EDP Sciences
Free access
Volume 401, Number 3, April III 2003
Page(s) 911 - 925
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20030171

A&A 401, 911-925 (2003)
DOI: 10.1051/0004-6361:20030171

CO emission and associated H I absorption from a massive gas reservoir surrounding the z = 3 radio galaxy B3 J2330+3927

C. De Breuck1, R. Neri2, R. Morganti3, A. Omont1, B. Rocca-Volmerange1, D. Stern4, M. Reuland5, W. van Breugel5, H. Röttgering6, S. A. Stanford5, 7, H. Spinrad8, M. Vigotti9 and M. Wright10

1  Institut d'Astrophysique de Paris, CNRS, 98bis boulevard Arago, 75014 Paris, France
    e-mail: [debreuck, omont, rocca]@iap.fr
2  Institut de Radioastronomie Millimétrique, 300 rue de la piscine, 38406 St. Martin-d'Hères, France
    e-mail: neri@iram.fr
3  ASTRON, Postbus 2, 7990 AA Dwingeloo, The Netherlands
    e-mail: morganti@nfra.nl
4  Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 169-327, Pasadena, CA 91109, USA
    e-mail: stern@zwolfkinder.jpl.nasa.gov
5  IGPP/LLNL, L-413, 7000 East Ave, Livermore, CA 94550, USA
    e-mail: [mreuland, wil]@igpp.ucllnl.org
6  Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands
    e-mail: rottgeri@strw.leidenuniv.nl
7  Department of Physics, University of California, Davis, CA 95616, USA
    e-mail: adam@igpp.ucllnl.org
8  Department of Astronomy, University of California, Berkeley, CA 94720, USA
    e-mail: spinrad@astro.berkeley.edu
9  Istituto di Radioastronomia del CNR, Via Gobetti 101, 40129 Bologna, Italy
    e-mail: vigotti@ira.bo.cnr.it
10  Radio Astronomy Laboratory, University of California, Berkeley, CA 94720, USA
    e-mail: mwright@astro.berkeley.edu

(Received 12 August 2002 / Accepted 7 February 2003 )

We present results of a comprehensive multi-frequency study of the radio galaxy B3 J2330+3927. The 1 $\farcs$9 wide radio source, consisting of 3 components, is bracketed by 2 objects in our Keck K-band image. Optical and near-IR Keck spectroscopy of these two objects yield $z=3.087\pm 0.004$. The brightest ( K=18.8) object has a standard type II AGN spectrum, and is the most likely location of the AGN, which implies a one-sided jet radio morphology. Deep 113 GHz observations with the IRAM Plateau de Bure Interferometer reveal CO  J=4-3 emission, which peaks at the position of the AGN. The CO line is offset by 500 ${\rm\,km\,s^{-1}}$ from the systemic redshift of the AGN, but corresponds very closely to the velocity shift of an associated $\ion{H}{I}$ absorber seen in Ly $\alpha$. This strongly suggests that both originate from the same gas reservoir surrounding the AGN host galaxy. Simultaneous 230 GHz interferometer observations find a ~ $3 \times$ lower integrated flux density when compared to single dish 250 GHz observations with MAMBO at the IRAM 30 m telescope. This can be interpreted as spatially resolved thermal dust emission at scales of 0 $\farcs$5 to 6´´. Finally, we present a $\tau < 1.3$% limit to the $\ion{H}{I}$ 21 cm absorption against the radio source, which represents the seventh non-detection out of 8 z>2 radio galaxies observed to date with the WSRT. We present mass estimates for the atomic, neutral, and ionized hydrogen, and for the dust, ranging from $M(\ion{H}{I})=2\times 10^7$  $M_{\odot}$ derived from the associated $\ion{H}{I}$ absorber in Ly $\alpha$ up to $M({\rm H}_2)=7\times 10^{10}$  $M_{\odot}$ derived from the CO emission. This indicates that the host galaxy is surrounded by a massive reservoir of gas and dust. The K-band companion objects may be concentrations within this reservoir, which will eventually merge with the central galaxy hosting the AGN.

Key words: galaxies: individual: B3 J2330+3927 -- galaxies: active -- galaxies: formation -- radio lines: galaxies -- cosmology: observations

Offprint request: C. De Breuck, debreuck@iap.fr

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© ESO 2003