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The 2 Micron All-Sky Survey (2MASS) will observe over one-million galaxies and extended Galactic sources covering the entire sky at wavelengths between 1 and 2 microns. The survey catalog will have both high completeness and reliability down to J = 15.0 and Ks = 13.5 mag, equivalent to 1.6 mJy and 2.9 mJy, respectively. This paper describes the basic algorithms used to detect and characterize extended sources in the 2MASS database and catalog. Critical procedures include tracking the point spread function, image background removal, artifact removal, photometry and basic parameterization, star-galaxy discrimination and object classification using a decision tree technique. Examples of extended sources encountered in 2MASS are given.Comment: Astronomical Journal, in press. See http://spider.ipac.caltech.edu/staff/jarrett/papers/2mass/paperI.htm

We measured the K-band luminosity function using a complete sample of 4192 morphologically-typed 2MASS galaxies with µ Ks = 20 mag/arcsec 2 isophotal magnitudes 7 < K 20 < 11.25 mag spread over 2.12 str. Early-type (T ≤ −0.5) and late-type (T > −0.5) galaxies have similarly shaped luminosity functions, α e = −0.92 ± 0.10 and α l = −0.87 ± 0.09. The early-type galaxies are brighter, M * e = −23.53 ± 0.06 mag compared to M * l = −22.98 ± 0.06 mag, but less numerous, n * e = (0.45 ± 0.06) × 10 −2 h 3 Mpc −3 compared to n * l = (1.01 ± 0.13) × 10 −2 h 3 Mpc −3 for H 0 = 100h km s −1 Mpc −1 , such that the late-type galaxies slightly dominate the K-band luminosity density, j late /j early = 1.17 ± 0.12. Our morphological classifications are internally consistent, consistent with previous classifications and lead to luminosity functions unaffected by the estimated uncertainties in the classifications. These luminosity functions accurately predict the K-band number counts and redshift distributions for K < ∼ 18 mag, beyond which the results depend on galaxy evolution and merger histories.

We present the results of the 2MASS Redshift Survey (2MRS), a ten-year project to map the full three-dimensional distribution of galaxies in the nearby Universe. The 2 Micron All-Sky Survey (2MASS) was completed in 2003 and its final data products, including an extended source catalog (XSC), are available on-line. The 2MASS XSC contains nearly a million galaxies with K s ≤ 13.5 mag and is essentially complete and mostly unaffected by interstellar extinction and stellar confusion down to a galactic latitude of |b| = 5 • for bright galaxies. Near-infrared wavelengths are sensitive to the old stellar populations that dominate galaxy masses, making 2MASS an excellent starting point to study the distribution of matter in the nearby Universe.We selected a sample of 44,599 2MASS galaxies with K s ≤ 11.75 mag and |b| ≥ 5 • (≥ 8 • towards the Galactic bulge) as the input catalog for our survey. We obtained spectroscopic observations for 11,000 galaxies and used previously-obtained velocities for the remainder of the sample to generate a redshift catalog that is 97.6% complete to well-defined limits and covers 91% of the sky. This provides an unprecedented census of galaxy (baryonic mass) concentrations within 300 Mpc.Earlier versions of our survey have been used in a number of publications that have studied the bulk motion of the Local Group, mapped the density and peculiar velocity fields out to 50 h −1 Mpc, detected galaxy groups, and estimated the values of several cosmological parameters.Additionally, we present morphological types for a nearly-complete sub-sample of 20,860 galaxies with K s ≤ 11.25 mag and |b| ≥ 10 • .