Sensitivity of the Cherenkov Telescope Array to TeV photon emission from the Large Magellanic Cloud

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 of >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 per cent 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

Prospects for γ-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array

Galaxy clusters are expected to be both dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster’s formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at γ-ray energies and are predicted to be sources of large-scale γ-ray emission due to hadronic interactions in the intracluster medium (ICM). In this paper, we estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse γ-ray emission from the Perseus galaxy cluster. We first perform a detailed spatial and spectral modelling of the expected signal for both the DM and the CRp components. For each case, we compute the expected CTA sensitivity accounting for the CTA instrument response functions. The CTA observing strategy of the Perseus cluster is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio X500 within the characteristic radius R500 down to about X500 < 3 × 10−3, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index αCRp = 2.3. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure αCRp down to about ∆αCRp ≃ 0.1 and the CRp spatial distribution with 10% precision, respectively. Regarding DM, CTA should improve the current ground-based γ-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to ∼ 5, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with τχ > 1027 s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario

Dark matter line searches with the Cherenkov Telescope Array

Monochromatic gamma-ray signals constitute a potential smoking gun signature for annihilating or decaying dark matter particles that could relatively easily be distinguished from astrophysical or instrumental backgrounds. We provide an updated assessment of the sensitivity of the Cherenkov Telescope Array (CTA) to such signals, based on observations of the Galactic centre region as well as of selected dwarf spheroidal galaxies. We find that current limits and detection prospects for dark matter masses above 300 GeV will be significantly improved, by up to an order of magnitude in the multi-TeV range. This demonstrates that CTA will set a new standard for gamma-ray astronomy also in this respect, as the world's largest and most sensitive high-energy gamma-ray observatory, in particular due to its exquisite energy resolution at TeV energies and the adopted observational strategy focussing on regions with large dark matter densities. Throughout our analysis, we use up-to-date instrument response functions, and we thoroughly model the effect of instrumental systematic uncertainties in our statistical treatment. We further present results for other potential signatures with sharp spectral features, e.g. box-shaped spectra, that would likewise very clearly point to a particle dark matter origin

Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

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 effective 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 diffuse astrophysical emission from that region. We report on the collaboration effort 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

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies

Applying a versatile, comprehensive, attribute-based waterhole classification scheme to ecosystem-based management challenges

Context. Understanding habitat suitability for feral animals across a landscape is important for conservation planning because the spatial and temporal availability of water provides critical limits to native biodiversity and the processes that threaten it. Previous attempts to support management actions on feral pig populations through predictions of population abundance, distribution and seasonal resource constraints have been confounded by a lack of knowledge, classification and mapping of waterholes – which are critical to their survival. Aims. In this paper, we aimed to apply a waterhole classification scheme for feral pig management to address gaps in our understanding of water and food availability through space and time, at scales relevant to feral animal movement and resource use. Methods. We utilise an attribute-based waterhole classification scheme for ecosystem-based management by defining a waterhole typology of feral pig habitat suitability and applying it spatially. Key results. Five attributes (water permanence, predictability of inundation, oceanic influence, dominant vegetation and shading) reflect many of the critical requirements for feral pig habitat in northern Australia. The attributes directly relate to the environmental constraints that exert population and behavioural pressure on feral pigs. These attributes were applied spatially in a specific hierarchy to group waterholes into 21 types. Conclusions. A waterhole typology that characterises within the context of their suitability for feral pig populations is foundational for systematic adaptive management and monitoring programs that aim to reduce the impact of threatening processes on freshwater ecosystems. Implications. Refining the mapping of important feral pig habitat variables (water and food) will greatly improve modelling approaches that aim to support data-driven management approaches, such as connectivity analysis and estimating population dynamics to inform culling programs. Here we demonstrate a significant increase in overlap with known feral pig distributions using a much smaller mapped effective management area when compared with previous best available spatial products

The structure and forms of physical activity in the City of Zagreb 2O14/2015

Abstract Background Physical inactivity is one of the biggest public health problems of the 21st century. It is carried through walking, cycling, job, sports, recreation. The aim of this paper is to evaluate the physical activity of the citizens of Zagreb according to sex, age and the type of physcal activity. Health-Enhancing Physical Activity recommendations are at least 150 of moderate or 75 vigorous minutes activity per week. Methods The research has been conducted by analyzing the data gained from the European Health Interview Survey (EHIS 2) from the World Health Organization that was carried out in Croatia during 2014. and 2015. There were collected the data on the frequency, duration and type of physical activity in the City of Zagreb. The target population was aged over 15 and included 446 inhabitants (188 men and 258 women) of the City of Zagreb. Results 24,5% of the total number of physically active persons exercise between 150 and 300 minutes per week. 45, 0 % respondents walk 10 to 29 minutes daily, 27, 1% walk 30-59 minutes daily, 14, 9% walk 1 or more hours a day. 1,2% respodents spend less then hour, 13, 6% spend 1 hour and 59 minutes, 18, 3% spend 2.00-2.59 hours and 8, 3% spend 3-3.59 hours on sport and recreation per week. 13, 8% of citizens spend 10-29 minutes a day cycling, 30.1% cycling 30-59 minutes a day, 12, 2% cycling 1 hour to 1 hour and 59 minutes and 2.4% spending more than 2 hours a day on a bicycle. When doing a professional job or work at home 43, 7% of respondents mostly sit or stand, 32,3% use moderate physical effort and 1, 5% of people perform hard work. 14.4% of respondents are engaged in sports, 11.9% cycling and 71, 9 % respondents walk 3-7 days a week. Conclusions Zagreb’s citizens are not sufficiently engaged in physical activity and carry out physical activity mainly while doing the job and walking. But those who are active meet weekly recommendations for duration of activity. Key messages Physical activity is one of the key health factors and one of the most effective ways of preventing chronic non-communicable diseases. There is a need of more public health interventions in order to promote recommended frequency, duration and different types of physical activity. </jats:sec

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

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