UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

First results from the UHRF: ultra-high-resolution observations of atomic interstellar lines towards ζ Ophiuchi

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. Green open access

[img]
Preview
Text
barlow95_uhrf.pdf - Published version

Download (3MB) | Preview

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 > 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
Downloads since deposit
9Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item