Resolving the Radio Emission from the Quasar P172+18 at z = 6.82

Journal Article · Sat May 01 04:00:00 EDT 2021 · The Astronomical Journal (Online)

DOI:https://doi.org/10.3847/1538-3881/ABE6AE· OSTI ID:23159209

Momjian, Emmanuel; Carilli, Christopher L. ^[1]; Bañados, Eduardo; Walter, Fabian ^[2]; Mazzucchelli, Chiara ^[3]

---

1. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
2. Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)
3. European Southern Observatory, Alonso de Cordova 3107, Vitacura, Region Metropolitana (Chile)

We present high angular resolution imaging of the quasar PSO J172.3556+18.7734 at z = 6.82 with the Very Long Baseline Array (VLBA). This source currently holds the record of being the highest redshift radio-loud quasar. These observations reveal a dominant radio source with a flux density of 398.4 ± 61.4 μJy at 1.53 GHz, a deconvolved size of 9.9 × 3.5 mas (52.5 × 18.6 pc), and an intrinsic brightness temperature of (4.7 ± 0.7) × 10{sup 7} K. A weak unresolved radio extension from the main source is also detected at the ∼3.1σ level. The total flux density recovered with the VLBA at 1.53 GHz is consistent with that measured with the Very Large Array (VLA) at a similar frequency. The quasar is not detected at 4.67 GHz with the VLBA, suggesting a steep spectral index with a limit of α{sub 4.67}{sup 1.53}<−1.55. The quasar is also not detected with the VLBA at 7.67 GHz. The overall characteristics of the quasar suggest that it is a very young radio source similar to lower redshift gigahertz peaked spectrum radio sources, with an estimated kinematic age of ∼10{sup 3} yr. The VLA observations of this quasar revealed a second radio source in the field 23.″1 away. This radio source, which does not have an optical or IR counterpart, is not detected with the VLBA at any of the observed frequencies. Its nondetection at the lowest observed VLBA frequency suggests that it is resolved out, implying a size larger than ∼0.″17. It is thus likely situated at lower redshift than the quasar.

• OSTI ID: 23159209
• Journal Information: The Astronomical Journal (Online), Journal Name: The Astronomical Journal (Online) Journal Issue: 5 Vol. 161; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

47 OTHER INSTRUMENTATION
79 ASTRONOMY AND ASTROPHYSICS
BRIGHTNESS
EMISSION
FLUX DENSITY
GHZ RANGE
QUASARS
RED SHIFT
RESOLUTION
SPECTRA