VLT/X-shooter spectroscopy of massive young stellar objects in the 30
  Doradus region of the Large Magellanic Cloud
  The process of massive star ($M\geq8~M_\odot$) formation is still poorly
understood. Observations of massive young stellar objects (MYSOs) are
challenging due to their rarity, short formation timescale, large distances,
and high circumstellar extinction. Here, we present the results of a
spectroscopic analysis of a population of MYSOs in the Large Magellanic Cloud
(LMC). We took advantage of the spectral resolution and wavelength coverage of
X-shooter (300-2500 nm), mounted on the European Southern Observatory Very
Large Telescope, to detect characteristic spectral features in a dozen MYSO
candidates near 30 Doradus, the largest starburst region in the Local Group
hosting the most massive stars known. The X-shooter spectra are strongly
contaminated by nebular emission. We used a scaling method to subtract the
nebular contamination from our objects. We detect H$\alpha,\beta$, [O I] 630.0
nm, Ca II infrared triplet, [Fe II] 1643.5 nm, fluorescent Fe II 1687.8 nm,
H$_2$ 2121.8 nm, Br$\gamma$, and CO bandhead emission in the spectra of
multiple candidates. This leads to the spectroscopic confirmation of 10
candidates as bona fide MYSOs. We compare our observations with photometric
observations from the literature and find all MYSOs to have a strong
near-infrared excess. We compute lower limits to the brightness and luminosity
of the MYSO candidates, confirming the near-infrared excess and the massive
nature of the objects. No clear correlation is seen between the Br$\gamma$
luminosity and metallicity. Combining our sample with other LMC samples results
in a combined detection rate of disk features such as fluorescent Fe II and CO
bandheads which is consistent with the Galactic rate (40\%). Most of our MYSOs
show outflow features.
