A Spitzer Space Telescope survey in the NOAO Deep-Wide Field in Boötes provides a complete , 8 µm-selected sample of galaxies to a limiting ( Vega ) magnitude of 13.5 .
In the 6.88 deg ^ { 2 } field sampled , 79 % of the 4867 galaxies have spectroscopic redshifts , allowing an accurate determination of the local ( z < 0.3 ) galaxy luminosity function .
Stellar and dust emission can be separated on the basis of observed galaxy colors .
Dust emission ( mostly PAH ) accounts for 80 % of the 8 µm luminosity , stellar photospheres account for 19 % , and AGN emission accounts for roughly 1 % .
A sub-sample of the 8 µm-selected galaxies have blue , early-type colors , but even most of these have significant PAH emission .
The luminosity functions for the total 8 µm luminosity and for the dust emission alone are both well fit by Schechter functions .
For the 8 µm luminosity function , the characteristic luminosity is \nu L _ { \nu } ^ { * } ( 8.0 ~ { } \micron ) = 1.8 \times 10 ^ { 10 } L _ { \sun } while for the dust emission alone it is 1.6 \times 10 ^ { 10 } L _ { \sun } .
The average 8 µm luminosity density at z < 0.3 is 3.1 \times 10 ^ { 7 } L _ { \sun } Mpc ^ { -3 } , and the average luminosity density from dust alone is 2.5 \times 10 ^ { 7 } L _ { \sun } Mpc ^ { -3 } .
This luminosity arises predominantly from galaxies with 8 µm luminosities ( \nu L _ { \nu } ) between 2 \times 10 ^ { 9 } and 2 \times 10 ^ { 10 } L _ { \sun } , i.e. , normal galaxies , not LIRGs or ULIRGs .