The<i>K</i>‐Band Galaxy Luminosity Function

Abstract

We measured the K-band luminosity function using a complete sample of 4192 morphologically-typed 2MASS galaxies with µKs = 20 mag/arcsec 2 isophotal magnitudes 7 &amp;lt; K20 &amp;lt; 11.25 mag spread over 2.12 str. Early-type (T ≤ −0.5) and late-type (T&amp;gt; −0.5) galaxies have similarly shaped luminosity functions, αe = −0.92 ± 0.10 and αl = −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 H0 = 100h km s −1 Mpc −1, such that the late-type galaxies slightly dominate the K-band luminosity density, jlate/jearly = 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 &amp;lt; ∼ 18 mag, beyond which the results depend on galaxy evolution and merger histories. 1 This publication makes use of data products from the Two Micron All Sky Survey (2MASS), which is a joint