Spitzer View of Young Massive Stars in the LMC HII Complexes. II. N159
  The HII complex N159 in the Large Magellanic Cloud (LMC) is used to study
massive star formation in different environments, as it contains three giant
molecular clouds (GMCs) that have similar sizes and masses but exhibit
different intensities of star formation. We identify candidate massive young
stellar objects (YSOs) using infrared photometry, and model their SEDs to
constrain mass and evolutionary state. Good fits are obtained for less evolved
Type I, I/II, and II sources. Our analysis suggests that there are massive
embedded YSOs in N159B, a maser source, and several ultracompact HII regions.
Massive O-type YSOs are found in GMCs N159-E and N159-W, which are associated
with ionized gas, i.e., where massive stars formed a few Myr ago. The third
GMC, N159-S, has neither O-type YSOs nor evidence of previous massive star
formation. This correlation between current and antecedent formation of massive
stars suggests that energy feedback is relevant. We present evidence that
N159-W is forming YSOs spontaneously, while collapse in N159-E may be
triggered. Finally, we compare star formation rates determined from YSO counts
with those from integrated H-alpha and 24 micron luminosities and expected from
gas surface densities. Detailed dissection of extragalactic GMCs like the one
presented here is key to revealing the physics underlying commonly used star
formation scaling laws.
