Towards a census of high-redshift dusty galaxies with $\mathit{Herschel}$: A selection of "500 $\mu$m-risers"

• Published in: Astronomy and astrophysics (Berlin) Vol. 614
• Main Authors: Bethermin, M., Álvarez-Márquez, J., Donevski, D., Buat, V., Boone, F., Pappalardo, C., Béthermin, M., Schreiber, C., Mazyed, F., Alvarez-Marquez, J., Duivenvoorden, S.
• Format: Journal Article
• Language: English
• Published: EDP Sciences 01.06.2018
• Subjects: Astrophysics; Sciences of the Universe
• ISSN: 0004-6361; 1432-0756
• DOI: 10.1051/0004-6361/201731888

$\mathit{Herschel}$ extragalactic surveys offer a unique opportunity to efficiently select a significant number of rare and massive dusty objects, and thus gain insight into the prodigious star-forming activity that takes place in the very distant Universe. To search for $z\geq4$ dusty star-forming galaxies, in this work we consider red SPIRE objects with fluxes rising from 250 $\mu$m to $500\:\mu$m (so-called "500 $\mu$m-risers"). We aim to implement a novel method to obtain a statistical sample of "500 $\mu$m-risers" and fully evaluate our selection inspecting different models of galaxy evolution. We consider one of the largest and deepest ${\it Herschel}$ surveys, the Herschel Virgo Cluster Survey. We develop a novel selection algorithm which links the source extraction and spectral energy distribution fitting. We select 133 "500 $\mu$m-risers" over 55 deg$^{2}$, imposing the criteria: $S_{500}>S_{350}>S_{250}$, $S_{250}>13.2$ mJy and $S_{500}>$30 mJy. Differential number counts are in a fairly good agreement with models, displaying better match than other existing samples. In order to interpret the statistical properties of selected sources, which has been proven as a very challenging task due the complexity of observed artefacts, we make end-to-end simulations including physical clustering and lensing. The estimated fraction of strongly lensed sources is $24^{+6}_{-5}\%$ based on models. We present the faintest known statistical sample of "500 $\mu$m-risers" and show that noise and strong lensing have crucial 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 $\mu$m-risers" and found it close to the total value measured in far-infrared. It indicates that colour selection is not a limiting effect to search for the most massive, dusty $z>4$ sources.