Vol. 633
1. Letters

The GALEX Ultraviolet Virgo Cluster Survey (GUViCS) VIII. Diffuse dust in the Virgo intra-cluster space

Dust is thought to be destroyed by sputtering in galaxy clusters, which are rich in X-ray emitting hot gas. However, some dust may still exist in shielded regions or from gas tails that have just been stripped from galaxies. Measurements of the amount of dust in clusters have derived extinctions between AV=0.004 and 0.5. The present work represents the first detection of diffuse dust in the intra-cluster medium of the Virgo cluster out to ~0.4 virial radius. The authors have used the near-ultraviolet-I colors of about 12000 background galaxies with redshifts 0.02 < z < 0.8, and find an average reddening E(B - V) ~ 0.042 mag within 1.5 degrees or 0.3 virial radius from the cluster’s center. Assuming a Large Magellanic Cloud extinction law, they derived an average visual extinction AV = 0.14, leading to a total dust mass of Md = 2.5 10^9Mo and hence a dust-to-gas mass ratio of Md/Mg = 3.0 x 10^-4, which is much lower than in the Milky Way. The far-infrared emission of the dust was not detected by Herschel at 250 micron; this means that either the dust temperature should be low, about 10 K, or that the dust has lower emissivity than usual. Nevertheless, this diffuse dust in the Virgo cluster must originate from the galaxies through tidal or ram-pressure stripping.