The halo of M49 and its environment as traced by planetary nebulae

Abstract

We investigate the stellar halo of the nearby elliptical Virgo-cluster galaxy M49 using Planetary Nebulae (PNe). M49 is the second-brightest galaxy of the Virgo cluster and is at the center of the Virgo subcluster B. We present an extended catalogue extracted from a narrow-band survey carried out with Subaru's Suprime Cam, consisting of 735 PNe down to a limiting magnitude of m5007 = 29.3. This PNe population traces the halo out to 155 kpc from the galaxy's center, which provides accurate measurement of the luminosity-specific PN-number (α-parameter) in the inner and outer regions of M49's halo. We are also able to determine the morphological variation of the planetary nebulae luminosity function (PNLF), that may trace different parent stellar populations. This enables us to identify the transition from the PN-scarce, possibly metal-rich, galaxy halo to the PN-rich, metal-poor, outer component.