Context :

Aims : We present a kinematic study of a sample of 298 planetary nebulas ( PNs ) in the outer halo of the central Virgo galaxy M87 ( NGC 4486 ) .
The line-of-sight velocities of these PNs are used to identify sub-components , to measure the angular momentum content of the main M87 halo , and to constrain the orbital distribution of the stars at these large radii .

Methods : We use Gaussian mixture modelling to statistically separate distinct velocity components and identify the M87 smooth halo component , its unrelaxed substructures , and the intra-cluster ( IC ) PNs .
We compute probability weighted velocity and velocity dispersion maps for the smooth halo , and its specific angular momentum profile ( \lambda _ { \mathrm { R } } ) and velocity dispersion profile .

Results : The classification of the PNs into smooth halo and ICPNs is supported by their different PN luminosity functions .
Based on a K-S test , we conclude that the ICPN line-of-sight velocity distribution ( LOSVD ) is consistent with the LOSVD of the galaxies in Virgo subcluster A .
The surface density profile of the ICPNS at 100 \mathrm { kpc } radii has a shallow logarithmic slope , - \alpha _ { ICL } \simeq - 0.8 , dominating the light at the largest radii .
Previous B-V colour and resolved star metallicity data indicate masses for the ICPN progenitor galaxies of a few \times 10 ^ { 8 } M _ { \odot } .
The angular momentum-related \lambda _ { \mathrm { R } } profile for the smooth halo remains below 0.1 , in the slow rotator regime , out to 135 kpc average ellipse radius ( 170 kpc major axis distance ) .
Combining the PN velocity dispersion measurements for the M87 halo with literature data in the central 15 kpc , we obtain a complete velocity dispersion profile out to R _ { avg } = 135 kpc .
The \sigma _ { halo } profile decreases from the central 400 kms ^ { -1 } to about 270 kms ^ { -1 } at 2-10 kpc , then rises again to \simeq 300 \pm 50 \mathrm { kms } ^ { -1 } at 50-70 kpc to finally decrease sharply to \sigma _ { \mathrm { halo } } \sim 100 \mathrm { kms } ^ { -1 } at R _ { avg } = 135 kpc .
The steeply decreasing outer \sigma _ { halo } profile and the surface density profile of the smooth halo can be reconciled with the circular velocity curve inferred from assuming hydrostatic equilibrium for the hot X-ray gas .
Because this rises to \mathrm { v _ { c,X } \sim 700 } \mathrm { kms ^ { -1 } } at 200 kpc , the orbit distribution of the smooth M87 halo is required to change strongly from approximately isotropic within R _ { avg } \sim 60 kpc to very radially anisotropic at the largest distances probed .

Conclusions : The extended LOSVD of the PNs in the M87 halo allows the identification of several subcomponents : the ICPNs , the “ crown ” accretion event , and the smooth M87 halo .
In galaxies like M87 , the presence of these sub-components needs to be taken into account to avoid systematic biases in estimating the total enclosed mass .
The dynamical structure inferred from the velocity dispersion profile indicates that the smooth halo of M87 steepens beyond R _ { avg } = 60 kpc and becomes strongly radially anisotropic , and that the velocity dispersion profile is consistent with the X-ray circular velocity curve at these radii without non-thermal pressure effects .