Herschel deep far-infrared counts through the Abell 2218 cluster-lens
Abstract
Gravitational lensing by massive galaxy clusters allows study of the population of intrinsically faint infrared galaxies that lie below the sensitivity and confusion limits of current infrared and submillimeter telescopes. We present ultra-deep PACS 100 and 160 microns observations toward the cluster lens Abell 2218, to penetrate the Herschel confusion limit. We derive source counts down to a flux density of 1 mJy at 100 microns and 2 mJy at 160 microns, aided by strong gravitational lensing. At these levels, source densities are 20 and 10 beams/source in the two bands, approaching source density confusion at 160 microns. The slope of the counts below the turnover of the Euclidean-normalized differential curve is constrained in both bands and is consistent with most of the recent backwards evolutionary models. By integrating number counts over the flux range accessed by Abell 2218 lensing (0.94-35 mJy at 100 microns and 1.47-35 mJy at 160 microns, we retrieve a cosmic infrared background (CIB) surface brightness of ~8.0 and ~9.9 nW m^-2 sr^-1, in the respective bands. These values correspond to 55% (+/- 24%) and 77% (+/- 31%) of DIRBE direct measurements. Combining Abell 2218 results with wider/shallower fields, these figures increase to 62% (+/- 25%) and 88% (+/- 32%) CIB total fractions, resolved at 100 and 160 microns, disregarding the high uncertainties of DIRBE absolute values.
Keywords
Cite
@article{arxiv.1005.1575,
title = {Herschel deep far-infrared counts through the Abell 2218 cluster-lens},
author = {B. Altieri and S. Berta and D. Lutz and J. -P. Kneib and L. Metcalfe and P. Andreani and H. Aussel and A. Bongiovanni and A. Cava and J. Cepa and L. Ciesla and A. Cimatti and E. Daddi and H. Dominguez and D. Elbaz and N. M. Forster Schreiber and R. Genzel and C. Gruppioni and B. Magnelli and G. Magdis and R. Maiolino and R. Nordon and A. M. Perez Garcia and A. Poglitsch and P. Popesso and F. Pozzi and J. Richard and L. Riguccini and G. Rodighiero and A. Saintonge and P. Santini and M. Sanchez-Portal and L. Shao and E. Sturm and L. J. Tacconi and I. Valtchanov and M. Wetzstein and E. Wieprecht},
journal= {arXiv preprint arXiv:1005.1575},
year = {2015}
}
Comments
Accepted for publication on the A&A Herschel Special Issue, final version