J/ApJ/813/120 High-resolution obs. of CO isotopologues in YSOs (Smith+, 2015)
Heterogeneity in 12CO/13CO abundance ratios toward solar-type young
stellar objects.
Smith R.L., Pontoppidan K.M., Young E.D., Morris M.R.
<Astrophys. J., 813, 120 (2015)>
=2015ApJ...813..120S 2015ApJ...813..120S (SIMBAD/NED BibCode)
ADC_Keywords: YSOs ; Spectra, infrared
Keywords: astrochemistry; infrared: stars; molecular processes;
protoplanetary disks; stars: protostars; stars: solar-type
Abstract:
This study reports an unusual heterogeneity in
[12C16O]/[13C16O] abundance ratios of carbon monoxide observed
in the gas phase toward seven ∼solar-mass young stellar objects (YSOs)
and three dense foreground clouds in the nearby star-forming regions,
Ophiuchus, Corona Australis, Orion, and Vela, and an isolated core,
L43. Robust isotope ratios were derived using infrared absorption
spectroscopy of the 4.7µm fundamental and 2.3µm overtone
rovibrational bands of CO at very high spectral resolution
(λ/Δλ∼95000), observed with the Cryogenic Infrared
Echelle Spectrograph (CRIRES) on the Very Large Telescope. We find
[12C16O]/[13C16O] values ranging from ∼85 to 165,
significantly higher than those of the local interstellar medium (ISM)
(∼65-69). These observations are evidence for isotopic heterogeneity
in carbon reservoirs in solar-type YSO environments, and encourage the
need for refined galactic chemical evolution models to explain the
12C/13C discrepancy between the solar system and local ISM. The
oxygen isotope ratios are consistent with isotopologue-specific
photodissociation by CO self-shielding toward the disks, VV CrA N and
HL Tau, further substantiating models predicting CO self-shielding on
disk surfaces. However, we find that CO self-shielding is an unlikely
general explanation for the high [12C16O]/[13C16O] ratios
observed in this study. Comparison of the solid CO against gas-phase
[12C16O]/[13C16O] suggests that interactions between CO ice
and gas reservoirs need to be further investigated as at least a
partial explanation for the unusually high [12C16O]/[13C16O]
observed.
Description:
Data for all targets were obtained as part of a European Southern
Observatory Large Program to observe ∼100 YSOs and protoplanetary
disks with the Cryogenic Infrared Echelle Spectrograph (CRIRES) at the
Very Large Telescope (VLT) in Chile. The CRIRES instrument is an
adaptive optics (AO)-assisted spectrometer that operates at very high
spectral resolving power (λ/Δλ-95000).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 60 18 Summary of observed targets
table4.dat 51 363 Optical depths and Doppler shifts for CO isotopologue
rovibrational lines used in deriving column densities
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See also:
II/332 : c2d Spitzer final data release (DR4) (Evans+, 2003)
J/A+A/581/A30 : Herschel maps of ρ Oph (Rebollido+, 2015)
J/A+A/576/A109 : YSOs APEX-CHAMP+ high-J CO maps (Yildiz+, 2015)
J/ApJS/205/5 : YSO candidates in nearby molecular clouds (Hsieh+, 2013)
J/AJ/145/94 : Protostar luminosities from 2 Spitzer surveys (Dunham+, 2013)
J/ApJS/201/11 : Mid-IR spectral variability atlas of YSOs (Kospal+, 2012)
J/A+A/519/A34 : YSOs in DROXO (Deep rho Oph XMM obs.) (Pillitteri+, 2010)
J/AJ/140/1214 : NIR spectroscopic survey of class I YSOs (Connelley+, 2010)
J/ApJS/181/321 : Properties of Spitzer c2d dark clouds (Evans+, 2009)
J/ApJ/703/1964 : Spectra of three nearby star-forming regions (Furlan+, 2009)
J/ApJ/692/973 : Protostars in Perseus, Serpens and Ophiuchus (Enoch+, 2009)
J/A+A/498/167 : Embedded sources in L1688 (van Kempen+, 2009)
J/ApJ/678/985 : c2d Spitzer survey of interstellar ices. I. (Boogert+, 2008)
J/A+A/470/605 : Halpha & [SII] images in HL/XZ Tau region (Movsessian+, 2007)
J/A+A/441/181 : Interstellar 12C/13C ratios (Casassus+, 2005)
J/AJ/130/1733 : Optical spectroscopy of ρ Oph stars (Wilking+, 2005)
J/ApJ/566/993 : rho Oph (Lynds 1688) cluster NICMOS imaging (Allen+, 2002)
J/A+A/359/113 : X-ray and IR study of Rho Oph dark cloud (Grosso+, 2000)
J/ApJ/438/813 : Stellar population in ρ Oph cloud core (Strom+, 1995)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- ID Target identifier
8- 11 A4 --- m_ID [ ,NS] Target identifier components
13 A1 --- f_ID [a] Flag on Target (1)
15- 16 I2 h RAh Hour of Right Ascension (J2000)
18- 19 I2 min RAm Minute of Right Ascension (J2000)
21- 25 F5.2 s RAs Second of Right Ascension (J2000)
27 A1 --- DE- Sign of the Declination (J2000)
28- 29 I2 deg DEd Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 37 F4.1 arcsec DEs Arcsecond of Declination (J2000)
39- 43 F5.3 um lambda1 [2.2/4.8] Lower spectral range
44 A1 --- --- [-]
45- 49 F5.3 um lambda2 [2.3/5] Upper spectral range
51- 60 A10 "Y/M/D" Date Observation date
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Note (1):
a = The non-coevality of these observations may contribute some level of
uncertainty to the derived isotopic abundances, as discussed
in the text.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- ID Target identifier
9 A1 --- m_ID [NS] Target identifier component
11- 16 A6 --- Iso Isotopologue identifier (12C16O, 12C17O, 12C18O,
or 13C16O)
18- 28 A11 --- Trans Transition
30- 34 F5.3 --- tau [0.02/4.6] Optical depth
36- 40 F5.3 --- e_tau [0.001/0.2] The 1σ uncertainty in tau
42- 46 F5.2 km/s VLSR [-0.4/10] Local Standard of Rest doppler
shift velocity
48- 51 F4.2 km/s e_VLSR [0/1] The 1σ uncertainty in VLSR
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Feb-2016