Intermediate-velocity gas observed towards the Shajn 147 SNR

¹ Department of Physics, Univ. of Wisconsin - La Crosse, La Crosse, WI 54601, USA e-mail: sallmen.shau@uwlax.edu
² Experimental Astrophysics Group, Space Sciences Laboratory, UC Berkeley, Berkeley, USA

Received: 16 January 2004
Accepted: 12 July 2004

Abstract

We present high-resolution spectra ( km s^-1) of the interstellar and interstellar absorption lines observed towards 3 early-type stars with distances of 360 to 1380 pc along the line-of-sight towards the 800 pc distant Shajn 147 (S147) Supernova Remnant (SNR). These data are supplemented with far-UV (912–1180 Å) aborption spectra of HD 36665 and HD 37318 recorded with the NASA Far Ultraviolet Spectroscopic Explorer () satellite. The observations reveal intermediate-velocity (IV) absorption features at V_helio = +92 km s^-1 towards HD 37318 and at and -52 km s^-1 towards HD 36665, in addition to several other gas cloud components with lower velocity. These IV components can be associated with the expansion of the SNR that has disrupted the surrounding interstellar gas.
The IV component at km s^-1 seen towards HD 37318 was detected only in the far-UV lines of and , suggesting that it is composed mainly of warm and ionized gas. The two IV components observed towards HD 36665 were detected in , , , , and , indicating that it is composed of both neutral and ionized gas shells. Highly ionized gas was detected in the λ 1032 Å  absorption line at km s^-1 towards both stars. This hot and highly ionized gas component is characterized by a columnn density ratio of N()/N() < 0.27, which is consistent with that predicted by current models of evolved SNRs. However, we cannot preclude its origin in the interstellar medium in line-of-sight to S147.
Column-density ratios of [Mg/Fe], [Al/Si],[Si/Fe], [N/Fe], [O/Fe] and [Na/Ca] have been derived for the IV gas components detected towards S147. Similar ratios have also been derived for fast-moving gas observed towards two other SNRs in order to gain some insight into the behavior of element abundances in the disturbed interstellar gas associated with these regions. In all cases except for Na and Ca, these elements appear to be present with near-solar abundance ratios.