Mirror, mirror on the outflow cavity wall. Near-infrared CO overtone disc emission of the high-mass YSO IRAS 11101-5829

Abstract

Aims: The inner regions of high-mass protostars are often invisible in the near-infrared. We aim to investigate the inner gaseous disc of IRAS11101-5829 through scattered light from the outflow cavity walls. Methods: We observed the environment of the high-mass young stellar object IRAS11101-5829 and the closest knots of its jet, HH135-136, with the VLT/SINFONI. We also retrieved archival data from the high-resolution long-slit spectrograph VLT/X-shooter. Results: We detect the first three bandheads of the $\upsilon =2-0$ CO vibrational emission for the first time in this object. It is coincident with continuum and Br$\gamma$ emission and extends up to $\sim 10000$ au to the north-east and $\sim 10000$ au to the south-west. The line profiles have been modelled as a Keplerian rotating disc assuming a single ring in LTE. The model output gives a temperature of $\sim 3000$ K, a CO column density of $\sim 1\times 10^{22}\mathrm{c}{\mathrm{m}}^{-2}$, and a projected Keplerian velocity $v_{\mathrm{K}}\sin i_{\mathrm{disc}}\sim 25\mathrm{km}{\mathrm{s}}^{-1}$, which is consistent with previous modelling in other high-mass protostars. In particular, the low value of $v_{\mathrm{K}}\sin i_{\mathrm{disc}}$ suggests that the disc is observed almost face-on, whereas the well-constrained geometry of the jet imposes that the disc must be close to edge-on. This apparent discrepancy is interpreted as the CO seen reflected in the mirror of the outflow cavity wall. Conclusions: From both jet geometry and disc modelling, we conclude that all the CO emission is seen through reflection by the cavity walls and not directly. This result implies that in the case of highly embedded objects, as for many high-mass protostars, line profile modelling alone might be deceptive and the observed emission could affect the derived physical and geometrical properties; in particular the inclination of the system can be incorrectly interpreted.

arXiv comment11 pages, 10 figures

References in corpus (23)

• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• X-shooter, the new wide band intermediate resolution spectrograph at the ESO Very Large Telescope
• SINFONI - Integral Field Spectroscopy at 50 milli-arcsecond resolution with the ESO VLT
• The inner regions of protoplanetary disks
• A disk of dust and molecular gas around a high-mass protostar
• Accretion disks in luminous young stellar objects
• A hot compact dust disk around a massive young stellar object
• A Near-Infrared Spectroscopic Survey of Class I Protostars
• A candidate circumbinary Keplerian disk in G35.20-0.74 N: A study with ALMA
• Evidence for an inner molecular disk around massive Young Stellar Objects
• VLT K-band spectroscopy of massive young stellar objects in (ultra-)compact HII regions
• The circumstellar disk, envelope, and bi-polar outflow of the Massive Young Stellar Object W33A
• The RMS Survey: Near-IR Spectroscopy of Massive Young Stellar Objects
• CO bandhead emission of massive young stellar objects: determining disc properties
• Investigating the inner discs of Herbig Ae/Be stars with CO bandhead and Br Gamma emission
• The first bird's-eye view of a gravitationally unstable accretion disk in high-mass star formation
• Tracing jet emission at the base of a high-mass YSO. First AMBER/VLTI observations of the Brγemission in IRAS 13481-6124
• Measuring the ionisation fraction in a jet from a massive protostar
• Exploring the dimming event of RW Aur A through multi-epoch VLT/X-Shooter spectroscopy
• HH135/HH136 - a luminous H${}_2$ outflow towards a high-mass protostar
• Blinded by the light: on the relationship between CO first overtone emission and mass accretion rate in massive young stellar objects
• Simultaneous monitoring of the photometric and polarimetric activity of the young star PV Cep in the optical/near-infrared bands