8116( 3) - 05/20/99 16:11 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8116 Version: 3 Check-in Date: 19-Feb-1999 12:52:32 1.Proposal Title: Spectroscopy of the Rapidly-Evolving, Chemically Inhomogeneous Planetary Nebula BD+30 3639 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: J. Harrington University of Maryland CoI: Dr. Kazimierz Borkowski North Carolina State University N ------------------------------------------------------------------------------------ 5. Abstract BD +30^degrees3639 is one of the most important and extensively observed of all planetary nebulae. One of the few PNe with X-ray emission from the shocked stellar wind, it is an approved AXAF target. ISO observations led to the unexpected discovery of crystalline silicates in this carbon- rich nebula. This, and other evidence, shows that BD+30 has undergone rapid chemical evolution, and is likely to show abundance anomalies and gradients in the ionized gas. We propose to obtain several long-slit near-UV and optical spectra of BD+30. This will enable us to map the C/O ratio with high spatial resolution (~ 0.2"). We will also obtain co- spatial determinations of the temperature and density, map the behavior of the enigmatic C II 4267 recombination line, and perhaps track the Si/C ratio. We propose 2nd-epoch observations to our earlier (1994) WFPC2 images to measure the angular expansion. To map the velocity field of BD+30 -- crucial to get its distance from the angular expans ion -- we will take echelle spectr a in the C II Lambda2326 line. Such detailed mapping is necessary in light of the discovery of high-velocity outflows, not only in molecular gas (CO, H_2), but even optical lines. These observations will complete a comprehensive picture of a PN which can open a window onto the final dredge-up and mass-loss phase of AGB evolution. ------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 2] Observations Description ------------------------ sectionSTIS Observations In all the non-echelle observations, we will use the 52x0.2 slit. In order to map BD+30 completely in the most important lines, C II Lambda2326 and O II Lambda2470, we will use the G230L grating and step the slit across the nebula, setting at 8 positions, separated by 0.6". We will avoid the bright central star. The slit pattern is shown in in Fig. 1, though we will rotate to a somewhat different position angle. The weaker of the two lines, O II, has a total flux (from IUE) of 2.4 * 10^-12 ergs cm^-2 s^-1, which translates into a surface brightness of 1.2 * 10^-13 ergs cm^-2 s^-1 arcsec^-2. For a 120s exposure, the ETC then gives a S/N of ~ 4 for each spatial resolution element. We thus take 16 min to map the nebula in these strong lines We also want to obtain other UV diagnostic lines which are much fainter. For this we can only afford one slit position; we will choose one of the pair that straddle the star. To resolve the density sensitive C III 19 07, 1909 doublet, we use G230M (18 84) and also cover Si III 1883, 1892 with this setting. A 10 min exposure integrated over 0.2" spatial elements will give a S/N ~ 10 for a line flux of 3 * 10^-12 ergs cm^-2 s^-1 spread uniformly over the nebula. Such a line flux is three times fainter than the predictions of ionization models. If the line is much fainter than this, as the IUE spectra indicate, we will have to resort to spatial averaging to go deeper. While our primary T_e indicator is the N II 5755/6584, we want to observe the N II 2139, 2143 doublet as a check (These lines have been seen in Orion with HST; they were in the least sensitive region for IUE and thus not seen with that instrument.). The N II 2140/6584 ratio is a sensitive T_e diagnostic. If it's values should disagree with those of 5755/6584, then we know that either (1) the densities are high enough to start collisionally de-exciting the N II lines, giving incorrect temperatures, or (2) we have a ``temperature fluctuation'' (t^2) problem. But since the N II 2139/2143 ratio is density sensitive, we can distinguish between the two possibilities. To observe the 2139, 43 lines, we will use the G230M (2176) grating. Again, a 10 min exposure will let us reach the fluxes