Far-infrared and molecular co emission from the host galaxies of faint quasars at z ∼ 6

Ran Wang, Jeff Wagg, Chris L. Carilli, Roberto Neri, Fabian Walter, Alain Omont, Dominik A. Riechers, Frank Bertoldi, Karl M. Menten, Pierre Cox, Michael A. Strauss, Xiaohui Fan, Linhua Jiang

Research output: Contribution to journalArticle

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Abstract

We present new millimeter and radio observations of nine z ∼ 6 quasars discovered in deep optical and near-infrared surveys. We observed the 250GHz continuum in eight of the nine objects and detected three of them. New 1.4GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250GHz detections and detected two of them. Combined with previous millimeter and radio observations, we study the far-infrared (FIR) and radio emission and quasar-host galaxy evolution with a sample of 18 z ∼ 6 quasars that are faint at UV and optical wavelengths (rest-frame 1450 magnitudes of m 1450 ≥ 20.2). The average FIR-to-active galactic nucleus (AGN) UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z ∼ 6 (m 1450 < 20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z ∼ 6 quasars, and the average luminosities of samples of submillimeter/millimeter-observed quasars at z ∼ 2-5, yields a relationship of L FIR L bol 0.62. Five of the 18 faint z ∼ 6 quasars have been detected at 250GHz. These 250GHz detections, as well as most of the millimeter-detected optically bright z ∼ 6 quasars, follow a shallower trend of ∼ L FIR L bol 0.45 defined by the starburst-AGN systems in local and high-z universe. The millimeter continuum detections in the five objects and molecular CO detections in three of them reveal a few × 108 M of FIR-emitting warm dust and 1010 M of molecular gas in the quasar host galaxies. All these results argue for massive star formation in the quasar host galaxies, with estimated star formation rates of a few hundred M yr-1. Additionally, the higher FIR-to-AGN luminosity ratio found in these 250GHz detected faint quasars also suggests a higher ratio between star formation rate and supermassive black hole accretion rate than the UV/optically most luminous quasars at z ∼ 6.

Original languageEnglish (US)
Article number101
JournalAstronomical Journal
Volume142
Issue number4
DOIs
StatePublished - Oct 2011

Fingerprint

quasars
radio
galaxies
active galactic nuclei
luminosity
near infrared
accretion
radio observation
dust
wavelength
star formation rate
continuums
detection
gas
rate
molecular gases
radio emission
massive stars
star formation
universe

Keywords

  • galaxies: active
  • galaxies: high-redshift
  • galaxies: starburst
  • molecular data
  • quasars: general

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Wang, R., Wagg, J., Carilli, C. L., Neri, R., Walter, F., Omont, A., ... Jiang, L. (2011). Far-infrared and molecular co emission from the host galaxies of faint quasars at z ∼ 6. Astronomical Journal, 142(4), [101]. https://doi.org/10.1088/0004-6256/142/4/101

Far-infrared and molecular co emission from the host galaxies of faint quasars at z ∼ 6. / Wang, Ran; Wagg, Jeff; Carilli, Chris L.; Neri, Roberto; Walter, Fabian; Omont, Alain; Riechers, Dominik A.; Bertoldi, Frank; Menten, Karl M.; Cox, Pierre; Strauss, Michael A.; Fan, Xiaohui; Jiang, Linhua.

In: Astronomical Journal, Vol. 142, No. 4, 101, 10.2011.

