Far-infrared observations of a massive cluster forming in the Monoceros R2 filament hub^⋆

¹ Cardiff School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff, Wales, CF24 3AA, UK
e-mail: T.Rayner@astro.cf.ac.uk
² I. Physik. Institut, University of Cologne, 50937 Cologne, Germany
³ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée G. Saint-Hilaire, 33615 Pessac, France
⁴ Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble, 38000 Grenoble, France
⁵ Laboratoire AIM, CEA/IRFU, CNRS/INSU, Université Paris Diderot, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
⁶ NRC, Herzberg Institute of Astrophysics, Victoria, V8P1A1, Canada
⁷ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
⁸ Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA
⁹ INAF–Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Roma, Italy
¹⁰ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
¹¹ Observatorio Astronómico Nacional (OAN), Apdo 112, 28803 Alcalá de Henares, Madrid, Spain
¹² Joint ALMA Observatory, 3107 Alonso de Cordova, 7630355 Vitacura, Santiago, Chile
¹³ Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 305-348, Republic of Korea
¹⁴ National Astronomical Observatory of Japan, Chile Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
¹⁵ ESA/ESAC, 28691 Villanueva de la Cañada, Madrid, Spain
¹⁶ INAF–Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
¹⁷ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
¹⁸ Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
¹⁹ The Rutherford Appleton Laboratory, Chilton, Didcot OX11 0NL, UK
²⁰ Department of Physics and Astronomy, The Open University, Milton Keynes, MK76 AA, UK

Received: 10 November 2016
Accepted: 21 August 2017

Abstract

We present far-infrared observations of Monoceros R2 (a giant molecular cloud at approximately 830 pc distance, containing several sites of active star formation), as observed at 70 μm, 160 μm, 250 μm, 350 μm, and 500 μm by the Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) instruments on the Herschel Space Observatory as part of the Herschel imaging survey of OB young stellar objects (HOBYS) Key programme. The Herschel data are complemented by SCUBA-2 data in the submillimetre range, and WISE and Spitzer data in the mid-infrared. In addition, C¹⁸O data from the IRAM 30-m Telescope are presented, and used for kinematic information. Sources were extracted from the maps with getsources, and from the fluxes measured, spectral energy distributions were constructed, allowing measurements of source mass and dust temperature. Of177 Herschel sources robustly detected in the region (a detection with high signal-to-noise and low axis ratio at multiple wavelengths), including protostars and starless cores, 29 are found in a filamentary hub at the centre of the region (a little over 1% of the observed area). These objects are on average smaller, more massive, and more luminous than those in the surrounding regions (which together suggest that they are at a later stage of evolution), a result that cannot be explained entirely by selection effects. These results suggest a picture in which the hub may have begun star formation at a point significantly earlier than the outer regions, possibly forming as a result of feedback from earlier star formation. Furthermore, the hub may be sustaining its star formation by accreting material from the surrounding filaments.