5925( 14) - 04/25/97 19:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5925 Version: 14 Check-in Date: 25-Apr-1997 17:39:13 1.Proposal Title: The Polarization and Emission Line Morphology of the Protogalaxy Candidate 3C 256 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Peter Eisenhardt Jet Propulsion Lab CoI: Buell Jannuzi Institute for Advanced Study N CoI: Richard Elston National Optical Astronomy Observatories N CoI: Patrick McCarthy Carnegie Observatories N CoI: Mark Dickinson Space Telescope Science Institute N CoI: George Djorgovski California Institute of Technology N ------------------------------------------------------------------------------------ 6. Abstract We propose imaging polarimetry and emission-line imaging observations of the distant radio galaxy 3C 256. It is the bluest known 3C radio galaxy, being bluer than a star forming dwarf Irr galaxy. It is also perhaps the best example of the alignment effect since it exhibits high surface brightness UV to IR continuum emission aligned with its radio axis. Its spectral energy distribution is reasonably well matched by a single 0.3 Gyr old starburst model, supporting the view that the alignment effect is due to star formation along the radio jet, and in this case may even have formed the bulk of the galaxy's stars. On the other hand, ground-based optical polarimetry shows that the UV emission from 3C 256 is highly polarized, consistent with much of the UV continuum being produced by scattering of a nuclear source. Thus, 3C 256 is an excellent object for testing the significance of two competing models for the alignment affect: stimulated star formation, and scattering of non-stellar nuclear continuum. Using high resolution emission-line imaging in Lyman alpha as well as broad band imaging polarimetry we will be able to study the distribution of the scattering centers, of emission-line producing clouds, and of star forming regions. These data will provide a direct measurement of the contribution of these processes to the strong alignment effect in 3C 256, and perhaps in radio galaxies in general. ------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 2] Observations Description ------------------------ At a declination of +23, the orbital visibility of 3C 256 is 53 minutes. We have conservatively allowed 13 minutes per orbit for guide star reacquisition, detector readout, and filter positioning, for a baseline value of 2400 seconds available for integration per orbit. NOTE: With the use of the LOW-SKY requirement on all exposures in Visits 02-05, this exposure time per orbit will be reduced. - Ray Lucas - 02/27/97 We wish to measure the integrated polarized flux in 3C 256 to at least 5 sigma. More importantly, we wish to test whether a significant fraction of the polarized flux arises from compact scattering sites. Note that Le Fevre et al (1988) discuss 3 (possibly 4) subcomponents in an R band image with 0.7" seeing. We set as a benchmark that half of the polarized flux is equally divided among 10 unresolved sources, and require that we detect such sources to 5 sigma. We selected F555W to maximize throughput with the polarizer over the wavelength range where it has good rejection of perpendicular light (4500 to 6500 Angstroms from Fig. 3.5 in the WFPC2 handbook). Using our measurement of the polarization, the F555W, POLQ, and WF parameters, we calculate that 5 orbits per polarizer setting are required to achieve our goals. To minimize instrumental polarization effects, we will use three telescope orientations separated by 60 degrees at different times of year and a single polarizer quad filter with WF3 (the most sensitive detector). WF3 is also the most frequently calibrated wide field chip according to the report on WFPC2 Polarization strategies by John Biretta and William Sparks. As each orientation will require the same S/N ratio, these observations will require a total of 15 orbits (3 orbits for each of three orientation angles of the polarization analyzer on the sky). Combining all of the settings will also provide a very high S/N (100:1 integrated) total flux image suitable for investigating substructure. Narrow band images will be obtained to map the location of the regions emitting Lyman alpha as diagnostics of the physical conditions in these regions. The F336W wide band WFPC2 filter covers the wavelengths of Lyman alpha at the redshift of 3C 256. Using McCarthy's (1988) measured Lyman alpha flux, the filter parameters for F336W, and the WF3 quantum efficiency, we calculate that this will require nine 2400 second orbits. Because of the large equivalent width of Lyman alpha (about 1000 Angstroms) we can use the F555W image for an off-line measurement. To minimize read noise, we will integrate for an entire orbit, using the multiple orbits/images per polarization and emission line measurement to provide detection and removal of cosmic ray events in the data. To reduce the impact of hot pixels, the nine F336W orbits will be divided into two visits at two positions separated by an integer plus 1/2 number of WF pixels in both x and y, allowing some subsampling. NOTE: THE STRATEGY ABOVE HAS BEEN MODIFIED TO THE FOLLOWING DUE TO MANY PROBLEMS WITH SCHEDULING THE ORIGINAL VERSION: WF3 will still be used for the F336W exposures. WF2 and WF4 will each now be used at 2 different ORIENT angles for the F555W POLQ exposures. Preferred ORIENT angles have now been worked out by the PI based on the limited intersection between GS availability and other constraints. One orbit of F336W exposure time has now been swapped for more exposure time on the polarimetry in order to even out the exposure times for all polarization angles, etc. The current (new) scenario has also been described to WFPC2 Scientist John Biretta by Ray Lucas and he believes it to be OK. The