Emission line galaxies behind the planetary nebula IC 5148: Potential for a serendipity survey with archival data

TL;DR

This paper reports the serendipitous discovery of six background emission line galaxies behind a planetary nebula using archival data, highlighting the potential of archival surveys for finding ELGs without bias.

Contribution

It demonstrates the potential of archival data to discover emission line galaxies serendipitously, expanding the scope of ELG studies beyond systematic surveys.

Findings

Six background ELGs discovered with redshifts 0.2057 to 0.8668.

Archival data can significantly extend ELG datasets without selection bias.

Serendipitous discoveries are feasible in small sky areas using existing data.

Abstract

During the start of a survey program using FORS2 long slit spectroscopy on planetary nebulae (PN) and their haloes, we serendipitously discovered six background emission line galaxies (ELG) with redshifts of z = 0.2057, 0.3137, 0.37281, 0.4939, 0.7424 and 0.8668. Thus they clearly do not belong to a common cluster structure. We derived the major physical properties of the targets. Since the used long slit covers a sky area of only 570 arcsec^2, we discuss further potential of serendipitous discoveries in archival data, beside the deep systematic work of the ongoing and upcoming big surveys. We conclude that archival data provide a decent potential for extending the overall data on ELGs without any selection bias.