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11.
Pybkgmodel - a background modelling toolbox for the CTA
Marcel C. Strzys, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: Despite the advancement in background rejection techniques, observation of the very-high-energy gamma-ray sky by imaging atmospheric Cherenkov telescopes (IACTs) are subject to an irreducible background from gamma-like hadron- or electron-induced air showers. The determination of this residual background is crucial for accurate spectral and spatial measurements. The Cherenkov Telescope Array (CTA) will become the next generation of IACTs. To unveil its full potential, the improved reconstruction performance of CTA needs to be coupled with a reliable background estimate across the entire field of view. This may become especially important in the case of the planned surveys of large areas of the sky. In this contribution we will present pybkgmodel, an open-source python software package de-veloped for CTA. It aims at providing in a consistent way the various background modelling methods, based on the experience from current IACTs such as H.E.S.S, MAGIC, and VERITAS. It is designed as a toolbox allowing a user to easily choose the optimal reconstruction approach for various target regions or a combination of several algorithms. We will introduce the design of the package as well as demonstrate its functionality using data for the CTA Large-Sized Telescope prototype (LST-1).
Keywords: Cherenkov Telescope Array, CTA, dark matter, standard model, dwarf spheroidal galaxies
Published in RUNG: 26.09.2023; Views: 784; Downloads: 6
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12.
Dark matter searches in dwarf spheroidal galaxies with the Cherenkov Telescope Array
F. G. Saturni, Saptashwa Bhattacharyya, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, published scientific conference contribution

Abstract: Dark matter (DM) is one of the major components in the Universe. However, at present its existence is still only inferred through indirect astronomical observations. DM particles can annihilate or decay, producing final-state Standard Model pairs that subsequently annihilate into high-energy �-rays. The dwarf spheroidal galaxies (dSphs) in the Milky Way DM halo have long been considered optimal targets to search for annihilating DM signatures in GeV-to-TeV �-ray spectra due to their high DM densities (hence high astrophysical factors), as well as the expected absence of intrinsic �-ray emission of astrophysical origin. For such targets, it is important to compute the amount of DM in their halos in a consistent way to optimize the �-ray data analysis. Such estimates directly affect the observability of DM signals in dSphs, as well as the DM constraints that can be derived in case of null detection. In this contribution, we present the results on the sensitivity of the Cherenkov Telescope Array (CTA) for DM annihilation and decay searches using planned observations of the Milky Way dSphs. We select the most promising targets among all presently known dwarf satellites, providing new determinations of their expected DM signal. This study shows an improvement of approximately an order of magnitude in sensitivity compared to current searches in similar targets. We also discuss the results in terms of cuspy and cored DM models, and investigate the sensitivity obtained by the combination of observations from different dSphs. Finally, we explore the optimal strategies for CTA observations of dSphs.
Keywords: Cherenkov Telescope Array, CTA, dark matter, standard model, dwarf spheroidal galaxies
Published in RUNG: 26.09.2023; Views: 827; Downloads: 4
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13.
Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre
Christopher Eckner, Saptashwa Bhattacharyya, Barbara MARČUN, Judit Pérez Romero, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Gabrijela Zaharijas, Marko Zavrtanik, Danilo Zavrtanik, Miha Živec, 2021, published scientific conference contribution

Abstract: High-energy gamma rays are promising tools to constrain or reveal the nature of dark matter, in particular Weakly Interacting Massive Particles. Being well into its pre-construction phase, the Cherenkov Telescope Array (CTA) will soon probe the sky in the 20 GeV - 300 TeV energy range. Thanks to its improved energy and angular resolutions as well as significantly larger e˙ective area when compared to the current generation of Cherenkov telescopes, CTA is expected to probe heavier dark matter, with unprecedented sensitivity, reaching the thermal annihilation cross-section at 1 TeV. This talk will summarise the planned dark matter search strategies with CTA, focusing on the signal from the Galactic centre. As observed with the Fermi LAT at lower energies, this region is rather complex and CTA will be the first ground-based observatory sensitive to the large scale di˙use astrophysical emission from that region. We report on the collaboration e˙ort to study the impact of such extended astrophysical backgrounds on the dark matter search, based on Fermi-LAT data in order to guide our observational strategies, taking into account various sources of systematic uncertainty.
Keywords: high-energy gamma rays, Cherenkov Telescope Array, dark matter, galactic centre
Published in RUNG: 18.09.2023; Views: 629; Downloads: 8
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14.
Sensitivity of the Cherenkov Telescope Array to TeV photon emission from the Large Magellanic Cloud
A. Acharyya, R. Adam, Saptashwa Bhattacharyya, Samo Stanič, Veronika Vodeb, Serguei Vorobiov, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Miha Živec, 2023, original scientific article

