The ALPINE–ALMA [C II] survey

Abstract

We present the first [C II] 158 μm luminosity function (LF) at z ∼ 5 from a sample of serendipitous lines detected in the ALMA Large Program to INvestigate [C II] at Early times (ALPINE). A study of the 118 ALPINE pointings revealed several serendipitous lines. Based on their fidelity, we selected 14 lines for the final catalog. According to the redshift of their counterparts, we identified eight out of 14 detections as [C II] lines at z ∼ 5, along with two as CO transitions at lower redshifts. The remaining four lines have an elusive identification in the available catalogs and we considered them as [C II] candidates. We used the eight confirmed [C II] and the four [C II] candidates to build one of the first [C II] LFs at z ∼ 5. We found that 11 out of these 12 sources have a redshift very similar to that of the ALPINE target in the same pointing, suggesting the presence of overdensities around the targets. Therefore, we split the sample in two (a “clustered” and “field” subsample) according to their redshift separation and built two separate LFs. Our estimates suggest that there could be an evolution of the [C II] LF between z ∼ 5 and z ∼ 0. By converting the [C II] luminosity to the star-formation rate, we evaluated the cosmic star-formation rate density (SFRD) at z ∼ 5. The clustered sample results in a SFRD ∼10 times higher than previous measurements from UV–selected galaxies. On the other hand, from the field sample (likely representing the average galaxy population), we derived a SFRD ∼1.6 higher compared to current estimates from UV surveys but compatible within the errors. Because of the large uncertainties, observations of larger samples will be necessary to better constrain the SFRD at z ∼ 5. This study represents one of the first efforts aimed at characterizing the demography of [C II] emitters at z ∼ 5 using a mm selection of galaxies.

The ALPINE-ALMA [C II] Survey: [C II] 158 μm Emission Line Luminosity Functions at z ∼ 4–6

“…-and many of them have multiple components and are clearly interacting. Several ALPINE papers (Béthermin et al 2020;Le Fèvre et al 2020;Loiacono et al 2020) discuss this property. Jones et al (2020) has focused on one triple merger system, deimos_cosmos_818760, with three [C II] components.…”

“…Our paper only considers Component a. Loiacono et al (2020) regards Component b as a part of the serendipitous [C II] detection sample.…”

“…The ALPINE surveys allow for the next best thing-i.e., search for serendipitous sources within the same ALMA data as our targets. This search was conducted by Loiacono et al (2020). In Section 4.2 we compare our results with those of Loiacono et al (2020) who compute the [C II] LFs using serendipitous [C II] sources in the ALPINE survey.…”

“…This search was conducted by Loiacono et al (2020). In Section 4.2 we compare our results with those of Loiacono et al (2020) who compute the [C II] LFs using serendipitous [C II] sources in the ALPINE survey. Because of potentially uncertain redshift identifications and strong clustering effects, the results from the serendipitous sources should be considered upper bounds.…”

“…Fortunately, with the 118 ALMA maps along separate pointings, searching for serendipitous [C II] emitters at 4.40<z<4.58 and 5.13<z<5.85 can quantify this effect. In a companion paper, Loiacono et al (2020) carried out a blind search for all line emitters within the 118 data cubes. They identified eight [C II] emitters at z∼5 confirmed by the optical spectroscopic redshifts, and four possible [C II] candidates with only photo-z.…”