2021A&A...656A.137G


Query : 2021A&A...656A.137G

2021A&A...656A.137G - Astronomy and Astrophysics, volume 656A, 137-137 (2021/12-1)

Low frequency radio properties of the z > 5 quasar population.

GLOUDEMANS A.J., DUNCAN K.J., ROTTGERING H.J.A., SHIMWELL T.W., VENEMANS B.P., BEST P.N., BRUGGEN M., CALISTRO RIVERA G., DRABENT A., HARDCASTLE M.J., MILEY G.K., SCHWARZ D.J., SAXENA A., SMITH D.J.B. and WILLIAMS W.L.

Abstract (from CDS):

Optically luminous quasars at z > 5 are important probes of super-massive black hole (SMBH) formation. With new and future radio facilities, the discovery of the brightest low-frequency radio sources in this epoch would be an important new probe of cosmic reionization through 21-cm absorption experiments. In this work, we systematically study the low-frequency radio properties of a sample of 115 known spectroscopically confirmed z > 5 quasars using the second data release of the Low Frequency Array (LOFAR) Two Metre Sky survey (LoTSS-DR2), reaching noise levels of ∼80 µJy beam–1 (at 144 MHz) over an area of ∼5720 deg2. We find that 41 sources (36%) are detected in LoTSS-DR2 at > 2σ significance and we explore the evolution of their radio properties (power, spectral index, and radio loudness) as a function of redshift and rest-frame ultra-violet properties. We obtain a median spectral index of -0.29–0.09+0.10 by stacking 93 quasars using LoTSS-DR2 and Faint Images of the Radio Sky at Twenty Centimetres (FIRST) data at 1.4 GHz, in line with observations of quasars at z < 3. We compare the radio loudness of the high-z quasar sample to a lower-z quasar sample at z ∼ 2 and find that the two radio loudness distributions are consistent with no evolution, although the low number of high-z quasars means that we cannot rule out weak evolution. Furthermore, we make a first order empirical estimate of the z = 6 quasar radio luminosity function, which is used to derive the expected number of high-z sources that will be detected in the completed LoTSS survey. This work highlights the fact that new deep radio observations can be a valuable tool in selecting high-z quasar candidates for follow-up spectroscopic observations by decreasing contamination of stellar dwarfs and reducing possible selection biases introduced by strict colour cuts.

Abstract Copyright: © ESO 2021

Journal keyword(s): quasars: general - galaxies: high-redshift - galaxies: active - radio continuum: galaxies

VizieR on-line data: <Available at CDS (J/A+A/656/A137): table1.dat>

Status at CDS : All or part of tables of objects will be ingested in SIMBAD with priority 1.

Simbad objects: 17

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Number of rows : 17
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 SDSS J000239.39+255034.8 QSO 00 02 39.403 +25 50 34.83           ~ 57 0
2 SDSS J001232.88+363216.1 QSO 00 12 32.8913865120 +36 32 16.043781804           ~ 2 0
3 SDSS J010013.02+280225.8 QSO 01 00 13.0246669824 +28 02 25.791716364           ~ 111 0
4 SDSS J015745.45+300110.7 QSO 01 57 45.44904 +30 01 10.6788           ~ 2 0
5 2MASS J07415470+2520294 QSO 07 41 54.7157646024 +25 20 29.575028292           ~ 9 0
6 QSO J0756+4104 QSO 07 56 18.139 +41 04 08.61   25.29 23.32     ~ 53 0
7 DELS J080305.42+313834.2 QSO 08 03 05.42 +31 38 34.2           ~ 2 0
8 QSO J0810+5105 QSO 08 10 54.316 +51 05 40.05           ~ 9 0
9 DELS J083946.88+390011.5 QSO 08 39 46.88 +39 00 11.5           ~ 2 0
10 SDSS J084035.08+562419.7 QSO 08 40 35.08848 +56 24 19.7712   24.95 23.93     ~ 52 0
11 NAME Lockman Hole reg 10 45 00.0 +58 00 00           ~ 808 0
12 PSO J172.3556+18.7734 QSO 11 29 25.36 +18 46 24.3           ~ 14 0
13 QSO J1427+3312 QSO 14 27 38.5412 +33 12 41.713         22.09 ~ 49 0
14 NAME NOAO Deep Wide Field reg 14 32 05.75 +34 16 47.5           ~ 371 0
15 NVSS J153050+104931 rG 15 30 49.90 +10 49 30.0           ~ 9 0
16 QSO J1609+3041 QSO 16 09.0 +30 41           ~ 10 0
17 ELAIS N1 reg 16 10 01 +54 30.6           ~ 377 0

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2023.01.31-01:48:09

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