A&A 380, 409-417 (2001)
DOI: 10.1051/0004-6361:20011442
Investigating the nature of the
submillimeter
selected galaxy SMM J02399-0136 with VLT spectropolarimetry
J. Vernet1, 2 and A. Cimatti2
1 European Southern Observatory, Karl Schwarzschild Str. 2, 85748 Garching bei München, Germany
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 50125 Firenze, Italy
(Received 8 August 2001 / Accepted 18 September 2001 )
Abstract
We present deep optical spectropolarimetry of
SMM J02399-0136 (z=2.8) done with the VLT Antu 8.2 m
telescope equipped with FORS1. Moderate continuum and emission line
polarization are measured (
). We do not detect broad lines
in scattered flux as would be expected for a type-2 object but rather
a polarization behaviour similar to BAL quasars. This classification
is confirmed by the detection of both high and low ionization broad
absorption troughs and a very red continuum. We argue that this object
shares several properties with local ULIGs such as Mrk 231 and other
ultraluminous infrared Lo-BAL quasars. However, the fact that the
ultraviolet spectrum is dominated by non-stellar radiation does not
prove that the dust that is thermally radiating in the far infrared is
predominantly heated by the AGN. Since the energy that we get in the
far-infrared is precisely that which is removed from the ultraviolet
spectrum, this could mean that the starburst is more dust-enshrouded
than the AGN due to a peculiar dust distribution. The
limits we place on the putative starburst contribution to the
restframe ultraviolet continuum together with constraints on the
amount of extinction provide an upper limit to the star formation
rate of about 2000 
yr-1, consistent with previously
claimed high star formation rates level in this object.
Key words: galaxies: active -- galaxies: starburst -- quasars: absorption lines -- techniques: polarimetric -- individual: SMM J02399-0136
Offprint request: J. Vernet, vernet@arcetri.astro.it
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