Unveiling the near-infrared structure of the massive-young stellar object NGC 3603 IRS 9A with sparse aperture masking and spectroastrometry

Abstract

Contemporary theory holds that massive stars gather mass during their initial phases via accreting disk-like structures. However, conclusive evidence for disks has remained elusive for the most massive young objects. This is mainly due to significant observational challenges. Incisive studies, even targeting individual objects, are therefore relevant to the progression of the field. NGC 3603 IRS 9A* is a young massive stellar object still surrounded by an envelope of molecular gas. Previous mid-infrared observations with long-baseline interferometry provided evidence for a disk of 50 mas diameter at its core. This work aims at a comprehensive study of the physics and morphology of IRS 9A at near-infrared wavelengths. New sparse aperture masking interferometry data taken with NACO/VLT at Ks and Lp filters were obtained and analysed together with archival CRIRES spectra of the H2 and BrG lines. The calibrated visibilities recorded at Ks and Lp bands suggest the presence of a partially resolved compact object of 30 mas at the core of IRS 9A, together with the presence of over-resolved flux. The spectroastrometric signal of the H2 line shows that this spectral feature proceeds from the large scale extended emission (300 mas) of IRS 9A, while the BrG line appears to be formed at the core of the object (20 mas). This scenario is consistent with the brightness distribution of the source for near- and mid-infrared wavelengths at various spatial scales. However, our model suffers from remaining inconsistencies between SED modelling and the interferometric data. Moreover, the BrG spectroastrometric signal indicates that the core of IRS 9A exhibits some form of complexity such as asymmetries in the disk. Future high-resolution observations are required to confirm the disk/envelope model and to flesh out the details of the physical form of the inner regions of IRS 9A.

Accepted to be published in Astronomy & Astrophysics, 13 pages, 14 figures

References in corpus (10)

• Spectro-astrometric imaging of molecular gas within protoplanetary disk gaps
• A hot compact dust disk around a massive young stellar object
• Protostellar Outflows and Radiative Feedback from Massive Stars
• The VLTI/MIDI survey of massive young stellar objects - Sounding the inner regions around intermediate- and high-mass young stars using mid-infrared interferometry
• Observing Simulated Protostars with Outflows: How Accurate are Protostellar Properties Inferred from SEDs?
• Accretion disks around massive stars: Hydrodynamic structure, stability and dust sublimation
• AMBER and CRIRES observations of the binary sgB[e] star HD 327083: evidence of a gaseous disc traced by CO bandhead emission
• VLTI/MIDI 10 micron interferometry of the forming massive star W33A
• On the massive young stellar object AFGL4176: High-spatial-resolution multi-wavelength observations and modeling
• CRIRES-VLT high-resolution spectro-astrometry as a tool in the search of small structures at the cores of Planetary Nebulae

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