The Local [CII] 158 um Emission Line Luminosity Function

TL;DR

This paper measures the local [CII] 158 um emission line luminosity function using a large galaxy sample, providing new insights into galaxy properties and their evolution, and comparing it with IR and CO luminosity functions.

Contribution

First measurement of the local [CII] 158 um luminosity function using Herschel data and a large galaxy sample, with implications for galaxy evolution studies.

Findings

The [CII] luminosity function agrees with the IR luminosity function.

A varying [CII]/CO ratio is proposed to reconcile [CII] and CO luminosity functions.

Evolution in the [CII] luminosity function is suggested, similar to cosmic star formation rate trends.

Abstract

We present, for the first time, the local [CII] 158 um emission line luminosity function measured using a sample of more than 500 galaxies from the Revised Bright Galaxy Sample (RBGS). [CII] luminosities are measured from the Herschel PACS observations of the Luminous Infrared Galaxies in the Great Observatories All-sky LIRG Survey (GOALS) and estimated for the rest of the sample based on the far-IR luminosity and color. The sample covers 91.3% of the sky and is complete at S_60 um > 5.24 Jy. We calculated the completeness as a function of [CII] line luminosity and distance, based on the far-IR color and flux densities. The [CII] luminosity function is constrained in the range ~10^(7-9) (Lo) from both the 1/V_max and a maximum likelihood methods. The shape of our derived [CII] emission line luminosity function agrees well with the IR luminosity function. For the CO(1-0) and [CII] luminosity functions to agree, we propose a varying ratio of [CII]/CO(1-0) as a function of CO luminosity, with larger ratios for fainter CO luminosities. Limited [CII] high redshift observations as well as estimates based on the IR and UV luminosity functions are suggestive of an evolution in the [CII] luminosity function similar to the evolution trend of the cosmic star formation rate density. Deep surveys using ALMA with full capability will be able to confirm this prediction.