Testing source confusion and identification capability in Cherenkov telescope array data

Abstract

The Cherenkov Telescope Array will provide the deepest survey of the Galactic Plane performed at very-high-energy gamma-rays. Consequently, this survey will unavoidably face the challenge of source confusion, i.e., the non-unique attribution of signal to a source due to multiple overlapping sources. Among the known populations of Galactic gamma-ray sources and given their extension and number, pulsar wind nebulae (PWNe, and PWN TeV halos) will be the most affected. We aim to probe source confusion of TeV PWNe in forthcoming CTA data. For this purpose, we performed and analyzed simulations of artificially confused PWNe with CTA. As a basis for our simulations, we applied our study to TeV data collected from the H.E.S.S. Galactic Plane Survey for ten extended and two point-like firmly identified PWNe, probing various configurations of source confusion involving different projected separations, relative orientations, flux levels, and extensions among sources. Source confusion, defined here to appear when the sum of the Gaussian width of two sources is larger than the separation between their centroids, occurred in ∼30% of the simulations. For this sample and 0.5○ of average separation between sources, we found that CTA can likely resolve up to 60% of those confused sources above 500 GeV. Finally, we also considered simulations of isolated extended sources to see how well they could be matched to a library of morphological templates. The outcome of the simulations indicates a remarkable capability (more than 95% of the cases studied) to match a simulation with the correct input template in its proper orientation.

The Dawes Review 11: From young to old: The evolutionary path of Pulsar Wind Nebulae

“…As we already said, thanks to their longer lifetime as gammaray emitters, middle aged PWNe will likely dominate the very high energy sky, possibly representing up to ∼ 60% of the Galactic sources, and a huge number of new detection (∼ 200) may be expected with the upcoming Cherenkov Telescope Array, thanks to its unprecedented angular and energy resolution (Remy et al, 2022;Fiori et al, 2022). A very challenging problem will be that of the source confusion in the crowded Galactic plane, that will reduce the number of identified sources with respect to theoretical estimate (Mestre et al, 2022). Moreover an additional source of confusion might be that of TeV halos associated with evolved pulsars.…”

“…• Proto-magnetar wind nebulae, and in general relativistic outflows from millisecond rotating newly born magnetars, have been invoked to explain both long (Usov 1992; Thompson 2007; Bucciantini et al 2007, 2008; Metzger et al 2011b) and short GRBs (Bucciantini et al 2012; Wang 2017; Metzger & Piro 2014; Rezzolla & Kumar 2015), mostly because the detection of the so called ‘late activity’ (Gompertz, O’Brien, & Wynn 2014; Rowlinson et al 2013) has made almost mandatory to assume long lived engines, hardly compatible with the timescale for disk accretion in a stellar mass black hole. The key idea is that the relativistic outflow that we think is at the origin of the prompt gamma-ray emission, is nothing else than the magneto-centrifugally driven neutrino-wind, coming from the cooling proto-NS.…”

From young to old: the evolutionary path of Pulsar Wind Nebulae

“…As we already said, thanks to their longer lifetime as gammaray emitters, middle aged PWNe will likely dominate the very high energy sky, possibly representing up to ∼ 60% of the Galactic sources, and a huge number of new detection (∼ 200) may be expected with the upcoming Cherenkov Telescope Array, thanks to its unprecedented angular and energy resolution (Remy et al, 2022;Fiori et al, 2022). A very challenging problem will be that of the source confusion in the crowded Galactic plane, that will reduce the number of identified sources with respect to theoretical estimate (Mestre et al, 2022). Moreover an additional source of confusion might be that of TeV halos associated with evolved pulsars.…”