Radio-loud fraction of z>6 quasars
Fuente:
arXiv
Enregistré dans:
| Auteurs principaux: | , , , , |
|---|---|
| Format: | Preprint |
| Publié: |
2024
|
| Sujets: | |
| Accès en ligne: | |
| Tags: |
Ajouter un tag
Pas de tags, Soyez le premier à ajouter un tag!
|
| _version_ | 1866913233779032064 |
|---|---|
| author | Keller, Pascal M. Thyagarajan, Nithyanandan Kumar, Ajay Kanekar, Nissim Bernardi, Gianni |
| author_facet | Keller, Pascal M. Thyagarajan, Nithyanandan Kumar, Ajay Kanekar, Nissim Bernardi, Gianni |
| contents | 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 $170\pm 36\,μ$Jy. This quasar is radio-quiet with radio-loudness, $R \equiv f_{5\text{~GHz}}/f_{ν,\text{4400 A}} = 2.4\pm0.5$. 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 $13.8\pm 3.9~μ$Jy and luminosity of $\log{L_{5~\mathrm{GHz}}/(\mathrm{W~Hz}^{-1})}=24.2\pm0.1$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_08732 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Radio-loud fraction of z>6 quasars Keller, Pascal M. Thyagarajan, Nithyanandan Kumar, Ajay Kanekar, Nissim Bernardi, Gianni Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics 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 $170\pm 36\,μ$Jy. This quasar is radio-quiet with radio-loudness, $R \equiv f_{5\text{~GHz}}/f_{ν,\text{4400 A}} = 2.4\pm0.5$. 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 $13.8\pm 3.9~μ$Jy and luminosity of $\log{L_{5~\mathrm{GHz}}/(\mathrm{W~Hz}^{-1})}=24.2\pm0.1$. |
| title | Radio-loud fraction of z>6 quasars |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2402.08732 |