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.
<Astron. Astrophys. 636, A54 (2020)>
=2020A&A...636A..54V 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☉) 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
Hα,β, [OI] 630.0nm, CaII infrared triplet, [FeII] 1643.5nm,
fluorescent FeII 1687.8nm, H2 2121.8nm, Brγ, 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 23 *A list of the VLT/X-shooter observations used
in the paper
sp/* . 22 Individual spectra
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Note on table1.dat: All observations were carried out under
ESO program 090.C-0346(A).
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See also:
J/other/Sci/359.69 : Massive stars in 30 Dor (Schneider+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Note (1): The object names are the same as defined by Walborn et al.
(2013AJ....145...98W 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
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 19 F19.14 nm lambda Wavelength
21- 44 E24.17 mW/m2 Flux Flux, lambda*Flambda (in erg/cm2/s)
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Acknowledgements:
Martijn van Gelder, vgelder(at)strw.leidenuniv.nl
(End) Martijn van Gelder [Leiden Obs.], Patricia Vannier [CDS] 13-Feb-2020