Optical and infrared observations of the young SMC blob N26 and its environment^⋆,⋆⋆

¹ LERMA, UMR 8112 du CNRS, Observatoire de Paris, 92195 Meudon, France
e-mail: gerard.testor@obspm.fr
² Department of Astronomy, University of Virginia , PO Box 400325, Charlottesville VA 22904, USA
³ Max-Planck-Institut fur Radioastronomie, 53121 Bonn, Germany
⁴ Université de Cergy-Pontoise, 95031 Cergy Cedex, France
⁵ The Johns Hopkins University, Department of Physics and Astronomy, 366 Bloomberg Center, 3400 N. Charles Street, Baltimore MD 21218, USA
⁶ Space Science Institute, 4750 Walnut St. Suite 205, Boulder CO 80301, USA

Received: 18 November 2011
Accepted: 6 February 2014

Abstract

Context. High-excitation compact H ii regions of the Magellanic Clouds are sites of recent massive star formation in low metallicity environments.

Aims. Detailed study of these regions and their environments using high-spatial resolution observations is necessary to better understand massive star formation, which is still an unsolved problem. We aim at a detailed study of the Small Magellanic Cloud compact H ii region N26, which is only ~4′′ in diameter.

Methods. This study is based on high spatial resolution imaging (~0.̋1–0.̋3) in JHKs and L′ bands, using the VLT equipped with the NAOS adaptive optics system. A larger region (~50 pc × 76 pc) was also imaged at medium spatial resolution, using the ESO 2.2 m telescope in optical wavelengths. We also used the JHKs archival data from the IRSF survey and the Spitzer Space Telescope SAGE-SMC survey.

Results. Our high-resolution JHKs data of the compact high-excitation H ii region N26 reveal a new, bright component (C) between the two already known optical components A and B. Components A and C are resolved into several stars. Component A is the main ionization source of N26 and coincides with the radio continuum source B0046-7333. A new compact H ii region with very faint [O iii] λ5007 emission has been discovered. In the mid-infrared, our field resembles a shell formed by filaments and dust clumps, coinciding with the molecular cloud SMCB2. Region N22, located in the center of the shell, is the most excited H ii region of the complex and seems to have created a cavity in SMCB2. We derive nebular parameters from spectra, and using color–magnitude and color–color diagrams, we identify stellar sources that show significant near-infrared excess emission in order to identify the best YSO candidates.