The radio spectral energy distribution of infrared-faint radio sources

A. Herzog; R. P. Norris; E. Middelberg; N. Seymour; L. R. Spitler; B. H C Emonts; T. M O Franzen; R. Hunstead; H. T. Intema; J. Marvil; Q. A. Parker; S. K. Sirothia; N. Hurley-Walker; M. Bell; G. Bernardi; Judd Bowman; F. Briggs; R. J. Cappallo; J. R. Callingham; A. A. Deshpande; K. S. Dwarakanath; B. Q. For; L. J. Greenhill; P. Hancock; B. J. Hazelton; L. Hindson; M. Johnston-Hollitt; A. D. Kapińska; D. L. Kaplan; E. Lenc; C. J. Lonsdale; B. McKinley; S. R. McWhirter; D. A. Mitchell; M. F. Morales; E. Morgan; J. Morgan; D. Oberoi; A. Offringa; S. M. Ord; T. Prabu; P. Procopio; N. Udaya Shankar; K. S. Srivani; L. Staveley-Smith; R. Subrahmanyan; S. J. Tingay; R. B. Wayth; R. L. Webster; A. Williams; C. L. Williams; C. Wu; Q. Zheng; K. W. Bannister; A. P. Chippendale; L. Harvey-Smith; I. Heywood; B. Indermuehle; A. Popping; R. J. Sault; M. T. Whiting

doi:10.1051/0004-6361/201527000

The radio spectral energy distribution of infrared-faint radio sources

A. Herzog, R. P. Norris, E. Middelberg, N. Seymour, L. R. Spitler, B. H C Emonts, T. M O Franzen, R. Hunstead, H. T. Intema, J. Marvil, Q. A. Parker, S. K. Sirothia, N. Hurley-Walker, M. Bell, G. Bernardi, Judd Bowman, F. Briggs, R. J. Cappallo, J. R. Callingham, A. A. DeshpandeK. S. Dwarakanath, B. Q. For, L. J. Greenhill, P. Hancock, B. J. Hazelton, L. Hindson, M. Johnston-Hollitt, A. D. Kapińska, D. L. Kaplan, E. Lenc, C. J. Lonsdale, B. McKinley, S. R. McWhirter, D. A. Mitchell, M. F. Morales, E. Morgan, J. Morgan, D. Oberoi, A. Offringa, S. M. Ord, T. Prabu, P. Procopio, N. Udaya Shankar, K. S. Srivani, L. Staveley-Smith, R. Subrahmanyan, S. J. Tingay, R. B. Wayth, R. L. Webster, A. Williams, C. L. Williams, C. Wu, Q. Zheng, K. W. Bannister, A. P. Chippendale, L. Harvey-Smith, I. Heywood, B. Indermuehle, A. Popping, R. J. Sault, M. T. Whiting

Earth and Space Exploration, School of (SESE)

Research output: Contribution to journal › Article › peer-review

10 Scopus citations

Abstract

Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z 1:7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims. Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods. We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results. We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (< 0:8; 74+6 9%), but we also find ultra-steep SEDs (< 1:3; 6+7 2%). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least 18+8 5% of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 M yr-1.

Original language	English (US)
Article number	A130
Journal	Astronomy and Astrophysics
Volume	593
DOIs	https://doi.org/10.1051/0004-6361/201527000
State	Published - Sep 1 2016

Keywords

Galaxies: active
Galaxies: high-redshift
Radio continuum: galaxies

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1051/0004-6361/201527000

Cite this

Herzog, A., Norris, R. P., Middelberg, E., Seymour, N., Spitler, L. R., Emonts, B. H. C., Franzen, T. M. O., Hunstead, R., Intema, H. T., Marvil, J., Parker, Q. A., Sirothia, S. K., Hurley-Walker, N., Bell, M., Bernardi, G., Bowman, J., Briggs, F., Cappallo, R. J., Callingham, J. R., ... Whiting, M. T. (2016). The radio spectral energy distribution of infrared-faint radio sources. Astronomy and Astrophysics, 593, Article A130. https://doi.org/10.1051/0004-6361/201527000

Herzog, A, Norris, RP, Middelberg, E, Seymour, N, Spitler, LR, Emonts, BHC, Franzen, TMO, Hunstead, R, Intema, HT, Marvil, J, Parker, QA, Sirothia, SK, Hurley-Walker, N, Bell, M, Bernardi, G, Bowman, J, Briggs, F, Cappallo, RJ, Callingham, JR, Deshpande, AA, Dwarakanath, KS, For, BQ, Greenhill, LJ, Hancock, P, Hazelton, BJ, Hindson, L, Johnston-Hollitt, M, Kapińska, AD, Kaplan, DL, Lenc, E, Lonsdale, CJ, McKinley, B, McWhirter, SR, Mitchell, DA, Morales, MF, Morgan, E, Morgan, J, Oberoi, D, Offringa, A, Ord, SM, Prabu, T, Procopio, P, Udaya Shankar, N, Srivani, KS, Staveley-Smith, L, Subrahmanyan, R, Tingay, SJ, Wayth, RB, Webster, RL, Williams, A, Williams, CL, Wu, C, Zheng, Q, Bannister, KW, Chippendale, AP, Harvey-Smith, L, Heywood, I, Indermuehle, B, Popping, A, Sault, RJ & Whiting, MT 2016, 'The radio spectral energy distribution of infrared-faint radio sources', Astronomy and Astrophysics, vol. 593, A130. https://doi.org/10.1051/0004-6361/201527000