predicted by our models. For these spectra, we can of course go deeper by binning along the slit -- with corresponding loss of spatial resolution. With acquisition and overheads, the (4 x 4m)+10m+10m exposures will fill one orbit. In the next orbit, we will use the same slit positions, but switch to the STIS/CCD. Using G750L, we will map the nebula at the inner 4 of the 8 slit positions with 4 min exposures. The resolution will be adequate for many important lines: N II 6584, HAlpha, O II 7319, 30, S II 6716, 30, S III 9068, 9531, etc. It is important that we be able to measure N II 5755, our primary temperature indicator. The surface brightness of this line is 2 * 10^- 14 ergs cm^-2 s^-1 arcsec^-2. This gives us S/N ~20 per spatial resolution element, which should allow accurate T_e de termination. If we are to separate the C II Lambda4267 recombination line from nearby features, we must use the higher resolution G430M (4194) grating. This also gives us the S II 4068, 78 lines. Aller and Hyung (1995) give a flux of ~ 3 * 10^-13 ergs cm^-2 s^-1 for this line, so a 600 sec exposure will give a S/N = 4.5. This line arises from the same ion, C^2+, as C III 1909, and we will map it along the same slit used for C III. The abundances given by the recombination lines are very controversial: in some objects they give C/H values 3-5 times higher than those derived from collisionally excited lines. Any opportunity to investigate this enigmatic line at high spatial resolution, with other diagnostic lines that may give clues to its behavior, could yeild important results. Finally, we will take a 4 min exposure with G430M (3680) to resolve the O II 3726, 29 doublet (See Fig. 1). These strong lines will give a S/N = 70. This will allow us to map the density along this slit; a high S/N is needed since at the electron densities of BD+30 (~ 2 * 10^4 cm^-3), this ratio is approaching its high density limit. \medskip The kinematics of the ionized shell in BD+30 can be derived from high spectral resolution observations of C II Lambda 2326 and O II Lambda 2470 emission lines. The average expansion velocity of the ionized shell is ~ 20 - 30 km s^-1, with higher-velocity (50 km s^-1) outflows seen in H_2 and CO. We need spectral resolution of ~ 10 km s^-1 to map such velocity fields. This can be done only with E230H echelle grating with the 6 * 0.2 slit -- for this slit, spectral resolution is approximately equal to 6 pixels in the dispersion direction (= 6 * 0.010 Angstrom = 0.06 Angstrom ~ 8 km s^-1 at Lambda 2326). Because of the fairly symmetric shape of the ionized shell, it is sufficient to map the velocity field in two principal directions, one along the axis of the bipolar outflow seen in the molecular gas, SE to NW, and another in the perpendicular direction. This can be accomplished in two independent visi ts, with slits located along these two principal directions (see the figure). We estimate that 30 min exposure time will be sufficient to obtain good spectra at each slit position, requiring two HST orbits. The C II Lambda2346 is a multiplet with rest wavelengths 2324.21, 2325.40, 2326.11, 2327.64, and 2328.84 Angstrom. We examined archival, high-dispersion IUE spectra of BD+30 and found that the strongest multiplet component has flux 8 * 10^-12 ergs cm^-2 s^-1. With the 2.5 arcsec nebular radius, this gives average surface brightness of 4 * 10^-13 ergs cm^-2 s^-1 arcsec^-2. The expected thermal width (FWHM) of the line at 10^4 K is 0.048 Angstrom (6.2 km s^-1). For our exposure time estimates, we assumed a slightly larger width (10 km s^-1 or 0.078 Angstrom) to account for possible presence of microturbulence. The flux at the line center is then ~ 5 * 10^-12 ergs cm^-2 s^-1 AA^-1 arcsec^-2. With the E230H diffuse source sensitivity of 2 * 10^9 counts s^-1 pix_lambda^-1 pix_s^-1 per incident flux in ergs cm ^-2 s^-1 AA^-1 arcsec^-2 for 0.2 a rcsec wide slit, we obtain 0.01 counts s^-1 pix_lambda^-1 pix_s^-1. As our resolution element, we take 7 spatial pixels (=7 * 0.029 arcsec = 0.20 arcsec) and 6 pixels in the dispersion direction. That gives 0.42 counts s^-1 per our resolution element. In 30 min integration time, we will have 750 counts per