0 Assigned ID: 217 ----- Attempting Submission 1 (Thu Apr 09 16:34:51 GMT 2015) ----- 0 ----- Attempting Submission 1 (Mon Jul 06 15:54:09 GMT 2015) ----- Galaxy mass assembly is driven dually by in-situ star formation and mergers, though which modes dominate in galaxies of different mass and at different epochs is poorly understood. These bimodal processes are thought to be mirrored in the formation mechanisms for ancient red and blue globular clusters (GC) present in massive galaxies. Whereas the red GCs are theorized to form in situ together with the core of the massive galaxy, the blue subpopulation is expected to have an external accreted origin. This scenario, however, continues presently untested. The proposed observations (2 orbits in the g and z filters using the ACS camera) will provide a direct test of this accretion hypothesis by characterizing the GC population of a massive galaxy that has survived untouched since its early assembly at z>2: NGC1277. If the accretion scenario is correct, the GC color distribution of NGC1277 will be unimodal (having only red GCs). This result would provide direct constraints on the early accretion and assembly of massive galaxies in the early universe. Filter choices and photometric depth: To conduct our observations, we are asking for one orbit each in the ACS F475W (g475) and F850LP (z850) bands to image NGC1277 and its GC system. Based on its declination, NGC~1277 is visible for 57 minutes in each orbit - with overheads the total integration time on source is ~2400s. The ACS ETC suggests that with one orbit, we will reach the GC luminosity function turnover magnitude of r~26.3 with S/N~10 - allowing us to obtain the necessary number of GCs, and with sufficient photometric precision to characterize the color distribution. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 12 false false false false SUPPORTED GALAXY ELLIPTICAL YES This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 ACS/WFC Imaging No No F475W ACS/WFC Imaging No No F850LP POS-TARG DITHER 0.265 LINE 0.187 false false 69.05 4 20.67 ACS-WFC-DITHER-BOX 1 false 1436197734164 C:\Users\itc\Documents\OP-cache\ngc1277_corrected_2-v01.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 14215 :visit-id "01" :proposal-version -1 :trans-version "20150609" :date "06-Jul-2015 16:48:54.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 2273792 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 14215 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 14215 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2974 :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 3307 :pcs-gap 0 ) (Tic-Orbit :proposal-id 14215 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3082 :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 3307 :pcs-gap 0 ) true 2 0