Please use this identifier to cite or link to this item:
http://hdl.handle.net/20.500.12386/35145
Title: | The radio-loud fraction of quasars at z > 6 | Authors: | Pascal M. Keller Nithyanandan Thyagarajan Ajay Kumar Nissim Kanekar BERNARDI, Gianni |
Issue Date: | 2024 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 528 | Issue: | 4 | First Page: | 5692 | Abstract: | Quasars at redshifts $z>6$ are an excellent probe of the formation and evolution of supermassive black holes in the early Universe. The population of radio-luminous quasars is of particular interest, as such quasars could potentially be used to study the neutral intergalactic medium during cosmic reionisation via H$\,$I 21$\,$cm absorption studies. However, the lack of deep radio observations of $z>6$ quasars leaves the population poorly constrained, and suitable candidates for an H$\,$I 21$\,$cm absorption study have yet to be found. In this work, we present Jansky Very Large Array (VLA) 1$-$2 GHz radio continuum observations of 138 quasars at redshifts $6.0 \leq z<7.6$. We detect the radio continuum emission of the $z=6.1$ quasar J1034-1425, with a 1.6 GHz flux density of $170\pm 36\,\mu$Jy. This quasar is radio-quiet with radio-loudness, $R \equiv f_{5\text{~GHz}}/f_{\nu,\text{4400 A}} = 2.4\pm0.5$. In addition, we detect 7 other quasars at z>6, which have previously been characterised in the literature at these frequencies. Using the full sample, we estimate the radio-loud fraction to be $3.8^{+6.2}_{-2.4}\%$, where the uncertainties are 95% confidence intervals. This is lower than recent estimates of the radio-loud fraction in the literature, but is still marginally consistent with no redshift evolution of the radio-loud fraction. We explore the undetected quasar population by stacking their continuum images at their optical positions and obtain a median stacked flux density of $13.8\pm 3.9~\mu$Jy and luminosity of $\log{L_{5~\mathrm{GHz}}/(\mathrm{W~Hz}^{-1})}=24.2\pm0.1$. | URI: | http://hdl.handle.net/20.500.12386/35145 | URL: | https://academic.oup.com/mnras/article/528/4/5692/7604003 http://arxiv.org/abs/2402.08732v1 |
ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stae418 | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
keller24.pdf | published version | 2.15 MB | Adobe PDF | View/Open |
Page view(s)
35
checked on Aug 31, 2024
Download(s)
8
checked on Aug 31, 2024
Google ScholarTM
Check
Altmetric
Altmetric
Items in DSpace are published in Open Access, unless otherwise indicated.