paper

IRAS FSC 15307+3252 -- Gravitationally Lensed Seyfert or Cannibal Elliptical at = 0.93?

arXiv:astro-ph/9605114 · doi:10.1086/177907

Abstract

We present the highest spatial and spectral resolution near-infrared data to date of the $\sim~10^{13}~h^{-2}~L_{\sun}$ {\sl IRAS} source FSC 15307+3252 at , apparently the most luminous galaxy in the known Universe. Deep -band (2.2 \micron) images taken in 0\farcs4 seeing at the W.\ M.\ Keck Telescope reveal three components within 2\arcsec. The dominant component has a surface brightness profile well-characterized by an law and a nucleus which is stellar in appearance with extended structure, possibly a second nucleus ~0\farcs5 away. Our 1.1--1.4~\micron\ spectrum shows strong emission lines of \oi\ \lam\lam6300, 6364; blended \ha~+~\nii\ \lam\lam6548, 6583; and \sii\ \lam\lam6716, 6731 with characteristics of Seyfert 2 galaxies. The \ha\ line also has a broad (1900 km~s) component. In light of the recent discovery that FSC 10214+4724, previously the most luminous known galaxy, is a gravitationally-lensed system, we explore the possibility that F15307 is also lensed. Quantitative arguments are inconclusive, but aspects of F15307's morphology do suggest lensing; the system bears a strong resemblance to quadruple-image gravitational lenses. On the other hand, given the profile, the close companions, and the active nucleus, F15307 may in fact be a giant elliptical galaxy caught in the act of galactic cannibalism, a scenario which could also account for its unparalleled luminosity.

AASTeX, 24 pages (19 text and 5 Postscript figures). To appear in the October 20, 1996 issue of the Astrophysical Journal. Corrected orientation of figures and also object positions in Table 1

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