8285( 4) - 07/27/99 13:24 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8285 Version: 4 Check-in Date: 19-Feb-1999 08:43:01 1.Proposal Title: Using STIS to Unravel Planetary Nebulae ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: William Latter California Institute of Technology CoI: Dr. A.G.G.M. Tielens SRON, University of Groningen N CoI: Dr. Susan R. Trammell University of North Carolina at Charlotte N CoI: Dr. Aditya Dayal Infrared Processing and Analysis N Center/JPL CoI: Dr. John H. Bieging Steward Observatory, University of Arizona N CoI: Dr. Joseph L. Hora Smithsonian Astrophysical Observatory N CoI: Dr. Douglas M. Kelly Steward Observatory, University of Arizona N ------------------------------------------------------------------------------------ 5. Abstract We will make new STIS observations to study the UV/visible light properties of the young planetary nebula NGC 7027. NGC 7027 and other objects in this class display remarkable complexity that has prevented a full understanding of post-asymptotic giant branch stellar evolution. With NICMOS we have imaged several such objects in molecular hydrogen and other filters. H2 emission can probe shocks (winds/jets) and the photodissociation region through near-IR emission. To unravel the complex structure (spatial and kinematic) and distinguish between excitation mechanisms (UV or shock), we are following our NICMOS observations with STIS. We will use STIS in various long slit modes (low and medium resolution and echelle) to achieve the following objectives: (i) Spatially separate shock structures from radiatively excited regions by looking at diagnostic lines such as SII, (ii) obtain kinematic information in the vicinity of the ionized gas--photodissociation region interface and ( iii) interpret the spatially resolved results from (i) and (ii) in light of the ``interacting stellar winds'' theories, in which the PN morphology is created as the fast PN wind plows into the slower, denser AGB wind. We require observations with HST to get the highest possible spatial resolution and stability for line ratio studies throughout the complex nebulae. Several emission lines have been selected to be observed at high spectral resolution for measurement of wind velocities and structure. ------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 2] Observations Description ------------------------ These time estimations have been made using the STIS Exposure Time Calculator (ETC) with known emission line fluxes and reasonable estimates for source size based on imaging. Attenuation of photons by dust into the UV is accounted for directly by only using previously observed lines. The slit position angles will need to be constrained to maximize the science return. However, relatively large ranges for the ORIENT will not restrict scheduling to significantly short periods. As a minimum, low resolution spectra over a broad wavelength range will be acquired. To separate clustered lines in the red, we will obtain medium resolution spectra for a limited wavelength range. Details of the observations follow. NGC 7027: We will acquire long-slit spectra with gratings G750M (2 tilt settings), G430L, and G750L at five 52"x0.1" slit positions oriented approximately parallel to the major axis of the nebula and separated by 2" (see Fig. 1). The intensity of the HBeta line in NGC 7027 is 7 .6X10^-11 erg s^-1 cm^-2, and the intensity of the most interesting lines range from ~ 0.05 I_HBeta (e.g. SII 6716 Angstrom) to ~ 8 I_HBeta (e.g. HAlpha; Keyes et al. 1990). Assuming that the line emission from NGC 7027 is spread uniformly over a surface area of 5"x5", we calculate that to obtain a S/N = 5 on the fainter lines, whose intensity might be 1/100 I_HBeta, we will require approximately 200s exposures at each slit position, at each of the medium resolution settings. The remainder of the 54 minute orbit visibility window will be used in associated overhead tasks, including a 60 second per exposure overhead and 30 seconds for slit motions. Hence, we will require 1 orbit to complete our planned observations for G750M. Using a similar calculation we find that we require another complete orbit for gratings G430L and G750L (covering 3050 to 10, 000 Angstrom) to obtain a S/N >= 5 on lines with intensity greater than 1/100 I_HBeta. We also will acquire long-slit (52"x0.5 ") spectra of NGC 7027 at two positions bracketing the photodissoci ation region, using the G140M grating to isolate the electronic transitions of H2 near 1250 Angstrom. Based on the H2 line strengths in the near-IR, a line width of 20 km/s, an emission region of 25 arcsec square, and A(V) = 1.5 to the H2 emitting region, we expect the UV line to have a surface brightness of ~ 2.0X10^-14 erg s^-1 cm^-2 ang^-1 arcsec^- 2. An exposure time of 1400s will give a S/N ~ 6.6, thus allowing us to obtain spectra at both spatial locations in one orbit. Given the uncertainty in this line strength estimation, we will increase this integration time by a factor of 2 (to 2800s) in each of the two positions -- requiring 2 orbits. To achieve our objective of obtaining information on the kinematics of the nebula, we will use the echelle grating E140H to observe two bright lines (Keyes et al. 1990): CIV (1550 Angstrom; 7.3X10^-10 erg s^-1 cm^-2) and HeII (1640 Angstrom; 2.4X10^-10 erg s^-1 cm^-2), at a resolution of ~ 100, 000. With the ETC we find that in 40 0s o f integration with the 6"x0.2" slit, we will obtain a S/N = 11 for the HeII line and a S/N = 24 for CIV. (Order overlap with the 6" slit is not expected to be a problem and will be handled in post-processing.) Thus we can obtain spectra at 5 distinct slit locations (2000s total exposure time) in one orbit. We require a total of 5 orbits for NGC 7027. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 3] Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7027 ISM, PLANETARY NEBULA, RA=21H 7M 1.83S +/- 0.3", J2000 V = 7.92+/-0.22 STAR, POST-AGB STAR, DEC=42D 14' 9.93" +/- 0.3", EJECTA PLATE-ID=00C8 Comments: Coordinates are from the GSC and confirmed from the DSS plate image using IRAF. Adjusted to match position of central star based on NICMOS observations. 