Herschel unveils a puzzling uniformity of distant dusty galaxies
Abstract
The Herschel Space Observatory enables us to accurately measure the bolometric output of starburst galaxies and active galactic nuclei (AGN) by directly sampling the peak of their far-infrared (IR) emission. Here we examine whether the spectral energy distribution (SED) and dust temperature of galaxies have strongly evolved since z~2.5. We use Herschel deep extragalactic surveys from 100 to 500um to compute total IR luminosities in galaxies down to the faintest levels, using PACS and SPIRE in the GOODS-North field (PEP and HerMES key programs). We show that measurements in the SPIRE bands can be used below the statistical confusion limit if information at higher spatial resolution is used to identify isolated galaxies whose flux is not boosted by bright neighbors. Below z~1.5, mid-IR extrapolations are correct for star-forming galaxies with a dispersion of only 40% (0.15dex), therefore similar to z~0 galaxies. This narrow distribution is puzzling when considering the range of physical processes that could have affected the SED of these galaxies. Extrapolations from only one of the 160um, 250um or 350um bands alone tend to overestimate the total IR luminosity. This may be explained by the lack of far-IR constraints around and above ~150um (rest-frame) on local templates. We also note that the dust temperature of luminous IR galaxies around z~1 is mildly colder by 10-15% than their local analogs and up to 20% for ULIRGs at z~1.6. Above z=1.5, distant galaxies are found to exhibit a substantially larger mid- over far-IR ratio, which could either result from stronger broad emission lines or warm dust continuum heated by a hidden AGN. Two thirds of the AGNs identified in the field with a measured redshift exhibit the same behavior as purely star-forming galaxies. Hence a large fraction of AGNs harbor star formation at very high SFR and in conditions similar to purely star-forming galaxies.
Keywords
Cite
@article{arxiv.1005.2859,
title = {Herschel unveils a puzzling uniformity of distant dusty galaxies},
author = {D. Elbaz and H. S. Hwang and B. Magnelli and E. Daddi and H. Aussel and B. Altieri and A. Amblard and P. Andreani and V. Arumugam and R. Auld and T. Babbedge and S. Berta and A. Blain and J. Bock and A. Bongiovanni and A. Boselli and V. Buat and D. Burgarella and N. Castro-Rodriguez and A. Cava and J. Cepa and P. Chanial and R. -R. Chary and A. Cimatti and D. L. Clements and A. Conley and L. Conversi and A. Cooray and M. Dickinson and H. Dominguez and C. D. Dowell and J. S. Dunlop and E. Dwek and S. Eales and D. Farrah and N. Forster Schreiber and M. Fox and A. Franceschini and W. Gear and R. Genzel and J. Glenn and M. Griffin and C. Gruppioni and M. Halpern and E. Hatziminaoglou and E. Ibar and K. Isaak and R. J. Ivison and G. Lagache and D. Le Borgne and E. Le Floc'h and L. Levenson and N. Lu and D. Lutz and S. Madden and B. Maffei and G. Magdis and G. Mainetti and R. Maiolino and L. Marchetti and A. M. J. Mortier and H. T. Nguyen and R. Nordon and B. O'Halloran and K. Okumura and S. J. Oliver and A. Omont and M. J. Page and P. Panuzzo and A. Papageorgiou and C. P. Pearson and I. Perez Fournon and A. M. Perez Garcıa and A. Poglitsch and M. Pohlen and P. Popesso and F. Pozzi and J. I. Rawlings and D. Rigopoulou and L. Riguccini and D. Rizzo and G. Rodighiero and I. G. Roseboom and M. Rowan-Robinson and A. Saintonge and M. Sanchez-Portal and P. Santini and M. Sauvage and B. Schulz and Douglas Scott and N. Seymour and L. Shao and D. L. Shupe and A. J. Smith and J. A. Stevens and E. Sturm and M. Symeonidis and L. Tacconi and M. Trichas and K. E. Tugwell and M. Vaccari and I. Valtchanov and J. Vieira and L. Vigroux and L. Wang and R. Ward and G. Wright and C. K. Xu and M. Zemcov},
journal= {arXiv preprint arXiv:1005.2859},
year = {2015}
}
Comments
Astronomy and Astrophysics, Herschel Special Issue, in press as a Letter; 5 pages