The distance to Complex M and the Intermediate Velocity Arch
Abstract
The Intermediate Velocity Arch is an association of Hi clouds lying within the broad limits l~110 deg-210 deg,b~50 deg-80 deg. We use high-resolution optical, and single-dish 21-cm, observations of 10 early-type halo star sightlines in this region to establish distance limits (0.4<=z<=3.5kpc) for seven IVCs that are part of the Arch. We re-examine a previous determination of upper and lower distance limits on the IVC Complex M using the closely aligned halo stars BD+382182 and HD93521. Our Hi spectra show no evidence of emission from Complex M, leading us to conclude that, while an upper distance limit of z<=3.5 kpc may be established, no useful lower distance determination can be made. Our new Hi observations allow new limits to be established on the metallicity of Complex M, and show C, O and Si variations with respect to solar abundances in the range +/-0.3 dex.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 1997
- DOI:
- 10.1093/mnras/289.1.83
- Bibcode:
- 1997MNRAS.289...83R
- Keywords:
-
- STARS: EARLY-TYPE;
- STARS: DISTANCES;
- ISM: CLOUDS;
- ISM: INDIVIDUAL: COMPLEX M;
- ISM: STRUCTURE