Observations of high-redshift quasars probe the growth of supermassive black holes and their connections to galaxy formation at the earliest epoch. We have been carrying out a systematic survey of the star formation and ISM properties in the host galaxies of z~6 quasars using millimeter dust continuum and molecular CO emission. In this survey, we recently discovered the first z~6 quasar-starburst merger system: radio-loud quasar CFHQS J1429+5447 (z=6.2) is detected as a bright 3.4 mJy source in millimeter continuum; high resolution EVLA imaging of CO(2-1) transition reveals two distinct peaks separated by 1.2" (6.9 kpc), and ~50 km/s in velocity space, strongly suggesting that this is a merging system with two intense star forming components, only one of which is in the active quasar phase. We propose deep HST WFC3/F105W, F140W observations to confirm the merger nature, and measure the size, morphology, UV-based star formation rate, and constrain the UV continuum slope of both the quasar host galaxy and its merging companion galaxy. Comparison of our HST and mm/CO observations with detailed cosmological simulations of high-redshift quasar formation will place this unique system in the evolutionary sequence of SMBH/galaxy coevolution, and test models of quasar formation. The proposed observation of CFHQS J1429+5447 also provides an important test case for the future high-z quasar host galaxy imaging with HST/JWST and ALMA. The observations include 5-orbit observations of an CFHQS z=6.2 quasars with WFC3/IR F105W and F140W, and 1-orbit observation of a nearby star to measure the PSF with WFC3/IR F105W and F140W. For the observations of the science target, we plan to do the 3-orbits observation with F140W first. Then if possible, please hold the observation for about 10~20 days to let us check the data and decide if we want to continue to do F105W or use the remaining 2 orbits in F140W to improve the S/N. AGN/QUASARS 12 false 0.0 0.0 false false false false SUPPORTED GALAXY HIGH REDSHIFT GALAXY QSO STARBURST Science target J2000 J2000 z'=21.45, J=20.64 STAR M III-I M V-IV a star for PSF 2MASS-J14282482+5443207 J2000 J2000 J=16.37, H=15.92, Ks=15.25 ACS/WFC Imaging No No F775W WFC3/IR Imaging No No F105W WFC3/IR Imaging No No F140W WFC3/IR Imaging No No F105W WFC3/IR Imaging No No F140W POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1 false Timing link suitability includes constraints ([02 After 01 by 30.0 to 40.0 days]) The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. 3-orbit observations of CFHQSJ1429+5447 with F140W. According to BOT, there are four bright 2MASS source J=13 to 16 in the field. We have defined a series of orient ranges. The goal is to avoid contaminations from spikes of the bright stars in the field. (Tic-Visit :proposal-id 12496 :visit-id "01" :proposal-version -1 :trans-version "20110509" :date "28-Sep-2011 15:30:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 5431648 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12496 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12496 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3022 :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 3445 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12496 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3022 :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 3445 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12496 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3022 :al-overhead-at-end 0 :internal-dur-at-end 711 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) false 3 0 Timing link suitability includes constraints ([02 After 01 by 30.0 to 40.0 days]) The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. 2-orbit observations of CFHQSJ1429+5447 with WFC3/IR F105W. According to BOT, there are four bright 2MASS source J=13 to 16 in the field. We have defined a series of orient ranges. The goal is to avoid contaminations from spikes of the bright stars in the field. we plan to do the 3-orbits observation with F140W first. Then if possible, please hold the observation for about 10~20 days to let us check the data and decide if we want to continue to do F105W or use the remaining 2 orbits in F140W to improve the S/N. (Tic-Visit :proposal-id 12496 :visit-id "02" :proposal-version -1 :trans-version "20110509" :date "28-Sep-2011 15:30:28.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 3621088 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12496 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12496 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3022 :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 3445 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12496 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3022 :al-overhead-at-end 0 :internal-dur-at-end 711 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) false 2 0 The scheduling data was generated by CASM 19.3. CASM was run in Phase II mode. Observations of the PSF star WFC3/IR F105W F140W. According to BOT, there are two bright 2MASS source J=13 to 15 close to the edge of the field. We have defined a series of orient ranges. The goal is to avoid contaminations from spikes of the bright stars in the field. (Tic-Visit :proposal-id 12496 :visit-id "03" :proposal-version -1 :trans-version "20110509" :date "28-Sep-2011 15:28:14.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2089024 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12496 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12496 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2911 :al-overhead-at-end 0 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3445 :pcs-gap 0 ) true 1 0