5956( 10) - 10/30/96 12:41 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5956 Version: 10 Check-in Date: 30-Oct-1996 12:37:11 1.Proposal Title: Mergers or Cooling Flows: the Nature of NGC4696 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: WILLIAM SPARKS SPACE TELESCOPE SCIENCE INSTITUTE CoI: Ferdinando Macchetto Space Telescope Science Institute N CoI: Robert Jedrzejewski Space Telescope Science Institute Y CoI: Daniel Golombek Space Telescope Science Institute N CoI: Marcella Carollo Sterrewacht, Leiden N ------------------------------------------------------------------------------------ 6. Abstract NGC4696, the central dominant galaxy in the Centaurus Cluster, is the key object in the controversy between cooling-flows and mergers. Do cooling-flows cause optical emission filaments in X--ray clusters, and do they dominate the physics of that environment, or are mergers responsible, thereby explaining the dustiness of the filaments and failure to detect `cooling' material? Pre-refurbishment FOC images show the nucleus of NGC4696 is double, with components separated by 0.26 arcsec. We propose to obtain FOS spectroscopy and WFPC2 images that would, if this is a genuine double nucleus, to all intents and purposes prove that the galaxy has undergone a recent merger. We will obtain quantitative information on the distribution of the gas, dust and stars in this archetypal galaxy at physically interesting length scales. ------------------------------------------------------------------------------------ Observations Description ------------------------ For the FOS target acquisition, we would perform an offset from a nearby star: binary search plus peakup on the star, then an (accurate) offset to the positions of each of the nuclei. (This process requires exactly one orbit of overhead only, and is the reason why the first spectrum in the observation summary form has an extra orbit of time.) The individual nuclei fluxes, as measured from the FOC images, have F_Lambda~ 8* 10^-18erg.s.^-1.cm^-2.Angstrom ^-1. The separation of the nuclei is only 0.26 arcsec and so HST spatial resolution is essential to obtain spectra of these two nuclei separately. (We have taken ground based work to the limit, and have already shown that there is kinematic substructure present, Carollo 1993.) We propose to use the FOS 0.3 arcsec aperture. For exposures of three orbits duration, 2500 s per orbit, using the FOS plus G570H grating, we estimate a continuum signal to noise per diode of between six and nine in each of the spectra. This will be adequate to determine the relative velocities of the two using standard cross-correlation techniques, and it will also be possible to measure individual absorption line indices, including NaD and Mgb. For WFPC2 imaging, we wish to obtain short exposures in V (F555W) and R (F702W), of order 5 min. duration each using the PC. These will serve as essential Early Acquisition Images to carry out the spectrographic acquisition above, and will provide excellent scientific data in their own right. We also require an image taken in the light of NII Lambda 6584Angstrom\\\\ (which is three times stronger than HAlpha) for which we will use the appropriate LRF filter. The corresponding field of view is 13 arcsec which covers the entire nuclear region and about half of the emission filament system. The V and R images will serve to enable correct continuum subtraction, with proper allowance for color effects introduced by the presence of dust. Typical emission line surface brightnesses are ~ 6.5* 10^-16erg.s.^- 1.cm^- 2.arcsec^-2 which translates for an 1800 sec exposure to a S/N of 20 per WFC pixel. The complete imaging part of the proposal requires one orbit. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5956( 10) - 10/30/96 12:41 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4696 Galaxy, elliptical, RA=12H 48M 49.2S +/- 1S,DEC=-41D 2000 V = 20 nucleus 18' 39.8" +/- 1" Comments: Flux is approximate nucleus flux 2 NGC4696-NUC1 Galaxy, Nucleus RA=12H 48M 49.2S +/- 1S,DEC=-41D 2000 V = 20 18' 39.8" +/- 1" Comments: Flux is approximate nucleus flux 3 NGC4696-NUC2 Galaxy, Nucleus RA-OFF=-0.012S+/- 0.001S,DEC- 2000 V = 20 OFF=0.24"+/- 0.01",FROM 2 Comments: Flux is approximate nucleus flux 4 NGC4696-PAR GALAXY RA=12H 48M 49.3S +/- 1S,DEC=-41D 2000 V = 20 18' 39.6" +/- 1' Comments: Parallel WFPC2 field 5 NGC4696- STAR RA=12H 48M 49.3S +/- 1S,DEC=-41D 2000 V = 20 OFFSET 18' 39.6" +/- 1" Comments: Offset star from EARLY ACQ image 5956( 10) - 10/30/96 12:41 - [ 2] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4696 WFPC2 IMAGE PC1 F555W 5407 CR-SPLIT=0.5 1 320 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4696 