resolution element, or S/N=27 (dark current and other backgrounds do not contribute much noise here). This S/N ratio is sufficient to map velocity fields in BD+30 with good precision. We verified our exposure time calculations for echelle spectra with the STIS ETC. Spectral order overlap will occur in echelle observations of diffuse sources with 6 * 0.2 slit. This is not a problem because C II Lambda2326 and O II Lambda2470 lines are the only strong nebular emission lines in this range of the spectrum (no other nebular lines were seen in IUE spectra of BD30 and our photoionization models are consistent with IUE observations). Possible contamination by faint scattered st ellar emission lines is also not i mportant because of the large (700 km s^-1) line widths -- even close to the star such contamination would merely reduce S/N for our observations. C II Lambda2326 is a multiplet, but its components will not overlap with each other in different orders in observations with E230H grating. We can actually use all multiplet components in our analysis of radial velocities, because of the known (constant) multiplet line ratios at high nebular densities of BD+30. E230H grating offers further advantage because both C II Lambda2326 and O II Lambda2470 lines can be observed at the same secondary tilt with central wavelength of 2413 Angstrom. sectionWFPC2 Observations Astrometric measurements with a precision of several miliarcsec require good quality data with high S/N ratio and with the fully sampled PSF. By far the strongest emission lines in BD+30 are HAlpha and N II Lambda6584 -- we propose imaging in both lines with the PC camera. The observations will be dithered to achieve the full HST spatial resolution. We w ill take a set of images in the HAlpha filter, F656N, using the same exposure time as the 1st epoch, 200s, at each of the three dither positions (with the CR- SPLIT option at each position). While imaging in HAlpha is our priority, allowing us to make a direct comparison with ground- based radio data, the ionized shell is actually more compact in N II Lambda6584. Proper motion measurements are likely to be more accurate in this case. We propose to take a set of N II Lambda6584 images with the same exposure time as HAlpha, using the F658N filter. WFPC2 observations in both emission lines require one HST orbit. plotoneslits.eps noindent Fig. 1. WFPC2 O IILambda3727 image of BD+30 3639, showing long slit positions. \medskip sectionReferences Aller, L.H. &\ Hyung, S. 1995, MNRAS, 276, 1101. Arnaud, K., Borkowski, K.J., &\ Harrington, J.P. 1996, ApJ, 462, L75. Bachiller, R., Huggins, J.P., Cox, P., &\ Forveille, T. 1991, A&A, 247, 525. Currie, D. G., et al. 1996, AJ, 112, 1115 Harrington, J.P., Lame, N.J., White, S.M. &\ Borkowski, K.J. 1997, AJ, 113, 2147. Kawamura, J. &\ Masson, C. 1996, ApJ, 461, 282. Pwa, T.H., Pottasch, S.R., &\ Mo, J.E. 1986, A&A, 164, 184. Shupe, D.L., et al. 1998, ApJ, 498, 267. Waters, L.B.F.M., et al. 1998, A&A, 331, L61. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PK64+5D1 ISM, PLANETARY NEBULA RA=19H 34M 45.25S +/- 0.07S, 2000 V = -66 V = 10.0+/-0.10 DEC=30D 30' 59.3" +/- 1.0", TYPE=WR PLATE-ID=000J A(V) = 1.26+/-0.09 SURF-LINE(2326)=4+/-1e-13 W-LINE(2326)=0.1+/-0.03 SIZE=5+/-0.5 Comments: V Flux refers to the central star. WE WILL NOT OBSERVE THE STAR. The science observations are of the surrounding nebula. Size refers to the nebula. Average line surface brightness is given. Quoted line width is the thermal width, actual width depends on the velocity field (max +/- 50 km/s). SURF- LINE(2470)=1.2+/-0.3E-13, W-LINE(2470)=0.1+/-0.03 SURF -LINE(6563)=1.9+/-0.3E-11, W-LINE(6563)=0.2+/-0.03 SURF-LINE(6584)=2.0+/-0.3E-11, W-LINE(6584)=0.1+/-0.03 SURF-LINE(3728)=4.0+/-0.3E-12, W-LINE(3728)=0.1+/-0.03 SURF-LINE(4267)=1.5+/-0.3E-14, W-LINE(4267)=0.1+/-0.03 8116( 3) - 05/20/99 16:11 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 230D TO 250D ORIENT 50D TO 70D 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PK64+5D1 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 3.0 S ONBOARD ACQ FOR 20 CD ------------------------------------------------------------------------------------------------------------------------------------ 