Detecting and characterizing pulsar haloes with the Cherenkov Telescope Array

The recently identified source class of pulsar haloes may be numerous and bright enough in the TeV range to constitute a large fraction of the sources that will be observed with the Cherenkov Telescope Array (CTA). In this work, we quantify the prospects for detecting and characterizing pulsar haloes in observations of the projected Galactic Plane Survey (GPS), using a simple phenomenological diffusion model for individual pulsar haloes and their population in the Milky Way. Our ability to uncover pulsar haloes and constrain their main physical parameters in the CTA GPS is assessed in the framework of a full spatial-spectral likelihood analysis of simulated survey observations, using the most recent estimates for the instrument response function and prototypes for the science tools. For a model setup representative of the halo around Geminga, we find that about three hundred objects could give rise to detectable emission in the GPS survey. Yet, only a third of them could be identified through their energy-dependent morphology, and only one-tenth of them would allow the derivation of strong constraints on key physical parameters like the magnitude or extent of suppressed diffusion around the pulsar. We also provide a list of known pulsars that could be hosting a detectable (Geminga-like) halo in the GPS and assess the robustness of our findings against several systematic uncertainties.Comment: 20 pages, 9 figures (6 in the main text, 3 in appendices); submitted to MNRAS; comments welcome

Meritev spektra moči iz večdelčne kozmološke simulacije in uporaba pri iskanju temne snovi

The nature of dark matter particle is one of the biggest puzzles in physics today. Gamma-rays (as measured by e.g. Fermi LAT NASA satellite) are particularly powerful ways to test one of the most popular particle physics proposal, WIMPs. However, to test particle physics properties via gamma-rays, dark matter clustering along a line of sight needs to be known. In this work we use the latest knowledge from N-body simulations of DM clustering to update the predictions of gamma-ray signal from dark matter annihilation in all dark matter halos at all redshifts, the so-called cosmological dark matter signal. This works makes part of the ongoing work within the Fermi LAT collaboration, which aims to update the search for the dark matter cosmological signal, previously performed in 2015. In the introductory chapters we review the basics of the $Lambda$CDM standard model of cosmology, the physics of DM clustering and its potential gamma-ray signals. We then focus on the calculation of the DM clustering contribution to the gamma ray signal, the so called flux multiplier $zeta$. We describe the two different approaches to calculating its value - the Power Spectrum approach, and the Halo Model approach. We discuss the technical aspects of both approaches and describe the quantities used in each of them with the aim to improve the existing results by using the state-of-art value for different functions, which became available since the last work in 2015. In the context of the halo model approach we prepare the machinery to re-evaluate theoretical prediction of DM signal that depends on DM clustering and derive the first results. In the context of the power spectrum approach, we measure the power spectrum of the full-box Lomonosov simulation and compare our results with the power spectrum measured of the Millennium and Millennium II simulations.Narava delcev temne snovi je dandanes ena največjih ugank v fiziki. Detekcija sevanja gama (izmerjeno na primer s satelitom Fermi LAT NASA) predstavlja še posebej močan način za preizkušanje enega najbolj priljubljenih kandidatov fizike delcev za opis temne snovi, WIMP. Ob tem je potrebno za preizkušanje fizikalnih lastnosti omenjenih delcev s sevanjem gama poznati zgoščenost temne snovi vzdolž smeri gledanja. V tem delu uporabljamo najnovejše znanje pridobljeno s pomočjo večdelčnih kozmoloških simulacij temne snovi, da z njim posodobimo napovedi signala sevanja gama, ki prihaja iz anihilacije temne snovi v vseh halojih temne snovi pri vseh rdečih premikih, tako imenovani - kozmološki signal temne snovi. To delo je del trenutnih prizadevanj Fermi LAT kolaboracije za posodobitev iskanja kozmološkega signala temne snovi, ki je bilo nazadnje izvedeno leta 2015. V uvodnih poglavjih pregledamo osnove $Lambda$CDM standardnega modela kozmologije, teoretični opis zgoščevanja temne snovi in možnosti temne snovi za sevanje gama svetlobe. V nadaljevanju se osredotočimo na izračun prispevka temne snovi k signalu sevanja gama, tako imenovani množitelj toka $zeta$. Opišemo dva različna pristopa za izračun njegove vrednosti - pristop spektra moči in pristop halo modela. Razpravljamo o tehničnih vidikih obeh pristopov in opišemo količine, ki so uporabljene v posameznem pristopu z namenom izboljšanja obstoječih rezultatov z uporabo posodobljenih funkcij, ki so postale na voljo od zadnje objave leta 2015. V okviru pristopa s halo modelom pripravimo enačbe za ponovno oceno teoretično napovedanega signala temne snovi, ki je odvisen od zgoščevanja temne snovi in njene porazdelitve po Vesolju, ter pridobimo prve rezultate. V okviru pristopa spektra moči izmerimo spekter moči iz polne simulacije Lomonosov in primerjamo naše rezultate s spektrom moči izmerjenim z uporabo simulacij Millennium in Millennium II

