Questioning a 3.5 keV dark matter emission line

TL;DR

This study searches for the 3.5 keV dark matter emission line in Chandra X-ray data near the Galactic Center, setting upper limits that are consistent with previous detections under certain dark matter profile assumptions.

Contribution

It provides the first dedicated search for the 3.5 keV line in the Milky Way halo using Chandra data, challenging or supporting dark matter origin hypotheses.

Findings

No clear detection of the 3.5 keV line in the data.

Upper flux limits are consistent with previous detections under conservative models.

Results are sensitive to the assumed dark matter density profile.

Abstract

Context. Recent findings of line emission at 3.5 keV in both individual and stacked X-ray spectra of galaxy clusters have been speculated to have dark matter origin. Aims. If the origin is indeed dark matter, the emission line is expected to be detectable from the Milky Way dark matter halo. Methods. We perform a line search in public Chandra X-ray observations of the region near Sgr A*. We derive upper limits on the line emission flux for the 2.0-9.0 keV energy interval and discuss their potential physical interpretations including various scenarios of decaying and annihilating dark matter. Results. While find no clear evidence for its presence, the upper flux limits are not inconsistent with the recent detections for conservative mass profiles of the Milky Way. Conclusions. The results depends mildly on the spectral modelling and strongly on the choice of dark matter profile.