The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)

Abstract

Aims. We present the first detection of diffuse dust in the intra-cluster medium of the Virgo cluster out to ∼0.4 virial radii, and study the radial variation of its properties on a radial scale of the virial radius. Methods. Analysing near-UV – i colours for a sample of ∼12 000 background galaxies with redshifts 0.02 < z < 0.8, we find significant colour reddening and relate it to variation in E(B − V) values. Results. The E(B − V) mean profile shows a dust component characterised by an average reddening E(B − V) ∼ 0.042 ± 0.004 mag within 1.5 degrees (∼0.3 rvir) from the cluster centre. Assuming a Large Magellanic Cloud extinction law, we derive an average visual extinction AV = 0.14 ± 0.01 for a total dust mass, Md = 2.5 ± 0.2 × 109 M⊙, hence a dust-to-gas mass ratio Md/Mg = 3.0 ± 0.3 × 10−4. Based on the upper limits on the flux density I250μm = 0.1 MJy sr−1 derived from Herschel data, we estimate an upper limit for the dust temperature of Td ∼ 10 K. However, similar densities can be obtained with dust at higher temperatures with lower emissivities. Conclusions. The Virgo cluster has diffuse dust in its intra-cluster medium characterised by different physical properties as those characterising the Milky Way dust. The diffuse dust in Virgo is transported into the cluster space through similar phenomena (stripping) as those building up the optical intra-cluster light, and it constitutes an additional cooling agent of the cluster gas.

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

“…• from the cluster centre (Longobardi et al 2020). More specifically, our results show the following:…”

“…Arnaboldi et al 2002;Aguerri et al 2005;Doherty et al 2009;Longobardi et al 2013Longobardi et al , 2015Longobardi et al , 2018aDurrell et al 2014;Hartke et al 2017;Mihos et al 2017). However, if ram-pressure actively strips gas and dust from the galaxies moving through the cluster (e.g Cortese et al 2010bCortese et al , 2012Verdugo et al 2015;Gullieuszik et al 2020;Longobardi et al 2020), it may become an additional key process that contributes to the build-up in the IC component. In a recent work, Longobardi et al (2020) first detected a diffuse dust component in the ICM of Virgo with a mass of 2.5 ± 0.2 × 10 9 M which is consistent with being the result of stripping phenomena happening out to a scale of 0.6 virial radii.…”

“…However, if ram-pressure actively strips gas and dust from the galaxies moving through the cluster (e.g Cortese et al 2010bCortese et al , 2012Verdugo et al 2015;Gullieuszik et al 2020;Longobardi et al 2020), it may become an additional key process that contributes to the build-up in the IC component. In a recent work, Longobardi et al (2020) first detected a diffuse dust component in the ICM of Virgo with a mass of 2.5 ± 0.2 × 10 9 M which is consistent with being the result of stripping phenomena happening out to a scale of 0.6 virial radii. We might then wonder whether the results presented in this work support this evidence.…”

“…7. Herschel FIR 250 µm images of NGC 4330, NGC 4522, and NGC 4654 (orange) overlaid on the mean extinction map of the Virgo intra-cluster dust (green and yellow trace mean values E(B−V) = 0 and E(B − V) = 0.07, respectively) by Longobardi et al (2020, here the regions in space that are contaminated by background clusters are in grey). The three galaxies are magnified by a factor of ∼13 to show the details of the FIR emission.…”

“…In this context, the Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE; Boselli et al 2018) is a new, blind Hα survey providing us with the largest and most in-depth information on the ionised gas emission in Virgo, revealing unknown tails of stripped gas in several cluster members. Additionally, the Virgo cluster has recently been shown to contain a diffuse IC dust (ICD) component that is widespread in the cluster ICM with a dust-to-gas mass ratio of M d /M g = 3.0 ± 0.3 × 10 −4 and it is likely transported into the IC space by stripping (Longobardi et al 2020).…”