SEARCHING FOR keV STERILE NEUTRINO DARK MATTER WITH X-RAY MICROCALORIMETER SOUNDING ROCKETS

Abstract

High-resolution X-ray spectrometers onboard suborbital sounding rockets can search for dark matter candidates that produce X-ray lines, such as decaying keV-scale sterile neutrinos. Even with exposure times and effective areas far smaller than XMM-Newton and Chandra observations, high-resolution, wide field of view observations with sounding rockets have competitive sensitivity to decaying sterile neutrinos. We analyze a subset of the 2011 observation by the X-ray Quantum Calorimeter instrument centered on Galactic coordinates =  = - l b 165 , 5 with an effective exposure of 106 s, obtaining a limit on the sterile neutrino mixing angle of q <´-sin 2 7.2 10 2 1 0at 95% CL for a 7 keV neutrino. Better sensitivity at the level of q~´-sin 2 2.1 10 2 1 1 at 95% CL for a 7 keV neutrino is achievable with future 300-s observations of the galactic center by the Micro-X instrument, providing a definitive test of the sterile neutrino interpretation of the reported 3.56 keV excess from galaxy clusters.

Constraints on the presence of a 3.5 keV dark matter emission line fromChandraobservations of the Galactic centre

“…At the moment, less than 100 ks of Chandra with an offset of ≈1deg spectra exist. Instead future improvements will come from increased spectral resolution of, for example, Astro-H and Micro-X microcalorimeters (Mitsuda et al 2014;Figueroa-Feliciano et al 2015), and mapping of the spatial morphology of the emission with existing instruments (XMM-Newton, Chandra, Suzaku).…”

Diluted equilibrium sterile neutrino dark matter

“…While the existence of this line in terms of statistical significance, as well as its interpretation as having a dark matter origin are still up for debate [83][84][85][86][87][88][89][90][91][92][93][94], the possibility remains intriguing, and various sterile neutrino dark matter models can have their parameters tailored to fit this particular scenario [29,30,[32][33][34][35][36]38]. Future Xray telescopes such as ASTRO-H and ATHENA, as well as microcalorimeter sounding rocket experiments such as Micro-X [95,96], with their high energy resolution, could help settle the verdict on this case one way or the other [97].…”

Micro-X Sounding Rocket: Transitioning from First Flight to a Dark Matter Configuration

“…A 33 • half-angle FOV instrument observes a dark matter flux that is 2700 times that of XMM-Newton [3], making up for the short sounding rocket exposure. Microcalorimeters provide the high resolution required to separate the monoenergetic signal from the background continuum and nearby atomic lines, as demonstrated by the XQC and Hitomi observations used to search for this line [3,9]. Modifying Micro-X for a large FOV makes it an excellent instrument for this observation.…”

“…All projections use the NFW profile from [10] to normalize to the expected flux to the Micro-X fields. The first is derived from the reported 3.53 keV flux from the Galactic Center with XMM-Newton [11] and used in previous Micro-X sensitivity projections [3], updated using a newer NFW profile [10]. The second is derived by matching the bestfit value of the 3.505 keV flux from Chandra observations of the COSMOS/CDFS fields ( = 223.6 • , b = -54.4 • ) [12].…”

“…Previous claims from [11], [12], and [13] are shown in red, maroon, and blue dots, respectively. Previous exclusion limits from X-ray observations (shaded) and XQC (black line [3]) are shown.…”