File Download
  Links for fulltext
     (May Require Subscription)
Supplementary

Article: Infrared-faint Radio Sources Remain Undetected at Far-infrared Wavelengths: Deep photometric observations using the Herschel Space Observatory

TitleInfrared-faint Radio Sources Remain Undetected at Far-infrared Wavelengths: Deep photometric observations using the Herschel Space Observatory
Authors
KeywordsTechniques: photometric
Galaxies: active
Galaxies: high-redshift
Galaxies: star formation
Infrared: galaxies
Issue Date2015
PublisherEDP Sciences. The Journal's web site is located at http://www.aanda.org
Citation
Astronomy & Astrophysics, 2015, v. 580, article no. A7 How to Cite?
AbstractContext. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims. This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods. A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results. All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any redshift; and (d) scaled and dust-obscured radio-loud quasars or compact steep spectrum sources. We estimated upper limits on the infrared luminosity, the black hole accretion rate, and the star formation rate of IFRS, which all agreed with corresponding numbers of HzRGs.
Persistent Identifierhttp://hdl.handle.net/10722/214492
ISSN
2019 Impact Factor: 5.636
2015 SCImago Journal Rankings: 2.446
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorHerzog, A-
dc.contributor.authorNorris, RP-
dc.contributor.authorMiddelberg, E-
dc.contributor.authorSpitler, LR-
dc.contributor.authorLeipski, C-
dc.contributor.authorParker, QA-
dc.date.accessioned2015-08-21T11:32:17Z-
dc.date.available2015-08-21T11:32:17Z-
dc.date.issued2015-
dc.identifier.citationAstronomy & Astrophysics, 2015, v. 580, article no. A7-
dc.identifier.issn0004-6361-
dc.identifier.urihttp://hdl.handle.net/10722/214492-
dc.description.abstractContext. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims. This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods. A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results. All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any redshift; and (d) scaled and dust-obscured radio-loud quasars or compact steep spectrum sources. We estimated upper limits on the infrared luminosity, the black hole accretion rate, and the star formation rate of IFRS, which all agreed with corresponding numbers of HzRGs.-
dc.languageeng-
dc.publisherEDP Sciences. The Journal's web site is located at http://www.aanda.org-
dc.relation.ispartofAstronomy & Astrophysics-
dc.rightsReproduced with permission from Astronomy & Astrophysics, © ESO 2015. The original publication is available at https://doi.org/10.1051/0004-6361/201425405-
dc.subjectTechniques: photometric-
dc.subjectGalaxies: active-
dc.subjectGalaxies: high-redshift-
dc.subjectGalaxies: star formation-
dc.subjectInfrared: galaxies-
dc.titleInfrared-faint Radio Sources Remain Undetected at Far-infrared Wavelengths: Deep photometric observations using the Herschel Space Observatory-
dc.typeArticle-
dc.identifier.emailParker, QA: quentinp@hku.hk-
dc.identifier.authorityParker, QA=rp02017-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1051/0004-6361/201425405-
dc.identifier.scopuseid_2-s2.0-84937459842-
dc.identifier.hkuros248975-
dc.identifier.volume580-
dc.identifier.spagearticle no. A7-
dc.identifier.epagearticle no. A7-
dc.identifier.isiWOS:000360020200007-
dc.publisher.placeFrance-

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats