Detection of non-thermal emission from the massive protostellar jet HH80-81 at low radio frequencies using GMRT

TL;DR

This study reports the first detection of non-thermal synchrotron emission from a massive protostellar jet at low radio frequencies using GMRT, revealing insights into magnetic fields and jet dynamics.

Contribution

It presents the first low-frequency radio detection of non-thermal emission from the HH80-81 protostellar jet, expanding understanding of jet physics at these wavelengths.

Findings

Detected non-thermal emission at 325, 610, and 1300 MHz.

Spectral indices of condensations are around -0.7.

Magnetic field estimates range from 116 to 180 microgauss.

Abstract

Low radio frequencies are favourable for the identification of emission from non-thermal processes such as synchrotron emission. The massive protostellar jet associated with IRAS 18162-2048 (also known as the HH80-81 system) has been imaged at low radio frequencies: 325, 610 and 1300 MHz, using the Giant Metrewave Radio Telescope, India. This is the first instance of detection of non-thermal emission from a massive protostellar jet at such low radio frequencies. The central region displays an elongated structure characteristic of the jet. In addition, the associated Herbig-Haro objects such as HH80, HH81, HH80N, and other condensations along the inner regions of the jet exhibit negative spectral indices. The spectral indices of most condensations are ~-0.7, higher than the value of -0.3 determined earlier using high frequency measurements. The magnetic field values derived using radio flux densities in the present work, under the assumption of equipartition near minimum energy condition, lie in the range 116-180 microgauss. We probe into the hard X-ray nature of a source that has been attributed to HH80, in an attempt to reconcile the non-thermal characteristics of radio and X-ray measurements. The flux densities of condensations at 610 MHz, measured nearly 11 yrs apart, display variability that could be ascribed to the cooling of condensations, and emphasize the importance of coeval or nearly-coeval measurements for estimation of spectral indices.