Context : The galaxy M49 ( NGC 4472 ) is the brightest early-type galaxy in the Virgo Cluster .
It is located in Subcluster B and has an unusually blue , metal-poor outer halo .
Planetary nebulae ( PNe ) are excellent tracers of diffuse galaxy and intragroup light .

Aims : We aim to present a photometric survey of PNe in the galaxy ’ s extended halo to characterise its PN population , as well as the surrounding intragroup light ( IGL ) of the Subcluster B .

Methods : PNe were identified based on their bright [ OIII ] 5007 Å emission and absence of a broad-band continuum through automated detection techniques .

Results : We identify 738 PNe out to a radius of \sim 155 \mathrm { kpc } from M49 ’ s centre from which we define a complete sample of 624 PNe within a limiting magnitude of m _ { \mathrm { 5007 ,lim } } = 28.8 .
Comparing the PN number density to the broad-band stellar surface brightness profile , we find a variation of the PN-specific frequency ( \alpha -parameter ) with radius .
The outer halo beyond 60 \mathrm { kpc } has a 3.2 times higher \alpha -parameter compared to the main galaxy halo ( \alpha _ { 2.5 , \mathrm { inner } } ^ { \mathrm { M 49 } } = ( 3.20 \pm 0.43 ) \times 10 ^ { -9 } % \mathrm { PN } L ^ { -1 } _ { \odot, \mathrm { bol } } ) , which is likely due to contribution from the surrounding blue IGL .
We use the Planetary Nebulae Luminosity Function ( PNLF ) as an indicator of distance and stellar population .
Its slope , which correlates empirically with galaxy type , varies within the inner halo .
In the eastern quadrant of M49 , the PNLF slope is shallower , indicating an additional localised , bright PN population following an accretion event , likely that of the dwarf irregular galaxy VCC1249 .
We also determined a distance modulus of \mu _ { \mathrm { PNLF } } = 31.29 ^ { +0.07 } _ { -0.08 } for M49 , corresponding to a physical distance of 18.1 \pm 0.6 \mathrm { Mpc } , which agrees with a recent surface-brightness fluctuations distance .

Conclusions : The PN populations in the outer halo of M49 are consistent with the presence of a main Sérsic galaxy halo with a slight ( B - V ) colour gradient of 10 ^ { -4 } \mathrm { mag } \mathrm { arcsec } ^ { -1 } surrounded by intragroup light with a very blue colour of ( B - V ) = 0.25 and a constant surface brightness \mu _ { V } = 28.0 \mathrm { mag arcsec } ^ { -2 } .