Astronomy and Astrophysics, volume 499, 455-464 (2009/5-4)
On the massive star content of the nearby dwarf irregular Wolf-Rayet galaxy IC 4662.
CROWTHER P.A. and BIBBY J.L.
Abstract (from CDS):
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. 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 Hii regions A1 and A2 lie deeply embedded within these regions. Wolf-Rayet stars are associated with a number of sources within IC 4662-A1 and A2, plus a third compact Hii 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. 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 (2004AJ....128.2170H
), IC 4662 would comfortably qualify as a starburst galaxy, since its star formation intensity would exceed 0.1M☉
galaxies: individual: IC 4662 - stars: Wolf-Rayet - ISM: HII regions - galaxies: star clusters - galaxies: starburst - galaxies: dwarf
Fig. 2, Table 4: [CB2009] A1-NW, [CB2009] AN-WRN (Nos A1-WR1 to A1-WR4, A2-WR1 to A2-WR3), [CB2009] AN-HII N (Nos A1-HII 1 to A1-HII 2, A2-HII 1 to A2-HII 2), [CB2009] A1-C1.
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