IPHAS discoveries of young stars towards Cyg OB2 and its southern periphery |
| |
Authors: | Jorick S Vink Janet E Drew Danny Steeghs Nick J Wright Eduardo L Martin Boris T Gänsicke Robert Greimel Jeremy Drake |
| |
Institution: | Armagh Observatory, College Hill, Armagh BT61 9DG;Imperial College of Science, Technology and Medicine, Blackett Laboratory, Exhibition Road, London SW7 2AZ;Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB;Department of Physics, University of Warwick, Coventry CV4 7AL;Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA;University College London, Department of Physics &Astronomy, Gower Street, London WC1E 6BT;Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife, Spain;Physics Department, University of Central Florida, Orlando, FL 32816, USA;Isaac Newton Group of Telescopes, Apartado de correos 321, E-38700 Santa Cruz de la Palma, Tenerife, Spain;Institut für Physik, Karl-Franzen Universität Graz, Universitätsplatz 5, 8010 Graz, Austria |
| |
Abstract: | We report on the discovery of over 50 strong Hα emitting objects towards the large OB association Cyg OB2 and the H ii region DR 15 on its southern periphery. This was achieved using the INT Photometric Hα Survey of the Northern Galactic Plane (IPHAS), combined with follow-up spectroscopy using the MMT multi-object spectrometer HectoSpec. We present optical spectra, supplemented with optical r ', i ' and H α photometry from IPHAS, and near-infrared J , H and K photometry from Two Micron All Sky Survey. The position of the objects in the ( J − H ) versus ( H − K ) diagram strongly suggests most of them are young. Many show Ca ii infrared triplet emission indicating that they are in a pre-main-sequence phase of evolution of T Tauri and Herbig Ae nature. Among these, we have uncovered pronounced clustering of T Tauri stars roughly a degree south of the centre of Cyg OB2, in an arc close to the H ii region DR 15, and the radio ring nebula G79.29+0.46, for which we discuss its candidacy as a luminous blue variable. The emission-line objects towards Cyg OB2 itself could be the brightest most prominent component of a population of lower mass pre-main-sequence stars that has yet to be uncovered. Finally, we discuss the nature of the ongoing star formation in Cyg OB2 and the possibility that the central OB stars have triggered star formation in the periphery. |
| |
Keywords: | stars: early-type stars: emission line Be stars: formation stars: individual: T Tauri stars: pre-main-sequence |
|
|