Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998larm.confe..91g&link_type=abstract
"IX Latin American Regional IAU Meeting, "Focal Points in Latin American Astronomy", held in Tonantzintla, Mexico, Nov 9-13, 199
Astronomy and Astrophysics
Astronomy
Scientific paper
The morphology and dynamics of supernova remnants (SNRs) appear to be strongly affected by the ambient circumstellar medium (CMS) as well as the interstellar medium (ISM). The study of the environs through atomic and/or molecular lines provides a three-dimensional picture of the medium into which a SNR expands. This information is crucial in understanding the characteristics of SNRs as observed in the different spectral bands, helping to disentangle the intrinsic and extrinsic factors which modify the morphology of SNRs. The aim of the present project is to investigate the distribution of the neutral hydrogen and the carbon monoxide in direction to the SNR G18.8+0.3 (Kes 67), in search for signatures that allow to disclose the role of the surrounding gas in the evolution of this remnant. To obtain the HI 21 cm images, a field of 2.5deg X 1.5deg around G18.8+0.3 was observed with an angular resolution of 14'.7 using the 64 m antenna at Parkes (Australia) in June 1995. The 12CO (J:0->1) and 13CO (J:0->1) data were obtained with the Nagoya University (Japan) 4 m antenna at Las Campanas (Chile). The angular resolution is 2'.7. Three fields (increasingly larger) were surveyed: the first toward the eastern bump of the shell, with a sampling of 2'; the second, covering the continuum shell and its immediate neighbourhood , with a sampling of 4'; and the third one, covering a larger area centered in the remnant, with a sampling of 8'. From the analysis of the HI 21 cm line data in the whole observed velocity interval, we find the existence of neutral gas likely to be associated with the SNR in the range +15 to +22 km/s . In this interval, the HI emission appears clearly distorted, surrounding the more flattened and brightest sides of the radio continuum source. The study of the CO distribution in the region shows that the molecular gas probably associated with G18.8+0.3 consists of a series of clouds forming an incomplete loop surrounding the most intense parts of the radio shell. This chain of clouds is detected from +10 km/s at the northeast, to +23 km/s at the south. The most conspicuous CO emission features are: a cloud which perfectly matches the northeastern edge of the SNR; a small concentration coinciding with a radio continuum indentation; and an elongated cloud to the southeast, which bends following the shape of the SNR's shell. Based on the above results, we estimate the systemic velocity of the SNR to be ~ +16 km/s , which produces a kinematic distance of about 1.8 kpc, according to the galactic rotation model by Fitch et al. (1989). The correlation between the flattest, most intense regions of the radio shell, with the most dense concentrations in the ISM, are a strong evidence of the medium having influenced the evolution of this SNR. Physical parameters of the associated gas are estimated.
Dubner Gloria
Giacani Elsa
Reynoso E.
Roth Marcel
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