WFPC2 IMAGE PC1 F702W 6895 CR-SPLIT=0.5 1 320 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4696 WFPC2 IMAGE LRF LRF 6640 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 5956( 10) - 10/30/96 12:41 - [ 3] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: ON HOLD removed as early acq update complete Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC4696-OFF FOS/RD ACQ/PEA 4.3 MIRROR SCAN-STEP-X=3.33,SCAN-STEP-Y=1.23 1 2 S ONBOARD ACQ FOR 21 SET K ,SEARCH-SIZE-X=2,SEARCH-SIZE-Y=6 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC4696-OFF FOS/RD ACQ/PEA 1.0 MIRROR SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 2 S ONBOARD ACQ FOR 22 SET K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC4696-OFF FOS/RD ACQ/PEA 0.5 MIRROR SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 2 S ONBOARD ACQ FOR 23 SET K ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC4696-OFF FOS/RD ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.11,SCAN-STEP-Y=0.11 1 20 S ONBOARD ACQ FOR 24 SET K ,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC4696-NUC FOS/RD ACCUM 0.3 G570H 1 1000 S expand; max dur 1000% 1 ------------------------------------------------------------------------------------------------------------------------------------ 25 NGC4696-PAR WFPC2 IMAGE WFALL F555W 5407 CR-SPLIT=NO 1 1000 S PAR WITH 24 ------------------------------------------------------------------------------------------------------------------------------------ 26 WAVE FOS/RD ACCUM 0.3 G570H 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 27 NGC4696-NUC FOS/RD ACCUM 0.3 G570H 1 2360 S 1 ------------------------------------------------------------------------------------------------------------------------------------ 28 NGC4696-PAR WFPC2 IMAGE WFALL F555W 5407 CR-SPLIT=NO 1 1500 S PAR WITH 27 ------------------------------------------------------------------------------------------------------------------------------------ 29 WAVE FOS/RD ACCUM 0.3 G570H 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC4696-NUC FOS/RD ACCUM 0.3 G570H 1 2360 S 1 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC4696-PAR WFPC2 IMAGE WFALL F555W 5407 CR-SPLIT=NO 1 1500 S PAR WITH 30 ------------------------------------------------------------------------------------------------------------------------------------ 32 WAVE FOS/RD ACCUM 0.3 G570H 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC4696-NUC FOS/RD ACCUM 0.3 G570H 1 2360 S 1 ------------------------------------------------------------------------------------------------------------------------------------ 34 NGC4696-PAR WFPC2 IMAGE WFALL F555W 5407 CR-SPLIT=NO 1 1500 S PAR WITH 33 ------------------------------------------------------------------------------------------------------------------------------------ 35 WAVE FOS/RD ACCUM 0.3 G570H 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 36 NGC4696-NUC FOS/RD ACCUM 0.3 G570H 1 2360 S 2 ------------------------------------------------------------------------------------------------------------------------------------ 37 NGC4696-PAR WFPC2 IMAGE WFALL F814W 7940 CR-SPLIT=NO 1 1500 S PAR WITH 36 ------------------------------------------------------------------------------------------------------------------------------------ 38 WAVE FOS/RD ACCUM 0.3 G570H 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 5956( 10) - 10/30/96 12:41 - [ 4] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 39 NGC4696-NUC FOS/RD ACCUM 0.3 G570H 1 2360 S 2 ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC4696-PAR WFPC2 IMAGE WFALL F814W 7490 CR-SPLIT=NO 1 1500 S PAR WITH 39 ------------------------------------------------------------------------------------------------------------------------------------ 41 WAVE FOS/RD ACCUM 0.3 G570H 1 DEF ------------------------------------------------------------------------------------------------------------------------------------ 5956( 10) - 10/30/96 12:41 - [ 5] Summary Form for Proposal 5956 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.5 SEARCH-SIZE-Y=6 SEARCH-SIZE-Y=2 SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=4 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 21 ONBOARD ACQ FOR 22 ONBOARD ACQ FOR 23 ONBOARD ACQ FOR 24 expand; max dur 1000% PAR WITH 24 PAR WITH 27 PAR WITH 30 PAR WITH 33 PAR WITH 36 PAR WITH 39 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F702W LRF MIRROR G570H F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4696 NGC4696-OFFSET NGC4696-NUC1 NGC4696-PAR WAVE NGC4696-NUC2 ------------------------------------------------------------------------------------------------------------------------------------