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Issue A&A
Volume 409, Number 3, October III 2003
Page(s) L41 - L45
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20031337



A&A 409, L41-L45 (2003)
DOI: 10.1051/0004-6361:20031337

Letter

Gas and dust in the Cloverleaf quasar at redshift 2.5

A. Weiß1, C. Henkel2, D. Downes3 and F. Walter4

1  IRAM, Avenida Divina Pastora 7, 18012 Granada, Spain
2  MPIfR, Auf dem Hügel 69, 53121 Bonn, Germany
3  IRAM, 300 rue de la Piscine, 38406 St-Martin-d'Héres, France
4  NRAO, PO Box O Socorro, NM, 87801, USA

(Received 22 August 2003 / Accepted 1 September 2003)

Abstract
We observed the upper fine structure line of neutral carbon, CI $(\rm ^3P_2\!\to^3\!P_1)$, ( $\nu_{\rm rest} = 809$ GHz), the ${^{12}{\rm CO}(J=3\!\to\!2)}$, line ( $\nu_{\rm rest} = 345$ GHz) and the 1.2 mm continuum emission from H1413+117 (Cloverleaf quasar, z=2.5) using the IRAM interferometer. Together with the detection of the lower fine structure line (Barvainis et al. 1997), the Cloverleaf quasar is now only the second extragalactic system, besides M 82, where both carbon lines have convincingly been detected. Our analysis shows that the carbon lines are optically thin and have an excitation temperature of ${{T}_{\rm ex}}$, $\approx$ 30 K. CO is subthermally excited and the observed line luminosity ratios are consistent with ${n({\rm H}_2)}$, $\approx$ 10 $^{3-4}\,{\rm cm}^{-3}$ at ${{T}_{\rm kin}}$,= 30-50 K. Using three independent methods (CI, dust, CO) we derive a total molecular gas mass (corrected for magnification) of $M({{\rm H}_2})$ $\approx$ 1.2 $\pm$ 0.3 $\times$ 10 $^{10}\,{{M}_{\odot}}$. Our observations suggest that the molecular disk extends beyond the region seen in CO(7-6) to a zone of more moderately excited molecular gas that dominates the global emission in CI, and the low J CO lines.


Key words: galaxies: formation -- galaxies: starburst -- galaxies: high-redshift quasars: emission lines -- quasars: individual H1413+117 -- cosmology: observations

Offprint request: A. Weiß, aweiss@iram.es

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