20 PK64+5D1 STIS/N ACCUM 6X0.2 E230H 2413 PATTERN=ALONG-SLIT,NUM-POS=2, 1 18.0 M POS TARG -0.4, 0.0 UV-MAM STEP-SIZE=0.35 A ------------------------------------------------------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 140D TO 160D ORIENT 320D TO 340D 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PK64+5D1 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 3.0 S ONBOARD ACQ FOR 20, 30, CD 40, 50 ------------------------------------------------------------------------------------------------------------------------------------ 20 PK64+5D1 STIS/N ACCUM 6X0.2 E230H 2413 PATTERN=ALONG-SLIT,NUM-POS=2, 1 18.0 M POS TARG -0.4, 0.0 UV-MAM STEP-SIZE=0.35 A ------------------------------------------------------------------------------------------------------------------------------------ 30 PK64+5D1 STIS/N ACCUM 52X0.2 G230L 2376 PATTERN=PERP-TO-SLIT,NUM-POS=6, 1 150.0 S POS TARG -2.0, 0.0 UV-MAM STEP-SIZE=0.8 A ------------------------------------------------------------------------------------------------------------------------------------ 40 PK64+5D1 STIS/N ACCUM 52X0.2 G230M 1884 1 8.0 M POS TARG -0.4, 0.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 PK64+5D1 STIS/N ACCUM 52X0.2 G230M 2176 1 8.0 M POS TARG -0.4, 0.0 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 7] Visit: 03 Visit Priority: Visit Requirements: SAME ORIENT AS 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PK64+5D1 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 3.0 S ONBOARD ACQ FOR 20, 30, CD 40 ------------------------------------------------------------------------------------------------------------------------------------ 20 PK64+5D1 STIS/C ACCUM 52X0.2 G430M 3680 CR-SPLIT=2 1 240.0 S POS TARG -0.4, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 30 PK64+5D1 STIS/C ACCUM 52X0.2 G430M 4194 CR-SPLIT=2 1 460.0 S POS TARG -0.4, 0.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 40 PK64+5D1 STIS/C ACCUM 52X0.2 G750L 7751 CR-SPLIT=2,PATTERN=PERP-TO-SLIT, 1 120.0 S POS TARG -1.2, 0.0 CD NUM-POS=4,STEP-SIZE=0.8 ------------------------------------------------------------------------------------------------------------------------------------ 50 CCDFLAT STIS/C ACCUM 52X0.2 G750L 7751 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 8] Visit: 04 Visit Priority: 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 ------------------------------------------------------------------------------------------------------------------------------------ 5 PK64+5D1 WFPC2 IMAGE PC1-FIX F658N ATD-GAIN=15 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 10 PK64+5D1 WFPC2 IMAGE PC1-FIX F658N DITHER-TYPE=LINE, 1 160.0 S DITHER-LINE-STEPS=3, DITHER-LINE-SPACING=0.2361, ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ 20 PK64+5D1 WFPC2 IMAGE PC1-FIX F656N ATD-GAIN=15 1 4.0 S ------------------------------------------------------------------------------------------------------------------------------------ 30 PK64+5D1 WFPC2 IMAGE PC1-FIX F656N DITHER-TYPE=LINE, 1 160.0 S DITHER-LINE-STEPS=3, DITHER-LINE-SPACING=0.2361, ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ 8116( 3) - 05/20/99 16:11 - [ 9] Summary Form for Proposal 8116 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND3 6X0.2 52X0.2 PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT STEP-SIZE=0.35 NUM-POS=2 STEP-SIZE=0.8 CR-SPLIT=2 NUM-POS=4 ATD-GAIN=15 DITHER-LINE-SPACING=0.2361 DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 230D TO 250D ORIENT 50D TO 70D ONBOARD ACQ FOR 20 POS TARG -0.4, 0.0 ORIENT 140D TO 160D ORIENT 320D TO 340D ONBOARD ACQ FOR 20, 30, 40, 50 POS TARG -2.0, 0.0 SAME ORIENT AS 02 ONBOARD ACQ FOR 20, 30, 40 POS TARG -1.2, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E230H G230L G230M G430M G750L F658N F656N ------------------------------------------------------------------------------------------------------------------------------------ Target Names PK64+5D1 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2413 2376 1884 2176 3680 4194 7751 ------------------------------------------------------------------------------------------------------------------------------------