Intracluster Planetary Nebulae in the Hydra I cluster

Using the Multislit Imaging Spectroscopy (MSIS) technique at the FORS2 spectrograph on VLT-UT1, we have identified 60 Intracluster Planetary Nebula (ICPN) candidates associated with the Intracluster Light (ICL) in the central region of the Hydra I cluster. Hydra I is a medium compact, relatively near (~50 Mpc), rich cluster in the southern hemisphere. Here we describe the criteria used to select emission sources and present the evidence for these PN candidates to be associated with the ICL in the Hydra I cluster. We also show, using the luminosity-specific planetary nebulae number, the alpha parameter, that the expected number of PNs associated with the stellar population of the central cD galaxy NGC 3311 in the cluster is close to the number of PNs detected.

💡 Research Summary

This paper presents a systematic search for intracluster planetary nebulae (ICPN) in the central region of the Hydra I galaxy cluster, employing the Multi‑Slit Imaging Spectroscopy (MSIS) technique on the FORS2 spectrograph at VLT‑UT1. Hydra I is a relatively nearby (≈50 Mpc), rich, medium‑compact cluster in the southern sky, making it an ideal target for probing low‑surface‑brightness intracluster light (ICL). The authors obtained deep MSIS observations covering a 6′ × 6′ field with 1″ slits and a 600 l mm⁻¹ grating, achieving a spectral resolution of R≈2000 around the