J/A+A/636/A54 Massive young stellar objects in 30 Doradus (van Gelder+, 2020) ================================================================================ VLT/X-shooter spectroscopy of massive young stellar objects in the 30 Doradus region of the Large Magellanic Cloud. van Gelder M.L., Kaper L., Japelj J., Ramirez-Tannus M.C., Ellerbroek L.E., Barba R.H., Bestenlehner J.M., Bik A., Graefener G., de Koter A., de Mink S.E., Sabbi E., Sana H., Sewilo M., Vink J.S., Walborn N.R. =2020A&A...636A..54V (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Stars, pre-main sequence ; YSOs ; Stars, OB ; Spectroscopy Keywords: stars: formation - stars: pre-main sequence - stars: massive - HII regions - galaxies: clusters: individual: 30 Doradus - Magellanic Clouds Abstract: The process of massive star (M>=8M_{sun}_) 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 (300-2500nm), which is 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}, [OI] 630.0nm, CaII infrared triplet, [FeII] 1643.5nm, fluorescent FeII 1687.8nm, H_2_ 2121.8nm, Br{gamma}, and CO bandhead emission in the spectra of multiple candidates. This leads to the spectroscopic confirmation of ten candidates as bona fide MYSOs. We compared our observations with photometric observations from the literature and find all MYSOs to have a strong near-infrared excess. We computed 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. Description: X-shooter spectra of massive YSOs in 30 Doradus are studied. The X-shooter spectra have been taken under medium-good weather conditions with seeing ranging from about 0.7" to 2". Our spectra were taken in nodding mode, splitting the integration time of each observation (except R135 and S3-K) into 4 nodding observations of each 670 s, 700 s, and 50 s for the UVB, VIS, and NIR arms, respectively. Given their brightness, the observation in the VIS arm was split into two for R135, S3-K, and S5. The slit length was 11" for each arm, and the width was 1.0", 0.9" and 0.6" for the UVB, VIS and NIR arms, respectively. This results in a resolving power of 5100, 8800 and 8100, respectively. For the objects S1, S3-K, S4, S5, S6, S8, and R135, a slit width of 0.4" was used in the NIR arm which corresponds to a resolving power of 11300. Unfortunately the atmospheric dispersion corrector was not working during our observations. The data were reduced using the X-shooter Workflow for Physical Mode Date Reduction version 2.9.3, implemented on ESO-Reflex version 2.8. The corrected spectra were for telluric features using the software tool molecfit version 1.2.0. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 100 23 *A list of the VLT/X-shooter observations used in the paper sp/* . 22 Individual spectra -------------------------------------------------------------------------------- Note on table1.dat: All observations were carried out under ESO program 090.C-0346(A). -------------------------------------------------------------------------------- See also: J/other/Sci/359.69 : Massive stars in 30 Dor (Schneider+, 2018) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Object Object name (1) 10- 11 I2 h RAh Right ascension (J2000) 13- 14 I2 min RAm Right ascension (J2000) 16- 20 F5.2 s RAs Right ascension (J2000) 22 A1 --- DE- Declination sign (J2000) 23- 24 I2 deg DEd Declination (J2000) 26- 27 I2 arcmin DEm Declination (J2000) 29- 33 F5.2 arcsec DEs Declination (J2000) 34 A1 --- n_pos [abc] Note on Pos (2) 36- 45 A10 "date" Obs.Date Observation date 47- 51 A5 s ExptimeU UVB exposure time 53- 57 A5 s ExptimeV VIS exposure time 59- 62 A4 s ExptimeN NIR exposure time 64- 66 F3.1 arcsec Seeing Seeing 68- 87 A20 --- Rem Remarks 89-100 A12 --- FileName Name of the spectrum file in subdirectory sp -------------------------------------------------------------------------------- Note (1): The object names are the same as defined by Walborn et al. (2013AJ....145...98W), [WBS2013] SNNA in Simbad, where we introduced additional letters if multiple or additional objects were identified on the X-shooter slit. Note (2): Note on position as follows: a = Position of S5-E b = Position of S10-A c = Position of S10-SW-A -------------------------------------------------------------------------------- Byte-by-byte Description of file: sp/* -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 F19.14 nm lambda Wavelength 21- 44 E24.17 mW/m2 Flux Flux, lambda*F_lambda_ (in erg/cm^2^/s) -------------------------------------------------------------------------------- Acknowledgements: Martijn van Gelder, vgelder(at)strw.leidenuniv.nl ================================================================================ (End) Martijn van Gelder [Leiden Obs.], Patricia Vannier [CDS] 13-Feb-2020