2 OFFSET-STAR STAR RA=21H 6M 57.84S +/- 0.2", J2000 V = 13.67+/-0.21 DEC=42D 14' 3.4" +/- 0.2", PLATE -ID=00C8 Comments: Acquisition star for NGC 7027. Coordinates are from the GSC. 8285( 4) - 07/27/99 13:24 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 7D TO 17D ORIENT 187D TO 197D SAME ORIENT AS 02 GROUP 01, 02 WITHIN 7 D On Hold Comments: Additional Comments: An acquisition of a nearby GSC star is made at the start of the first orbit. All exposure POS TARGs are relative to the central star of NGC 7027 as measured from NICMOS images. A flat field exposure is made for the G750L observations. The G750M do not extend to longer than 7000 Ang, so no flat is needed. This visit needs to be done at the same ORIENT as visit 2 (the MAMA observations). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 OFFSET-STAR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1 S ONBOARD ACQ FOR 2 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7027 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=3 1 115 S POS TARG 2.72, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7027 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=3 1 115 S POS TARG 1.36, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC7027 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=3 1 115 S CD ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC7027 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=3 1 115 S POS TARG -1.36, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7027 STIS/C ACCUM 52X0.1 G430L 4300 CR-SPLIT=3 1 115 S POS TARG -2.72, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC7027 STIS/C ACCUM 52X0.1 G750L 7751 CR-SPLIT=3 1 115 S POS TARG 2.72, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC7027 STIS/C ACCUM 52X0.1 G750L 7751 CR-SPLIT=3 1 115 S POS TARG 1.36, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC7027 STIS/C ACCUM 52X0.1 G750L 7751 CR-SPLIT=3 1 115 S CD ------------------------------------------------------------------------------------------------------------------------------------ 10 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC7027 STIS/C ACCUM 52X0.1 G750L 7751 CR-SPLIT=3 1 115 S POS TARG -1.36, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC7027 STIS/C ACCUM 52X0.1 G750L 7751 CR-SPLIT=3 1 115 S POS TARG -2.72, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC7027 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=3 1 270 S POS TARG 2.72, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC7027 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=3 1 270 S POS TARG 1.36, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC7027 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=3 1 270 S CD ------------------------------------------------------------------------------------------------------------------------------------ 16 NGC7027 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=3 1 270 S POS TARG -1.36, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC7027 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=3 1 270 S POS TARG -2.72, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 7] Visit: 02 Visit Priority: Visit Requirements: ORIENT 7D TO 17D ORIENT 187D TO 197D SAME ORIENT AS 01 GROUP 01, 02 WITHIN 7 D On Hold Comments: Additional Comments: An acquistion on a nearby GSC is made at the start of the first orbit. All exposure POS TARGs are relative to the central star of NGC 7027 as measured from NICMOS images. This visit needs to be at the same ORIENT as visit 1 (the CCD observations). Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 OFFSET-STAR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1 S ONBOARD ACQ FOR 2 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7027 STIS/F ACCUM 52X0.5 G140M 1272 1 2800 S POS TARG 2.72, 0 UV-MAM A Comments: First H2 slit position. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7027 STIS/F ACCUM 52X0.5 G140M 1272 1 2800 S POS TARG -4.4, 0 UV-MAM A Comments: Second H2 slit position. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC7027 STIS/F ACCUM 6X0.2 E140H 1598 1 450 S POS TARG 2.72, 5 UV-MAM A Comments: This is the first echelle UV observation. The following slit positions are placed diagonally from South-East going to the North-West of the object. This is done in hopes of sampling the jet. The slit is long enough that "non-jet" material will be well sampled as well. The long slit will cause order overlap. The line placement is such that this should not be a major problem and can be handled in post-processing. ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC7027 STIS/F ACCUM 6X0.2 E140H 1598 1 450 S POS TARG 1.36, 3.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7027 STIS/F ACCUM 6X0.2 E140H 1598 1 450 S POS TARG 0.0, 0.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC7027 STIS/F ACCUM 6X0.2 E140H 1598 1 450 S POS TARG -1.36,-3.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 8] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC7027 STIS/F ACCUM 6X0.2 E140H 1598 1 450 S POS TARG -2.72,-5.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8285( 4) - 07/27/99 13:24 - [ 9] Summary Form for Proposal 8285 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 52X0.5 6X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT CR-SPLIT=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 7D TO 17D ORIENT 187D TO 197D SAME ORIENT AS 02 GROUP 01, 02 WITHIN 7 D ONBOARD ACQ FOR 2 POS TARG 2.72, 0 POS TARG 1.36, 0 POS TARG -1.36, 0 POS TARG -2.72, 0 ORIENT 7D TO 17D ORIENT 187D TO 197D SAME ORIENT AS 01 GROUP 01, 02 WITHIN 7 D POS TARG -4.4, 0 POS TARG 2.72, 5 POS TARG 1.36, 3.0 POS TARG 0.0, 0.0 POS TARG -1.36,-3.0 POS TARG -2.72,-5.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G750L G750M G140M E140H ------------------------------------------------------------------------------------------------------------------------------------ Target Names OFFSET-STAR NGC7027 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 7751 6581 1272 1598 ------------------------------------------------------------------------------------------------------------------------------------