Detecting and characterizing pulsar haloes with the Cherenkov Telescope Array

International audienceThe recently identified source class of pulsar haloes may be numerous and bright enough in the TeV range to constitute a large fraction of the sources that will be observed with the Cherenkov Telescope Array (CTA). In this work, we quantify the prospects for detecting and characterizing pulsar haloes in observations of the projected Galactic Plane Survey (GPS), using a simple phenomenological diffusion model for individual pulsar haloes and their population in the Milky Way. Our ability to uncover pulsar haloes and constrain their main physical parameters in the CTA GPS is assessed in the framework of a full spatial-spectral likelihood analysis of simulated survey observations, using the most recent estimates for the instrument response function and prototypes for the science tools. For a model setup representative of the halo around Geminga, we find that about three hundred objects could give rise to detectable emission in the GPS survey. Yet, only a third of them could be identified through their energy-dependent morphology, and only one-tenth of them would allow the derivation of strong constraints on key physical parameters like the magnitude or extent of suppressed diffusion around the pulsar. We also provide a list of known pulsars that could be hosting a detectable (Geminga-like) halo in the GPS and assess the robustness of our findings against several systematic uncertainties

Detecting and characterizing pulsar haloes with the Cherenkov Telescope Array

International audienceThe recently identified source class of pulsar haloes may be numerous and bright enough in the TeV range to constitute a large fraction of the sources that will be observed with the Cherenkov Telescope Array (CTA). In this work, we quantify the prospects for detecting and characterizing pulsar haloes in observations of the projected Galactic Plane Survey (GPS), using a simple phenomenological diffusion model for individual pulsar haloes and their population in the Milky Way. Our ability to uncover pulsar haloes and constrain their main physical parameters in the CTA GPS is assessed in the framework of a full spatial-spectral likelihood analysis of simulated survey observations, using the most recent estimates for the instrument response function and prototypes for the science tools. For a model setup representative of the halo around Geminga, we find that about three hundred objects could give rise to detectable emission in the GPS survey. Yet, only a third of them could be identified through their energy-dependent morphology, and only one-tenth of them would allow the derivation of strong constraints on key physical parameters like the magnitude or extent of suppressed diffusion around the pulsar. We also provide a list of known pulsars that could be hosting a detectable (Geminga-like) halo in the GPS and assess the robustness of our findings against several systematic uncertainties

Investigating the VHE Gamma-ray Sources Using Deep Neural Networks

The upcoming Cherenkov Telescope Array (CTA) will dramatically improve the point-source sensitivity compared to the current Imaging Atmospheric Cherenkov Telescopes (IACTs). One of the key science projects of CTA will be a survey of the whole Galactic plane (GPS) using both southern and northern observatories, specifically focusing on the inner galactic region. We extend a deep learning-based image segmentation software pipeline (autosource-id) developed on Fermi-LAT data to detect and classify extended sources for the simulated CTA GPS. Using updated instrument response functions for CTA (Prod5), we test this pipeline on simulated gamma-ray sources lying in the inner galactic region (specifically 0∘<l<20∘, |b|<4∘) for energies ranging from 30 GeV to 100 TeV. Dividing the source extensions ranging from 0.03∘ to 1∘ in three different classes, we find that using a simple and light convolutional neural network achieves 97% global accuracy in separating the extended sources from the point-like sources. The neural net architecture including other data pre-processing codes is available online

