J/ApJ/900/104 IR high-res. sp. of hot cores of AFGL2591 & AFGL2136 (Barr+, 2020)
High-resolution infrared spectroscopy of hot molecular gas in AFGL 2591 and
AFGL 2136: accretion in the inner regions of disks around massive young stellar
objects.
Barr A.G., Boogert A., DeWitt C.N., Montiel E., Richter M.J., Lacy J.H.,
Neufeld D.A., Indriolo N., Pendleton Y., Chiar J., Tielens A.G.G. M
<Astrophys. J., 900, 104 (2020)>
=2020ApJ...900..104B 2020ApJ...900..104B
ADC_Keywords: Spectra, infrared; YSOs; Star Forming Region; Line Profiles;
Atomic physics; Interstellar medium
Keywords: Astrophysical processes ; Astrochemistry ; Chemical abundances ;
Star formation ; Star forming regions ; Interstellar line absorption ;
Infrared astronomy
Abstract:
We have performed a high-resolution 4-13µm spectral survey of the
hot molecular gas associated with the massive protostars AFGL 2591 and
AFGL 2136, utilizing the Echelon Cross Echelle Spectrograph (EXES) on
board the Stratospheric Observatory for Infrared Astronomy, and the
iSHELL instrument and Texas EchelonCross Echelle Spectrograph (TEXES)
on the NASA Infrared Telescope Facility (IRTF). Here we present the
results of this survey with analysis of CO, HCN, C2H2, NH3, and CS,
deriving the physical conditions for each species. Also from the IRTF,
iSHELL data at 3µm for AFGL 2591 are presented that show HCN and
C2H2 in emission. In the EXES and TEXES data, all species are detected
in absorption, and temperatures and abundances are found to be high
(600K and 10-6, respectively). Differences of up to an order of
magnitude in the abundances of transitions that trace the same
ground-state level are measured for HCN and C2H2. The mid-infrared
continuum is known to originate in a disk, hence we attribute the
infrared absorption to arise in the photosphere of the disk. As
absorption lines require an outwardly decreasing temperature gradient,
we conclude that the disk is heated in the midplane by viscous heating
due to accretion. We attribute the near-IR emission lines to
scattering by molecules in the upper layers of the disk photosphere.
The absorption lines trace the disk properties at 50 au where
high-temperature gas-phase chemistry is taking place. Abundances are
consistent with chemical models of the inner disk of Herbig disks.
Description:
AFGL 2591 VLA 3 and AFGL 2136 IRS1 were observed with the EXES
spectrometer on board the Stratospheric Observatory for Infrared
Astronomy (SOFIA) flying observatory as part of SOFIA program 05_0041.
Observations span 2017 Mar 17 to 2019 Apr 26 with R=55000 resolution.
AFGL 2591 and AFGL 2136 were also observed with iSHELL at the IRTF
telescope on Maunakea at a spectral resolving power of 80000.
See Section 2.4.
Objects:
----------------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------------
20 29 24.8 +40 11 19.6 AFGL 2591 VLA3 = AFGL 2591
18 22 26.385 -13 30 11.97 AFGL 2136 IRS1 = AFGL 2136
----------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table4.dat 112 168 Line parameters for AFGL 2591 VLA3
table5.dat 112 200 Line parameters for AFGL 2136 IRS1
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See also:
J/ApJ/696/471 : MIR spectroscopy of NGC 7538 IRS 1 (Knez+, 2009)
J/MNRAS/420/1656 : RMS compact HII regions distances (Urquhart+, 2012)
J/A+A/558/A24 : The VLTI/MIDI survey of Massive YSOs (Boley+, 2013)
J/MNRAS/430/1125 : RMS survey: NIR spectroscopy of massive YSOs (Cooper+, 2013)
J/A+A/551/A43 : AFGL 2591 multi-wavelength maps (Johnston+, 2013)
J/ApJS/208/11 : Red MSX Source Survey: massive protostars (Lumsden+, 2013)
J/MNRAS/437/1791 : RMS survey: molecular observations (Urquhart+, 2014)
J/A+A/620/A31 : ALMA maps of G17.64+0.16 (Maud+, 2018)
J/A+A/627/L6 : ALMA Long Baseline maps of G17.64+0.16 (Maud+, 2019)
Byte-by-byte Description of file: table[45].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 28 A28 --- Sp Species (1)
30- 46 A17 --- Tr Transition (1)
48- 54 F7.4 um lambda [2.98/13.71] Wavelength (1)
56- 61 F6.1 K El [0/5305] Energy of the lower level of the
transition (1)
63- 65 I3 --- gl [1/414] Statistical weight of the lower level (1)
67- 70 F4.1 s-1 Aij [0.7/68.2] Einstein A coefficient of the
transition (1)
72- 76 F5.1 km/s vlsr [-22.2/32.5] Centroid velocity of the line
78- 80 F3.1 km/s e_vlsr [0.1/1.4] Uncertainty in vlsr
82- 85 F4.1 km/s dV [1.5/15.2] FWHM of line
87- 89 F3.1 km/s e_dV [0/4.2]? Uncertainty in dV
91- 95 F5.3 --- t0 [0.008/0.7] Optical depth at line center
97- 101 F5.3 --- e_t0 [0.001/0.07] Uncertainty in t0
103- 107 F5.1 10-7 Nl/NH [0.5/222.3]? Abundance in the lower level of
the transition
109- 112 F4.1 10-7 e_Nl/NH [0.1/71.6]? Uncertainty in Nl/NH
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Note (1): Line data were taken from the HITRAN database
(Gordon+ 2017JQSRT.203....3G 2017JQSRT.203....3G).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Dec-2021