Streams as a Production Line: What Virgo's Tidal Features Must Supply to Build Its Intracluster Light

Between the smooth intracluster light of a cluster and the galaxies that supply it stands a population of visible intermediates: tidal streams, shells, and plumes caught in the act of dissolving. This paper budgets three catalogued Virgo systems, the shell system of M49 at 3.0e+09 solar luminosities, the outer plume of M87 at 1.2e+09, and the M84-M86 plume at 8.0e+08, and asks what production rate of such events Virgo's diffuse component requires. At a mass-to-light ratio of 2.5 the three carry 7.5e+09, 3.0e+09, and 2.0e+09 solar masses; if each represents a quarter of its progenitor's stars, the progenitors weighed 3.0e+10, 1.2e+10, and 8.0e+09 solar masses. Supplying a cluster-wide diffuse mass of 1.6e11 solar masses over ten billion years from M49-class events alone would take 21 of them, 2.1 per billion years; from plume-class events, 53 at 5.3 per billion years. Virgo's sky currently shows of order one such event per line of sight generation, so the required rates are consistent with the observed stream population if a typical stream remains recognisable for a few hundred million years. The streams are not decoration on the diffuse component; at the required rates they are its production line, observed mid-operation.