Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system

Abstract

Context: Hydrides of the most abundant heavier elements are fundamental molecules in cosmic chemistry. Some of them trace gas irradiated by UV or X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a prototypical region of high-mass star formation. Methods: W3 IRS5 was observed by HIFI on the Herschel Space Observatory with deep integration (about 2500 s) in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines are found mostly in absorption, but also appear to exhibit weak emission (P-Cyg-like). Emission requires high density, thus originates most likely near the protostar. This is corroborated by the absence of line shifts relative to the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong absorption components at a velocity shifted relative to W3 IRS5, which are attributed to foreground clouds. Conclusions: The molecular column densities derived from observations correlate well with the predictions of a model that assumes the main emission region is in outflow walls, heated and irradiated by protostellar UV radiation.

arXiv commentAstronomy and Astrophysics Letters, in press

References in corpus (16)

• Interstellar OH+, H2O+ and H3O+ along the sight-line to G10.6-0.4
• Herschel/HIFI observations of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction
• X-ray chemistry in envelopes around young stellar objects
• First interstellar detection of OH+
• Physical-chemical modeling of the low-mass protostar IRAS 16293-2422
• Detection of interstellar oxidaniumyl: abundant H2O+ towards the star-forming regions DR21, Sgr B2, and NGC6334
• Multidimensional chemical modelling, II. Irradiated outflow walls
• Water in massive star-forming regions: HIFI observations of W3 IRS5
• Subarcsecond mid-infrared and radio observations of the W3 IRS5 protocluster
• Strong CH+ J=1-0 emission and absorption in DR21
• Millimeter interferometry of W3 IRS5: A Trapezium in the making
• Herschel-HIFI detections of hydrides towards AFGL 2591 (Envelope emission versus tenuous cloud absorption)
• Influence of UV radiation from a massive YSO on the chemistry of its envelope
• Tracing high energy radiation with molecular lines near deeply embedded protostars
• Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sgr B2(M)
• Variations in H2O+/H2O ratios toward massive star-forming regions

Cited by in corpus (47)

• 2021 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• 2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• Interstellar water chemistry: from laboratory to observations
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• The Chemistry of Interstellar OH+, H2O+, and H3O+: Inferring the Cosmic Ray Ionization Rates from Observations of Molecular Ions
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• Astrochemistry of dust, ice and gas: introduction and overview
• Interstellar Hydrides
• Submillimeter absorption from SH+, a new widespread interstellar radical, 13CH+ and HCl
• The chemistry of ions in the Orion Bar I. - CH+, SH+, and CF+: The effect of high electron density and vibrationally excited H2 in a warm PDR surface
• [CII] absorption and emission in the diffuse interstellar medium across the Galactic Plane
• Discovery of interstellar mercapto radicals (SH) with the GREAT instrument on SOFIA
• X-ray impact on the protoplanetary disks around T Tauri stars
• Water in massive star-forming regions: HIFI observations of W3 IRS5
• Abundances of sulphur molecules in the Horsehead nebula. First NS+ detection in a photodissociation region
• Spatially extended OH+ emission from the Orion Bar and Ridge
• Herschel-HIFI detections of hydrides towards AFGL 2591 (Envelope emission versus tenuous cloud absorption)
• Observational evidence for dissociative shocks in the inner 100 AU of low-mass protostars using Herschel-HIFI
• OH+ in astrophysical media: state-to-state formation rates, Einstein coefficients and inelastic collision rates with He
• WISH VI. Constraints on UV and X-ray irradiation from a survey of hydrides in low- to high-mass YSOs
• Tracing the sources of cosmic rays with molecular ions
• First Results of an ALMA Band 10 Spectral Line Survey of NGC 6334I: Detections of Glycolaldehyde (HC(O)CH${}_2$OH) and a New Compact Bipolar Outflow in HDO and CS
• H3O+ Line Emission from Starbursts and AGNs
• Variations in H2O+/H2O ratios toward massive star-forming regions
• Unusual Low Temperature Reactivity of Water. The CH + H2O Reaction as a Source of Interstellar Formaldehyde?
• Formation of interstellar SH${}^{+}$ from vibrationally excited H${}_2$: Quantum study of S${}^{+}$ + H${}_2$ $\rightleftarrows$ SH${}^{+}$ + H reactions and inelastic collisions
• Unveiling the chemistry of interstellar CH: Spectroscopy of the 2 THz $N=2\leftarrow 1$ ground state line
• Rotational spectrum of molecular ion NH^+ as a probe for alpha- and m_e/m_p-variation
• Rovibrationally-Resolved Photodissociaton of SH${}^{+}$
• First hyperfine resolved far-infrared OH spectrum from a star-forming region
• Detection of CH+, SH+, and their 13C- and 34S- isotopologues toward PKS1830-211
• The ionization rates of galactic nuclei and disks from Herschel/HIFI observations of water and its associated ions
• The GADOT Galaxy Survey: Dense Gas and Feedback in Herschel-Selected Starburst Galaxies at Redshifts 2 to 6
• Revised spectroscopic parameters of SH${}^{+}$ from ALMA and IRAM 30 m observations
• Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds
• Searches for Interstellar HCCSH and H${}_2$CCS
• The Herschel-HIFI view of mid-IR quiet massive protostellar objects
• The role of highly vibrationally excited H2 initiating the N chemistry: Quantum study and 3-sigma detection of NH emission in the Orion Bar PDR
• Hyperfine excitation of SH${}^{+}$ by H
• Electron-impact excitation of diatomic hydride cations II: OH${}^{+}$ and SH${}^{+}$
• Sensitivity of the isotopologues of hydronium to variation of the electron-to-proton mass ratio
• Molecular tracers of radiative feedback in Orion (OMC-1). Widespread CH+ (J=1-0), CO (10-9), HCN (6-5), and HCO+ (6-5) emission
• The first results from the Herschel-HIFI mission
• An accurate set of H${}_3$O${}^{+}-$ H${}_2$ collisional rate coefficients for non-LTE modelling of warm interstellar clouds
• Population of ground and lowest excited states of Sulfur via the dissociative recombination of SH+ in the diffuse interstellar medium
• High Resolution Laboratory Spectroscopy
• Ionic photofragmentation cross sections of the HS+ H2S+ and HCl+ molecular ions near the 2p threshold