Contribution

It demonstrates the application of infrared spectrographs like WINERED for indirect dark matter detection, providing new constraints in the eV mass range.

Findings

No detectable line photons were observed, leading to stringent decay limits.

Established the most restrictive constraints to date on dark matter decay in the 1.8-2.7 eV range.

Data can also constrain other photon spectra from dwarf spheroidal galaxies.

Abstract

The identity of dark matter has been a mystery in astronomy, cosmology, and particle theory for about a century. Bessho, Ikeda, and Yin (2022), three of the current authors, proposed using the state-of-the-art infrared spectrographs, including WINERED at $6.5$m Magellan Clay telescope and NIRSpec at James Webb Space Telescope, as efficient detectors for the indirect detection of dark matter with the mass around eV by measuring the line photons from the dark matter two body decays. Applying this concept, we have performed spectrographic observations of dwarf spheroidal galaxies (dSphs) Leo V and Tucana II using WINERED by utilizing an object-sky-object nodding observation technique for background subtraction. We present the first result from this dark matter search. Employing zero consistent flux data after the sky subtraction, we have established one of the most stringent limits to date on dark matter decaying into line photons in the mass range of $1.8-2.7\,$eV. Our data can also be applied to constrain other spectra of photons from the dSphs.