@article{4f78167899124814818b3073b122b4a7,

title = "The radio spectral energy distribution of infrared-faint radio sources",

abstract = "Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z 1:7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims. Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods. We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results. We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (< 0:8; 74+6 9%), but we also find ultra-steep SEDs (< 1:3; 6+7 2%). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least 18+8 5% of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 M yr-1.",

keywords = "Galaxies: active, Galaxies: high-redshift, Radio continuum: galaxies",

author = "A. Herzog and Norris, {R. P.} and E. Middelberg and N. Seymour and Spitler, {L. R.} and Emonts, {B. H C} and Franzen, {T. M O} and R. Hunstead and Intema, {H. T.} and J. Marvil and Parker, {Q. A.} and Sirothia, {S. K.} and N. Hurley-Walker and M. Bell and G. Bernardi and Judd Bowman and F. Briggs and Cappallo, {R. J.} and Callingham, {J. R.} and Deshpande, {A. A.} and Dwarakanath, {K. S.} and For, {B. Q.} and Greenhill, {L. J.} and P. Hancock and Hazelton, {B. J.} and L. Hindson and M. Johnston-Hollitt and Kapi{\'n}ska, {A. D.} and Kaplan, {D. L.} and E. Lenc and Lonsdale, {C. J.} and B. McKinley and McWhirter, {S. R.} and Mitchell, {D. A.} and Morales, {M. F.} and E. Morgan and J. Morgan and D. Oberoi and A. Offringa and Ord, {S. M.} and T. Prabu and P. Procopio and {Udaya Shankar}, N. and Srivani, {K. S.} and L. Staveley-Smith and R. Subrahmanyan and Tingay, {S. J.} and Wayth, {R. B.} and Webster, {R. L.} and A. Williams and Williams, {C. L.} and C. Wu and Q. Zheng and Bannister, {K. W.} and Chippendale, {A. P.} and L. Harvey-Smith and I. Heywood and B. Indermuehle and A. Popping and Sault, {R. J.} and Whiting, {M. T.}",

note = "Publisher Copyright: {\textcopyright} ESO 2016.",

year = "2016",

month = sep,

day = "1",

doi = "10.1051/0004-6361/201527000",

language = "English (US)",

volume = "593",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

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TY - JOUR

T1 - The radio spectral energy distribution of infrared-faint radio sources

AU - Herzog, A.

AU - Norris, R. P.

AU - Middelberg, E.

AU - Seymour, N.

AU - Spitler, L. R.

AU - Emonts, B. H C

AU - Franzen, T. M O

AU - Hunstead, R.

AU - Intema, H. T.

AU - Marvil, J.

AU - Parker, Q. A.

AU - Sirothia, S. K.

AU - Hurley-Walker, N.

AU - Bell, M.

AU - Bernardi, G.

AU - Bowman, Judd

AU - Briggs, F.

AU - Cappallo, R. J.

AU - Callingham, J. R.

AU - Deshpande, A. A.

AU - Dwarakanath, K. S.

AU - For, B. Q.

AU - Greenhill, L. J.

AU - Hancock, P.

AU - Hazelton, B. J.

AU - Hindson, L.

AU - Johnston-Hollitt, M.

AU - Kapińska, A. D.

AU - Kaplan, D. L.

AU - Lenc, E.

AU - Lonsdale, C. J.

AU - McKinley, B.

AU - McWhirter, S. R.

AU - Mitchell, D. A.

AU - Morales, M. F.

AU - Morgan, E.

AU - Morgan, J.

AU - Oberoi, D.

AU - Offringa, A.

AU - Ord, S. M.

AU - Prabu, T.

AU - Procopio, P.

AU - Udaya Shankar, N.

AU - Srivani, K. S.

AU - Staveley-Smith, L.

AU - Subrahmanyan, R.

AU - Tingay, S. J.

AU - Wayth, R. B.

AU - Webster, R. L.

AU - Williams, A.

AU - Williams, C. L.

AU - Wu, C.

AU - Zheng, Q.

AU - Bannister, K. W.

AU - Chippendale, A. P.

AU - Harvey-Smith, L.

AU - Heywood, I.

AU - Indermuehle, B.

AU - Popping, A.

AU - Sault, R. J.

AU - Whiting, M. T.

PY - 2016/9/1

Y1 - 2016/9/1

N2 - Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z 1:7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims. Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods. We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results. We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (< 0:8; 74+6 9%), but we also find ultra-steep SEDs (< 1:3; 6+7 2%). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least 18+8 5% of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 M yr-1.

AB - Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z 1:7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims. Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods. We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results. We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (< 0:8; 74+6 9%), but we also find ultra-steep SEDs (< 1:3; 6+7 2%). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least 18+8 5% of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 M yr-1.

KW - Galaxies: active

KW - Galaxies: high-redshift

KW - Radio continuum: galaxies

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UR - http://www.scopus.com/inward/citedby.url?scp=84990177619&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201527000

DO - 10.1051/0004-6361/201527000

M3 - Article

AN - SCOPUS:84990177619

SN - 0004-6361

VL - 593

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A130

ER -

The radio spectral energy distribution of infrared-faint radio sources

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