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GMRT detections of low-mass young stars at 323 and 608 MHz

Published version
Peer-reviewed

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Type

Article

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Authors

Ainsworth, RE 
Scaife, AMM 
Green, DA 
Coughlan, CP 
Ray, TP 

Abstract

We present the results of a pathfinder project conducted with the Giant Metrewave Radio Telescope (GMRT) to investigate protostellar systems at low radio frequencies. The goal of these investigations is to locate the break in the free-free spectrum where the optical depth equals unity in order to constrain physical parameters of these systems, such as the mass of the ionised gas surrounding these young stars. We detect all three target sources, L1551 IRS 5 (Class I), T Tau and DG Tau (Class II), at frequencies 323 and 608 MHz (wavelengths 90 and 50 cm, respectively). These are the first detections of low mass young stellar objects (YSOs) at such low frequencies. We combine these new GMRT data with archival information to construct the spectral energy distributions for each system and find a continuation of the optically thin free-free spectra extrapolated from higher radio frequencies to 323 MHz for each target. We use these results to place limits on the masses of the ionised gas and average electron densities associated with these young systems on scales of ~1000 au. Future observations with higher angular resolution at lower frequencies are required to constrain these physical parameters further.

Description

Keywords

radiation mechanisms: thermal, stars: individual: L1551 IRS 5, stars: individual: T Tauri, stars: individual: DG Tauri, stars: pre-main-sequence, radio continuum: stars

Journal Title

Monthly Notices of the Royal Astronomical Society

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

Publisher

Oxford University Press (OUP)
Sponsorship
Science and Technology Facilities Council (ST/K006096/1)
We thank the staff of the GMRT who have made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. REA, TPR and CPC acknowledge support from Science Foundation Ireland under grant 13/ERC/I2907. AMS gratefully acknowledges support from the European Research Council under grant ERC-2012-StG-307215 LODESTONE. DAG thanks the Science and Technology Facilities Council for support. We thank the anonymous referee for their helpful and constructive comments to clarify this manuscript.