Near to long-term forecasts in x-ray and gamma-ray bands: Are we entering the era of dark matter astronomy?

We assess galactic dark matter (DM) sensitivities to photons from annihilation and decay using the spatial and kinematic information determined by state-of-the-art simulations in the Latte suite of feedback in realistic environments (FIRE-2). For kinematic information, we study the energy shift pattern of DM narrow emission lines predicted in FIRE-2 and discuss its potential as a DM-signal diagnosis, showing for the first time the power of symmetric observations around l = 0° . We find that the exposures needed to resolve the line separation of DM to gas by XRISM at 5 σ to be large, ≳4 Ms , while exposures are smaller for Athena (≲ 50 ks) and Lynx (≲ 100 ks). We find that large field-of-view exposures remain the most sensitive methods for the detection of DM annihilation or decay by the DM-emission signals in the field of view dominating the velocity information. The ∼4 sr view of the Galactic Center region by the wide field monitor (WFM) aboard the eXTP mission will be highly sensitive to DM signals, with a prospect of ∼105 to 106 events from the 3.5 keV line in a 100 ks exposure, with the range dependent on the photon acceptance in WFM's field of view. We also investigate detailed full-sky emission maps for both DM annihilation and decay signals-evaluating the signal-to-noise for a DM detection with realistic x-ray and gamma-ray backgrounds-as a guideline for what could be a forthcoming era of DM astronomy.