Abstract
We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the z = 6.326 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is by far the most optically luminous and is a radio-quiet quasar with the most massive black hole known at z > 6. The VLBA observations have a synthesized beam size of 12.10 mas 5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6 9.0 μJy beam-1 and a total flux density of 88 19 μJy. The position of the radio peak is consistent with that from SDSS in the optical and Chandra in the X-ray. The radio source is marginally resolved by the VLBA observations. A 2D Gaussian fit to the image constrains the source size to (7.1 3.5) mas (3.1 1.7) mas. This corresponds to a physical scale of (40 20) pc (18 10) pc. We estimate the intrinsic brightness temperature of the VLBA source to be TB = (1.6 1.2) 107 K. This is significantly higher than the maximum value in normal star-forming galaxies, indicating an active galactic nucleus (AGN) origin for the radio continuum emission. However, it is also significantly lower than the brightness temperatures found in highest-redshift radio-loud quasars. J0100+2802 provides a unique example for studying the radio activity in optically luminous and radio-quiet AGNs in the early universe. Further observations at multiple radio frequencies will accurately measure the spectral index and address the dominant radiation mechanism of the radio emission.
Original language | English (US) |
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Article number | L20 |
Journal | Astrophysical Journal Letters |
Volume | 835 |
Issue number | 2 |
DOIs | |
State | Published - Feb 1 2017 |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Keywords
- galaxies: active
- galaxies: high-redshift
- quasars: individual (SDSS J010013.02+280225.8)
- radio continuum: galaxies