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We use a 0.7-m telescope in the framework of the Halos and Environments ofNearby Galaxies (HERON) survey to probe low surface brightness structures innearby galaxies. One of our targets, UGC 4599, is usually classified as anearly-type galaxy surrounded by a blue ring making it a potential Hoag's Objectanalog. Prior photometric studies of UGC 4599 were focused on its bright coreand the blue ring. However, the HERON survey allows us to study its faintextended regions. With an eight hour integration, we detect an extremely faintouter disk with an extrapolated central surface brightness of$\mu_\mathrm{0,d}(r)=25.5$ mag arcsec$^{-2}$ down to 31 mag arcsec$^{-2}$ and ascale length of 15 kpc. We identify two distinct spiral arms of pitch angle~6{\deg} surrounding the ring. The spiral arms are detected out to ~45 kpc inradius and the faint disk continues to ~70 kpc. These features are also seen inthe GALEX FUV and NUV bands, in a deep u-band image from the 4.3m LowellDiscovery Telescope (which reveals inner spiral structure emerging from thecore), and in HI. We compare this galaxy to ordinary spiral and ellipticalgalaxies, giant low surface brightness (GLSB) galaxies, and Hoag's Objectitself using several standard galaxy scaling relations. We conclude that thepseudobulge and disk properties of UGC 4599 significantly differ from those ofHoag's Object and of normal galaxies, pointing toward a GLSB galaxy nature andfilamentary accretion of gas to generate its outer disk.

The haloes and environments of nearby galaxies (HERON) -- III. A 45 kpc spiral structure in the GLSB galaxy UGC 4599