Vla and Carma Observations of Protostars in the Cepheus Clouds: Sub-Arcsecond Proto-Binaries Formed via Disk Fragmentation

Abstract

We present observations of three Class 0/I protostars (L1157-mm, CB230 IRS1, and L1165-SMM1) using the Karl G. Jansky Very Large Array (VLA) and observations of two (L1165-SMM1 and CB230 IRS1) with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The VLA observations were taken at wavelengths of λ = 7.3 mm, 1.4 cm, 3.3 cm, 4.0 cm, and 6.5 cm with a best resolution of ∼0. 06 (18 AU) at 7.3 mm. The L1165-SMM1 CARMA observations were taken at λ = 1.3 mm with a best resolution of ∼ 0. 3 (100 AU), and the CB230 IRS1 observations were taken at λ = 3.4 mm with a best resolution of ∼3 (900 AU). We find that L1165-SMM1 and CB230 IRS1 have probable binary companions at separations of ∼0. 3 (100 AU) from detections of secondary peaks at multiple wavelengths. The position angles of these companions are nearly orthogonal to the direction of the observed bipolar outflows, consistent with the expected protostellar disk orientations. We suggest that these companions may have formed from disk fragmentation; turbulent fragmentation would not preferentially arrange the binary companions to be orthogonal to the outflow direction. For L1165-SMM1, both the 7.3 mm and 1.3 mm emission show evidence of a large (R > 100 AU) disk. For the L1165-SMM1 primary protostar and the CB230 IRS1 secondary protostar, the 7.3 mm emission is resolved into structures consistent with ∼ 20 AU radius disks. For the other protostars, including L1157-mm, the emission is unresolved, suggesting disks with radii < 20 AU. Subject headings: ISM: individual (CB230) -ISM: individual (L1165) -ISM: individual (L1157) -planetary systems: proto-planetary disks -stars: formation * Mass was computed with sub/millimeter bolometer data assuming an isothermal temperature. † Mass measured using the envelope extinction of the 8 µm background emission in Tobin et al. (2010b).

Gravitoturbulent dynamos in astrophysical discs

“…where Q is the Toomre parameter (Toomre 1964), cs is the sound speed, Ω the orbital frequency, and Σ0 the background surface density. It is believed that 50% of class 0 and 10-20% of class I PP discs might be unstable to GI (Tobin et al 2013;Mann et al 2015). In particular, the detection of spiral arms and streamers, recently imaged at NIR wavelengths in Ophiuchi and FU Ori systems, supports the idea that their discs are gravitationally unstable (Christiaens et al 2014;Liu et al 2016;Dong et al 2016).…”

SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

“…Indeed, sources that present a strong misalignment (IRAS03282, NGC 1333 IRAS4A, L1448N, L1448-2A, or CB230) are all close multiples (Maury et al, in prep. ;Launhardt 2004;Chandler et al 2005;Choi 2005;Tobin et al 2013Tobin et al , 2016. SVS13-A does host a close multiple but it is a Class I.…”

“…The north-south CO outflows seem to be driven by the western protostar IRS1. More recent 7 mm high-resolution observations of IRS1 led to the detection of two continuum sources separated by ∼100 au, which have an unresolved primary source at the origin of the outflow and an extended companion source located in a direction perpendicular to the outflow direction (Tobin et al 2013). Velocity field.…”

TADPOL: A 1.3 mm SURVEY OF DUST POLARIZATION IN STAR-FORMING CORES AND REGIONS

“…The wide companion (CB 230 IRS2) is located 10 from CB 230 IRS1 and is not observed at wavelengths longer than 24 μm Massi et al 2008;Launhardt et al 2013); however, IRS 2 does seem to drive a CO outflow (Launhardt 2001). The close companion to IRS 1 (IRS 1B) was recently discovered by Tobin et al (2013a) and is separated from IRS 1 by 0. 3 (100 AU) (see Figure 34 for maps).…”