The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. II. A Statistical Characterization of Class 0 and Class I Protostellar Disks

Abstract

We have conducted a survey of 328 protostars in the Orion molecular clouds with the Atacama Large Millimeter/ submillimeter Array at 0.87 mm at a resolution of ∼0 1 (40 au), including observations with the Very Large Array at 9mm toward 148 protostars at a resolution of ∼0 08 (32 au). This is the largest multiwavelength survey of protostars at this resolution by an order of magnitude. We use the dust continuum emission at 0.87 and 9mm to measure the dust disk radii and masses toward the Class 0, Class I, and flat-spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The mean dust disk radii for the Class 0, Class I, and flat-spectrum protostars are -+ 44.9 3.4 5.8 , -+ 37.0 3.0 4.9 , and -+ 28.5 2.3 3.7 au, respectively, and the mean protostellar dust disk masses are 25.9 -+ 4.0 7.7 , -+ 14.9 2.2 3.8 , -+11.6 1.93.5 Å M , respectively. The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. At least 146 protostellar disks (35% of 379 detected 0.87 mm continuum sources plus 42 nondetections) have disk radii greater than 50 au in our sample. These properties are not found to vary significantly between different regions within Orion. The protostellar dust disk mass distributions are systematically larger than those of Class II disks by a factor of >4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase.

Formation and Evolution of Disks Around Young Stellar Objects

“…Note that the opacity of the dust emission can also pose challenges for the characterization of molecular line emission from protostellar disks. The typically higher mass of protostellar disks as compared to proto-planetary disks (Tobin et al 2015b;Tychoniec et al 2018;Maury et al 2019;Williams et al 2019;Tobin et al 2020) can result in the disks being optically thick submm/mm wavelengths. This not only prevents tracing all the disk mass from the dust continuum, but the opaque continuum will also absorb molecular line emission, preventing the measurement of molecular gas emission and the characterization of the kinematics.…”

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. IV. Unveiling the Embedded Intermediate-Mass Protostar and Disk within OMC2-FIR3/HOPS-370

“…We make use of data from two ALMA bands, a single band of VLA data, and near-infrared spectroscopy in our study of HOPS-370. The ALMA 0.87mm observations and the VLA 9mm observations have already been detailed in Tobin et al (2019Tobin et al ( , 2020; we only briefly describe those observations. The new ALMA 1.3mm observations and near-infrared spectroscopic observations are described in more detail, along with their reduction procedures.…”

“…The bandwidth and spectral resolution of the spectral windows were 937.5MHz with 0.489km s −1 channels and 234.375MHz with 0.128km s −1 channels. Additional details of the data reduction and imaging are provided in Tobin et al (2019Tobin et al ( , 2020. The data are available from the Harvard Dataverse (Tobin 2019a).…”

“…We used the Ka-band receivers with 3 bit samplers, providing a 4GHz baseband centered at 36.9GHz (8.1 mm) and the other baseband centered at 29GHz (1.05 cm). Additional details of the data reduction and imaging are provided in Tobin et al (2019Tobin et al ( , 2020; the reduced data are also available for download through the Harvard Dataverse (Tobin 2019c).…”

Super-rotating protostellar jets

“…In addition, there is no evidence for a protobinary system in the dust continuum within the ALMA at 1.3 mm data at 400 au spatial resolution ( Fig. 1) nor in ALMA at 0.87 mm and VLA at 9 mm observations at 40 au resolution 8 . Thus, it is not plausible to consider that the jet are composed of twin flows.…”