AMEGO: Exploring the Extreme Multimessenger Universe

Abstract

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a Probe-class mission concept that will provide essential contributions to multimessenger astrophysics in the next decade. AMEGO operates both as a Compton and pair telescope to achieve unprecedented sensitivity between 200 keV and >5 GeV. The instrument consists of four subsystems. A double-sided strip silicon Tracker gives a precise measure of the first Compton scatter interaction and tracks of pair-conversion products. A novel CdZnTe Low Energy Calorimeter with excellent position and energy resolution surrounds the bottom and sides of the Tracker to detect the Compton-scattered photons which enhances the polarization and narrow-line sensitivity. A thick CsI High Energy Calorimeter contains the high-energy Compton and pair events. The instrument is surrounded by a plastic anti-coincidence detector to veto the cosmic-ray background. We have performed detailed simulations to predict the telescope performance and are currently building a prototype instrument. The AMEGO prototype, known as ComPair, will be tested at the High Intensity Gamma-Ray Source in 2021, followed by a balloon flight in Fall of 2022. In this presentation we will give an overview of the science motivation, a description of the observatory, and an update of the prototype instrument development.

ALP induced polarization effects on photons from galaxy clusters

“…In particular, since polarization measurements are more complex than those concerning the spectrum, we expect an energy resolution worsened by a factor 4 − 5. By considering the energy resolution of spectrum-measuring observatories in the X-ray band [97] and HE range [48][49][50], we expect that the energy resolution for polarization studies could likely be of 15 − 20 bins per decade in the X-ray band and of 8 − 10 bins per decade in the HE range.…”

“…The binned data in Fig. 3 show that the stability of the Π L value with respect to the energy in the HE range makes its detectability easier than in the X-ray band with observatories such as COSI [47], e-ASTROGAM [48,49] and Amego [50]. From Fig.…”

“…In addition, photon-ALP interaction has recently been discovered as a way to measure emitted photon polarization [44]. These studies are crucial in order to find new hints at ALP existence and they are timely, since new observatories measuring photon polarization have been launched or proposed in the X-ray band like IXPE [45] and Polstar [46] and in the high-energy (HE) band such as COSI [47], e-ASTROGAM [48,49] and AMEGO [50].…”

“…Moreover, we study the propagation of the photon-ALP beam in all the crossed regions (galaxy cluster, extragalactic space, Milky Way) by using stateof-the-art knowledge. In the considered scenarios ALPs manifestly induce photon polarization effects which are expected to be detectable by current and planned satellite missions [45][46][47][48][49][50]. We believe that the HE range is the most promising window to search for ALP-induced polarization effects.…”

High-energy gamma- and cosmic-ray observations with future space-based GAMMA-400 gamma-ray telescope

“…It is necessary to note that at present some projects of the gamma-ray telescopes are developed for further investigations of the gamma-ray emission after Fermi-LAT: e-ASTROGAM (DeAngelis et al, 2018) and AMEGO (Kierans et al, 2021) in the medium energy and HERD (Cattaneo et al, 2019) and AMS-100 (Schael et al, 2019) in high-energy range. Performance of these telescopes in comparison with GAMMA-400 and Fermi-LAT is presented in Table 2.…”