12964( 2) - 29-Jun-2012 20:43:34 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12964 Version: 2 Check-in Time: 29-Jun-2012 20:43:34 STScI Edit Number: 0 Title Probing the outermost halo in a giant galaxy: is it metal-poor and where does it end? ------------------------------------------------------------------------------------ Type Cycle GO 20 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Marina Rejkuba European Southern Observatory - Germany Y CoI: Dr. William E. Harris McMaster University N CoI: Dr. Gretchen L. H. Harris University of Waterloo N CoI: Dr. Laura Greggio Osservatorio Astronomico di Padova N CoI: Mr. Oscar Alberto Gonzalez European Southern Observatory - Germany N CoI: Dr. Helmut Jerjen Australian National University N ------------------------------------------------------------------------------------ Abstract Centaurus A (NGC 5128), the nearest gE/S0 galaxy is taking up an increasingly important role in stellar population and galaxy evolution studies with the potential to rival the Local Group members. From our previous HST-based studies of its red-giant population, we know that ~80% of its halo stars are old (11-13 Gyr), and relatively metal-rich ([Fe/H] ~ -0.5). In contrast, new measurements of the outer-halo of NGC 3379 (Leo group), and of M31 revealed the classically metal-poor component (as the Milky Way halo) at radii beyond R~10 R(eff) where the metal-rich stars disappear. This extremely extended "outermost halo" -- which has long been suspected to exist in giant galaxies but has been hard to isolate -- may be the evolutionary relic of the first stars formed in the extended dark-matter potential well of the galaxy at its earliest stages. This triggers the question whether such an extended halo also exists around NGC 5128 and what is its composition? We propose to use WFC3 and ACS in parallel to probe the NGC 5128 halo to its outermost detectable limits beyond 15 effective radii, in search for its oldest, most metal-poor stars. Combined with our earlier HST work, which has sampled the metallicity distribution function (MDF) from 10 to 38 kpc (1.5-7 Reff), we will obtain a complete MDF profile extending from the outer bulge to the farthest limits of the halo. This study will be the first for any gE galaxy, and it will add entirely new constraints to understanding its formation history. We will be able to assess the relative importance of halo stars produced by protogalactic dwarfs at the beginning of hierarchical merging vs. late accretion from dwarf satellites. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is an imaging program with WFC3 and ACS/WFC in Coordinated Parallel mode on 5 target fields surveying the outer halo of NGC 5128. Each field is imaged in F814W and F606W filters. The parallel observations with ACS/WFC use the same filters and essentially augment the total field size. Very accurate pointing is not necessary and the orientation angle is set to avoid the bright stars in the ACS parallel, and could also be slightly more relaxed accepting some loss of area due to bright stars if necessary for scheduling. The two orbits for each target are placed within a visit in order to obtain the two filters for each 12964( 2) - 29-Jun-2012 20:43:34 - [ 2] pointing for the same field orientation. Each field is imaged with 2 orbits, one orbit per filter. Within each orbit a set of 3 dithered observations using WFC3-UVIS-DITHER-LINE-3PT pattern are taken for each filter, for both primary and the parallel instrument in the same filter. The 3 primary (WFC3) exposures are packed within each orbit such that the overheads are minimized and the total exposure time maximized. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12964( 2) - 29-Jun-2012 20:43:34 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5128-F5 GALAXY, ELLIPTICAL, RA=13H28M0.5500S +/- 0.1", J2000 V = 25.0 +/- 0.2 V magnitude is tip of HALO, RADIO GALAXY DEC=-42D14'37.40" +/- 0.1" red-giant branch in NGC 5128 Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5128-F6 GALAXY, ELLIPTICAL, RA=13H29M10.0200S +/- 0.1", J2000 V = 25.0 +/- 0.2 HALO, RADIO GALAXY DEC=-41D51'21.40" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5128-F7 GALAXY, ELLIPTICAL, RA=13H31M28.7300S +/- 0.1", J2000 V = 25.0 +/- 0.2 HALO, RADIO GALAXY DEC=-41D16'44.60" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-5128-F8 GALAXY, ELLIPTICAL, RA=13H23M20.3000S +/- 0.1", J2000 V = 25.0 +/- 0.2 HALO, RADIO GALAXY DEC=-42D47'10.30" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-5128-F9 GALAXY, ELLIPTICAL, RA=13H20M30.0000S +/- 0.1", J2000 V = 25.0 +/- 0.2 HALO, RADIO GALAXY DEC=-42D30'0.00" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 12964( 2) - 29-Jun-2012 20:43:34 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 12964( 2) - 29-Jun-2012 20:43:34 - [ 5] Visit: 01 Visit Requirements: SCHED 100%; ORIENT 35D TO 88 D; ORIENT 125D TO 226 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5128-F5 WFC3/UVI ACCUM UVIS F814W 1 2380 S PATTERN 3 1-2; PAR 2 S see below WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5128-F5 ACS/WFC ACCUM WFC F814W 1 2100 S see below ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5128-F5 WFC3/UVI ACCUM UVIS F606W 1 2490 S PATTERN 3 3-4; PAR 4 S see below WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-5128-F5 ACS/WFC ACCUM WFC F606W 1 2270 S see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5128-F5 1 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 792 S S NGC-5128-F5 1 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 792 S S NGC-5128-F5 1 WFC3/UVI ACCUM UVIS F814W 3 none none none 1 792 S S NGC-5128-F5 2 ACS/WFC ACCUM WFC F814W 1 none none none 1 710 S NGC-5128-F5 2 ACS/WFC ACCUM WFC F814W 2 none none none 1 760 S NGC-5128-F5 2 ACS/WFC ACCUM WFC F814W 3 none none none 1 667 S NGC-5128-F5 3 WFC3/UVI ACCUM UVIS F606W 1 none none none 2 832 S S NGC-5128-F5 3 WFC3/UVI ACCUM UVIS F606W 2 none none none 2 832 S S NGC-5128-F5 3 WFC3/UVI ACCUM UVIS F606W 3 none none none 2 832 S S NGC-5128-F5 4 ACS/WFC ACCUM WFC F606W 1 none none none 2 768 S NGC-5128-F5 4 ACS/WFC ACCUM WFC F606W 2 none none none 2 795 S NGC-5128-F5 4 ACS/WFC ACCUM WFC F606W 3 none none none 2 707 S 12964( 2) - 29-Jun-2012 20:43:34 - [ 6] Visit: 02 Visit Requirements: SCHED 100%; ORIENT 160D TO 190 D; ORIENT 265D TO 360 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5128-F6 WFC3/UVI ACCUM UVIS F814W 1 2380 S PATTERN 3 1-2; PAR 2 S see below WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5128-F6 ACS/WFC ACCUM WFC F814W 1 2100 S see below ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5128-F6 WFC3/UVI ACCUM UVIS F606W 1 2490 S PATTERN 3 3-4; PAR 4 S see below WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-5128-F6 ACS/WFC ACCUM WFC F606W 1 2270 S see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5128-F6 1 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 792 S S NGC-5128-F6 1 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 792 S S NGC-5128-F6 1 WFC3/UVI ACCUM UVIS F814W 3 none none none 1 792 S S NGC-5128-F6 2 ACS/WFC ACCUM WFC F814W 1 none none none 1 710 S NGC-5128-F6 2 ACS/WFC ACCUM WFC F814W 2 none none none 1 760 S NGC-5128-F6 2 ACS/WFC ACCUM WFC F814W 3 none none none 1 667 S NGC-5128-F6 3 WFC3/UVI ACCUM UVIS F606W 1 none none none 2 832 S S NGC-5128-F6 3 WFC3/UVI ACCUM UVIS F606W 2 none none none 2 832 S S NGC-5128-F6 3 WFC3/UVI ACCUM UVIS F606W 3 none none none 2 832 S S NGC-5128-F6 4 ACS/WFC ACCUM WFC F606W 1 none none none 2 768 S NGC-5128-F6 4 ACS/WFC ACCUM WFC F606W 2 none none none 2 795 S NGC-5128-F6 4 ACS/WFC ACCUM WFC F606W 3 none none none 2 707 S 12964( 2) - 29-Jun-2012 20:43:34 - [ 7] Visit: 03 Visit Requirements: SCHED 100%; ORIENT 0D TO 110 D; ORIENT 177D TO 359 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5128-F7 WFC3/UVI ACCUM UVIS F814W 1 2380 S PATTERN 3 1-2; PAR 2 S see below WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5128-F7 ACS/WFC ACCUM WFC F814W 1 2100 S see below ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5128-F7 WFC3/UVI ACCUM UVIS F606W 1 2490 S PATTERN 3 3-4; PAR 4 S see below WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-5128-F7 ACS/WFC ACCUM WFC F606W 1 2270 S see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5128-F7 1 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 792 S S NGC-5128-F7 1 