The Halos and Environments of Nearby Galaxies (HERON) I: Imaging, Sample Characteristics, and Envelope Diameters.

We use a dedicated 0.7-m telescope to image the halosof 119 galaxiesin the Local Volume to $\mu_r \sim 28-30$ mag/arcsec$^2$. The sample is primarily from the 2MASS Large GalaxyAtlas and extendedto include nearby dwarf galaxiesand more distant giant ellipticals, and spans fully the galaxycolour-magnitude diagram including the blue cloud and red sequence. We present an initial overview, including deep images of our galaxies. Our observations reproduce previously reported low surface brightnessstructures, including extendedplumes in M51, and a newly discovered tidally extended dwarf galaxyin NGC7331. Low surface brightnessstructures, or "envelopes", exceeding 50 kpc in diameter are found mostly in galaxieswith $M_V<-20.5$, and classic interaction signatures are infrequent. Defining a halodiameter at the surface brightness28 mag/arcsec$^2$, we find that halodiameter is correlated with total galaxyluminosity. Extendedsignatures of interaction are found throughout the galaxycolour-magnitude diagram without preference for the red or blue sequences, or the green valley. Large envelopes may be found throughout the colour-magnitude diagram with some preference for the bright end of the red sequence. Spiral and S0 galaxieshave broadly similar sizes, but ellipticals extendto notably greater diameters, reaching 150 kpc. We propose that the extendedenvelopes of disk galaxiesare dominated by an extension of the disk population rather than by a classical population II halo.