VLT/NACO near-infrared imaging and spectroscopy of N88A in the SMC
  We present near-infrared imaging and spectroscopic high spatial resolution
observations of the SMC region N88 containing the bright, excited, extincted
and compact H II region N88A of size ~ 1 pc. To investigate its stellar content
and reddening, N88 was observed using spectroscopy and imagery in the JHKs- and
L'-band at a spatial resolution of ~ 0.1-0.3", using the VLT UT4 equipped with
the NAOS adaptive optics system. In order to attempt to establish if the origin
of the infra-red (IR) excess is due to bright nebulosity, circumstellar
material and/or local dust, we used Ks vs J-K colour-magnitude (CM) and JHK
colour-colour (CC) diagrams, as well as L' imagery.Our IR-data reveal in the
N88 area an IR-excess fraction of geq 30 per cent of the detected stars,as well
as an unprecedently detailed morphology of N88A. It consists of an embedded
cluster of ~3.5" (~ 1 pc) in diameter, of at least thirteen resolved stars
superposed with an unusual bright continuum centered on a very bright star. The
four brightest stars in this cluster lie red-ward of H-K geq 0.45 mag, and
could be classified as young stellar object (YSO) candidates. Four other
probable YSO candidates are also detected in N88 along a south-north bow-shaped
thin H2 filament at ~ 7" east of the young central bright star. At 0.2" east of
this star, a heavily embedded core is detected that could be a massive class I
protostar candidate. The 2.12 mu H2 image of N88A resembles a shell of diameter
~ 3" ~ 0.9 pc) centered on the bright star. The line ratios of H2 2-1 S(1) and
1-0 S(0) relative to 1-0 S(1), as well as the presence of high v lines, are
indicative of photodissociation regions, rather than shocks.
