Radio continuum observations of Class I protostellar discs in Taurus: constraining the greybody tail at centimetre wavelengths★

Abstract

We present deep 1.8 cm (16 GHz) radio continuum imaging of seven young stellar objects in the Taurus molecular cloud. These objects have previously been extensively studied in the submm to near-infrared range and their spectral energy distributions modelled to provide reliable physical and geometrical parameters. We use these new data to constrain the properties of the long-wavelength tail of the greybody spectrum, which is expected to be dominated by emission from large dust grains in the protostellar disc. We find spectra consistent with the opacity indices expected for such a population, with an average opacity index of β = 0.26 ± 0.22 indicating grain growth within the discs. We use spectra fitted jointly to radio and submm data to separate the contributions from thermal dust and radio emission at 1.8 cm and derive disc masses directly from the cm-wave dust contribution. We find that disc masses derived from these flux densities under assumptions consistent with the literature are systematically higher than those calculated from submm data, and meet the criteria for giant planet formation in a number of cases.

The VLA Nascent Disk And Multiplicity Survey of Perseus Protostars (VANDAM). IV. Free-Free Emission from Protostars: Links to Infrared Properties, Outflow Tracers, and Protostellar Disk Masses

“…This is in agreement with Pech et al (2016), who show for a smaller sample of protostars consistent fluxes between Class 0 and Class I. However, other sample-limited studies suggest that the radio emission mechanisms could be different for Class 0 and Class I protostars (AMI Consortium: Scaife et al 2011). Spearman's rank correlation coefficient and probability of no correlation is shown in the top-right corner.…”

The Disappearing Envelope Around the Transitional Class I Object L43

“…The millimeter measurements using interferometry toward L43, which show the compact feature, suggest dust growth in the vicinity of the central star (< 500 AU). Recent observations have also revealed that SEDs of Class 0 and Class I sources show such small β values (Kwon et al 2009;Scaife et al 2012). Our result supports dust growth at an early stage of star formation.…”

GMRT detections of low-mass young stars at 323 and 608 MHz

“…It is important to disentangle these two emission mechanisms simultaneously as it has been shown that considering freefree and thermal dust components separately can give vastly different values for the spectral slope and normalisation of each component (e.g. Scaife et al 2012). This can have implications when determining physical parameters from the free-free spectra (such as gas mass and electron density) and the thermal dust spectra (such as disc mass and grain size).…”

“…Extended soft (< 1 keV) X-ray emission has been detected from the DG Tau jet out to 5 arcsec coincident with the optical outflow, and both hard (> 1 keV) and soft emission has been observed from the source (Güdel et al 2008). In the radio, DG Tau has been shown to have a compact and elongated morphology close to the source in the direction of the optical outflow and possesses a spectral index typical of free-free emission at frequencies between 5-20 GHz (Cohen et al 1982;Cohen & Bieging 1986;Rodríguez et al 2012;Scaife et al 2012;Lynch et al 2013;Ainsworth et al 2013).…”