An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and the far-infrared/radio correlation

• Published in: Monthly notices of the Royal Astronomical Society 2014-07, Vol.442 (1), p.577-588
• Main Authors: Thomson, A. P., Ivison, R. J., Simpson, J. M., Swinbank, A. M., Smail, Ian, Arumugam, V., Alexander, D. M., Beelen, A., Brandt, W. N., Chandra, I., Dannerbauer, H., Greve, T. R., Hodge, J. A., Ibar, E., Karim, A., Murphy, E. J., Schinnerer, E., Sirothia, S., Walter, F., Wardlow, J. L., van der Werf, P.
• Format: Article
• Language: English
• Subjects: Astronomy; Radio astronomy; Stars & galaxies
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stu839

We present a study of the radio properties of 870 μm-selected submillimetre galaxies (SMGs), observed at high resolution with Atacama Large Millimeter Array (ALMA) in the Extended Chandra Deep Field South. From our initial sample of 76 ALMA SMGs, we detect 52 SMGs at >3... significance in Karl G. Jansky Very Large Array 1400 MHz imaging, of which 35 are also detected at >3... in new 610 MHz Giant Metre-Wave Radio Telescope imaging. Within this sample of radio-detected SMGs, we measure a median radio spectral index ... =-0.79±0.06, (with inter-quartile range α = [-1.16, -0.56]) and investigate the far-infrared/radio correlation via the parameter q^sub IR^, the logarithmic ratio of the rest-frame 8-1000 μm flux and monochromatic radio flux. Our median q^sub IR^ = 2.56 ± 0.05 (inter-quartile range q^sub IR^ = [2.42, 2.78]) is higher than that typically seen in single-dish 870 μm-selected sources (q^sub IR^ ~ 2.4), which may reflect the fact that our ALMA-based study is not biased to radio-bright counterparts, as previous samples were. Finally, we search for evidence that q^sub I R^ and α evolve with age in a codependent manner, as predicted by starburst models: the data populate the predicted region of parameter space, with the stellar mass tending to increase along tracks of q^sub IR^ versus α in the direction expected, providing the first observational evidence in support of these models. (ProQuest: ... denotes formulae/symbols omitted.)