The GLEAM 200-MHz local radio luminosity function for AGN and star-forming galaxies
Franzen, TMO
Seymour, N
Sadler, EM
Mauch, T
White, SV
Jackson, CA
Chhetri, R
Quici, B
Bell, ME
Callingham, JR
Dwarakanath, KS
For, B
Gaensler, BM
Hancock, PJ
Hindson, L
Hurley-Walker, N
Johnston-Hollitt, M
Kapińska, AD
Lenc, E
McKinley, B
Morgan, J
Offringa, AR
Procopio, P
Staveley-Smith, L
Wayth, RB
Wu, C
Zheng, Q
- Publisher:
- Cambridge University Press (CUP)
- Publication Type:
- Journal Article
- Citation:
- Publications of the Astronomical Society of Australia, 2021, 38, pp. e041
- Issue Date:
- 2021-09-06
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the-gleam-200-mhz-local-radio-luminosity-function-for-agn-and-star-forming-galaxies.pdf | Published version | 3.95 MB | Adobe PDF |
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Full metadata record
Field | Value | Language |
---|---|---|
dc.contributor.author | Franzen, TMO | |
dc.contributor.author | Seymour, N | |
dc.contributor.author | Sadler, EM | |
dc.contributor.author | Mauch, T | |
dc.contributor.author | White, SV | |
dc.contributor.author | Jackson, CA | |
dc.contributor.author | Chhetri, R | |
dc.contributor.author | Quici, B | |
dc.contributor.author | Bell, ME | |
dc.contributor.author | Callingham, JR | |
dc.contributor.author | Dwarakanath, KS | |
dc.contributor.author | For, B | |
dc.contributor.author | Gaensler, BM | |
dc.contributor.author | Hancock, PJ | |
dc.contributor.author | Hindson, L | |
dc.contributor.author | Hurley-Walker, N | |
dc.contributor.author | Johnston-Hollitt, M | |
dc.contributor.author | Kapińska, AD | |
dc.contributor.author | Lenc, E | |
dc.contributor.author | McKinley, B | |
dc.contributor.author | Morgan, J | |
dc.contributor.author | Offringa, AR | |
dc.contributor.author | Procopio, P | |
dc.contributor.author | Staveley-Smith, L | |
dc.contributor.author | Wayth, RB | |
dc.contributor.author | Wu, C | |
dc.contributor.author | Zheng, Q | |
dc.date.accessioned | 2022-05-14T03:46:16Z | |
dc.date.available | 2022-05-14T03:46:16Z | |
dc.date.issued | 2021-09-06 | |
dc.identifier.citation | Publications of the Astronomical Society of Australia, 2021, 38, pp. e041 | |
dc.identifier.issn | 1323-3580 | |
dc.identifier.issn | 1448-6083 | |
dc.identifier.uri | http://hdl.handle.net/10453/157340 | |
dc.description.abstract | <jats:title>Abstract</jats:title> <jats:p>The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76–227 MHz of the entire southern sky (Declination <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline1.png" /> <jats:tex-math> $<\!{+}30^{\circ}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>) with an angular resolution of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline2.png" /> <jats:tex-math> ${\approx}2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> arcmin. In this paper, we combine GLEAM data with optical spectroscopy from the 6dF Galaxy Survey to construct a sample of 1 590 local (median <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline3.png" /> <jats:tex-math> $z \approx 0.064$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>) radio sources with <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline4.png" /> <jats:tex-math> $S_{200\,\mathrm{MHz}} > 55$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> mJy across an area of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline5.png" /> <jats:tex-math> ${\approx}16\,700\,\mathrm{deg}^{2}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73% are fuelled by an active galactic nucleus (AGN) and 27% by star formation. We present the local radio luminosity function for AGN and star-forming (SF) galaxies at 200 MHz and characterise the typical radio spectra of these two populations between 76 MHz and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline6.png" /> <jats:tex-math> ${\sim}1$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> GHz. For the AGN, the median spectral index between 200 MHz and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline7.png" /> <jats:tex-math> ${\sim}1$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> GHz, <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline8.png" /> <jats:tex-math> $\alpha_{\mathrm{high}}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, is <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline9.png" /> <jats:tex-math> $-0.600 \pm 0.010$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> (where <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline10.png" /> <jats:tex-math> $S \propto \nu^{\alpha}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>) and