BARLOW, MJ;
CRAWFORD, IA;
DIEGO, F;
DRYBURGH, M;
FISH, AC;
HOWARTH, ID;
SPYROMILIO, J;
(1995)
First results from the UHRF: ultra-high-resolution observations of atomic interstellar lines towards ζ Ophiuchi.
Monthly Notices of the Royal Astronomical Society
, 272
(2)
pp. 333-345.
10.1093/mnras/272.2.333.
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Abstract
We present ultra-high-resolution observations of optical interstellar lines towards ζOph obtained during the commissioning phase of the new Ultra-High-Resolution Facility (UHRF) at the AAT. The UHRF has achieved its design resolving power of R≈106, and has very clearly resolved hyperfine splitting in three of the 11 identified Na I D-line velocity components towards ζ Oph. In addition, the intrinsic line profiles of the 3s-4p Na I doublet at 3302 Å have been measured for the first time. 12 velocity components are identified in the interstellar Ca II K-line absorption profile, of which seven have definite velocity counterparts in the Na I profile. Three of the Na I velocity components have b-values which correspond to a gas temperature of about 200 K, for the case of pure thermal broadening. The strongest component in the sightline (-14.8 km s-1) was found to have a b-value of 0.6+0.2−0.1kms−1, corresponding to a temperature of 500 K. If a true gas kinetic temperature of 54 K is assumed to apply to this component, from the H2 rotational excitation temperature previously measured for the ζ Oph sightline, then the observed Na I and Fe I line profiles both imply an rms turbulent velocity of 0.4 km s-1 within the cloud, just less than the local sound speed. The observed Ca II linewidths are all significantly larger than those of the corresponding Na I components. The Ca IIcomponents are interpreted as arising from warm neutral material (intercloud medium) surrounding cooler clouds, while half of the Na I components arise from cool clouds and half arise from warm intercloud material. The measured Na I/CaII column density ratios, and the inferred temperatures, are consistent with a model in which calcium is heavily depleted on to grains in cool clouds but is restored to the gas phase by impact desorption in the warm intercloud medium.
| Type: | Article |
|---|---|
| Title: | First results from the UHRF: ultra-high-resolution observations of atomic interstellar lines towards ζ Ophiuchi |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/272.2.333 |
| Publisher version: | https://doi.org/10.1093/mnras/272.2.333 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | line, profiles-instrumentation, spectrographs-stars, individual, ζ oph-ism, atoms-ism, clouds |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10096162 |
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