Abstract: A deep survey of the Large Magellanic Cloud at ∼ 0.1−100 TeV photon energies with the Cherenkov Telescope Array is planned. We assess the detection prospects based on a model for the emission of the galaxy, comprising the four known TeV emitters, mock populations of sources, and interstellar emission on galactic scales. We also assess the detectability of 30 Doradus and SN 1987A, and the constraints that can be derived on the nature of dark matter. The survey will allow for fine spectral studies of N 157B, N 132D, LMC P3, and 30 Doradus C, and half a dozen other sources should be revealed, mainly pulsar-powered objects. The remnant from SN 1987A could be detected if it produces cosmic-ray nuclei with a flat power-law spectrum at high energies, or with a steeper index 2.3−2.4 pending a flux increase by a factor > 3−4 over ∼ 2015−2035. Large-scale interstellar emission remains mostly out of reach of the survey if its > 10 GeV spectrum has a soft photon index ∼ 2.7, but degree-scale 0.1 − 10 TeV pion-decay emission could be detected if the cosmic-ray spectrum hardens above >100 GeV. The 30 Doradus star-forming region is detectable if acceleration efficiency is on the order of 1 − 10% of the mechanical luminosity and diffusion is suppressed by two orders of magnitude within < 100 pc. Finally, the survey could probe the canonical velocity-averaged cross section for self-annihilation of weakly interacting massive particles for cuspy Navarro-Frenk-White profiles.
Keywords: very-high energy (VHE) gamma-rays, Cherenkov Telescope Array Observatory, Large Magellanic Cloud, pulsar wind nebulas, galaxiesstar-forming regions, cosmic rays, dark matter
Published in RUNG: 02.06.2023; Views: 1178; Downloads: 1
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15.
Copper bioavailability and leaching in conventional and organic viticulture under environmental stress
Erika Jež, Elisa Pellegrini, Marco Contin, 2023, original scientific article

Abstract: The continuous use of Cu-based fungicides in viticulture has caused Cu accumulation in soils, which represents a major environmental and toxicological concern. The purpose of this study was to verify whether the organic management would be more resilient to temperature and moisture stresses in comparison to conventional practices. Two organic and two conventional vineyard soils, contrasting in pH, were exposed for six months to temperature stress (29 °C), moisture stress (10% water holding capacity—WHC), and combined stresses (29 °C—10% WHC). Main soil properties, Cu speciation, bioavailability, and leaching were monitored before and after 6 months’ incubation. Results confirm that the increase of temperature caused a decrease in both total organic carbon (TOC) and dissolved organic carbon (DOC) (up to 19% and 49%, respectively), a decrease in available ammonium, and an increase in nitrate. Moisture stress tends to mitigate some of these changes. Despite that, changes of Cu bioavailability and leaching were limited and rarely significant. Moreover, no regular trends between conventional and organic management could be observed. Changes in soil pH and total N (TN) appeared as the most influencing properties to regulate Cu behavior in vineyard soils. Calcareous soils were more resistant to environmental stresses compared to acid soils, regardless of the type of management (conventional or organic).
Keywords: soil copper, climate changes, soil organic matter, organic viticulture, BCR speciation
Published in RUNG: 22.02.2023; Views: 1206; Downloads: 20
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Classification of gamma-ray targets for velocity-dependent and subhalo-boosted dark-matter annihilation
Thomas Lacroix, Gaetán Facchinetti, Judit Pérez Romero, Martin Stref, Julien Lavalle, David Maurin, Miguel Sánchez-Conde, original scientific article

