We use a dedicated 0.7-m telescope to image the halos of 119 galaxies in the Local Volume to µ r ∼ 28 − 30 mag/arcsec 2 . The sample is primarily from the 2MASS Large Galaxy Atlas and extended to include nearby dwarf galaxies and more distant giant ellipticals, and spans fully the galaxy colour-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 brightness structures, including extended plumes in M 51, and a newly discovered tidally extended dwarf galaxy in NGC 7331. Low surface brightness structures, or "envelopes", exceeding 50 kpc in diameter are found mostly in galaxies with M V < −20.5, and classic interaction signatures are infrequent. Defining a halo diameter at the surface brightness 28 mag/arcsec 2 , we find that halo diameter is correlated with total galaxy luminosity. Extended signatures of interaction are found throughout the galaxy colour-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 galaxies have broadly similar sizes, but ellipticals extend to notably greater diameters, reaching 150 kpc. We propose that the extended envelopes of disk galaxies are dominated by an extension of the disk population rather than by a classical population II halo.

We present an analysis of the pitch angle distribution function (PADF) for nearby galaxies and its resulting black hole mass function (BHMF) via the well-known relationship between pitch angle and black hole mass. Our sample consists of a subset of 74 spiral galaxies from the Carnegie-Irvine Galaxy Survey with absolute B-band magnitude MB>−19.12 mag and luminosity distance DL≤25.4 Mpc, which is an extension of a complementary set of 140 more luminous (MB≤−19.12 mag) late-type galaxies. We find the PADFs of the two samples are, somewhat surprisingly, not strongly dissimilar; a result that may hold important implications for spiral formation theories. Our data show a distinct bimodal population manifest in the pitch angles of the Sa–Sc types and separately the Scd–Sm types, with Sa–Sc types having tighter spiral arms on average. Importantly, we uncover a distinct bifurcation of the BHMF, such that the Sa–Sc galaxies typically host so-called “supermassive” black holes (M•≳106M⊙), whereas Scd–Sm galaxies accordingly harbor black holes that are “less-than-supermassive” (M•≲106M⊙). It is amongst this latter population of galaxies where we expect fruitful bounties of elusive intermediate-mass black holes (IMBHs), through which a better understanding will help form more precise benchmarks for future generations of gravitational wave detectors.

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