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 792 S S NGC-5128-F7 1 WFC3/UVI ACCUM UVIS F814W 3 none none none 1 792 S S NGC-5128-F7 2 ACS/WFC ACCUM WFC F814W 1 none none none 1 710 S NGC-5128-F7 2 ACS/WFC ACCUM WFC F814W 2 none none none 1 760 S NGC-5128-F7 2 ACS/WFC ACCUM WFC F814W 3 none none none 1 667 S NGC-5128-F7 3 WFC3/UVI ACCUM UVIS F606W 1 none none none 2 832 S S NGC-5128-F7 3 WFC3/UVI ACCUM UVIS F606W 2 none none none 2 832 S S NGC-5128-F7 3 WFC3/UVI ACCUM UVIS F606W 3 none none none 2 832 S S NGC-5128-F7 4 ACS/WFC ACCUM WFC F606W 1 none none none 2 768 S NGC-5128-F7 4 ACS/WFC ACCUM WFC F606W 2 none none none 2 795 S NGC-5128-F7 4 ACS/WFC ACCUM WFC F606W 3 none none none 2 707 S 12964( 2) - 29-Jun-2012 20:43:34 - [ 8] Visit: 04 Visit Requirements: SCHED 100%; ORIENT 50D TO 320 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5128-F8 WFC3/UVI ACCUM UVIS F814W 1 2380 S PATTERN 3 1-2; PAR 2 S see below WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5128-F8 ACS/WFC ACCUM WFC F814W 1 2100 S see below ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5128-F8 WFC3/UVI ACCUM UVIS F606W 1 2490 S PATTERN 3 3-4; PAR 4 S see below WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-5128-F8 ACS/WFC ACCUM WFC F606W 1 2270 S see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5128-F8 1 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 792 S S NGC-5128-F8 1 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 792 S S NGC-5128-F8 1 WFC3/UVI ACCUM UVIS F814W 3 none none none 1 792 S S NGC-5128-F8 2 ACS/WFC ACCUM WFC F814W 1 none none none 1 710 S NGC-5128-F8 2 ACS/WFC ACCUM WFC F814W 2 none none none 1 760 S NGC-5128-F8 2 ACS/WFC ACCUM WFC F814W 3 none none none 1 667 S NGC-5128-F8 3 WFC3/UVI ACCUM UVIS F606W 1 none none none 2 832 S S NGC-5128-F8 3 WFC3/UVI ACCUM UVIS F606W 2 none none none 2 832 S S NGC-5128-F8 3 WFC3/UVI ACCUM UVIS F606W 3 none none none 2 832 S S NGC-5128-F8 4 ACS/WFC ACCUM WFC F606W 1 none none none 2 768 S NGC-5128-F8 4 ACS/WFC ACCUM WFC F606W 2 none none none 2 795 S NGC-5128-F8 4 ACS/WFC ACCUM WFC F606W 3 none none none 2 707 S 12964( 2) - 29-Jun-2012 20:43:34 - [ 9] Visit: 05 Visit Requirements: SCHED 100%; ORIENT 130D TO 206 D; ORIENT 240D TO 290 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC-5128-F9 WFC3/UVI ACCUM UVIS F814W 1 2380 S PATTERN 3 1-2; PAR 2 S see below WITH 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5128-F9 ACS/WFC ACCUM WFC F814W 1 2100 S see below ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5128-F9 WFC3/UVI ACCUM UVIS F606W 1 2490 S PATTERN 3 3-4; PAR 4 S see below WITH 3 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-5128-F9 ACS/WFC ACCUM WFC F606W 1 2270 S see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5128-F9 1 WFC3/UVI ACCUM UVIS F814W 1 none none none 1 792 S S NGC-5128-F9 1 WFC3/UVI ACCUM UVIS F814W 2 none none none 1 792 S S NGC-5128-F9 1 WFC3/UVI ACCUM UVIS F814W 3 none none none 1 792 S S NGC-5128-F9 2 ACS/WFC ACCUM WFC F814W 1 none none none 1 710 S NGC-5128-F9 2 ACS/WFC ACCUM WFC F814W 2 none none none 1 760 S NGC-5128-F9 2 ACS/WFC ACCUM WFC F814W 3 none none none 1 667 S NGC-5128-F9 3 WFC3/UVI ACCUM UVIS F606W 1 none none none 2 832 S S NGC-5128-F9 3 WFC3/UVI ACCUM UVIS F606W 2 none none none 2 832 S S NGC-5128-F9 3 WFC3/UVI ACCUM UVIS F606W 3 none none none 2 832 S S NGC-5128-F9 4 ACS/WFC ACCUM WFC F606W 1 none none none 2 768 S NGC-5128-F9 4 ACS/WFC ACCUM WFC F606W 2 none none none 2 795 S NGC-5128-F9 4 ACS/WFC ACCUM WFC F606W 3 none none none 2 707 S 12964( 2) - 29-Jun-2012 20:43:34 - [ 10] Summary Form for Proposal 12964 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS, WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0D TO 110 D, ORIENT 125D TO 226 D, ORIENT 130D TO 206 D, ORIENT 160D TO 190 D, ORIENT 177D TO 359 D, ORIENT 240D TO 290 D, ORIENT 265D TO 360 D, ORIENT 35D TO 88 D, ORIENT 50D TO 320 D, PAR 2 WITH 1, PAR 4 WITH 3, PATTERN 3 1-2, PATTERN 3 3-4, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC-5128-F5, NGC-5128-F6, NGC-5128-F7, NGC-5128-F8, NGC-5128-F9 ------------------------------------------------------------------------------------------------------------------------------------