Detecting and characterizing pulsar haloes with the Cherenkov Telescope Array

International audienceThe recently identified source class of pulsar haloes may be numerous and bright enough in the TeV range to constitute a large fraction of the sources that will be observed with the Cherenkov Telescope Array (CTA). In this work, we quantify the prospects for detecting and characterizing pulsar haloes in observations of the projected Galactic Plane Survey (GPS), using a simple phenomenological diffusion model for individual pulsar haloes and their population in the Milky Way. Our ability to uncover pulsar haloes and constrain their main physical parameters in the CTA GPS is assessed in the framework of a full spatial-spectral likelihood analysis of simulated survey observations, using the most recent estimates for the instrument response function and prototypes for the science tools. For a model setup representative of the halo around Geminga, we find that about three hundred objects could give rise to detectable emission in the GPS survey. Yet, only a third of them could be identified through their energy-dependent morphology, and only one-tenth of them would allow the derivation of strong constraints on key physical parameters like the magnitude or extent of suppressed diffusion around the pulsar. We also provide a list of known pulsars that could be hosting a detectable (Geminga-like) halo in the GPS and assess the robustness of our findings against several systematic uncertainties

Sensitivity to keV-MeV dark matter from cosmic-ray scattering with current and the upcoming ground-based arrays CTA and SWGO

A wealth of astrophysical and cosmological observational evidence shows that the matter content of the universe is made of about 85% of non-baryonic dark matter. Huge experimental efforts have been deployed to look for the direct detection of dark matter via their scattering on target nucleons, their production in colliders, and their indirect detection via their annihilation products. Inelastic scattering of high-energy cosmic rays off dark matter particles populating the Milky Way halo would produce secondary gamma rays in the final state from the decay of the neutral pions produced in such interactions, providing a new avenue to probe dark matter properties. We compute here the sensitivity for H.E.S.S.-like observatory, a current-generation ground-based Cherenkov telescopes, to the expected gamma-ray flux from collisions of Galactic cosmic rays and dark matter in the center of the Milky Way. We also derive sensitivity prospects for the upcoming Cherenkov Telescope Array (CTA) and Southern Wide-field Gamma-ray Observatory (SWGO). The expected sensitivity allows us to probe a poorly-constrained range of dark matter masses so far, ranging from keV to sub-GeV, and provide complementary constraints on the dark matter-proton scattering cross section traditionally probed by deep underground direct dark matter experiments

Expected exclusion limits to TeV dark matter from the Perseus Cluster with the Cherenkov Telescope Array

Clusters of galaxies are the largest gravitationally-bound structures in the Universe. They are composed of galaxies and gas (approximately 15% of the total mass) mostly dark matter (DM, accounts up to 85% of the total mass). If the DM is composed of Weakly Interacting Massive Particles (WIMPs), galaxy clusters represent one of the best targets to search for gamma-ray signals induced by the decay of WIMPs, with masses around the TeV scale. Due to its sensitivity and energy range of operation (from 20 GeV to 300 TeV), the Cherenkov Telescope Array (CTA) Observatory has a unique opportunity to test WIMPs with masses close to the unitarity limit. This will complement the searches for DM from other gamma-ray observatories as well as direct and collider experiments. The CTA Observatory is planning to search for gamma-ray emission, either its origin may be cosmic-ray (CR) or DM related, in the Perseus galaxy cluster during the first years of operation. In this poster, we will present the software created to perform the analysis using the ctools software and the corresponding results

Sensitivity of the Cherenkov Telescope Array to the gamma-ray emission from neutrino sources detected by IceCube

Gamma-ray observations of the astrophysical neutrino sources are fundamentally important for understanding the underlying neutrino production mechanism. We investigate the Cherenkov Telescope Array (CTA) ability to detect the very-high-energy (VHE) gamma-ray counterparts to the neutrino-emitting Active Galaxies. The CTA performance under different configurations and array layouts is computed based on the neutrino and gamma-ray simulations of steady and transient types of sources, assuming that the neutrino events are detected with the IceCube neutrino telescope. The CTA detection probability is calculated for both CTA sites taking into account the visibility constraints. We find that, under optimal observing conditions, CTA could observe the VHE gamma-ray emission from at least 3 neutrino events per year