Disks and Outflows in the Intermediate-mass Star Forming Region NGC 2071 IR

TL;DR

This study uses ALMA and VLA observations to analyze the disks and outflows of protostars in NGC 2071 IR, revealing disk structures, kinematics, and potential jet precession in an intermediate-mass star forming region.

Contribution

First detailed kinematic analysis of disks and outflows in NGC 2071 IR using multi-wavelength observations and analytic modeling.

Findings

Disks around IRS1 and IRS3 are resolved and show velocity gradients.

IRS3 is a binary system with a total mass of 1.4-1.5 solar masses.

Outflow directions are often misaligned with jet axes, suggesting precession.

Abstract

We present ALMA band 6/7 (1.3 mm/0.87 mm) and VLA Ka band (9 mm) observations toward NGC 2071 IR, an intermediate-mass star forming region. We characterize the continuum and associated molecular line emission towards the most luminous protostars, i.e., IRS1 and IRS3, on ~100 au (0. 2") scales. IRS1 is partly resolved in millimeter and centimeter continuum, which shows a potential disk. IRS3 has a well resolved disk appearance in millimeter continuum and is further resolved into a close binary system separated by ~40 au at 9 mm. Both sources exhibit clear velocity gradients across their disk major axes in multiple spectral lines including C18O, H2CO, SO, SO2, and complex organic molecules like CH3OH, 13CH3OH and CH3OCHO. We use an analytic method to fit the Keplerian rotation of the disks, and give constraints on physical parameters with a MCMC routine. The IRS3 binary system is estimated to have a total mass of 1.4-1.5$M_\odot$. IRS1 has a central mass of 3-5$M_\odot$ based on both kinematic modeling and its spectral energy distribution, assuming that it is dominated by a single protostar. For both IRS1 and IRS3, the inferred ejection directions from different tracers, including radio jet, water maser, molecular outflow, and H2 emission, are not always consistent, and for IRS1, these can be misaligned by ~50$^{\circ}$. IRS3 is better explained by a single precessing jet. A similar mechanism may be present in IRS1 as well but an unresolved multiple system in IRS1 is also possible.