We present an all-sky catalog of 451 nearby galaxies, each having an individual distance estimate D P 10 Mpc or a radial velocity V LG < 550 km s À1 . The catalog contains data on basic optical and H i properties of the galaxies, in particular, their diameters, absolute magnitudes, morphological types, circumnuclear region types, optical and H i surface brightnesses, rotational velocities, and indicative mass-to-luminosity and H i massto-luminosity ratios, as well as a so-called tidal index, which quantifies the galaxy environment. We expect the catalog completeness to be roughly 70%-80% within 8 Mpc. About 85% of the Local Volume population are dwarf (dIr, dIm, and dSph) galaxies with M B > À17:0, which contribute about 4% to the local luminosity density, and roughly 10%-15% to the local H i mass density. The H i mass-to-luminosity and the H i mass-tototal (indicative) mass ratios increase systematically from giant galaxies toward dwarfs, reaching maximum values about 5 in solar units for the most tiny objects. For the Local Volume disklike galaxies, their H i masses and angular momentum follow Zasov's linear relation, expected for rotating gaseous disks being near the threshold of gravitational instability, favorable for active star formation. We found that the mean local luminosity density exceeds 1.7-2.0 times the global density, in spite of the presence of the Tully void and the absence of rich clusters in the Local Volume. The mean local H i density is 1.4 times its ''global'' value derived from the H i Parkes Sky Survey. However, the mean local baryon density b (<8 Mpc) ¼ 2:3% consists of only a half of the global baryon density, b ¼ (4:7 AE 0:6)% (Spergel et al., published in 2003). The mean-square pairwise difference of radial velocities is about 100 km s À1 for spatial separations within 1 Mpc, increasing to $300 km s À1 on a scale of $3 Mpc. We also calculated the integral area of the sky occupied by the neighboring galaxies. Assuming the H i size of spiral and irregular galaxies to be 2.5 times their standard optical diameter and ignoring any evolution effect, we obtain the expected number of the line-of-sight intersections with the H i galaxy images to be dn=dz $ 0:4, which does not contradict the observed number of absorptions in QSO spectra.

The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D < 4 Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small & large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of ∼ 10 4 in luminosity and star formation rate. The survey data consists of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST), supplemented with archival data and new Wide Field Planetary Camera (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m F 475W = 28.0 mag, m F 606W = 27.3 mag, and m F 814W = 27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump (RC). The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both the ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

The recently initiated Arecibo Legacy Fast ALFA (ALFALFA) survey aims to map $7000 deg 2 of the high Galactic latitude sky visible from Arecibo, providing a H i line spectral database covering the redshift range between À1600 and 18,000 km s À1 with $5 km s À1 resolution. Exploiting Arecibo's large collecting area and small beam size, ALFALFA is specifically designed to probe the faint end of the H i mass function in the local universe and will provide a census of H i in the surveyed sky area to faint flux limits, making it especially useful in synergy with wide-area surveys conducted at other wavelengths. ALFALFA will also provide the basis for studies of the dynamics of galaxies within the Local Supercluster and nearby superclusters, allow measurement of the H i diameter function, and enable a first wide-area blind search for local H i tidal features, H i absorbers at z < 0:06, and OH megamasers in the redshift range 0:16 < z < 0:25. Although completion of the survey will require some 5 years, public access to the ALFALFA data and data products will be provided in a timely manner, thus allowing its application for studies beyond those targeted by the ALFALFA collaboration. ALFALFA adopts a two-pass, minimum intrusion, drift scan observing technique that samples the same region of sky at two separate epochs to aid in the discrimination of cosmic signals from noise and terrestrial interference. Survey simulations, which take into account large-scale structure in the mass distribution and incorporate experience with the ALFA system gained from tests conducted during its commissioning phase, suggest that ALFALFA will detect on the order of 20,000 extragalactic H i line sources out to z $ 0:06, including several hundred with H i masses M H i < 10 7:5 M .

We present HST/ACS images and color-magnitude diagrams for 24 nearby galaxies in and near the constellation of Centaurus with radial velocities V LG < 550 km s −1 . Distances are determined based on the luminosities of stars at the tip of the red giant branch that range from 3.0 Mpc to 6.5 Mpc. The galaxies are concentrated in two spatially separated groups around Cen A (NGC 5128) and M 83 (NGC 5236). The Cen A group itself has a mean distance of 3.76±0.05 Mpc, a velocity dispersion of 136 kms −1 , a mean harmonic radius of 192 kpc, and an estimated orbital/virial mass of (6.4 − 8.1) · 10 12 M ⊙ . This elliptical dominated group is found to have a relatively high mass-to-light ratio: M/L B = 125 M ⊙ /L ⊙ . For the M 83 group we derived a mean distance of 4.79±0.10 Mpc, a velocity dispersion of 61 km s −1 , a mean harmonic radius of 89 kpc, and estimated orbital/virial mass of (0.8 − 0.9) · 10 12 M ⊙ . This spiral dominated group is found to have a relatively low M/L B = 34 M ⊙ /L ⊙ . The radius of the zero-velocity surface around Cen A lies at R 0 = 1.40 ± 0.11 Mpc. implying a total mass within R 0 of M T = (6.0 ± 1.4) · 10 12 M ⊙ . This value is in good agreement with the Cen A virial/orbital mass estimates and provides confirmation of the relatively high M/L B of this elliptical-dominated group. The centroids of both the groups, as well as surrounding field galaxies, have very small peculiar velocities, < 25 km s −1 , with respect to the local Hubble flow with H 0 = 68 km s −1 Mpc −1 .

Abstract. We present Hubble Space Telescope/WFPC2 images of the galaxies NGC 2366, NGC 2976, NGC 4236, IC 2574, DDO 53, DDO 82, DDO 165, Holmberg I, Holmberg II, Holmberg IX, K52, K73, BK3N, Garland, and A0952+69 in the M 81 complex. Their true distance moduli, derived from the brightness of the tip of the red giant branch, lie in the range of 27. m 52 (NGC 2366) to 28. m 30 (DDO 165), with a median of 27. m 91, which is typical for other known M 81 group members. Using distances and radial velocities of about 50 galaxies in and around the M 81/NGC 2403 complex, we find the radius of the zero-velocity surface of the M 81 group to be R0 = (1.05 ± 0.07) Mpc, which yields a total mass M (R0) = (1.6 ± 0.3) × 10 12 M and a total mass-to-luminosity ratio M (R0)/LB = (38 ± 7) M /L . The total mass within R0 agrees well with the sum of masses estimated via the virial theorem (1.2 × 10 12 M ) and from orbital motions (2.0 × 10 12 M ) of companions around M 81 and NGC 2403. We suggest that most of the dark matter in the group is concentrated around the luminous matter, allowing us to explain the observed asymmetry of the peculiar motions of the M 81 companions. M 81 itself has a peculiar velocity of about 130 km s −1 with respect to the local Hubble flow, but the centroid of the M 81/NGC 2403 complex is almost at rest with respect to Hubble flow (vpec < 35 km s −1 ).