Volume 499, Number 2, May IV 2009
|Page(s)||455 - 464|
|Published online||19 March 2009|
On the massive star content of the nearby dwarf irregular Wolf-Rayet galaxy IC 4662 *
Department of Physics & Astronomy, Hicks Building, University of Sheffield, Hounsfield Road, Sheffield S3 7RH, UK e-mail: Paul.Crowther@sheffield.ac.uk
Accepted: 11 March 2009
Aims. We investigate the massive stellar content of the nearby dwarf irregular Wolf-Rayet galaxy IC 4662, and consider its global star forming properties in the context of other metal-poor galaxies, namely the SMC, IC 10 and NGC 1569.
Methods. Very Large Telescope/FORS2 imaging and spectroscopy plus archival Hubble Space Telescope/ACS imaging datasets permit us to spatially identify the location, number and probable subtypes of Wolf-Rayet stars within this galaxy. We also investigate suggestions that a significant fraction of the ionizing photons of the two giant H ii regions A1 and A2 lie deeply embedded within these regions.
Results. Wolf-Rayet stars are associated with a number of sources within IC 4662-A1 and A2, plus a third compact H ii region to the north west of A1 (A1-NW). Several sources appear to be isolated, single (or binary) luminous nitrogen sequence WR stars, while extended sources are clusters whose masses exceed the Orion Nebula Cluster by, at most, a factor of two. IC 4662 lacks optically visible young massive, compact clusters that are common in other nearby dwarf irregular galaxies. A comparison between radio and Hα-derived ionizing fluxes of A1 and A2 suggests that 30–50% of their total Lyman continuum fluxes lie deeply embedded within these regions.
Conclusions. The star formation surface density of IC 4662 is insufficient for this galaxy to qualify as a starburst galaxy, based upon its photometric radius, R25. If instead, we were to adopt the V-band scale length RD from Hunter & Elmegreen, IC 4662 would comfortably qualify as a starburst galaxy, since its star formation intensity would exceed 0.1 yr-1 kpc-2.
Key words: galaxies: individual: IC 4662 / stars: Wolf-Rayet / ISM: HII regions / galaxies: star clusters / galaxies: starburst / galaxies: dwarf
© ESO, 2009
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.