Mid-infrared interferometry of the massive young stellar object NGC 2264 IRS 1

Abstract

Context. The optically invisible infrared-source NGC 2264 IRS 1 lying north of the Cone Nebula is thought to be a massive young stellar object (∼10 M ). Although strong infrared excess clearly shows that the central object is surrounded by large amounts of circumstellar material, no information about the spatial distribution of this circumstellar material has been available until now. Aims. We used the ESO Very Large Telescope Interferometer to perform long-baseline interferometric observations of NGC 2264 IRS 1 in the mid-infrared regime. Our observations resolve the circumstellar material around NGC 2264 IRS 1, provide the first direct measurement of the angular size of the mid-infrared emission, and yield direct constraints on the spatial distribution of the dust. Methods. We analyze the spectrally dispersed interferometric data taken with MIDI at two different position angles and baseline lengths. We use different approaches (a geometrical model, a temperature-gradient model, and radiative transfer models) to jointly model the observed interferometric visibilities and the spectral energy distribution. Results. The derived visibility values between ∼0.02 and ∼0.3 show that the mid-infrared emission is clearly resolved. The characteristic size of the MIR-emission region is ∼30−60 AU; this value is typical for other YSOs with similar or somewhat lower luminosities. A comparison of the sizes for the two position angles shows a significant elongation of the dust distribution. Simple spherical envelope models are therefore inconsistent with the data. The radiative transfer modeling of our data suggests that we observe a geometrically thin and optically thick circumstellar disk with a mass of about 0.1 M . Conclusions. Our modeling indicates that NGC 2264 IRS 1 is surrounded by a flat circumstellar disk that has properties similar to disks typically found around lower-mass young stellar objects. This result supports the assumption that massive young stellar objects form via accretion from circumstellar disks.

Accretion disks in luminous young stellar objects

“…11), which could be interpreted as due to a disk or due to outflow cavity wall emission (Boley et al, 2013). Subsequent RT modeling in a few studies suggests that the geometry of the N-band emission is consistent with that of an equatorially flattened structure (Follert et al, 2010;Grellmann et al, 2011). The power of interferometry is that the various contributions to the correlated fluxes is the flux weighted by the size; at milli-arcsecond resolution the envelope emission is almost resolved out, and any contribution by an unresolved structure (e.g., a disk) will become evident.…”

Probing the envelopes of massive young stellar objects with diffraction limited mid-infrared imaging

“…However, in some other cases, the mas-scale MIR emission of MYSOs is suggested to be (at least partially) located in a circumstellar disc (see e.g. Follert et al 2010;de Wit et al 2011;Grellmann et al 2011). In other words, there are hints that the N-band emission, resolved with interferometry, is not completely dominated by envelope emission.…”

“…Follert et al 2010;Vehoff et al 2010;de Wit et al 2011;Grellmann et al 2011). In particular, an exemplary result is delivered by Kraus et al (2010) using the Very Large Telescope Interferometer (VLTI) and the near-infrared beam-combiner AMBER.…”

On the massive young stellar object AFGL 4176

“…As previously noted, however, in the case of AFGL 4176, no outflow components have been detected (De Buizer 2003;De Buizer et al 2009). For a broader discussion of these and other sources, we refer to the work by Grellmann et al (2011).…”