Research output: Contribution to journalArticle

Wang, R, Wagg, J, Carilli, CL, Neri, R, Walter, F, Omont, A, Riechers, DA, Bertoldi, F, Menten, KM, Cox, P, Strauss, MA, Fan, X & Jiang, L 2011, 'Far-infrared and molecular co emission from the host galaxies of faint quasars at z ∼ 6', Astronomical Journal, vol. 142, no. 4, 101. https://doi.org/10.1088/0004-6256/142/4/101
Wang, Ran ; Wagg, Jeff ; Carilli, Chris L. ; Neri, Roberto ; Walter, Fabian ; Omont, Alain ; Riechers, Dominik A. ; Bertoldi, Frank ; Menten, Karl M. ; Cox, Pierre ; Strauss, Michael A. ; Fan, Xiaohui ; Jiang, Linhua. / Far-infrared and molecular co emission from the host galaxies of faint quasars at z ∼ 6. In: Astronomical Journal. 2011 ; Vol. 142, No. 4.
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abstract = "We present new millimeter and radio observations of nine z ∼ 6 quasars discovered in deep optical and near-infrared surveys. We observed the 250GHz continuum in eight of the nine objects and detected three of them. New 1.4GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250GHz detections and detected two of them. Combined with previous millimeter and radio observations, we study the far-infrared (FIR) and radio emission and quasar-host galaxy evolution with a sample of 18 z ∼ 6 quasars that are faint at UV and optical wavelengths (rest-frame 1450 magnitudes of m 1450 ≥ 20.2). The average FIR-to-active galactic nucleus (AGN) UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z ∼ 6 (m 1450 < 20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z ∼ 6 quasars, and the average luminosities of samples of submillimeter/millimeter-observed quasars at z ∼ 2-5, yields a relationship of L FIR L bol 0.62. Five of the 18 faint z ∼ 6 quasars have been detected at 250GHz. These 250GHz detections, as well as most of the millimeter-detected optically bright z ∼ 6 quasars, follow a shallower trend of ∼ L FIR L bol 0.45 defined by the starburst-AGN systems in local and high-z universe. The millimeter continuum detections in the five objects and molecular CO detections in three of them reveal a few × 108 M ⊙ of FIR-emitting warm dust and 1010 M ⊙ of molecular gas in the quasar host galaxies. All these results argue for massive star formation in the quasar host galaxies, with estimated star formation rates of a few hundred M ⊙ yr-1. Additionally, the higher FIR-to-AGN luminosity ratio found in these 250GHz detected faint quasars also suggests a higher ratio between star formation rate and supermassive black hole accretion rate than the UV/optically most luminous quasars at z ∼ 6.",
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AU - Walter, Fabian

AU - Omont, Alain

AU - Riechers, Dominik A.

AU - Bertoldi, Frank

AU - Menten, Karl M.

AU - Cox, Pierre

AU - Strauss, Michael A.

AU - Fan, Xiaohui

AU - Jiang, Linhua

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N2 - We present new millimeter and radio observations of nine z ∼ 6 quasars discovered in deep optical and near-infrared surveys. We observed the 250GHz continuum in eight of the nine objects and detected three of them. New 1.4GHz radio continuum data have been obtained for four sources, and one has been detected. We searched for molecular CO (6-5) line emission in the three 250GHz detections and detected two of them. Combined with previous millimeter and radio observations, we study the far-infrared (FIR) and radio emission and quasar-host galaxy evolution with a sample of 18 z ∼ 6 quasars that are faint at UV and optical wavelengths (rest-frame 1450 magnitudes of m 1450 ≥ 20.2). The average FIR-to-active galactic nucleus (AGN) UV luminosity ratio of this faint quasar sample is about two times higher than that of the bright quasars at z ∼ 6 (m 1450 < 20.2). A fit to the average FIR and AGN bolometric luminosities of both the UV/optically faint and bright z ∼ 6 quasars, and the average luminosities of samples of submillimeter/millimeter-observed quasars at z ∼ 2-5, yields a relationship of L FIR L bol 0.62. Five of the 18 faint z ∼ 6 quasars have been detected at 250GHz. These 250GHz detections, as well as most of the millimeter-detected optically bright z ∼ 6 quasars, follow a shallower trend of ∼ L FIR L bol 0.45 defined by the starburst-AGN systems in local and high-z universe. The millimeter continuum detections in the five objects and molecular CO detections in three of them reveal a few × 108 M ⊙ of FIR-emitting warm dust and 1010 M ⊙ of molecular gas in the quasar host galaxies. All these results argue for massive star formation in the quasar host galaxies, with estimated star formation rates of a few hundred M ⊙ yr-1. Additionally, the higher FIR-to-AGN luminosity ratio found in these 250GHz detected faint quasars also suggests a higher ratio between star formation rate and supermassive black hole accretion rate than the UV/optically most luminous quasars at z ∼ 6.

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KW - molecular data

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