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Issue A&A
Volume 436, Number 3, June IV 2005
Page(s) 825 - 835
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20042304



A&A 436, 825-835 (2005)
DOI: 10.1051/0004-6361:20042304

The extended Lyman-$\alpha$ emission surrounding the z = 3.04 radio-quiet QSO1205-30: Primordial infalling gas illuminated by the quasar?

M. Weidinger1, 2, P. Møller2, J. P. U. Fynbo1, 3 and B. Thomsen1

1  Institute of Physics and Astronomy, University of Aarhus, Ny Munkegade, 8000 Århus C, Denmark
    e-mail: michaelw@phys.au.dk
2  European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
3  Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark

(Received 3 November 2004 / Accepted 2 March 2005 )

Abstract
We present spectroscopic observations obtained with the FORS1 instrument on the ESO VLT under good seeing conditions of the radio-quiet $z_{\rm em}=3.04$ quasar Q1205-30 and its associated extended Ly$\alpha$ emission. The extended Ly$\alpha$ emission was originally found in a deep narrow band image targeting a $z_{\rm abs} \approx z_{\rm em}$ Lyman-limit system in the spectrum of the QSO. Using spectral point-spread function fitting to subtract the QSO spectrum, we clearly detect the extended Ly$\alpha$ emission as well as two foreground galaxies at small impact parameters ( $2.12\,\pm\, 0.04$ and $2.77\,\pm\, 0.07$ arcsec). The redshifts of the two foreground galaxies are found to be z=0.4732 and z=0.865. We determine the redshift and velocity profile for the extended Ly$\alpha$ emission, and analyzing the velocity offsets between eight QSO emission lines we refine the quasar redshift determination. We use the new redshifts to infer the geometry of the complex. We find that the extended Ly$\alpha$ emission is clearly associated with the quasar. A Ly$\alpha$ luminosity of $5.6\times 10^{43}~{\rm ~erg~s}^{-1}$ places this extended emission at the high luminosity end of the few previous detections around radio-quiet quasars. The extended Ly$\alpha$ emission is best explained by hydrogen falling into the dark matter halo inhabited by the quasar.


Key words: galaxies: quasars: absorption lines -- galaxies: quasars: emission lines -- galaxies: quasars: individual: QSO1205-30 -- methods: data analysis

SIMBAD Objects



© ESO 2005


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