9489( 4) - 02/01/02 07:29 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9489 Version: 4 Check-in Date: 01-Feb-2002 07:28:22 1.Proposal Title: Determining the Physical Processes, Origin, and Fate of Cometary Knots in the Helix Nebula ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: C. O'Dell Vanderbilt University CoI: Dr. W. J. Henney Instituto de Astronomia, Universidad N Nacional Autonoma de Mexico CoI: Prof. Gary J. Ferland University of Kentucky N CoI: Prof. Bruce Balick University of Washington N CoI: Dr. Arsen Hajian United States Naval Observatory N ------------------------------------------------------------------------------------ 5. Abstract We propose to acquire STIS slitless spectra of a well defined cometary knot in the inner part of the the Helix Nebula while at the same time making WFPC2 and NICMOS H_2 images in the outer parts. This program exploits a unique opportunity to pursue one scientific goal simultaneously with three HST instruments. The primary goal is to determine accurately the structure of the cometary knots in their neutral cores and their ionized zones, thus allowing development of models that can predict their future in terms of dissipation (or not) as they enter the ISM. The STIS spectra will detail the ionized structure of an inner knot, the NICMOS H_2 will supplement WFPC2 dust extinction information in detailing the structure of the neutral cores, and the WFPC2 observations will determine the general characteristics in the outer regions, thus allowing us to establish how they originate. Only the HST has sufficient spatial resolution to undertake this project. Understanding these cometary knots is essential for understanding the process of recycling material into the ISM for they contain about half of all the material being inserted by planetary nebulae. ------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 2] Observations Description ------------------------ The observations will be eight orbits of STIS observations with complementary coordinated parallel observations with WFPC2 and NICMOS/NIC3+NIC2. Since samples of these observations were made as part of program GO-7286, one can safely scale to predict the quality of the new data. Acquisition of the faint cometary knot will be made by offsets from the same acquisition star used in program GO- 7286. This was trouble-free before and since the same position angle was used, the same guide stars should be available. All STIS spectra will be made with the 52x2" slit. The targeted cometary knot (Helix 378-801) will fit nicely into the projection of this slit (as shown in Fig.1- left of the previous section). Operating in this ``slitless" mode allows one to accurately subtract the background signal from the nebula and trace the distribution of surface brightness in emission lines from different ions. The GO-7286 10 minute exposure gave a maximum signal at the peak brightness of the N II 6883 Angstrom\ line of 66 counts. This can be used to determine the exposure times necessary for the present program. We'll use the remainder of the acquisition orbit and a second orbit to build up a total exposure time in the G750M(6581) setting to 67 additional minutes. This setting covers the strong H Alpha\ (6563 Angstrom) and N II (6548+6583 Angstrom) lines and also the weaker S II (6717+6731 Angstrom) lines at a total signal 7.7 times the original. One orbit will be necessary to get an adequate signal for the G430M(4961) setting which covers O III 4959+5007 Angstrom\ and HBeta. O III emission is intrinsically weak in the cometary knots and the longer exposure (total signal about 700 counts) is necessary for adequately defining the nebular background that must be subtracted. O I emission at 6300+6363 Angstrom\ will arise from the local ionization front in the cusp of the cometary knots and will be covered with two orbits in the G750M(6252) setting, which should be adequate if the ratio of O I to H Alpha\ emission is that theoretically expected when looking at an ionization front. Three orbits will be necessary in the G750M(5734) setting to reach the 5577 Angstrom\ O I and 5755 Angstrom\ N II auroral lines. This is worth the observing time as the lines are direct indicators of the local electron temperature, whose determination is one of the primary scientific goals of this program. The O I auroral line, which falls in the same setting as the 5755 Angstrom line, will probably be too weak, but the N II line should be about one percent of the 6583 Angstrom\ line, so that the 120 minutes total exposure time on the former will allow adequate photometry. These exposure times of the STIS program drive the requirement for a total of 8 orbits. Within this the WFPC2 parallel observations will be distributed as 2 1/2 orbits for F656N, 2 orbits for F658N, 3 orbits for F502N, (with 1/2 orbit for acquisition), which will bring all of the images up to a similar 3 times higher signal than at present. Within the 8 orbits we'll use 4 1/2 orbits for the H_2 F212N filter and 3 orbits for the adjacent background filter F215N, whereas our GO-7286 program could allow only one orbit for each of these filters. It is fully recognized that the NIC3 images will probably once again be out of focus, but if they are of similar focus the much higher S/N allowed by these longer exposures will make them quite useful. We recognize that NICMOS observations are uncertain until the success of the new cooler has been determined. The NIC3 observations proposed are an important ingredient of this program, but the primary components are the STIS and WFPC2 observations. The NIC2 observations are more exploratory since they are not repeats of GO-7286 observations (other filters were observed, without success). The NIC2 observations may not yield useful results since that field of view is smaller than for NIC3 and it will lie in a faint outer portion of the Helix (essentially straight down from NIC3 in Fig.2). Nevertheless, it would be a mistake not to include it in the observing program since the system can accommodate these parallel observations, as was done during the execution of GO-7286. