I'm just reading the latest paper I can find on this ..
"The Sudden Death of the Nearest Quasar" by Schawinski, Evans et al, Dated 1st Nov 2010 (ie: prior to the GalaxyZoo's announcement at the beginning of the thread).
They say …
Quote:
The Voorwerp is a large (11 × 16 kiloparsec) cloud of ionized gas 45,000-70,000 lightyears away from the nucleus of the galaxy IC 2497, embedded in a larger reservoir of atomic hydrogen (J ́ozsa et al. 2009), with a mass of several times 109M⊙ (see Figure 1). The optical spectrum of the Voorwerp is dominated by a powerful [O iii] λ5007 emission line and shows little detectable continuum.
The presence of other emission lines with high ionization potentials, such as [He ii] and [Ne v], together with the narrowness of the emission lines suggest that the Voorwerp is being photoionized by the hard continuum of an active galactic nucleus (AGN; an accreting supermassive black hole), rather than by other processes such as star formation or shocks (such as might be induced by a jet; Lintott et al. 2009).
Radio observations of IC 2497 reveal a nuclear source and a jet hotspot in the nucleus, and a large kiloparsec-scale structure that may be a jet (J ́ozsa et al. 2009; Rampadarath et al. 2010).
The Voorwerp lies where this jet meets the Hi reservoir and coincides with a local decrement in atomic hydrogen presumably due to photoionization. An actively accreting black hole at the centre of IC 2497 is therefore the only plausible source of ionization that can account for the emission seen from the Voorwerp.
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More in next post.
Cheers