JOYS+: Analyses of OCN

Springer Link (Chiba Institute of Technology)

Abstract

Context. Nitrogen-bearing molecules are generally more difficult to observe than oxygen-bearing ones in both gas and ice, mainly due to the lower abundance of nitrogen in the interstellar medium. Therefore, the formation pathways of many of these species is still under debate. Aims. Studies prior to the launch of the James Webb Space Telescope (JWST) did not have the sensitivity to observe ices toward the youngest and most deeply embedded Class 0 objects. The time is now ripe to study nitrogen-bearing molecules toward ice-rich Class 0 and Class I objects with the JWST. Here we focus on OCN−, CH3CN, C2H5CN, NO, and N2O in ices to better understand their formation. Methods. We used the data from JWST Observations of Young protoStars (JOYS+) program. Particularly, we studied the objects that have the JWST NIRSpec-IFU observations (8 Class 0 and 11 Class I) to measure the ice column densities of the targeted molecules. Results. We firmly detect OCN− in ices for all these objects, tentatively detect CH3CN, C2H5CN, and N2O toward three sources, and find upper limits on the NO abundance in ices. The OCN−/CO2 ratios are found to be higher by a factor of ~2–3 for the objects that have a visible CO2 (15.2 μm) double peak (a sign of ice thermal processing), which points to the moderate effect of temperature on OCN− production. Considering H2O, CO2, and OCN− relations with AV, we tentatively find that OCN− forms at a later stage compared to H2O and CO2. We find that the ratios of CH3CN, C2H5CN, and N2O with respect to OCN− are relatively constant within one order of magnitude across our objects, likely suggesting that they have similar ice environments. The upper limit abundances of NO are around one order of magnitude lower than what was previously predicted in ices of a mature protoplanetary disk to explain the gas-phase detection of this molecule in the disk. This indicates that gas-phase NO may be a product of another molecule such as N2O in the ices. Conclusions. We conclude that after OCN− forms, it can increase at higher temperatures by only a factor of ~2–3, and thus OCN− detection alone does not imply ice heating. Large-sample studies of OCN− toward pre-stellar cores will be useful to further confirm the formation timeline of this molecule.

Authors 14

1. Pooneh Nazari

   European Southern Observatory

   Affiliation as printed

   European Southern Observatory , Karl-Schwarzschild-Strasse 2 , 85748 Garching , Germany

2. N. G. C. Brunken Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , Netherlands

3. K. Slavicinska Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , Netherlands

4. Ewine F. van Dishoeck Aachen Leiden Observatory

   Leiden University · Max Planck Institute for Extraterrestrial Physics · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , Netherlands

   Max Planck Institut für Extraterrestrische Physik (MPE) , Giessenbachstrasse 1 , 85748 Garching , Germany

5. W.R.M. Rocha Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , Netherlands

6. Adwin C. A. Boogert

   University of Hawaiʻi at Mānoa

   Affiliation as printed

   Institute for Astronomy , University of Hawai'i at Manoa , 2680 Woodlawn Drive , Honolulu , HI 96822 , USA

7. M.G. Navarro

   Astronomical Observatory of Rome · National Institute for Astrophysics

   Affiliation as printed

   INAF-Osservatorio Astronomico di Roma , Via di Frascati 33 , 00078 Monte Porzio Catone , Italy

8. Valentin J. M. Le Gouellec

   Institute of Space Sciences · Institut d'Estudis Espacials de Catalunya

   Affiliation as printed

   Institut d'Estudis Espacials de Catalunya (IEEC) , c/ Gran Capitá , 2-4 , 08034 Barcelona , Spain

   Institut de Cienciès de l'Espai (ICE-CSIC) , Campus UAB , Carrer de Can Magrans S/N , E-08193 Cerdanyola del Vallès , Spain

9. Logan Francis Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , P.O. Box 9513 , 2300 RA Leiden , Netherlands

10. Łukasz Tychoniec
11. A. Caratti o Garatti

    Astronomical Observatory of Capodimonte

    Affiliation as printed

    INAF-Osservatorio Astronomico di Capodimonte , Salita Moiariello 16 , 80131 Napoli , Italy

12. C. Gieser

    Max Planck Institute for Astronomy

    Affiliation as printed

    Max Planck Institute for Astronomy , Königstuhl 17 , 69117 Heidelberg , Germany

13. T. P. Greene

    California Institute of Technology · Infrared Processing and Analysis Center

    Affiliation as printed

    IPAC , California Institute of Technology , MC 100-22 , 1200 E. California Blvd. , Pasadena , CA , 91125 , USA

14. Patrick J Kavanagh

    National University of Ireland, Maynooth

    Affiliation as printed

    Department of Physics , Maynooth University , Maynooth , Co. 13 Kildare , Ireland