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7293- ISM, Planetary Nebula, RA=22H 29M 39.05S +/- 0.02S, J2000 V = 16.7+/-0.1 ACQSTARB Cometary Nebula DEC=-20D 47' 39.1" +/- 0.5", B-V = 0.4+/-0.1 PLATE-ID=04I5 Coordinate Source: GUIDE_STAR_CATALOG Comments: Position is that successfully used in GO-7286. 2 NGC7293- ISM, Planetary Nebula, RA-OFF=-1.27S+/- 0.01S, DEC-OFF= J2000 V = 20.0+/-0.1 OFFSETD Cometary Nebula -22.3"+/- 0.1", FROM 1 B-V = 0.0+/-0.1 Coordinate Source: OTHER_SOURCE Comments: No broad-band magnitudes available for this object. Offset is that successfully used in GO-7286. 9489( 4) - 02/01/02 07:29 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 51.0345D TO 51.0345D On Hold Comments: Additional Comments: This ORIENT value is that successfully used in GO-7286. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 101 NGC7293-ACQ STIS/C ACQ F28X50L MIRROR 1 2 S STARB CD P ------------------------------------------------------------------------------------------------------------------------------------ 102 NGC7293-ACQ STIS/C ACQ/PEA 52X0.2 MIRROR 1 2 S STARB CD K ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC7293-OFF STIS/C ACCUM 52X2 G750M 6581 1 33 M PAR 111-115 WITH 110-110 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 111 NGC7293-OFF NIC1 MULTIAC NIC1 F166N SAMP-SEQ=STEP256,NSAMP=19 1 DEF SETD CUM Comments: Coordinated Parallel with 110 ------------------------------------------------------------------------------------------------------------------------------------ 112 NGC7293-OFF NIC2 MULTIAC NIC2 F212N SAMP-SEQ=STEP256,NSAMP=19 1 DEF SETD CUM Comments: Coordinated Parallel with 110 ------------------------------------------------------------------------------------------------------------------------------------ 113 NGC7293-OFF NIC3 MULTIAC NIC3 F212N SAMP-SEQ=STEP256,NSAMP=19 1 DEF SETD CUM Comments: Coordinated Parallel with 110 ------------------------------------------------------------------------------------------------------------------------------------ 114 NGC7293-OFF WFPC2 IMAGE WFALL F547M 5476 CR-SPlIT=NO 3 100 S SETD Comments: Coordinated Parallel with 110 ------------------------------------------------------------------------------------------------------------------------------------ 115 NGC7293-OFF WFPC2 IMAGE WFALL F656N 6564 1 23 M SETD Comments: Coordinated Parallel with 110 ------------------------------------------------------------------------------------------------------------------------------------ 120 NGC7293-OFF STIS/C ACCUM 52X2 G750M 6581 1 44 M PAR 121-124 WITH 120-120 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 121 NGC7293-OFF NIC1 MULTIAC NIC1 F164N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 120 ------------------------------------------------------------------------------------------------------------------------------------ 122 NGC7293-OFF NIC2 MULTIAC NIC2 F215N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 120 ------------------------------------------------------------------------------------------------------------------------------------ 123 NGC7293-OFF NIC3 MULTIAC NIC3 F215N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 120 ------------------------------------------------------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 5] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 124 NGC7293-OFF WFPC2 IMAGE WFALL F658N 6590 1 38 M SETD Comments: Coordinated Parallel with 120 ------------------------------------------------------------------------------------------------------------------------------------ 130 NGC7293-OFF STIS/C ACCUM 52X2 G750M 5734 1 40 M PAR 131-134 WITH 130-130 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 131 NGC7293-OFF NIC1 MULTIAC NIC1 F166N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 130 ------------------------------------------------------------------------------------------------------------------------------------ 132 NGC7293-OFF NIC2 MULTIAC NIC2 F212N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 130 ------------------------------------------------------------------------------------------------------------------------------------ 133 NGC7293-OFF NIC3 MULTIAC NIC3 F212N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 130 ------------------------------------------------------------------------------------------------------------------------------------ 134 NGC7293-OFF WFPC2 IMAGE WFALL F502N 5012 1 38 M SETD Comments: Coordinated Parallel with 130 ------------------------------------------------------------------------------------------------------------------------------------ 140 NGC7293-OFF STIS/C ACCUM 52X2 G750M 5734 1 44 M PAR 141-144 WITH 140-140 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 141 NGC7293-OFF NIC1 MULTIAC NIC1 F164N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 140 ------------------------------------------------------------------------------------------------------------------------------------ 142 NGC7293-OFF NIC2 MULTIAC NIC2 F215N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 140 ------------------------------------------------------------------------------------------------------------------------------------ 143 NGC7293-OFF NIC3 MULTIAC NIC3 F215N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 140 ------------------------------------------------------------------------------------------------------------------------------------ 144 NGC7293-OFF WFPC2 IMAGE WFALL F656N 6564 1 38 M SETD Comments: Coordinated Parallel with 140 ------------------------------------------------------------------------------------------------------------------------------------ 150 NGC7293-OFF STIS/C ACCUM 52X2 G750M 5734 1 44 M PAR 151-154 WITH 150-150 