Volume 559, November 2013
|Number of page(s)||20|
|Section||Interstellar and circumstellar matter|
|Published online||20 November 2013|
DIGIT survey of far-infrared lines from protoplanetary discs
1 Universidad Autónoma de Madrid, Dpto. Física Teórica, Fac. de Ciencias, Campus de Cantoblanco, 28049 Madrid, Spain
2 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson AZ 85719, USA
3 Max Planck Institut für Extraterrestriche Physik, Giessenbachstrasse 1, 85748 Garching, Germany
4 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
5 The University of Texas at Austin, Department of Astronomy, 2515 Speedway, Stop C1400, Austin TX 78712-1205, USA
6 Dept. of Astrophysics, CAB (CSIC-INTA), ESAC Campus, PO Box 78, 28691 Villanueva de la Cañada, Spain
7 Kavli Institute for Astronomy and Astrophysics, Yi He Yuan Lu 5, 100871 Beijing, PR China
8 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
9 Anton Pannekoek Astronomical Institute, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
10 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
11 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands
Received: 17 January 2013
Accepted: 12 August 2013
CO is an important component of a protoplanetary disc as it is one of the most abundant gas phase species. Furthermore, observations of CO transitions can be used as a diagnostic of the gas, tracing conditions in both the inner and outer disc. We present Herschel/PACS spectroscopy of a sample of 22 Herbig Ae/Be (HAEBEs) and eight T Tauri stars (TTS), covering the pure rotational CO transitions from J = 14 → 13 up to J = 49 → 48. CO is detected in only five HAEBEs, namely AB Aur, HD 36112, HD 97048, HD 100546, and IRS 48, and in four TTS, namely AS 205, S CrA, RU Lup, and DG Tau. The highest transition detected is J = 36 → 35 with Eup of 3669 K, seen in HD 100546 and DG Tau. We construct rotational diagrams for the discs with at least three CO detections to derive Trot and find average temperatures of 270 K for the HAEBEs and 485 K for the TTS. The HD 100546 star requires an extra temperature component at Trot ~ 900–1000 K, suggesting a range of temperatures in its disc atmosphere, which is consistent with thermo-chemical disc models. In HAEBEs, the objects with CO detections all have flared discs in which the gas and dust are thermally decoupled. We use a small model grid to analyse our observations and find that an increased amount of flaring means higher line flux, as it increases the mass in warm gas. CO is not detected in our flat discs as the emission is below the detection limit. We find that HAEBE sources with CO detections have high LUV and strong PAH emission, which is again connected to the heating of the gas. In TTS, the objects with CO detections are all sources with evidence of a disc wind or outflow. For both groups of objects, sources with CO detections generally have high UV luminosity (either stellar in HAEBEs or due to accretion in TTS), but this is not a sufficient condition for the detection of the far-IR CO lines.
Key words: circumstellar matter / protoplanetary disks
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Appendices are available in electronic form at http://www.aanda.org
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.