the median spectral index within the GLEAM band, <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline11.png" /> <jats:tex-math> $\alpha_{\mathrm{low}}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, is <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline12.png" /> <jats:tex-math> $-0.704 \pm 0.011$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. For the SF galaxies, the median value of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline13.png" /> <jats:tex-math> $\alpha_{\mathrm{high}}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> is <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline14.png" /> <jats:tex-math> $-0.650 \pm 0.010$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> and the median value of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline15.png" /> <jats:tex-math> $\alpha_{\mathrm{low}}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> is <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline16.png" /> <jats:tex-math> $-0.596 \pm 0.015$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. Among the AGN population, flat-spectrum sources are more common at lower radio luminosity, suggesting the existence of a significant population of weak radio AGN that remain core-dominated even at low frequencies. However, around 4% of local radio AGN have ultra-steep radio spectra at low frequencies (<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358021000369_inline17.png" /> <jats:tex-math> $\alpha_{\mathrm{low}} < -1.2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>). These ultra-steep-spectrum sources span a wide range in radio luminosity, and further work is needed to clarify their nature.</jats:p> | |
dc.language | en | |
dc.publisher | Cambridge University Press (CUP) | |
dc.relation.ispartof | Publications of the Astronomical Society of Australia | |
dc.relation.isbasedon | 10.1017/pasa.2021.36 | |
dc.rights | info:eu-repo/semantics/closedAccess | |
dc.subject | 0201 Astronomical and Space Sciences, 0299 Other Physical Sciences | |
dc.subject.classification | Astronomy & Astrophysics | |
dc.title | The GLEAM 200-MHz local radio luminosity function for AGN and star-forming galaxies | |
dc.type | Journal Article | |
utslib.citation.volume | 38 | |
utslib.for | 0201 Astronomical and Space Sciences | |
utslib.for | 0299 Other Physical Sciences | |
pubs.organisational-group | /University of Technology Sydney | |
pubs.organisational-group | /University of Technology Sydney/Faculty of Science | |
pubs.organisational-group | /University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences | |
utslib.copyright.status | closed_access | * |
dc.date.updated | 2022-05-14T03:46:11Z | |
pubs.publication-status | Published | |
pubs.volume | 38 |
Abstract:
Abstract
The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) is a radio continuum survey at 76–227 MHz of the entire southern sky (Declination
$<\!{+}30^{\circ}$
) with an angular resolution of
${\approx}2$
arcmin. In this paper, we combine GLEAM data with optical spectroscopy from the 6dF Galaxy Survey to construct a sample of 1 590 local (median
$z \approx 0.064$
) radio sources with
$S_{200\,\mathrm{MHz}} > 55$
mJy across an area of
${\approx}16\,700\,\mathrm{deg}^{2}$
. From the optical spectra, we identify the dominant physical process responsible for the radio emission from each galaxy: 73% are fuelled by an active galactic nucleus (AGN) and 27% by star formation. We present the local radio luminosity function for AGN and star-forming (SF) galaxies at 200 MHz and characterise the typical radio spectra of these two populations between 76 MHz and
${\sim}1$
GHz. For the AGN, the median spectral index between 200 MHz and
${\sim}1$
GHz,
$\alpha_{\mathrm{high}}$
, is
$-0.600 \pm 0.010$
(where
$S \propto \nu^{\alpha}$
) and the median spectral index within the GLEAM band,
$\alpha_{\mathrm{low}}$
, is
$-0.704 \pm 0.011$
. For the SF galaxies, the median value of
$\alpha_{\mathrm{high}}$
is
$-0.650 \pm 0.010$
and the median value of
$\alpha_{\mathrm{low}}$
is
$-0.596 \pm 0.015$
. Among the AGN population, flat-spectrum sources are more common at lower radio luminosity, suggesting the existence of a significant population of weak radio AGN that remain core-dominated even at low frequencies. However, around 4% of local radio AGN have ultra-steep radio spectra at low frequencies (
$\alpha_{\mathrm{low}} < -1.2$
). These ultra-steep-spectrum sources span a wide range in radio luminosity, and further work is needed to clarify their nature.
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