$\vec {HST}$ observations of the LMC compact H II region N 11A

Abstract

Abstract. We present a study of the LMC compact H ii region N 11A using Hubble Space Telescope imaging observations which resolve N 11A and reveal its unknown nebular and stellar features. The presence of a sharp ionization front extending over more than 4 (1 pc) and fine structure filaments as well as larger loops indicate an environment typical of massive star formation regions, in agreement with high [O iii]/Hβ line ratios. N 11A is a young region, as deduced from its morphology, reddening, and especially high local concentration of dust, as indicated by the Balmer decrement map. Our observations also reveal a cluster of stars lying towards the central part of N 11A. Five of the stars are packed in an area less than 2 (0.5 pc), with the most luminous one being a mid O type star. N 11A appears to be the most evolved compact H ii region in the Magellanic Clouds so far studied.

C+emission from the Magellanic Clouds

“…Three O3 stars have been identified in the LH 10 association ). An even younger compact object, N 11A (IC 2116, Mac Low et al 1998Nazé et al 2001;Heydari-Malayeri et al 2001), occurs in the same area. The location and apparent age difference of LH 10 and LH 9, as well as the gas kinematics, have led to the suggestion that the formation of LH 10 and other stellar groups was triggered by the expanding shells emanating from LH 9 Rosado et al 1996;Barba et al 2003;Hatano et al 2006;Mokiem et al 2007).…”

$\vec{HST}$ study of the LMC compact star-forming region N83B

“…#29 and #28, may have been triggered by the eastward expansion of the shell nebula according to the sequential star formation model (Elmegreen & Lada 1977). There are many cases in the literature for which this mechanism has been put forward to explain the observations, in particular that of the SMC H ii region N88A (Heydari-Malayeri et al 1999b).…”

“…At the distance of the Magellanic Clouds this corresponds to sizes of more than 50 pc for normal H ii regions and 1 to 3 pc for the blobs. HEBs are in fact associated with young massive stars just leaving their pre-natal molecular cloud (see Heydari-Malayeri et al 1999c for references). Paper I investigated several physical characteristics of N83B-1, such as the emission spectrum, excitation, extinction, gas density, chemical composition, abundances, etc.…”

Active Star Formation in the N11B Nebula in the Large Magellanic Cloud: A Sequential Star Formation Scenario Confirmed

“…These authors proposed that the nebular morphology of N11A is a good example of the champagne model (Tenorio-Tagle 1979;Bodenheimer et al 1979), in the stage when the newborn stars disrupt the molecular cavity. Small nebular emission filaments discovered by Heydari-Malayeri et al (2001) are located on the south-west border of the nebular knot, and show arcs pointing toward the direction where the CO emission has a sharp edge, indicating an abrupt drop of the molecular gas density. This morphology suggests that the compact group of stars could be blowing this side of its stellar nursery, in a similar morphological picture to that seen towards Knot 1 in the 30 Dor Nebula (Rubio et al 1998;Walborn et al 1999a;Walborn, Maíz-Apellániz & Barbá 2002).…”

“…In the case of N11A, the optical compact group of stars is visible indicating that the molecular cloud lies behind the stars and that they have evacuated a cavity towards our line of sight. This conclusion is supported by the fact that the O star has a relatively low reddening, A V = 0.6, probably due only to dust mixed with the ionised gas (Heydari-Malayeri et al 2001). These authors proposed that the nebular morphology of N11A is a good example of the champagne model (Tenorio-Tagle 1979;Bodenheimer et al 1979), in the stage when the newborn stars disrupt the molecular cavity.…”