VLA cm-wave survey of young stellar objects in the Oph A cluster: constraining extreme UV- and X-ray-driven disk photoevaporation

Abstract

Observations of young stellar objects (YSOs) in centimeter bands can probe the continuum emission from growing dust grains, ionized winds, and magnetospheric activity, which are intimately connected to the evolution of protoplanetary disks and the formation of planets. We have carried out sensitive continuum observations toward the Ophiuchus A star-forming region using the Karl G. Jansky Very Large Array (VLA) at 10 GHz over a field-of-view of 6 with a spatial resolution of θ maj × θ min ∼ 0 . 4 × 0 . 2. We achieved a 5 µJy beam −1 root-mean-square noise level at the center of our mosaic field of view. Among the eighteen sources we detected, sixteen are YSOs (three Class 0, five Class I, six Class II, and two Class III) and two are extragalactic candidates. We find that thermal dust emission generally contributes less that 30% of the emission at 10 GHz. The radio emission is dominated by other types of emission such as gyro-synchrotron radiation from active magnetospheres, free-free emission from thermal jets, free-free emission from the outflowing photo-evaporated disk material, and/or synchrotron emission from accelerated cosmic-rays in jet or protostellar surface shocks. These different types of emission could not be clearly disentangled. Our non-detections towards Class II/III disks suggest that extreme UV-driven photoevaporation is insufficient to explain the disk dispersal, assuming that the contribution of UV photoevaporating stellar winds to radio flux does not evolve with time. The sensitivity of our data cannot exclude photoevaporation due to X-ray photons as an efficient mechanism for disk dispersal. Deeper surveys with the Square Kilometre Array will be able to provide strong constraints on disk photoevaporation.A. Coutens et al.: VLA cm-wave survey of young stellar objects in the Oph A cluster

Observing protoplanetary discs with the Square Kilometre Array -- I. Characterising pebble substructure caused by forming planets

“…The resulting on-sky surface brightness distribution is shown in Figure 2, and results in a total disc integrated flux density of 0.15 mJy, which is comparable to the free-free corrected measurements of dust continuum emission from young discs at similar frequencies (e.g. HL Tau, Carrasco-González et al 2019; the ρ Oph A members, Coutens et al 2019).…”

“…In addition, the extremely large collecting area of SKA1 will result in sensitivities that are a factor of 3-4 higher than those currently available with the JVLA dishes. Several works have examined the potential that the SKA has in providing significant contributions in our understanding of star and planet formation (Hoare et al 2015;Testi et al 2015), and pathfinder studies using the JVLA have started to determine optimal targets for first observations (Coutens et al 2019). However, there are currently no detailed investigations on the potential for the SKA to characterise the cm-dust component of planet forming discs.…”

The JCMT Transient Survey: Four-year Summary of Monitoring the Submillimeter Variability of Protostars

“…also found a smaller strongly collimated outflow associated this component. Interestingly, VLA 1623 B was determined to be variable at centimeter wavelengths byCoutens et al (2019).…”

The JCMT Transient Survey: Four Year Summary of Monitoring the Submillimeter Variability of Protostars

“…Santangelo et al (2015) also found a smaller strongly collimated outflow associated this component. Interestingly, VLA 1623 B was determined to be variable at centimeter wavelengths by Coutens et al (2019). The submillimeter light curve for secular source Orion NGC 2068, V1647 Ori is presented in Figure B.7.…”