# On the existence of bright IR galaxies at z>2: tension between Herschel and SCUBA-2 results?

## TL;DR

This paper examines the discrepancies between Herschel and SCUBA-2 sub-millimetre surveys regarding the existence of bright IR galaxies at z>2, highlighting how selection biases and SED assumptions influence the inferred galaxy evolution.

## Contribution

It demonstrates the impact of selection biases, incompleteness, and SED assumptions on IR luminosity function derivations from sub-mm surveys, emphasizing the need for broad IR wavelength coverage.

## Key findings

- Long-wavelength surveys may miss warm SED galaxies.
- Spectral energy distribution assumptions significantly affect IR luminosity estimates.
- Using wide IR spectral coverage reduces uncertainties and biases.

## Abstract

Recent derivations of the galaxy star formation rate density (SFRD) obtained from sub-millimetre (sub-mm) surveys (e.g., SCUBA-2) show a tension with previous works based on Herschel and multi-wavelength data. Some of these works claim that the SFRD derived by pushing the Herschel surveys beyond z~2 are incorrect. However, the current sub-mm surveys obtained from SCUBA-2 data and the methods used to construct the total infrared (IR) luminosity function (LF) and the SFRD could be affected by some limitations. Here we show how these limitations (i.e., selection bias and incompleteness effects) might affect the total IR LF, making the resulting dusty galaxy evolution of difficult interpretation. In particular, we find that the assumed spectral energy distribution (SED) plays a crucial role in the total IR LF derivation, moreover, we confirm that the long-wavelength (e.g., 850-micron) surveys can be incomplete against "warm" SED galaxies, and that the use of a wide spectral coverage of IR wavelengths is crucial to limit the uncertainties and biases.