We study the inverse Compton scattering of solar photons by Galactic cosmic-ray electrons. We show that the g-ray emission from this process is substantial, with the maximum flux in the direction of ...the Sun; the angular distribution of the emission is broad. This previously neglected foreground should be taken into account in studies of the diffuse Galactic and extragalactic g-ray emission. Furthermore, observations by GLAST can be used to monitor the heliosphere and determine the electron spectrum as a function of position from distances as large as Saturn's orbit to close proximity of the Sun, thus enabling unique studies of solar modulation. This paves the way for the determination of other Galactic cosmic-ray species, primarily protons, near the solar surface, which will lead to accurate predictions of g-rays from p-p interactions in the solar atmosphere. These albedo g-rays will be observable by GLAST, allowing the study of deep atmospheric layers, magnetic field(s), and cosmic-ray cascade development. The latter is necessary to calculate the neutrino flux from p-p interactions at higher energies (>1 TeV). Although this flux is small, it is a "guaranteed flux" in contrast to other astrophysical sources of neutrinos and may be detectable by km super(3) neutrino telescopes of the near future, such as IceCube. Since the solar core is opaque for very high energy neutrinos, directly studying the mass distribution of the solar core may thus be possible.
Abstract
The Fermi Bubbles (FBs) are a pair of large-scale ellipsoidal structures extending above and below the Galactic plane almost symmetrically aligned with the Galactic center. After more than ...10 yr since their discovery, their nature and origin remain unclear. Unveiling the primary emission mechanisms, whether hadronic or leptonic, is considered to be the main tool to shed light on the topic. We explore the potential key role of MeV observations of the FB, and we provide a recipe to determine the sensitivity of Compton and Compton-pair telescopes to the extended emission of the FB. We illustrate the capabilities of the Imaging Compton Telescope COMPTEL, the newly selected NASA MeV mission Compton Spectrometer and Imager, as well as the expectations for a potential future Compton-pair telescope such as the All-sky Medium Energy Gamma-ray Observatory eXplorer.
We calculate the -ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids (MBAs), Jovian and Neptunian Trojan asteroids, and Kuiper Belt objects (KBOs) ...using the Moon as a template. We show that the -ray albedo for the Main Belt, Trojans, and Kuiper Belt strongly depends on the small-body size distribution of each system. Based on an analysis of the Energetic Gamma-Ray Experiment Telescope (EGRET) data we infer that the diffuse emission from the MBAs, Trojans, and KBOs has an integrated flux of less than image cm super(-2) s super(-1) (100-500 MeV), which corresponds to image12 times the lunar albedo, and may be detectable by the forthcoming Gamma-Ray Large Area Space Telescope (GLAST). If detected by GLAST, it can provide unique direct information about the number of small bodies in each system that is difficult to assess by any other method. In addition, the KBO albedo flux can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of MBAs, Trojans, and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the asteroid -ray albedo has to be taken into account when analyzing weak -ray sources close to the ecliptic, especially near the Galactic center, and signals at high Galactic latitudes, such as the extragalactic -ray emission. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center.
The LSST DESC DC2 Simulated Sky Survey Abolfathi, Bela; Alonso, David; Armstrong, Robert ...
The Astrophysical journal. Supplement series,
03/2021, Letnik:
253, Številka:
1
Journal Article
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Abstract
We describe the simulated sky survey underlying the second data challenge (DC2) carried out in preparation for analysis of the Vera C. Rubin Observatory Legacy Survey of Space and Time ...(LSST) by the LSST Dark Energy Science Collaboration (LSST DESC). Significant connections across multiple science domains will be a hallmark of LSST; the DC2 program represents a unique modeling effort that stresses this interconnectivity in a way that has not been attempted before. This effort encompasses a full end-to-end approach: starting from a large
N
-body simulation, through setting up LSST-like observations including realistic cadences, through image simulations, and finally processing with Rubin’s LSST Science Pipelines. This last step ensures that we generate data products resembling those to be delivered by the Rubin Observatory as closely as is currently possible. The simulated DC2 sky survey covers six optical bands in a wide-fast-deep area of approximately 300 deg
2
, as well as a deep drilling field of approximately 1 deg
2
. We simulate 5 yr of the planned 10 yr survey. The DC2 sky survey has multiple purposes. First, the LSST DESC working groups can use the data set to develop a range of DESC analysis pipelines to prepare for the advent of actual data. Second, it serves as a realistic test bed for the image processing software under development for LSST by the Rubin Observatory. In particular, simulated data provide a controlled way to investigate certain image-level systematic effects. Finally, the DC2 sky survey enables the exploration of new scientific ideas in both static and time domain cosmology.
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