Towards a census of high-redshift dusty galaxies with Herschel. A selection of "500 μm-risers"
Abstract
Context. Over the last decade a large number of dusty star-forming galaxies has been discovered up to redshift z = 2 - 3 and recent studies have attempted to push the highly confused Herschel SPIRE surveys beyond that distance. To search for z ≥ 4 galaxies they often consider the sources with fluxes rising from 250 μm to 500 μm (so-called "500 μm-risers"). Herschel surveys offer a unique opportunity to efficiently select a large number of these rare objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe.
Aims: We aim to implement a novel method to obtain a statistical sample of 500 μm-risers and fully evaluate our selection inspecting different models of galaxy evolution.
Methods: We consider one of the largest and deepest Herschel surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. To fully quantify selection biases we make end-to-end simulations including clustering and lensing.
Results: We select 133 500 μm-risers over 55 deg2, imposing the criteria: S500 > S350 > S250, S250 > 13.2 mJy and S500 > 30 mJy. Differential number counts are in fairly good agreement with models, displaying a better match than other existing samples. The estimated fraction of strongly lensed sources is 24+6-5% based on models.
Conclusions: We present the faintest sample of 500 μm-risers down to S250 = 13.2 mJy. We show that noise and strong lensing have an important impact on measured counts and redshift distribution of selected sources. We estimate the flux-corrected star formation rate density at 4 < z < 5 with the 500 μm-risers and find it to be close to the total value measured in far-infrared. This indicates that colour selection is not a limiting effect to search for the most massive, dusty z > 4 sources.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2018
- DOI:
- 10.1051/0004-6361/201731888
- arXiv:
- arXiv:1709.00942
- Bibcode:
- 2018A&A...614A..33D
- Keywords:
-
- galaxies: evolution;
- galaxies: statistics;
- galaxies: photometry;
- galaxies: star formation;
- galaxies: high-redshift;
- infrared: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 28 pages, 13 figures, version accepted for publication in A&