J/ApJ/813/120 High-resolution obs. of CO isotopologues in YSOs (Smith+, 2015) ================================================================================ Heterogeneity in ^12^CO/^13^CO abundance ratios toward solar-type young stellar objects. Smith R.L., Pontoppidan K.M., Young E.D., Morris M.R. =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 [^12^C^16^O]/[^13^C^16^O] 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 4.7{mu}m fundamental and 2.3{mu}m overtone rovibrational bands of CO at very high spectral resolution ({lambda}/{Delta}{lambda}~95000), observed with the Cryogenic Infrared Echelle Spectrograph (CRIRES) on the Very Large Telescope. We find [^12^C^16^O]/[^13^C^16^O] 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 ^12^C/^13^C 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 [^12^C^16^O]/[^13^C^16^O] ratios observed in this study. Comparison of the solid CO against gas-phase [^12^C^16^O]/[^13^C^16^O] suggests that interactions between CO ice and gas reservoirs need to be further investigated as at least a partial explanation for the unusually high [^12^C^16^O]/[^13^C^16^O] 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 ({lambda}/{Delta}{lambda}-95000). File Summary: -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- See also: II/332 : c2d Spitzer final data release (DR4) (Evans+, 2003) J/A+A/581/A30 : Herschel maps of {rho} 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 ^12^C/^13^C ratios (Casassus+, 2005) J/AJ/130/1733 : Optical spectroscopy of {rho} 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 {rho} 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 -------------------------------------------------------------------------------- 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 1{sigma} 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 1{sigma} uncertainty in VLSR ------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Feb-2016