Heterogeneity in ${}^{12}$CO/${}^{13}$CO Ratios Toward Solar-Type Young Stellar Objects

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 YSOs and three dense foreground clouds in the nearby star-forming regions, Ophiuchus, Corona Australis, Orion, 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 resolution ($\lambda$/$\Delta$$\lambda \approx 95,000$), observed with the CRIRES spectrograph on the Very Large Telescope. We find [${}^{12}$C${}^{16}$O]/[${}^{13}$C${}^{16}$O] values ranging from ~ 85 to 165, significantly higher than those of the local interstellar medium (~ 65 to 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.

16 pages, 14 figures, 7 tables. Accepted for publication in The Astrophysical Journal

References in corpus (10)

• The COMPLETE Survey of Star-Forming Regions: Phase I Data
• Spectro-astrometric imaging of molecular gas within protoplanetary disk gaps
• Desorption of CO and O2 interstellar ice analogs
• Spatial mapping of ices in the Oph-F core: A direct measurement of CO depletion and the formation of CO2
• Laboratory H2O:CO2 ice desorption data: entrapment dependencies and its parameterization with an extended three-phase model
• The nature of the Class I population in Ophiuchus as revealed through gas and dust mapping
• Galactic interstellar 18O/17O ratios - a radial gradient?
• Line formation in solar granulation VII. CO lines and the solar C and O isotopic abundances
• High-precision C17O, C18O and C16O measurements in young stellar objects: analogues for CO self-shielding in the early solar system
• Dynamical Stability of Imaged Planetary Systems in Formation: Application to HL Tau

Cited by in corpus (34)

• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• The ALMA-PILS survey: Isotopic composition of oxygen-containing complex organic molecules toward IRAS 16293-2422B
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• The 13O-rich atmosphere of a young accreting super-Jupiter
• Sulfur chemistry in protoplanetary disks: CS and H2CS
• Scanning disk rings and winds in CO at 0.01-10 au: a high-resolution $M$-band spectroscopy survey with IRTF-iSHELL
• The 12CO/13CO isotopologue ratio of a young, isolated brown dwarf. Possibly distinct formation pathways of super-Jupiters and brown dwarfs
• 13C17O suggests gravitational instability in the HL Tau disc
• Multiple nitrogen reservoirs in a protoplanetary disk at the epoch of comet and giant planet formation
• The ESO SupJup Survey I: Chemical and isotopic characterisation of the late L-dwarf DENIS J0255-4700 with CRIRES${}^{+}$
• Radiation thermo-chemical models of protoplanetary disks. Grain and polycyclic aromatic hydrocarbon charging
• An unbiased spectral line survey observation toward the low-mass star-forming region L1527
• A new method for direct measurement of isotopologue ratios in protoplanetary disks: a case study of the ${}^{12}$CO/${}^{13}$CO ratio in the TW Hya disk
• 1000 AU Exterior Arcs Connected to the Protoplanetary Disk around HL Tau
• Implications of Captured Interstellar Objects for Panspermia and Extraterrestrial Life
• Feeding cosmic star formation: Exploring high-redshift molecular gas with CO intensity mapping
• JOYS+ study of solid state ${}^{12}$C/${}^{13}$C isotope ratios in protostellar envelopes: Observations of CO and CO${}_2$ ice with JWST
• Unusual Isotopic Abundances in a Fully-Convective Stellar Binary
• Interstellar Now! Missions to and Sample Returns from Nearby Interstellar Objects
• Physical and Chemical Conditions of the Protostellar Envelope and the Protoplanetary Disk in HL Tau
• Depletion and fractionation of nitrogen in collapsing cores
• IGRINS spectroscopy of Class I sources: IRAS 03445+3242 and IRAS 04239+2436
• High-Resolution Mid-Infrared Spectroscopy of GV Tau N: Surface Accretion and Detection of Ammonia in a Young Protoplanetary Disk
• Water UV-Shielding in the Terrestrial Planet-Forming Zone: Implications for Oxygen-18 Isotope Anomalies in H2-18O Infrared Emission and Meteorites
• Star Cluster Formation in Orion A
• 3D modelling of HCO${}^{+}$ and its isotopologues in the low-mass proto-star IRAS16293$-$2422
• Signs of outflow feedback from a nearby young stellar object on the protostellar envelope around HL Tau
• Carbon Isotope Fractionation of Complex Organic Molecules in Star-Forming Cores
• Can Isotopologues Be Used as Biosignature Gases in Exoplanet Atmospheres?
• A CO-to-H${}_2$ ratio of $\approx 10^{-5}$ towards the Herbig Ae star HK Ori
• Tracking the evolutionary stage of protostars by the abundances of astrophysical ices
• The Wanderer: Charting WASP-77A b's Formation and Migration Using a System-Wide Inventory of Carbon and Oxygen Abundances
• Protoplanetary Disk Chemistry
• Setting the Stage: The Early History of the Solar System