J/A+A/666/A26 L-band spectra of 10 massive young stellar objects (Barr+, 2022)
Surveying the inner structure of massive young stellar objects using
L-band spectroscopy.
Barr A., Li J., Boogert A., Lee A., DeWitt C., Tielens A.
<Astron. Astrophys. 666, A26 (2022)>
=2022A&A...666A..26B 2022A&A...666A..26B (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Spectra, infrared
Keywords: astrochemistry - stars: formation - circumstellar matter
Abstract:
We present results from a high spectral resolution (6 km s-1) survey
of five massive protostars in the wavelength range of 2.95 and 3.25um,
conducted with iSHELL at the InfraRed Telescope Facility (IRTF). Our
targets are Mon R2 IRS 2, Mon R2 IRS 3, AFGL 2136, Orion BN and S140
IRS 1. Two of our five targets (Mon R2 IRS 3 and AFGL 2136) show
transitions from organic species, with MonR2 IRS 3 showing HCN lines
in emission, and AFGL 2136 showing HCN and C2H2 lines in absorption.
The velocity of the emission lines of HCN of MonR2 IRS 3A are
consistent with CO emission features in lines up to J=26, as both are
red-shifted with respect to the systemic velocity. Carbon monoxide
lines also show blue-shifted absorption. This P-Cygni line profile,
commonly observed towards massive young stellar objects, is likely due
to an expanding shell, which is supported by sub-millimetre velocity
maps of HCN. Alternatively HCN emission may arise from the upper
layers of a disk photosphere, as has been suggested for the massive
protostar AFGL 2591. Absorption lines in AFGL 2136 may either
originate in foreground cloud or in the disk photosphere. For a
foreground cloud, the data require that the foreground gas only covers
the source partially (0.3) at 13um. In contrast, absorption lines at 3
and 7um require a covering factor of >0.9. Analysing the 13um HCN
absorption lines in terms of absorption by gas in the photosphere of a
disk, results in physical conditions that are consistent over all
three vibrational modes. C2H2 absorption lines reveal an
increasing temperature and abundance with decreasing wavelength,
indicative of a radial abundance gradient. We conclude that the disk
model is the best interpretation of the absorption lines of AFGL 2136.
Description:
All objects were observed as part of program 2021A095 with iSHELL
(Rayner et al. 2016, SPIE, 9908, 990884) at the Infrared Telescope
Facility (IRTF) on Mauna kea. Observations were taken in the L2 mode,
at a resolving power of 50000 (6km/s), using a slit with of 0.75".
Targets were nodded along the slit to allow for subtraction of sky and
telescope emission. The extracted A and B spectra were then averaged.
The continuum signal-to-noise (S/N) values per resolution element were
>300 for all sources except AFGL 2136 for which only a S/N of 100 was
achieved. Flat fields for both science target and standard stars were
taken using iSHELL's internal lamp.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 72 10 List of spectra
sp/* . 10 Individual spectra
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Simbad name
21- 22 I2 h RAh Right ascension (J2000)
24- 25 I2 min RAm Right ascension (J2000)
27- 31 F5.2 s RAs Right ascension (J2000)
33 A1 --- DE- Declination sign (J2000)
34- 35 I2 deg DEd Declination (J2000)
37- 38 I2 arcmin DEm Declination (J2000)
40- 43 F4.1 arcsec DEs Declination (J2000)
45- 49 I5 --- N Number of lines in spectrum
51- 72 A22 --- FileName Name of the spectrum file in subdirectory sp
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Byte-by-byte Description of file (#): sp/*
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Bytes Format Units Label Explanations
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8- 16 F9.7 um lambda Wavelength
21- 34 E14.8 10mW/m2/nm Flux Flux (in erg/s/cm2/Å)
40- 52 E13.8 10mW/m2/nm e_Flux Flux error (in erg/s/cm2/Å)
60- 70 F11.7 --- Flag Flag
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Acknowledgements:
Andrew Barr, barr(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 23-Aug-2022