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 151 NGC7293-OFF NIC1 MULTIAC NIC1 F166N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 150 ------------------------------------------------------------------------------------------------------------------------------------ 152 NGC7293-OFF NIC2 MULTIAC NIC2 F212N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 150 ------------------------------------------------------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 153 NGC7293-OFF NIC3 MULTIAC NIC3 F212N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 150 ------------------------------------------------------------------------------------------------------------------------------------ 154 NGC7293-OFF WFPC2 IMAGE WFALL F658N 6590 1 38 M SETD Comments: Coordinated Parallel with 150 ------------------------------------------------------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 7] Visit: 02 Visit Priority: Visit Requirements: ORIENT 51.0345D TO 51.0345D On Hold Comments: Additional Comments: This ORIENT value is that successfully used in GO-7286. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 201 NGC7293-ACQ STIS/C ACQ F28X50L MIRROR 1 2 S STARB CD P ------------------------------------------------------------------------------------------------------------------------------------ 202 NGC7293-ACQ STIS/C ACQ/PEA 52X0.2 MIRROR 1 2 S STARB CD K ------------------------------------------------------------------------------------------------------------------------------------ 210 NGC7293-OFF STIS/C ACCUM 52X2 G750M 6252 1 33 M PAR 211-214 WITH 210-210 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 211 NGC7293-OFF NIC1 MULTIAC NIC1 F164N SAMP-SEQ=STEP256,NSAMP=19 1 DEF SETD CUM Comments: Coordinated Parallel with 210 ------------------------------------------------------------------------------------------------------------------------------------ 212 NGC7293-OFF NIC2 MULTIAC NIC2 F215N SAMP-SEQ=STEP256,NSAMP=19 1 DEF SETD CUM Comments: Coordinated Parallel with 210 ------------------------------------------------------------------------------------------------------------------------------------ 213 NGC7293-OFF NIC3 MULTIAC NIC3 F215N SAMP-SEQ=STEP256,NSAMP=19 1 DEF SETD CUM Comments: Coordinated Parallel with 210 ------------------------------------------------------------------------------------------------------------------------------------ 214 NGC7293-OFF WFPC2 IMAGE WFALL F502N 5012 1 30 M SETD Comments: Coordinated Parallel with 210 ------------------------------------------------------------------------------------------------------------------------------------ 220 NGC7293-OFF STIS/C ACCUM 52X2 G750M 6252 1 44 M PAR 221-224 WITH 220-220 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 221 NGC7293-OFF NIC1 MULTIAC NIC1 F166N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 220 ------------------------------------------------------------------------------------------------------------------------------------ 222 NGC7293-OFF NIC2 MULTIAC NIC2 F212N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 220 ------------------------------------------------------------------------------------------------------------------------------------ 223 NGC7293-OFF NIC3 MULTIAC NIC3 F212N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 220 ------------------------------------------------------------------------------------------------------------------------------------ 224 NGC7293-OFF WFPC2 IMAGE WFALL F656N 6564 1 38 M SETD Comments: Coordinated Parallel with 220 ------------------------------------------------------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 8] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 230 NGC7293-OFF STIS/C ACCUM 52X2 G430M 4961 1 39 M PAR 231-234 WITH 230-230 SETD CD ------------------------------------------------------------------------------------------------------------------------------------ 231 NGC7293-OFF NIC1 MULTIAC NIC1 F164N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 230 ------------------------------------------------------------------------------------------------------------------------------------ 232 NGC7293-OFF NIC2 MULTIAC NIC2 F215N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 230 ------------------------------------------------------------------------------------------------------------------------------------ 233 NGC7293-OFF NIC3 MULTIAC NIC3 F215N SAMP-SEQ=STEP256,NSAMP=21 1 DEF SETD CUM Comments: Coordinated Parallel with 230 ------------------------------------------------------------------------------------------------------------------------------------ 234 NGC7293-OFF WFPC2 IMAGE WFALL F658N 6590 1 38 M SETD Comments: Coordinated Parallel with 230 ------------------------------------------------------------------------------------------------------------------------------------ 9489( 4) - 02/01/02 07:29 - [ 9] Summary Form for Proposal 9489 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.2 52X2 NIC1 NIC2 NIC3 WFALL ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD NIC1 NIC2 NIC3 WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM MULTIACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SAMP-SEQ=STEP256 NSAMP=19 CR-SPlIT=NO NSAMP=21 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 51.0345D TO 51.0345D PAR 111-115 WITH 110-110 PAR 121-124 WITH 120-120 PAR 131-134 WITH 130-130 PAR 141-144 WITH 140-140 PAR 151-154 WITH 150-150 PAR 211-214 WITH 210-210 PAR 221-224 WITH 220-220 PAR 231-234 WITH 230-230 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750M F166N F212N F547M F656N F164N F215N F658N F502N G430M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC7293-ACQSTARB NGC7293-OFFSETD ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 6581 5476 6564 6590 5734 5012 6252 4961 ------------------------------------------------------------------------------------------------------------------------------------