Magnetic field estimates from the X-ray synchrotron emitting rims of the 30 Dor C superbubble and the implications for the nature of 30 Dor C's TeV emission

Abstract

The 30 Dor C superbubble is unique for its synchrotron X-ray shell, as well as being the first superbubble to be detected in TeV $\gamma$-rays, though the dominant TeV emission mechanism, i.e., leptonic or hadronic, is still unclear. We aim to use new Chandra observations of 30 Dor C to resolve the synchrotron shell in unprecedented detail and to estimate the magnetic ($B$) field in the postshock region, a key discriminator between TeV $\gamma$-ray emission mechanisms. We extracted radial profiles in the 1.5-8 keV range from various sectors around the synchrotron shell and fitted these with a projected and point spread function convolved postshock volumetric emissivity model to determine the filament widths. We then calculated the postshock magnetic field strength from these widths. We found that most of the sectors were well fitted with our postshock model and the determined $B$-field values were low, all with best fits $\lesssim 20\mu$G. Upper limits on the confidence intervals of three sectors reached $\gtrsim 30\mu$G though these were poorly constrained. The generally low $B$-field values suggests a leptonic-dominated origin for the TeV $\gamma$-rays. Our postshock model did not provide adequate fits to two sectors. We found that one sector simply did not provide a clean enough radial profile, while the other could be fitted with a modified model where the projected profile falls off abruptly below $\sim 0.8$ times the shell radius, yielding a postshock $B$-field of 4.8 (3.7-11.8) $\mu$G which is again consistent with the leptonic TeV $\gamma$-ray mechanism. Alternatively, the observed profiles in these sectors could result from enhancements around a shock-cloud interaction as suggested in previous works. The average $B$-field determined around the X-ray synchrotron shell of 30 Dor C suggests the leptonic scenario as the dominant emission mechanism for the TeV $\gamma$-rays.

arXiv comment16 pages, 14 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (38)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• On the Absorption of X-rays in the Interstellar Medium
• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• The Spitzer Space Telescope Mission
• Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I: Overview and Initial Results
• Supernova remnants: the X-ray perspective
• On the magnetic fields and particle acceleration in Cas A
• Magnetic Field Amplification in Tycho and other Shell-type Supernova Remnants
• Toward Understanding the Cosmic-ray Acceleration at Young Supernova Remnants Interacting with Interstellar Clouds: Possible Applications to RX J1713.7-3946
• Analytical solutions for energy spectra of electrons accelerated by nonrelativistic shock-waves in shell type supernova remnants
• Turbulence and Magnetic Field Amplification in Supernova Remnants: Interactions Between A Strong Shock Wave and Multi-Phase Interstellar Medium
• Observational signatures of particle acceleration in supernova remnants
• The exceptionally powerful TeV gamma-ray emitters in the Large Magellanic Cloud
• The X-ray synchrotron emission of RCW 86 and the implications for its age
• H.E.S.S. observations of RX J1713.7-3946 with improved angular and spectral resolution; evidence for gamma-ray emission extending beyond the X-ray emitting shell
• RCW 86: A Type Ia Supernova in a Wind-Blown Bubble
• Fast Variability of Nonthermal X-Ray Emission in Cassiopeia A: Probing Electron Acceleration in Reverse-Shocked Ejecta
• Star Forming Dense Cloud Cores in the TeV γ-ray SNR RX J1713.7-3946
• The many sides of RCW 86: a type Ia supernova remnant evolving in its progenitor's wind bubble
• Thermal and Non-thermal X-Rays from the LMC Super Bubble 30 Dor C
• Surround & Squash: The Interstellar Medium around Scorpius Centaurus OB2
• Proper Motions of H-alpha filaments in the Supernova Remnant RCW 86
• Non-thermal X-rays and interstellar gas toward the γ-ray supernova remnant RX J1713.7-3946: Evidence for X-ray enhancement around CO and HI clumps
• Magnetic-Field Amplification in the Thin X-ray Rims of SN1006
• Evolution of the Radio Remnant of Supernova 1987A: Morphological Changes from Day 7000
• The first broad-band X-ray images and spectra of the 30 Doradus region in the LMC
• XMM-Newton study of 30 Dor C and a newly identified MCSNR J0536-6913 in the Large Magellanic Cloud
• Discovery of Molecular and Atomic Clouds Associated with the Magellanic Superbubble 30 Doradus C
• Confronting the Superbubble Model with X-ray Observations of 30 Dor C
• Energy Dependence of Synchrotron X-Ray Rims in Tycho's Supernova Remnant
• The Refined Shock Velocity of the X-Ray Filaments in the RCW 86 Northeast Rim
• The properties of non-thermal X-ray filaments in young supernova remnants
• Prospects for CTA observations of the young SNR RX J1713.7-3946
• Suzaku Observation of 30Dor C: A Supernova Remnant with the Largest Non-Thermal Shell
• Measurement of the X-ray proper motion in the south-east rim of RX J1713.7-3946
• Multi-frequency observations of a superbubble in the LMC: The case of LHA 120-N 70
• A Spatially Resolved Study of X-ray Properties in Superbubble 30 Dor C with $XMM-Newton$
• Physical Nature of the [S II]-Bright Shell Nebulae N70 and N185

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