Science Keywords: Select from 2 to 5 items. Science Keywords is a required field. Number is a required field. 0 Assigned ID: 1627 ----- Attempting Submission 1 (Mon Dec 11 15:57:21 GMT 2017) ----- Joint XMM/HST Update by ACS Instrument Scientist Coe after discussion with PI: added drizzling and combined all 3 orbits into one visit. -255481847 ----- Attempting Submission 1 (Thu Jan 11 00:56:41 GMT 2018) ----- ----- Attempting Submission 2 (Thu Jan 25 21:11:13 GMT 2018) ----- Fossil groups 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 gravitational potential wells. The measured concentration parameters seem to be high indicating early formation epochs but some recent observations contradict that scenario. We propose a discriminatory test, using intracluster light to mass ratio, combining short XMM and HST observations for a classic massive fossil group. We will use a newly developed method for measuring ICL that is independent of arbitrary assumptions about light distribution and that has provided new robust results. This test will allow us to set independent constraints on formation mechanisms and ages of these peculiar (but numerous) systems. We based our estimation of the exposure times on our previous experience in Jimenez-Teja & Dupke (2016,2018) with the HST ACS and the CICLE algorithm. In this work CICLE has been successfully applied to the dynamically very active Pandora system (Abell 2744), formed by 4 merging clusters, fact that made the calculation of the ICL fraction a highly complex task. Note that this FG (z=0.112) is 3 times closer than the Pandora cluster and has been specially selected to be as relaxed as possible, so the determination of the ICL fraction with ACS data would be straighforward. The CICLE method does not rely on arbitrary cut-off or assumptions on the light distribution of galaxies, but only relies on the information contained in the data, studying the two-dimensional 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 from ACS/WFC. We need a S/N of ~2.5-3 to obtain results of similar precision (or better) that those we obtained for Pandora. To achieve this S/N in the images of this FG with the F606W filter, ACS ETC estimates a number of 2-3 orbits, which is what we requested. In Jimenez-Teja & Dupke 2016 we found that the CICLE yielded a high ICL fraction in the F814W filter for the cluster Abell 2744, which was consistent with other works in the literature. Given the lower redshift of RX-J10074257+3800462, a bluer filter was preferable to study the ICL in this Fossil Group proposed here. Furthermore, in Jimenez-Teja & Dupke 2018, we performed a multiwavelength analysis of the ICL fraction in a larger sample of eleven clusters, observing that the ICL fraction color gradient in the F435W and F606W filters was the most representative figure to characterize the dynamical state (merging or relaxed) of the systems. The objectives of this proposal can be significant enhanced by that extra information as well, since not just the age of the system but its current dynamical state could be ascertained. Therefore, we request that one of 3 orbits approved to us be used with F435W to verity the color gradient and the other 2 with F606W. Despite the small reduction in significance from the F606W filter observation, the result will be much more informative. Galaxies and the IGM 6 false false false false false false SUPPORTED CLUSTER OF GALAXIES GROUP This object was generated by the targetselector and retrieved from the NED database.This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F435W POS-TARG DITHER 3.034 LINE false false 4 85.29 ACS-WFC-DITHER-LINE 1 false 1516867695497 /Users/dcoe/ACS/review/15443/OP-cache/15443_mod-v01.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. all 3 orbits (Tic-Visit :proposal-id 15443 :visit-id "01" :proposal-version -1 :trans-version "20171009" :date "25-Jan-2018 03:08:15.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 3410688 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15443 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15443 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2924 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3260 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15443 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3038 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3260 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15443 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3037 :al-overhead-at-end 0 :internal-dur-at-end 347 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3260 :pcs-gap 0 ) true 3 0