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The Most Luminous Seyfert 2 Galaxy Known (1Mar94)
(from NOAO HIGHLIGHTS!, NOAO Newsletter No. 37, 1 March 1994)

The IRAS Faint Source Catalog (FSC) source 10214+4724 has been
identified with a non-stellar object at a redshift of 2.286, making it
among most bolometrically luminous objects known. The origin of the
extreme luminosity of FSC10214+4724 is a problem.  Two competing ideas
are that it is a heavily obscured AGN or a site of prodigious star
formation.  To sort out such possibilities, R. Elston (CTIO), P.J.
McCarthy (OCIW), P. Eisenhardt (JPL), M. Dickenson (U. of California,
Berkeley), H. Spinrad (U. of California, Berkeley), B. Jannuzi (Inst.
for Advanced Study, Princeton) and P.  Maloney (U. of Colorado,
Boulder) obtained near-IR spectra of FSC10214+4724, using CRSP on the
KPNO 4-m telescope.  The IR spectra are the key to understanding the
source as they allow observation of the optical forbidden lines O [III]
and N [II] at its high redshift.

The CRSP spectra sampled the highly-redshifted regions around Ha and
Hbeta.  The emission line ratios of N [II] 6584/Ha = 1.1 +- 0.2 and O [III]
5007/Hbeta >  20 lead to a classification of FSC1024+4724 as Seyfert 2,
placing it out of the range of any known star-forming galaxy.  It thus
appears that the photoionization of its narrow line region is dominated
by an AGN and not star formation.  Any star formation region would have
to be more heavily obscured than the AGN, a rather contrived solution.
Following the upgrade of the CRSP spectrometer to a 256 x 256 InSb
array, Elston used the KPNO 4-m to reobserve the spectrum near Ha in
FSC10214+4724.  Not only does the new array offer larger wavelength
coverage, which is critical for the detection of broad quasar emission
lines, it offers better performance.  The spectrum in the figure was
obtained at a resolution of about 550 in 1 hour through thin cirrus on
the KPNO 4-m in November 1993.  A S/N of about 3 is present in the
continuum which has K = 16.5.  No broad line emission is seen outside
of the Ha and N [II] blend, suggesting that the red continuum in
FSC10214+4724 is not due to a heavily reddened quasar, but rather is
similar to that in other Seyfert 2 galaxies.  Indeed, this Seyfert 2
type spectrum is very similar to other ultra-luminous IRAS selected
galaxies making it seem that FSC10214+4724 is the luminous extreme of
this class of galaxy rather than a new type of object.

                      [Figure not included]

Elston et al. also obtained a deep H band image of FSC10214+4724 while
they obtained near-IR polarimetry.  This image showed that
FSC10214+4724 was dominated by a bright point source and had several
nearby companions.  They argue that given their red colors and
brightness they are much more similar to a group of early type galaxies
at moderate redshift rather than a group of objects at the redshift of
FSC10214+4724.  To help explain such a rather improbable superposition
they suggest that FSC10214+4724 may be gravitationally amplified by the
foreground group.  Recent Keck images by Mathews et al.  may support
this idea as they show FSC10214+4724 to have "arc" like extensions
extending around the nearest companion to the north.

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