0 Assigned ID: 1259 ----- Attempting Submission 1 (Fri Sep 30 11:28:32 GMT 2016) ----- HST Phase I Proposal 1259 (a1201_cy24mc.apt) successfully submitted. Receipt: # 1259-1 ----- Attempting Submission 2 (Fri Sep 30 14:13:43 GMT 2016) ----- Resubmission after making small adjustment (~2 arcsec) to target coordinates. -2064111135 ----- Attempting Submission 1 (Thu Dec 15 09:20:14 GMT 2016) ----- ----- Attempting Submission 2 (Wed Jan 04 12:02:26 GMT 2017) ----- Abell 1201 is a cluster of galaxies at z=0.17, with a brightest cluster galaxy (BCG) which acts as a gravitational lens to a background surce at z=0.45. The lensing configuration is unusual, with a single bright arc formed at small radius (~5kpc), where the stars are expected to contribute substantially to the total lensing mass. Using VLT/MUSE data, we have recently discovered a faint counter-image to the main arc, located just 0.6" from the lens centre. This image is not predicted at all in lensing models which incorporate the mass contributions from stars (following the observed light profile) and dark matter. Modelling shows that the formation of the counter-image requires additional mass at small radius. Possible solutions include (a) imposing a gradient of the stellar-mass-to-light ratio, reflecting a heavier initial mass function (IMF) in the galaxy centre, or (b) adding a central black hole with mass above ten billion solar masses, comparable to the largest dynamical measurements. The first scenario would be relevant to ongoing controversies concering possible non-standard IMFs in massive elliptical galaxies. The second explanation would be the first lensing-based detection of a central black hole, with implications for the still sparsely-populated upper end of the black hole scaling relations. The two alternative models yield different predictions for the morphology of the counter-image. Our proposed WFC3/UVIS observations will establish whether the image is (a) a radial arc, supporting the IMF gradient interpretation, or (b) a compact counter-image, confirming the ultra-massive black hole scenario. HST resolution is essential for this measurement. The target is a z=0.17 cluster-dominant elliptical galaxy, with an unusual gravitational-lensing arc system. The particular aim of these observations is to get improved information on a very faint inner counter-image to the main arc, buried behind the bright elliptical. We observe in a blue bandpass (F390W), to improve contrast between the star-forming background galaxy and the red foreground galaxy. We also take imaging in a red bandpass (F814W), to help model the stellar mass distribution in the lens. The observation should be fairly straightforward, with a simple five-point small-dither pattern in each band for cosmic ray and detector defect rejection. The dither is a typical N+1/2 pixel "box", with an additional "central" position. But since the observations get split over three orbits, pointing offset errors probably introduce their own significant random dither at similar level. We elected to use post-flash to mitigate CTE losses in the F814W where the exposures are short; we also use the C1K1C-CTE aperture to keep target close to the amplifier. Galaxies Massive Black Holes and their Hosts 3 false false false false false false SUPPORTED CLUSTER OF GALAXIES GRAVITATIONAL LENS RICH CLUSTER This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F814W 1483531315104 /tmp/OPVisit7972821150392606291.xml The scheduling data was generated by CASM 24.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14886 :visit-id "02" :proposal-version -1 :trans-version "20160601" :date "04-Jan-2017 12:01:54.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 2309952 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14886 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14886 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2885 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14886 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2996 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14886 :visit-id "02" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2996 :al-overhead-at-end 116 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3218 :pcs-gap 0 ) true 3 0