Astronomy and Astrophysics, volume 443, 525-533 (2005/11-4)
CaII K observations of QSOs in the line-of-sight to the Magellanic Bridge.
SMOKER J.V., KEENAN F.P., THOMPSON H.M.A., BRUENS C., MULLER E., LEHNER N., LEE J.-K. and HUNTER I.
Abstract (from CDS):
We describe medium-resolution spectroscopic observations taken with the ESO Multi-Mode Instrument (44Sc emmi) in the Ca44Sc II K line (λair=3933.661Å) towards 7 QSOs located in the line-of-sight to the Magellanic Bridge. At a spectral resolution R=λ/Δλ=6000, five of the sightlines have a signal-to-noise (S/N) ratio of ∼20 or higher. Definite Ca absorption due to Bridge material is detected towards 3 objects, with probable detection towards two other sightlines. Gas-phase Ca44Sc II K Bridge and Milky Way abundances or lower limits for the all sightlines are estimated by the use of Parkes 21-cm H44Sc I emission line data. These data only have a spatial resolution of 14-arcmin compared with the optical observations which have milli-arcsecond resolution. With this caveat, for the three objects with sound Ca44Sc II K detections, we find that the ionic abundance of Ca44Sc II K relative to H44Sc I, A=log(N(CaK)/N(H44Sc I)) for low-velocity Galactic gas ranges from -8.3 to -8.8dex, with H44Sc I column densities varying from 3-6x1020cm–2. For Magellanic Bridge gas, the values of A are ∼0.5dex higher, ranging from ~-7.8 to -8.2dex, with N(H44Sc I)=1-5x1020cm–2. Higher values of A correspond to lower values of N(H44Sc I), although numbers are small. For the sightline towards B0251-675, the Bridge gas has two different velocities, and in only one of these is Ca44Sc II tentatively detected, perhaps indicating gas of a different origin or present-day characteristics (such as dust content), although this conclusion is uncertain and there is the possibility that one of the components could be related to the Magellanic Stream. Higher signal-to-noise Ca44Sc II K data and higher resolution H44Sc I data are required to determine whether A changes with N(H44Sc I) over the Bridge and if the implied difference in the metalicity of the two Bridge components towards B0251-675 is real.
galaxies: Magellanic Clouds - galaxies: Seyfert - ISM: abundances
View the reference in ADS
To bookmark this query, right click on this link: simbad:2005A&A...443..525S and select 'bookmark this link' or equivalent in the popup menu