The neutral gas environment of the young supernova remnant SN 1006 (G327.6+14.6)

Abstract

Using the Australia Telescope Compact Array, we have carried out a survey of the H i emission in the direction of the bilateral supernova remnant (SNR) SN 1006 (G327.6+14.6). The angular resolution of the data is 4.07×3.00, and the rms noise ∼39 mJy/beam (∼0.3 K). To recover structures at low spatial frequencies, single dish data have been added to the interferometric images. We have also studied the 12CO emission in the transitions J = 1–0 and J = 2–1, looking for very compact clumps of molecular gas as possible sites for the acceleration of electrons and nuclei to TeV energies associated with the γ-ray source detected on the NE limb of SN 1006. These molecular gas observations produced only marginal detections. From the present observations we conclude that the distribution of the surrounding neutral gas had no strong influence in shaping this SNR with a bilateral appearance. Intrinsic factors may have contributed to the present morphology. The remnant of SN 1006 appears to be evolving in a smooth environment with an atomic volume density n0 ∼ 0.3 cm−3. The existence of an H i concentration projected on the center of SN 1006 suggests an upper limit of ∼−20 km s−1 on the systemic velocity of the SNR. This limit is compatible with a distance to the SNR of about 1.7 kpc, in good agreement with previous estimates. An extended H i cloud with volume density ∼0.5 cm−3 is detected towards the NW border of SN 1006. This concentration may be responsible for the formation of the bright Balmer filaments observed in SN 1006. The absorbing column density towards SN 1006 has been estimated to be N h ∼ 6.8 × 1020 cm−2, in good agreement with previous suggestions based on X-ray results.