Gas and dust in the beta Pictoris moving group as seen by the Herschel Space Observatory^⋆

¹ Centro de Astrobiología (INTA–CSIC) – Depto. Astrofísica, POB 78, ESAC Campus, 28691 Villanueva de la Cañada, Spain
e-mail: riviere@astro.rug.nl
² Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
³ Astronomy Department, University of California, Berkeley, CA 94720-3411, USA
⁴ UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France
⁵ Laboratorio Franco-Chileno de Astronomia, UMI 3386: CNRS – U de Chile/PUC/U Conception, Santiago, Chile
⁶ Department of Astronomy, University of Maryland, College Park, MD 230742, USA
⁷ Dep. de Física Teórica, Fac. de Ciencias, UAM Campus Cantoblanco , 28049 Madrid, Spain
⁸ Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität Jena, Schillergäßchen 2–3, 07745 Jena, Germany
⁹ Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA
¹⁰ ALMA, Avda Apoquindo 3846, Piso 19, Edificio Alsacia, Las Condes, 755-0108 Santiago, Chile

Received: 23 October 2013
Accepted: 27 March 2014

Abstract

Context. Debris discs are thought to be formed through the collisional grinding of planetesimals, and then can be considered as the outcome of planet formation. Understanding the properties of gas and dust in debris discs can help us comprehend the architecture of extrasolar planetary systems. Herschel Space Observatory far-infrared (IR) photometry and spectroscopy have provided a valuable dataset for the study of debris discs gas and dust composition. This paper is part of a series of papers devoted to the study of Herschel-PACS observations of young stellar associations.

Aims. This work aims at studying the properties of discs in the beta Pictoris moving group (BPMG) through far-IR PACS observations of dust and gas.

Methods. We obtained Herschel-PACS far-IR photometric observations at 70, 100, and 160 μm of 19 BPMG members, together with spectroscopic observations for four of them. These observations were centred at 63.18 μm and 157 μm, aiming to detect [OI] and [CII] emission. We incorporated the new far-IR observations in the SED of BPMG members and fitted modified blackbody models to better characterise the dust content.

Results. We have detected far-IR excess emission towards nine BPMG members, including the first detection of an IR excess towards HD 29391.The star HD 172555, shows [OI] emission, while HD 181296 shows [CII] emission, expanding the short list of debris discs with a gas detection. No debris disc in BPMG is detected in both [OI] and [CII]. The discs show dust temperatures in the range 55–264 K, with low dust masses (<6.6 × 10^-5 M_⊕ to 0.2 M_⊕) and radii from blackbody models in the range 3 to ~82 AU. All the objects with a gas detection are early spectral type stars with a hot dust component.