The 24 Micron Source Counts in Deep Spitzer Space Telescope Surveys**This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Academic Article uri icon


  • Galaxy source counts in the infrared provide strong constraints on the evolution of the bolometric energy output from distant galaxy populations. We present the results from deep 24 m imaging from Spitzer surveys, which include 5 104 sources to an 80% completeness of 60 Jy. The 24 m counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with a super-Euclidean rate between 0.4 and 4 mJy, and converge below 0.3 mJy. The 24 m counts exceed expectations from nonevolving models by a factor of 10 at Sv 0.1 mJy. The peak in the differential number counts corresponds to a population of faint sources that is not expected from predictions based on 15 m counts from the Infrared Space Observatory. We argue that this implies the existence of a previously undetected population of infrared-luminous galaxies at z 1-3. Integrating the counts to 60 Jy, we derive a lower limit on the 24 m background intensity of 1.9 0.6 nW m-2 sr-1 of which the majority (60%) stems from sources fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60 Jy contribute 0.8-0.4+0.9 n W m-2 sr-1 to the background, which provides an estimate of the total 24 m background of 2.7-0.7+1.1 m-2 sr-1.

published proceedings

  • The Astrophysical Journal Supplement Series

author list (cited authors)

  • Papovich, C., Dole, H., Egami, E., Le Floch, E., Prez-Gonzlez, P. G., Alonso-Herrero, A., ... Young, E. T.

citation count

  • 280

complete list of authors

  • Papovich, C||Dole, H||Egami, E||Le Floc’h, E||Pérez-González, PG||Alonso-Herrero, A||Bai, L||Beichman, CA||Blaylock, M||Engelbracht, CW||Gordon, KD||Hines, DC||Misselt, KA||Morrison, JE||Mould, J||Muzerolle, J||Neugebauer, G||Richards, PL||Rieke, GH||Rieke, MJ||Rigby, JR||Su, KYL||Young, ET

publication date

  • September 2004