Abstract: Gamma-ray observations have long been used to constrain the properties of dark matter (DM), with a strong focus on weakly interacting massive particles annihilating through velocity-independent processes. However, in the absence of clear-cut observational evidence for the simplest candidates, the interest of the community in more complex DM scenarios involving a velocity-dependent cross-section has been growing steadily over the past few years. We present the first systematic study of velocity-dependent DM annihilation (in particular p-wave annihilation and Sommerfeld enhancement) in a variety of astrophysical objects, not only including the well-studied Milky Way dwarf satellite galaxies, but nearby dwarf irregular galaxies and local galaxy clusters as well. Particular attention is given to the interplay between velocity dependence and DM halo substructure. Uncertainties related to halo mass, phase-space and substructure modelling are also discussed in this velocity-dependent context. We show that, for s-wave annihilation, extremely large subhalo boost factors are to be expected, up to 10^11 in clusters and up to 10^6–10^7 in dwarf galaxies where subhalos are usually assumed not to play an important role. Boost factors for p-wave annihilation are smaller but can still reach 10^3 in clusters. The angular extension of the DM signal is also significantly impacted, with e.g. the cluster typical emission radius increasing by a factor of order 10 in the s-wave case. We also compute the signal contrast of the objects in our sample with respect to annihilation happening in the Milky Way halo. Overall, we find that the hierarchy between the brightest considered targets depends on the specific details of the assumed particle-physics model.
Keywords: dark matter theory, dwarf galaxies, galaxy clusters, gamma-ray theory
Published in RUNG: 27.01.2023; Views: 1265; Downloads: 0
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19.
Sensitivity of CTA to gamma-ray emission from the Perseus galaxy cluster
Judit Pérez Romero, published scientific conference contribution

Abstract: In these proceedings we summarize the current status of the study of the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. Gamma-ray emission is expected in galaxy clusters both from interactions of cosmic rays (CR) with the intra-cluster medium, or as a product of annihilation or decay of dark matter (DM) particles in case they are weakly interactive massive particles (WIMPs). The observation of Perseus constitutes one of the Key Science Projects to be carried out by the CTA Consortium. In this contribution, we focus on the DM-induced component of the flux. OurDMmodelling includes the substructures we expect in the main halo which will boost the annihilation signal significantly. We adopt an ON/OFF observation strategy and simulate the expected gamma-ray signals. Finally we compute the expected CTA sensitivity using a likelihood maximization analysis including the most recent CTA instrument response functions. In absence of signal, we show that CTA will allow us to provide stringent and competitive constraints on TeV DM, especially for the case of DM decay.
Keywords: dark matter, gamma-ray astronomy, galaxy clusters, cosmic rays and astroparticles
Published in RUNG: 27.01.2023; Views: 1113; Downloads: 15
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20.
Spatial extension of dark subhalos as seen by Fermi-LAT and the implications for WIMP constraints
Javier Coronado-Blázquez, Miguel Sánchez-Conde, Judit Pérez Romero, Alejandra Aguirre-Santaella, 2022, original scientific article

Abstract: Spatial extension has been hailed as a “smoking gun” in the gamma-ray search of dark galactic subhalos, which would appear as unidentified sources for gamma-ray telescopes. In this work, we study the sensitivity of the Fermi-LAT to extended subhalos using simulated data based on a realistic sky model. We simulate spatial templates for a set of representative subhalos, whose parameters were derived from our previous work with N-body cosmological simulation data. We find that detecting an extended subhalo and finding an unequivocal signal of angular extension requires, respectively, a flux 2 to 10 times larger than in the case of a pointlike source. By studying a large grid of models, where parameters such as the WIMP mass, annihilation channel, or subhalo model are varied significantly, we obtain the response of the LAT as a function of the product of annihilation cross-section times the J-factor. Indeed, we show that spatial extension can be used as an additional “filter” to reject subhalos candidates among the pool of unidentified LAT sources, as well as a smoking gun for positive identification. For instance, typical angular extensions of a few tenths of a degree are expected for the considered scenarios. Finally, we also study the impact of the obtained LAT sensitivity to such extended subhalos on the achievable dark matter constraints, which are a few times less constraining than comparable point-source limits.
Keywords: dark matter, cosmic rays and astroparticles, gamma-ray astronomy, particle astrophysics, particle dark matter
Published in RUNG: 26.01.2023; Views: 1407; Downloads: 0
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