Neutral Hydrogen in the Direction of the VELA Supernova Remnant

Details Neutral Hydrogen in the Direction of the VELA Supernova Remnant Neutral Hydrogen in the Direction of the VELA Supernova Remnant

Aug 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aj....116..813d&link_type=abstract

The Astronomical Journal, Volume 116, Issue 2, pp. 813-822.

Astronomy and Astrophysics

Astronomy

24

Ism: H I, Ism: Individual: Name: Vela Supernova Remnant, Ism: Structure, Radio Continuum, Ism: Supernova Remnants

Scientific paper

We have carried out a study of the distribution and kinematics of the neutral hydrogen in the direction of the Vela supernova remnant (SNR). A field of 6.8d x 5.4d centered at l = 264.1d, b = -1.6d was surveyed using the Parkes 64 m radio telescope (half-power beamwidth 14.7′ at 21 cm). Nearly 2300 H i profiles were obtained with a grid spacing of 7.5′. The presence of a thin, almost circular H i shell, centered at v = 1.6 +/- 0.8 km s^-1, is revealed. This shell delineates the outer border of the X-ray emission as shown in the ROSAT observations of Aschenbach, Egger, & Trümper and wraps around the receding part of the remnant. In addition, two higher velocity features possibly associated with Vela are observed at about -30 and 30 km s^-1. These features are interpreted as gas accelerated by the expansion of the supernova shock. The low systemic velocity observed suggests a distance shorter than 500 pc for the Vela SNR. The H i shell is ~7 deg in diameter and expands at v ~ 30 km s^-1. By assuming a distance of 350 pc, we calculate for this shell a linear radius of 22 pc, a swept-up mass of ~1200-2300 M_&sun;, and an atomic preshock density of ~1-2 cm^-3. The kinetic energy transferred by the supernova shock into the interstellar medium is ~(1-2) x 10^49 ergs, while the initial energy of the explosion is estimated to be ~(1-2.5) x 10^51 ergs. We present the distribution of the column density of the neutral material absorbing the X-radiation, an essential parameter in the analysis of X-ray data. A comparison between the H i and Hα emission suggests that the H i shell contains embedded dust that might be responsible for increased optical absorption in this region. On the other hand, the brightest arc-shaped optical filaments associated with the western side of Vela show good correspondence with the H i features. From a comparison between the H i and Molonglo Observatory Synthesis Telescope 843 MHz radio continuum emission, we find that the outermost arched radio filaments correlate well with the main ridge of the H i shell. No strong inhomogeneities were found in the ambient H i medium in the direction of Vela X (the central nebula, powered by the pulsar PSR B0833-45).

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