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The galaxy M49 (NGC 4472) is the brightest early-type galaxy in the VirgoCluster. It is located in Subcluster B and has an unusually blue, metal-poorouter halo. Planetary nebulae (PNe) are excellent tracers of diffuse galaxy andintragroup light. We present a photometric survey of PNe in the galaxy'sextended halo to characterise its PN population, as well as the surroundingintragroup light (IGL) of the Subcluster B. PNe were identified based on theirbright [OIII]5007 \AA\ emission and absence of a broad-band continuum. Weidentify 738 PNe out to a radius of 155 kpc from M49's centre from which wedefine a complete sample of 624 PNe within a limiting magnitude of m_5007=28.8.Comparing the PN number density to the broad-band stellar surface brightnessprofile, we find a variation of the PN-specific frequency (alpha-parameter)with radius. The outer halo beyond 60 kpc has a 3.2 times higheralpha-parameter compared to the main galaxy halo, which is likely due tocontribution from the surrounding blue IGL. We use the Planetary NebulaeLuminosity Function (PNLF) as an indicator of distance and stellar population.Its slope, which correlates empirically with galaxy type, varies within theinner halo. In the eastern quadrant of M49, the PNLF slope is shallower,indicating an additional localised, bright PN population following an accretionevent, likely that of the dwarf irregular galaxy VCC1249. We also determined adistance modulus of mu = 31.29+/-0.08 for M49, corresponding to a physicaldistance of 18.1+/-0.6 Mpc, which agrees with a recent surface-brightnessfluctuations distance. The PN populations in the outer halo of M49 areconsistent with the presence of a main Sersic galaxy halo with a slight (B-V)colour gradient of 10${}^{-4}$ mag/arcsec surrounded by intragroup light with avery blue colour of (B-V)=0.25 and a constant surface brightness mu_V=28.0mag/arcsec${}^2$.

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