PI has conferred with Larry Petro and Harry Ferguson about background light and now believes that the levels will be acceptable although if scheduled at the new preferred ORIENT angles, this should certainly not be a problem. IT IS STRONGLY DESIRED THAT ALL THE OBSERVATIONS BE COMPLETED BEFORE THE SECOND SERVICING MISSION. Visits 2 and 3 should be done back-to-back, and Visits 4 and 5 should be done back-to-back as well. In addition to this, the two pairs of visits ( 2-3 and 4-5 ) should be done contiguously as well, if at all possible. In case this is not possible, Visits 2-3 should still be done before Visits 4-5 as the direction of change in the ORIENT angle between the two is commensurate with the direction of the nominal roll of the spacecraft over time. This is the reason for the SEQ WITHIN requirement rather than a GROUP WITHIN being used. The desire to make them all contiguous is expressed via the SEQ WITHIN 24H requirement also, with the 24H period merely being an estimate which should be somewhat less than the actual time interval that will be required in order to force them to be contiguous as per the description in the Phase II Proposal Instructions which states that if a smaller interval is picked than is possible, then the visits will be put as close together as is possible. - Ray Lucas - 18 April, 1996. It was not possible to fit the observations in Visits 02-05 in before the second servicing mission. The PI has also decided that LOW-SKY should be used on all exposures in Visits 02-05 and that the SEQ WITHIN requirement can be relaxed to 48H instead of 24H, so this has been done. - Ray Lucas - 27 February, 1997 Inspection of guide star availability shows that a 45D change in roll using both WF2 and WF4 is difficult to achieve. It is only possible using FGS 1 and only for small ranges in roll. I selected 135D/91D as meeting guide star and sun exclusion constraints. - Peter Eisenhardt - 11 March 1997 After having trouble getting Visits 4 and 5 to schedule with Peter's latest version, I got more SPSS experts involved and they in turn brought in the SOGS programmers who looked at the problem in greater detail and saw trouble. There were still problems with the 135D/91D scenario described by Peter above since both RPS2 and TRANS/Spike apparently do not handle the ORIENTs etc. at these boundary areas properly in all cases. Apparently the ORIENT 91D cannot be achieved at the time it was thought, so I am trying ORIENT 94D to see if that gets any better. Although the nominal period when ORIENT 94D can be achieved spans the time before and after the new FGS1 will be used, I do not want to restrict this program to using only FGS2 and 3 given the difficulty it already has with guide stars, so I am using the regular scenarios instead of the FGS23-only used in the SM2 SMOV period. The LRP group has stated that they would prefer to handle this constraint with a USC to force the observations to be taken on 97.139 or later without my putting an AFTER 97.139 requirement on the observations, so I will remind them of this but am otherwise leaving it up to them if this version of the program can be made to schedule. - Ray Lucas - 4 April, 1997 Trying ORIENT 93D for Visits 04 and 05 since that is preferred by PI if at all possible. Also deleted SEQ WITHIN requirement for Visits 02-05 with PI's blessing in order to make it easier for the calendar builders. - Ray Lucas - 4/17/97 Real Time Justification ----------------------- None. Calibration Justification ------------------------- None. Additional Comments ------------------- None, except those in Fixed Target List and Visit comments and Exp Log line comments. ------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 3C256 GALAXY,HIGH REDSHIFT RA=11H 18M 04.20S +/- 0.04S, 1950 Z = R = 22.44 GALAXY,PROTOGALAXY,RADI DEC= 23D 44' 20.3" +/- 0.5" 1.819 V-R = 0.25 O GALAXY,STARBURST B-V = 0.27 Comments: THE R MAGNITUDE IS FOR THE BRIGHTEST KNOT IN LEFEVRE 1988 AND IS GIVEN BECAUSE IT MAY BE UNRESOLVED. 5925( 14) - 04/25/97 19:13 - [ 5] Visit: 01 Visit Requirements: ORIENT 120D TO 120D 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 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2500 S POS TARG 0.,0. Comments: Do exposures 1-4 at default aperture position. ------------------------------------------------------------------------------------------------------------------------------------ 2 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S POS TARG 0.25, 0.25 Comments: Dither exposures 5-8 by non-integer pixel shift of ~2.5 WF pixels in both x and y. ------------------------------------------------------------------------------------------------------------------------------------ 6 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S SAME POS AS 5 ------------------------------------------------------------------------------------------------------------------------------------ 7 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S SAME POS AS 5 ------------------------------------------------------------------------------------------------------------------------------------ 8 3C256 WFPC2 IMAGE WF3 F336W CR-SPLIT=NO 1 2700 S SAME POS AS 5 ------------------------------------------------------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 6] Visit: 02 Visit Requirements: ORIENT 135D TO 135D On Hold Comments: Additional Comments: Visits 2-3 should be done back-to-back. Visits 4-5 should be done back-to- back. Blocks of Visits 2-3 and 4-5 should be done back-to-back as well, if at all possible. The WITHIN 48H is just intended to require them all to schedule together ( as closely as is possible in normal practice ) as per the Phase II Proposal Instructions even though they may not all fit within that time. The ORIENT range may vary by +/- 3 degrees from 135D for Visits 2 and 3, but they should both be done at the SAME ORIENT. However guide stars are not available for ORIENT > 135. Visits 2-3 should still be done sequentially before Visits 4-5 in case they cannot all be done contiguously because the change in ORIENT angle from 135D to 91D is commensurate with the direction of the change in the nominal spacecraft roll over time. NOTE: The ORIENTs in Visits 4-5 have been changed from 91D to 93D and SEQ WITHIN requirement has been deleted. