9178( 4) - 07/20/01 09:08 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9178 Version: 4 Check-in Date: 20-Jul-2001 09:08:07 1.Proposal Title: NGC 2610: A Benchmark for Photoionization Physics ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: J. Harrington University of Maryland CoI: Dr. Kazimierz Borkowski North Carolina State University N ------------------------------------------------------------------------------------ 5. Abstract While it is commonly thought that photoionized gases are well understood and that codes that model them have been tested exhaustively, this is not the case. Tests have been spotty and are undermined by the morphological complexity revealed by HST. It has proved difficult to model high-T, high-excitation objects. There is a fundamental need for clean observational tests of our photoionization codes. NGC 2610 is a high- excitation planetary nebula which, even at HST resolution, is smooth and symmetric. Due to its high ionization -- helium is He^++ throughout -- it has a meager optical spectrum. But its high electron temperature (18, 000 K) results in very strong ultraviolet lines. It is the best object we know of to test the performance of photoionization codes without the complication of morphological substructures. With a radius of 18", STIS long-slit observations will provide excellent spatial resolution to test against models. We propose STIS observations with a wide slit to observe lines of H I, He II, C III, C IV, N IV, N V, O III, O IV, Ne III, Ne IV, and Ne V from 1240Angstrom to 6563Angstrom. He II Lambda1640/Lambda4686 will determine the (small) reddening accurately. These observations will provide a benchmark against which we can test our understanding of high T_e nebulae, which are ubiquitous in low abundance environments, but which have proved difficult to model. ------------------------------------------------------------------------------------ 9178( 4) - 07/20/01 09:08 - [ 2] Observations Description ------------------------ Because NGC 2610 is a smooth, extended object of fairly low surface brightness, we will use the STIS 52x2" slit. The slit will be placed with the star ~2" off the end of the detector -- orientation is not critical -- and we will thus get a radial cut from near the center out through the nebula. Consistent with the 2" slit, we can bin groups of 20 CCD or 40 MAMA pixels (1" along the slit) and still have ~16 data points along the nebular radius. Most lines are isolated and can be measured with the low dispersion gratings, G140L, G230L, and G430L. However, the medium resolution gratings will be needed to separate N V 1240 from geocoronal LAlpha, O III 1663 from He II 1640, and O III 4363 from H>~mma 4340. Since the only line we need from the G750 grating is HAlpha, we will use G750M to resolve any faint, flanking N II 6548, 6583. We want to achieve S/N ratios of 10 or better for the sort of benchmark standard that is our objective. The line which puts the greatest demands on our program is O III Lambda1663. From the IUE data, the surface brightness in this line is 2* 10^-15 ergs/ cm^2/s/arcsec^2. For a 40 min exposure, the STIS Spectroscopic ETC gives a S/N of 1.9. Binning over 40 pixels along the slit then would give us an acceptable S/N of 12 in this line. The other critical line, O III Lambda4363, has a flux of 4.2* 10^-16 ergs/cm^2/s/arcsec^2. The ETC yields a S/N of 5.5 for a 15 min exposure (with 4x4 binning). Thus for 20 pixels along the slit, we should achieve a S/N ratio of 12. The other lines are stronger, but the overheads come into play. We calculate that we will need 4 orbits, with exposures allocated as follows: 1st orbit: aquisition and 1st MAMA exposure -- G140L, 35 min 2nd orbit: 2nd MAMA exposure -- G140M(1663), 40 min 3rd orbit: 3rd MAMA exposure -- G140M(1240), 25 min; G240L, 10 min. 4rd orbit: CCD exposure -- G430M(4363), 15 min; G430L, 5 min, G750M(6563), 5 min. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9178( 4) - 07/20/01 09:08 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2610 ISM, PLANETARY NEBULA RA=8H 33M 23.36S +/- 0.02S, DEC= 2000 V=88 V = 15.97+/-0.05 -16D 8' 57.3" +/- 0.3", PLATE- B-V = -0.30 ID=02BZ TYPE=O E(B-V) = 0.10+/-0.03 Coordinate Source: GUIDE_STAR_CATALOG 9178( 4) - 07/20/01 09:08 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 10 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.35 Coordinate_Frame POS-TARG Pattern_Orient 90 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9178( 4) - 07/20/01 09:08 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 175D TO 60D ORIENT 120D TO 130D SCHED 60% On Hold Comments: Additional Comments: Avoid putting slit at position angles 25 to 135 deg. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC2610 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 5.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC2610 STIS/F ACCUM 52X2 G140L 1425 1 19.0 M POS TARG -4.0,-9.0 UV-MAM PATTERN 10 A ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC2610 STIS/F ACCUM 52X2 G140M 1665 1 23.0 M POS TARG -4.0,-9.0 UV-MAM PATTERN 10 A ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC2610 STIS/F ACCUM 52X2 G140M 1222 1 13.0 M POS TARG -4.0,-9.0 UV-MAM PATTERN 10 A ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC2610 STIS/N ACCUM 52X2 G230L 2376 1 12.0 M POS TARG -4.0,-12.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9178( 4) - 07/20/01 09:08 - [ 6] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 01 SCHED 60% 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 ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC2610 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 5.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 70 NGC2610 STIS/C ACCUM 52X2 G430M 4451 CR-SPLIT=2 1 900.0 S POS TARG -4.0,-12.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 80 NGC2610 STIS/C ACCUM 52X2 G430L 4300 CR-SPLIT=2 1 340.0 S POS TARG -4.0,-12.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 90 NGC2610 STIS/C ACCUM 52X2 G750M 6768 CR-SPLIT=2 1 300.0 S POS TARG -4.0,-12.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 9178( 4) - 07/20/01 09:08 - [ 7] Summary Form for Proposal 9178 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 175D TO 60D ORIENT 120D TO 130D SCHED 60% POS TARG -4.0,-9.0 PATTERN 10 POS TARG -4.0,-12.0 SAME ORIENT AS 01 SCHED 60% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L G140M G230L G430M G430L G750M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2610 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 1665 1222 2376 4451 4300 6768 ------------------------------------------------------------------------------------------------------------------------------------