Characterizing Dark Matter from X-ray Observations of Elliptical Galaxies

An unknown spectral line at E ∼3.5 keV has been recently observed by using X-ray observations of dark matter dense regions in various astrophysical objects. This spectral feature is interpreted as an emission from decaying dark matter and become one of the hot topics in the field. In order to study a potentially similar scenario, we have selected very long (∼2 Ms) Chandra stacked data of nearby dark-matter reservoirs, elliptical galaxies. Our preliminary analysis shows no clear evidence of such emission from local elliptical galaxies. Based on our results, we discuss the constraints and also do not totally exclude the possible 3.5 keV line emission in those sources.