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2400 S LOW-SKY POS TARG 0.,0. POLQ Comments: Do exposures 1-2 at default aperture position. ------------------------------------------------------------------------------------------------------------------------------------ 2 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 1 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 3 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY POS TARG 0.5,0.5 POLQ Comments: Do exposures 3-4 with integer pixel dither of ~5 WF pixels in both x and y. ------------------------------------------------------------------------------------------------------------------------------------ 4 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 3 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 7] Visit: 03 Visit Requirements: ORIENT 135D TO 135D SAME ORIENT AS 2 On Hold Comments: Additional Comments: Must be at SAME ORIENT AS VISIT 02. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2400 S LOW-SKY POS TARG 0.,0. POLQ Comments: Do exposures 1-2 at default aperture position. ------------------------------------------------------------------------------------------------------------------------------------ 2 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 1 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 3 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY POS TARG 0.5,0.5 POLQ Comments: Do exposures 3-4 with integer pixel dither of ~5 WF pixels in both x and y. ------------------------------------------------------------------------------------------------------------------------------------ 4 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 3 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 8] Visit: 04 Visit Requirements: ORIENT 93D TO 93D On Hold Comments: Additional Comments: Visits 2-3 should be done back-to-back. Visits 4-5 should be done back-to- back. Blocks of Visits 2-3 and 4-5 should be done back-to-back as well, if at all possible. The WITHIN 48H is just intended to require them all to schedule together ( as closely as is possible in normal practice ) as per the Phase II Proposal Instructions even though they may not all fit within that time. The 91D ORIENT is the smallest allowed by sun exclusion and LOW SKY. The ORIENT range may vary by + 3/- 0 degrees from 91D for Visits 4 and 5, but they should both be done at the SAME ORIENT. Visits 2-3 should still be done sequentially before Visits 4-5 in case they cannot all be done contiguously because the change in ORIENT angle from 135D to 91D is commensurate with the direction of the change in the nominal spacecraft roll over time. NOTE: Visit 4-5 ORIENT has been adjusted from 91D to 93D and SEQ WITHIN requirement has been deleted. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2400 S LOW-SKY POS TARG 0.,0. POLQ Comments: Do exposures 1-2 at default aperture position. ------------------------------------------------------------------------------------------------------------------------------------ 2 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 1 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 3 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY POS TARG 0.5,0.5 POLQ Comments: Do exposures 3-4 with integer pixel dither of ~5 WF pixels in both x and y. ------------------------------------------------------------------------------------------------------------------------------------ 4 3C256 WFPC2 IMAGE WF2 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 3 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 9] Visit: 05 Visit Requirements: ORIENT 93D TO 93D SAME ORIENT AS 4 On Hold Comments: Additional Comments: Must be at SAME ORIENT AS VISIT 04. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2400 S LOW-SKY POS TARG 0.,0. POLQ Comments: Do exposures 1-2 at default aperture position. ------------------------------------------------------------------------------------------------------------------------------------ 2 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 1 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 3 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY POS TARG 0.5,0.5 POLQ Comments: Do exposures 3-4 with integer pixel shift of ~5 WF pixels in both x and y. ------------------------------------------------------------------------------------------------------------------------------------ 4 3C256 WFPC2 IMAGE WF4 F555W, CR-SPLIT=NO 1 2500 S LOW-SKY SAME POS AS 3 POLQ ------------------------------------------------------------------------------------------------------------------------------------ 5925( 14) - 04/25/97 19:13 - [ 10] Summary Form for Proposal 5925 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 120D TO 120D POS TARG 0.,0. SAME POS AS 1 POS TARG 0.25, 0.25 SAME POS AS 5 ORIENT 135D TO 135D LOW-SKY POS TARG 0.,0. LOW-SKY SAME POS AS 1 LOW-SKY POS TARG 0.5,0.5 LOW-SKY SAME POS AS 3 ORIENT 135D TO 135D SAME ORIENT AS 2 ORIENT 93D TO 93D ORIENT 93D TO 93D SAME ORIENT AS 4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F555W,POLQ ------------------------------------------------------------------------------------------------------------------------------------ Target Names 3C256 ------------------------------------------------------------------------------------------------------------------------------------