3 to 12 millimetre studies of dense gas towards the western rim of supernova remnant RX J1713.7-3946

TL;DR

This study investigates dense gas regions near supernova remnant RX J1713.7-3946 using millimeter observations and models cosmic-ray diffusion, revealing suppressed cosmic-ray entry into dense cores which affects gamma-ray and X-ray emissions.

Contribution

It provides new high-density gas measurements and models cosmic-ray diffusion effects in the supernova remnant environment, offering insights into cosmic-ray transport and gamma-ray emission mechanisms.

Findings

Dense gas >10^4cm^-3 confirmed in cores

Mass estimates are an order of magnitude smaller than previous CO-based estimates

Suppressed cosmic-ray diffusion can prevent low-energy cosmic-rays from entering dense cores

Abstract

The young X-ray and gamma-ray-bright supernova remnant RXJ1713.7-3946 (SNR G347.3-0.5) is believed to be associated with molecular cores that lie within regions of the most intense TeV emission. Using the Mopra telescope, four of the densest cores were observed using high-critical density tracers such as CS(J=1-0,J=2-1) and its isotopologue counterparts, NH3(1,1) and (2,2) inversion transitions and N2H+(J=1-0) emission, confirming the presence of dense gas >10^4cm^-3 in the region. The mass estimates for Core C range from 40M_{\odot} (from CS(J=1-0)) to 80M_{\odot} (from NH3 and N2H+), an order of magnitude smaller than published mass estimates from CO(J=1-0) observations. We also modelled the energy-dependent diffusion of cosmic-ray protons accelerated by RXJ1713.7-3946 into Core C, approximating the core with average density and magnetic field values. We find that for considerably suppressed diffusion coefficients (factors \chi=10^{-3} down to 10^{-5} the galactic average), low energy cosmic-rays can be prevented from entering the inner core region. Such an effect could lead to characteristic spectral behaviour in the GeV to TeV gamma-ray and multi-keV X-ray fluxes across the core. These features may be measurable with future gamma-ray and multi-keV telescopes offering arcminute or better angular resolution, and can be a novel way to understand the level of cosmic-ray acceleration in RXJ1713.7-3946 and the transport properties of cosmic-rays in the dense molecular cores.