The Luminous z$=2.286$ IRAS Source FSC10214$+$4724 Contains a Hidden AGN

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Session 119 -- Starbursts and Seyfert 2s
Oral presentation, Saturday, January 15, 10:15-11:45, Crystal Forum Room (Crystal City Marriott)

[119.05] The Luminous z$=2.286$ IRAS Source FSC10214$+$4724 Contains a Hidden AGN

B.T.Jannuzi (IAS), R.Elston (NOAO/CTIO), G.D.Schmidt, P.S.Smith (Univ. of Az)

There is debate over the power generator of the luminous high redshift (z$=2.286$) IRAS source FSC10214$+$4724: a burst of star formation (Rowan-Robinson et al. 1993) and/or an AGN (cf. Lawrence et al. 1993). Our optical spectrophotopolarimetry of this object confirms the detection by Lawrence et al. of highly polarized UV emission and reveals that the narrow line emission is polarized to the same degree as the continuum emission. The similar degree of polarization and consistent position angle for all of the polarized emission suggests that the same polarization mechanism is responsible for producing all of the observed polarized flux and a substantial fraction of the total observed UV and optical emission. As discussed by Lawrence et al., the large degree of polarization (17 \%) and the presence of detectable UV emission makes it virtually impossible that dichroic absorption by dust is the cause of the polarized emission. This leaves scattering by either electrons or dust as the the polarizing mechanism. The presence of polarized narrow lines requires that the scatters are cold ($<10^5 $ K), most probably dust. Assuming that the polarized emission is produced by dust scattering we can recover the spectrum that is incident on the scattering medium. The derived UV spectrum has a power law index between -0.9 and -3.0, considerably different from what would be expected from a young burst of star formation, but similar to many AGN. Our observations are consistent with the observed UV-optical emission being produced by an obscured AGN.

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