Protostellar Outflows at the EarliesT Stages (POETS). VIII. The jets in the intermediate-mass star-forming region G105.42+9.88 (alias LkHα 234)

Abstract

Our aim is to investigate the protostellar jets inside the young stellar object (YSO) cluster G105.42+9.88 (alias LkH$α$ 234). This is one of the least luminous targets of the Protostellar Outflows at the EarliesT Stages (POETS) survey, which has been recently carried out to study young outflow emission on scales of 10-100 au. The combination of multi-epoch water maser very long baseline interferometry (VLBI) observations with sensitive Jansky Very Large Array (JVLA) continuum and Large Binocular Telescope (LBT) H$_2$ 2.12 $μ$m observations, allows us to study the protostellar outflows from the intermediate-mass binary system VLA 3A and 3B, separated by ~0.22", and from VLA 2, an intermediate-mass YSO placed ~1" to northwest of VLA 3. Toward VLA 2, the 2001 and 2011 Very Long Baseline Array (VLBA) observations consistently show that the water masers are tracing a jet. The analysis of the 3D flow velocities proves that the jet is magneto-centrifugally launched in a magnetohydrodynamic (MHD) disk wind (DW). We infer launch radii in the range 10-50 au for the streamlines traced by the water masers. The global VLBI 2023 water maser observations indicate that the jet propagation can be hindered by a very dense clump placed northeast of VLA 2 and that is consistent with the large-scale LBT H$_2$ emission, tracing only the southwest lobe of the VLA 2 jet. Instead, the parallel jets emitted by the nearby YSOs VLA 3A and 3B can be reliably tracked with the H$_2$ emission at scales of a few 10" to both the southwest and the northeast. In particular, northeast of VLA 3 the direction of these two jets crosses a linear chain of spaced H$_2$ knots, which is a clear signature of an episodic jet. The variable ejection from VLA 3B, witnessed by the water masers at scales of ~10 au, could be the origin of the episodic jet observed at larger scales.