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تسجيل مستخدم جديدCreating a high-resolution picture of Cygnus with the Cherenkov Telescope Array
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The Cygnus region hosts one of the most remarkable star-forming regions in the Milky Way. Indeed, the total mass in molecular gas of the Cygnus X complex exceeds 10 times the total mass of all other nearby star-forming regions. Surveys at all wavelengths, from radio to gamma-rays, reveal that Cygnus contains such a wealth and variety of sources---supernova remnants (SNRs), pulsars, pulsar wind nebulae (PWNe), H II regions, Wolf-Rayet binaries, OB associations, microquasars, dense molecular clouds and superbubbles---as to practically be a galaxy in microcosm. The gamma-ray observations along reveal a wealth of intriguing sources at energies between 1 GeV and tens of TeV. However, a complete understanding of the physical phenomena producing this gamma-ray emission first requires us to disentangle overlapping sources and reconcile discordant pictures at different energies. This task is made more challenging by the limited angular resolution of instruments such as the Fermi Large Area Telescope, ARGO-YBJ, and HAWC and the limited sensitivity and field of view of current imaging atmospheric Cherenkov telescopes (IACTs). The Cherenkov Telescope Array (CTA), with its improved angular resolution, large field of view, and order of magnitude gain in sensitivity over current IACTs, has the potential to finally create a coherent and well-resolved picture of the Cygnus region between a few tens of GeV and a hundred TeV. We describe a proposed strategy to study the Cygnus region using CTA data, which combines a survey of the whole region at $65^{circ} < l < 85^{circ}$ and $-3.5^{circ} < b < 3.5^{circ} $ with deeper observations of two sub-regions that host rich groups of known gamma-ray sources.
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Surveys open up unbiased discovery space and generate legacy datasets of long-lasting value. One of the goals of imaging arrays of Cherenkov telescopes like CTA is to survey areas of the sky for faint very high energy gamma-ray (VHE) sources, especia
lly sources that would not have drawn attention were it not for their VHE emission (e.g. the Galactic dark accelerators). More than half the currently known VHE sources are to be found in the Galactic plane. Using standard techniques, CTA can carry out a survey of the region |l|<60 degrees, |b|<2 degrees in 250 hr (1/4th the available time per year at one location) down to a uniform sensitivity of 3 mCrab (a Galactic Plane survey). CTA could also survey 1/4th of the sky down to a sensitivity of 20 mCrab in 370 hr of observing time (an all-sky survey), which complements well the surveys by the Fermi/LAT at lower energies and extended air shower arrays at higher energies. Observations in (non-standard) divergent pointing mode may shorten the all-sky survey time to about 100 hr with no loss in survey sensitivity. We present the scientific rationale for these surveys, their place in the multi-wavelength context, their possible impact and their feasibility. We find that the Galactic Plane survey has the potential to detect hundreds of sources. Implementing such a survey should be a major goal of CTA. Additionally, about a dozen blazars, or counterparts to Fermi/LAT sources, are expected to be detected by the all-sky survey, whose prime motivation is the search for extragalactic dark accelerators.
Misaligned AGN (MAGNs), i.e., radio-loud AGNs with the jet not pointing directly towards us, represent a new class of GeV emitters revealed by the Fermi space telescope. Although they comprise only a small fraction of the high-energy sources, MAGNs a
re extremely interesting objects offering a different perspective to study high-energy processes with respect to blazars. The aim of this work is to evaluate the impact of the new-generation Cherenkov Telescope Array (CTA) on the MAGN class and propose possible observational strategies to optimize their detection.
The Cherenkov Telescope Array is a next generation ground-based gamma-ray observatory de- signed to detect photons in the 20 GeV to 300 TeV energy range. With a sensitivity improvement of up to one order of magnitude on the entire energy range with r
espect to currently operating facilities, coupled with significantly better angular resolution, the array will be used to address many open questions in high-energy astrophysics. In addition, CTA will explore the ultra-high energy (E >50 TeV) window with great sensitivity for the first time. CTA is expected to reveal a detailed picture of the Galactic plane at the highest energies, and to discover around one hundred new supernova remnants and many hundreds of pulsar wind nebulae, according to current population estimates. The ability of the observatory to resolve such a large number of Galactic sources is one of the challenges to be faced. In this paper, we will present the first simulated scan of the Galactic plane with a realistic observation strategy, with particular attention to the potential source confusion. We will also present prospects for morphological studies of extended sources, such as the young SNR RX J1713.7-39.
The Cherenkov Telescope Array (CTA) will be the next generation of ground based gamma-ray telescopes allowing us to study very high energy phenomena in the Universe. CTA aims to gain about a factor of ten in sensitivity compared to current experiment
s, extending the accessible gamma-ray energy range from a few tens of GeV to some hundreds of TeV. This increased gamma-ray source sensitivity, as well as the expected enhanced energy and spatial resolution, will allow exciting new insights in some key science topics. Additionally, CTA will provide a full sky-coverage by featuring the array located in two sites in the Northern and Southern hemispheres. This paper will describe the status of CTA and highlight some of CTAs key science themes; namely the origin of relativistic cosmic particles, the study of cosmological effects on gamma-ray propagation and the search for annihilating dark matter particles.
The Cherenkov Telescope Array, CTA, will be the major global observatory for very high energy gamma-ray astronomy over the next decade and beyond. The scientific potential of CTA is extremely broad: from understanding the role of relativistic cosmic
particles to the search for dark matter. CTA is an explorer of the extreme universe, probing environments from the immediate neighbourhood of black holes to cosmic voids on the largest scales. Covering a huge range in photon energy from 20 GeV to 300 TeV, CTA will improve on all aspects of performance with respect to current instruments. The observatory will operate arrays on sites in both hemispheres to provide full sky coverage and will hence maximize the potential for the rarest phenomena such as very nearby supernovae, gamma-ray bursts or gravitational wave transients. With 99 telescopes on the southern site and 19 telescopes on the northern site, flexible operation will be possible, with sub-arrays available for specific tasks. CTA will have important synergies with many of the new generation of major astronomical and astroparticle observatories. Multi-wavelength and multi-messenger approaches combining CTA data with those from other instruments will lead to a deeper understanding of the broad-band non-thermal properties of target sources. The CTA Observatory will be operated as an open, proposal-driven observatory, with all data available on a public archive after a pre-defined proprietary period. Scientists from institutions worldwide have combined together to form the CTA Consortium. This Consortium has prepared a proposal for a Core Programme of highly motivated observations. The programme, encompassing approximately 40% of the available observing time over the first ten years of CTA operation, is made up of individual Key Science Projects (KSPs), which are presented in this document.
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