Radio Sources in the Nearby Universe

Abstract

We identified 15,658 NVSS radio sources among the 55,288 2MASX galaxies brighter than $k_\\mathrm{20fe} = 12.25$ at $\\lambda = 2.16\\,\\mu\\mathrm{m}$ and covering the $\\Omega =7.016$ sr of sky defined by J2000 $\\delta > -40^\\circ$ and $\\vert b \\vert > 20^\\circ$. The complete sample of 15,043 galaxies with 1.4 GHz flux densities $S \\geq 2.45 \\mathrm{~mJy}$ contains a 99.9% spectroscopically complete subsample of 9,517 galaxies with $k_\\mathrm{20fe} \\leq 11.75$. We used only radio and infrared data to quantitatively distinguish radio sources powered primarily by recent star formation from those powered by active galactic nuclei. The radio sources with $\\log[L(\\mathrm{W~Hz}^{-1})] > 19.3$ that we used to derive the local spectral luminosity and power-density functions account for $>99$% of the total 1.4~GHz spectral power densities $U_\\mathrm{SF} = (1.54 \\pm 0.20) \\times 10^{19} \\mathrm{~W~Hz}^{-1} \\mathrm{~Mpc}^{-3}$ and $U_\\mathrm{AGN} = (4.23 \\pm 0.78) \\times 10^{19} \\mathrm{~W~Hz}^{-1} \\mathrm{~Mpc}^{-3}$ in the universe today, and the spectroscopic subsample is large enough that the quoted errors are dominated cosmic variance. The recent comoving star-formation rate density indicated by $U_\\mathrm{SF}$ is $\\psi \\approx 0.015~ M_\\odot \\mathrm{~yr}^{-1} \\mathrm{~Mpc}^{-3}$.