H₂ flows in the Corona Australis cloud and their driving sources^⋆

¹ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
² Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Ave. Gran Bretaña 1111, Playa Ancha, Casilla 53, Valparaíso, Chile
³ Joint Astronomy Center, 660 N. A’ohoku Pl, Hilo, Hawaii 96720, USA
⁴ NASA Headquarters, Science Mission Directorate, 300 E St SW, Washington, DC 20546, USA
⁵ Aryabhatta Research Institute of Observational Sciences, Nainital 263129, India
e-mail: nanda@astro.up.pt

Received: 9 March 2011
Accepted: 2 August 2011

Abstract

Aims. We uncover the H₂ flows in the Corona Australis molecular cloud and in particular identify the flows from the Coronet cluster.

Methods. A deep, near-infrared H₂v = 1–0 S(1), 2.122 μm-line, narrow-band imaging survey of the R CrA cloud core was carried out. The nature of all candidate-driving sources in the region was evaluated using data available from the literature and also by fitting the spectral energy distributions (SED) of each source either with an extincted photosphere or YSO model. Archival Spitzer-IRAC and MIPS data was used to obtain photometry, which was combined with USNO, 2MASS catalogs and millimeter photometry from the literature, to build the SEDs. We identify the best candidate-driving source for each outflow by comparing the flow properties, available proper motions, and the known/estimated properties of the driving sources. We also adopted the thumbrule of outflow power as proportional to source luminosity and inversely proportional to the source age to reach a consensus.

Results. Continuum-subtracted, narrow-band images reveal several new Molecular Hydrogen emission-line Objects (MHOs). Together with previously known MHOs and Herbig-Haro objects we catalog at least 14 individual flow components of which 11 appear to be driven by the R CrA aggregate members. The flows originating in the Coronet cluster have lengths of  ~0.1–0.2 pc. Eight out of nine submillimeter cores mapped in the Coronet cluster region display embedded stars driving an outflow component. Roughly 80% of the youngest objects in the Coronet are associated with outflows. The MHO flows to the west of the Coronet display lobes moving to the west and vice-versa, resulting in nondetections of the counter lobe in our deep imaging. We speculate that these counter flows may be experiencing a stunting effect in penetrating the dense central core.

Conclusions. Although this work has reduced the ambiguities for many flows in the Coronet region, one of the brightest H₂ feature (MHO2014) and a few fainter features in the region remain unassociated with a clear driving source. The flows from Coronet, therefore, continue to be interesting targets for future studies.