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

AbstractLow 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, us...

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Published inMonthly notices of the Royal Astronomical Society Vol. 474; no. 3; pp. 3808 - 3816
Main Authors Vig, S, Veena, V S, Mandal, S, Tej, A, Ghosh, S K
Format Journal Article
LanguageEnglish
Published London Oxford University Press 01.03.2018
Subjects
Elongated structure
Herbig-Haro objects
Magnetic fields
Protostars
Radio frequency
Radio telescopes
Spectra
Thermal emission
India
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Summary:AbstractLow 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, steeper than the value of -0.3 determined earlier using high-frequency measurements. The magnetic field values derived using radio flux densities in this work, under the assumption of equipartition near minimum energy condition, lie in the range 116-180 μG. 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 yr 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.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stx3032