The Local Group Census: searching for PNe in IC 1613, WLM and GR8

Abstract

In the framework of the Local Group Census (LGC), a survey of the Local Group (LG) galaxies above Dec=$-30^\circ$, which is aimed at surveying their populations with strong emission lines, we have searched for planetary nebulae (PNe) in the low-metallicity dwarf irregular galaxies IC1613, WLM, GR8. Two new candidate PNe have been found in IC1613, one in WLM and none in GR8. The observations presented in this paper, together with the previous results from the LGC, represent the first step in the study of the PN population in low-metallicity, dwarf irregular galaxies of the Local Group. They will be followed by deep spectroscopy to confirm their nature and to study their physical-chemical properties. We used the observed number of PNe in each LG galaxy to estimate a lower limit to the mass of the intermediate-age population which was compared to the Star Formation Rate (SFR) of LG dwarf galaxies. These results are in agreement with those from accurate star formation history (SFH) analysis for these small galaxy systems.