Unveiling the Nature of Fossil Groups with XMM-HST II: Reducing Variance

Science Keywords: Select from 2 to 5 items. Science Keywords is a required field. Small GO Proposals are not allowed in Cycle 26 unless they are Joint Programs. 0 Assigned ID: 615 ----- Attempting Submission 1 (Tue Nov 27 14:52:16 GMT 2018) ----- Joint HST/XMM 0 ----- Attempting Submission 1 (Thu Jan 10 07:25:01 GMT 2019) ----- Unveiling the Nature of Fossil Groups with XMM-HST II: Reducing Variance Fossil groups (FGs) present a puzzle to theories of structure formation. Despite the low number of bright galaxies, their high velocity dispersions and high T X seem to indicate cluster-like potential wells. Their measured c200 are high indicating early formation epochs, in contradiction with the observed lack of expected large cool cores. We have proposed a discriminatory test, using the intracluster light to mass ratio (ICLf/M) in FGs, using XMM and HST. The pilot study was successful and suggests that FGs are not merging and show high ICLf/M ratios in comparison to relaxed systems. We propose to increase the sample of bonafide FGs complementing XMM and HST archived observations to account for sample variance, allowing us to reliably constrain their formation mechanisms and ages. We based our estimation of the exposure times on our previous experience with the HST ACS and the CICLE algorithm applied to several clusters including a CLASH clusters and the FG J1007+3800. CICLE only relies on the information contained in the data, studying the 2D distribution of the light and using the change of intensity curvature to determine where the galaxy ends and the ICL starts. For this reason high quality imaging is required, as that of ACS/WFC. We need S/N of ~2.5-3 to obtain results of similar precision (or better) than those we obtained for J1007+3800. To achieve this S/N in the images of these FGs we would repeat the same exposures as with exposures, i.e., 1 orbit with the F435W filter and 2 orbits with the F606W filter. Based on our previous experience we would like to ask to follow the same setup suggested by Dan Coe, i.e., to split in multiple (3 or 4) exposures to help reject cosmic rays in final stacked images. The dithered exposures should also cover the gap between the two ACS detectors. They will also mitigate against bad detector pixels and improve the resolution of stacked (drizzled) images. Galaxies and the IGM 6 false false false false false false false SUPPORTED CLUSTER OF GALAXIES GROUP POOR CLUSTER YES J2000 J2000 CLUSTER OF GALAXIES GROUP POOR CLUSTER YES J2000 J2000 CLUSTER OF GALAXIES GROUP INTERACTING GALAXY POOR CLUSTER YES J2000 J2000 ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F435W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F435W ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F435W POS-TARG DITHER 3.058944 LINE 6.039452 false false 179.702031 4 85.329042 ACS-WFC-DITHER-BOX 1

false

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