Aims. We investigate the diffuse light in the outer regions of the nearby elliptical galaxy M 87 in the Virgo cluster, in the transition region between galaxy halo and intracluster light (ICL). Methods. The diffuse light is traced using planetary nebulas (PNs). The surveyed areas are imaged with a narrow-band filter centred on the redshifted [OIII]λ5007 Å emission line at the Virgo cluster distance (the on-band image) and with a broad-band V-filter (the off-band image). All PNs are identified through the on-off band technique using automatic selection criteria based on the distribution of the detected sources in the colour-magnitude diagram and the properties of their point-spread function.Results. We present the results of an imaging survey for PNs within a total effective area of 0.43 deg 2 , covering the stellar halo of M 87 up to a radial distance of 150 kpc. We extract a catalogue of 688 objects down to m 5007 = 28.4, with an estimated residual contamination from foreground stars and background Lyα galaxies, which amounts to ∼35% of the sample. This is one of the largest extragalactic PN samples in number of candidates, magnitude depth, and radial extent, which allows us to carry out an unprecedented photometric study of the PN population in the outer regions of M 87. We find that the logarithmic density profile of the PN distribution is shallower than the surface brightness profile at large radii. This behaviour is consistent with a model where the luminosity specific PN numbers for the M 87 halo and ICL are different. Because of the depth of this survey we are also able to study the shape of the PN luminosity function (PNLF) in the outer regions of M 87. We find a slope for the PNLF that is steeper at fainter magnitudes than the standard analytical PNLF formula and adopt a generalised model that treats the slope as a free parameter. Conclusions. The logarithmic PN number density profile is consistent with the superposition of two components associated with the halo of M 87 and with the ICL, which have different α parameters. We derive α 2.5,halo = (1.10,bol and α 2.5,ICL = (3.29,bol for the halo and the intracluster stellar components, respectively. The fit of the generalised formula to the empirical PNLF for the M 87 halo returns a value for the slope of 1.17 and a preliminary distance modulus to the M 87 halo of 30.74. Comparing the PNLF of M 87 and the M 31 bulge, both normalised by the sampled luminosity, the M 87 PNLF contains fewer bright PNs and has a steeper slope towards fainter magnitudes.

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Hα+ [NII] imaging survey carried out with MegaCam at the Canada-France-Hawaii Telescope. During pilot observations taken in the spring of 2016 we observed NGC 4330, an intermediate mass (M * 10 9.8 M ) edge-on star forming spiral currently falling into the core of the Virgo cluster. While previous Hα observations showed a clumpy complex of ionised gas knots outside the galaxy disc, new deep observations revealed a low surface brightness ∼ 10 kpc tail exhibiting a peculiar filamentary structure. The filaments are remarkably parallel to one another and clearly indicate the direction of motion of the galaxy in the Virgo potential. Motivated by the detection of these features which indicate ongoing gas stripping, we collected literature photometry in 15 bands from the far-UV to the far-IR and deep optical long-slit spectroscopy using the FORS2 instrument at the ESO Very Large Telescope. Using a newly developed Monte Carlo code that jointly fits spectroscopy and photometry, we reconstructed the star formation histories in apertures along the major axis of the galaxy. Our results have been validated against the output of CIGALE, a fitting code which has been previously used for similar studies. We found a clear outside-in gradient with radius of the time when the quenching event started: the outermost radii were stripped ∼ 500 Myr ago, while the stripping reached the inner 5 kpc from the centre in the last 100 Myr. Regions at even smaller radii are currently still forming stars fueled by the presence of HI and H 2 gas. When compared to statistical studies of the quenching timescales in the local Universe we find that ram pressure stripping of the cold gas is an effective mechanism to reduce the transformation times for galaxies falling into massive clusters. Future systematic studies of all the active galaxies observed by VESTIGE in the Virgo cluster will extend these results to a robust statistical framework.

Aims. We present a spectroscopic study of a sample of 287 planetary nebulas (PNs) around the brightest cluster galaxy (BCG) M 87 in Virgo A, of which 211 are located between 40 kpc and 150 kpc from the galaxy centre. With these data we can distinguish the stellar halo from the co-spatial intracluster light (ICL) and study both components separately. Methods. We obtained PN velocities with a high resolution FLAMES/VLT survey targeting eight fields in a total area of ∼0.4 deg 2 . We identified PNs from their narrow and symmetric redshifted λ5007 Å [OIII] emission line, the presence of the second λ4959 Å [OIII] emission line, and the absence of significant continuum. We implement a robust technique to measure the halo velocity dispersion from the projected phase-space to identify PNs associated with the M 87 halo and ICL. Using photometric magnitudes, we construct PN luminosity functions (PNLFs), which are complete down to m 5007 = 28.8. Results. The velocity distribution of the spectroscopically confirmed PNs is bimodal, containing a narrow component centred on the systemic velocity of the BCG and an off-centred broader component, which we identify as halo and ICL, respectively. We find that 243 PNs are part of the velocity distribution of the M 87 halo, while the remaining subsample of 44 PNs are intracluster PNs (ICPNs). Halo and ICPNs have different spatial distributions: the number density of halo PNs follow the galaxy's surface brightness profile, whereas the ICPNs are characterised by a shallower power-law profile, I ICL ∝ R γ with γ in the range [−0.34, −0.04]. No evidence is found for an asymmetry in the halo and ICPN density distributions when the NW and SE fields are studied separately. A study of the composite PN number density profile confirms the superposition of different PN populations associated with the M 87 halo and the ICL, characterised by different PN specific numbers α. We derive α halo = 1.06 × 10 −8 N PN L −1 ,bol and α ICL = 2.72 × 10 −8 N PN L −1 ,bol , respectively. The M 87 halo PNLF has fewer bright PNs and a steeper slope towards faint magnitudes than the ICPNLF, and both are steeper than the standard PNLF for the M 31 bulge. Moreover, the ICPNLF has a dip at ∼1−1.5 mag fainter than the bright cut-off, reminiscent of the PNLFs of systems with extended star formation history, such as M 33 or the Magellanic clouds. Conclusions. The BCG halo of M 87 and the Virgo ICL are dynamically distinct components with different density profiles and velocity distributions. Moreover, the different α-parameter values and PNLF shapes of the halo and ICL indicate distinct parent stellar populations, consistent with the existence of a gradient towards bluer colours at large radii. These results reflect the hierarchical build-up of the Virgo cluster.