Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5354 Report Date: 18-Jul-95:17:13 Version: ********** Check-in Date: ********** 1.Proposal Title: IMAGING IN THE CRAB NEBULA ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID INTERSTELLAR MEDIUM GO Sub Category SN & SNR ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Kris Davidson 2710 USA 612-624-5711 ------------------------------------------------------------------------------------ 7. Abstract We propose to obtain two types of WFPC2 images of selected bright filaments in the Crab Nebula. High-spatial-resolution images of the brightest visual-wavelength emission lines will provide density profiles across gas condensations, to improve ionization models that are used to study chemical composition in this very important SNR. (The same images are also useful for some other problems.) Low-spatial- resolution images of UV emission lines will be used to discover whether any UV- bright spots exist in the Crab Nebula, possibly caused by additional heating mechanisms or other circumstances. The proposed images will be used in conjunction with Cycle 3 FOS results and continuing ground-based observations and ionization/abundance calculations. The observations proposed here are essentially similar to those in GO 2340, a Cycle 1 project that was never done, partly because of the HST's optical defect. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 11.79 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5354 PI: Kris Davidson Proposal Title: IMAGING IN THE CRAB NEBULA ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Kris Davidson 2710 USA William Blair 2380 USA Robert Fesen 1830 USA Richard Henry 3060 USA Gordon Macalpine 2660 USA Alan Uomoto 2380 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. All of these are WFPC2 exposures targeted in the Crab Nebula -- - (1) High spatial resolution: Filters F502N, F656N, F658N, and F673N to image [OIII], H- alpha, [NII], and [SII]. One image each, except that each image should be divided into 2 or preferably 3 separate exposures (see below). Integration time nearly 2 hours per filter. ...Supplementing these, an image should be made with filter F547M, to provide underlying continuum background to be removed from the emission-line images. An exposure time of about an hour is adequate for the F547M image (divided into 2 or 3 parts). - (2) Low spatial resolution UV exploratory image: The main UV image uses filter F170W to observe CIV 1548 + HeII 1640 + NIII 1750 + CIII 1908 emission. Total integration time about 2 hours, divided into 2 separate exposures. Underlying continuum is important here, necessitating a UV continuum image using either F300W or F336W (the former is listed in the OSF), with > 0.5-hour integration time. - All exposures are at nearly the same target location, EXCEPT that it is advantageous to shift position by a few pixels between sub- exposures, so instrumental defects don't always cover the same parts of the SNR. - ---- Note, concerning INSTRUMENT ORIENTATION: ---- In order to place important Crab Nebula filaments in all three WF CCD chips simultaneously, the +U3 axis should point approximately eastward. Because of the Crab's location near the ecliptic, the HST automatically has the desired orientation throughout the period January--April of any year. Thus, although the desired orientation is specified by an ORIENT special requirement in our observing plan, we expect this to be an "easy" requirement because it matches the nominal spacecraft orientation anyway, if the observations are done in the time period mentioned above. (The requested orientation is not absolutely essential for this project, but it is very desirable.) Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Theoretical models predict that a typical gas condensation in the Crab Nebula should have ionization structure with a scale size of the order of 0.2". Based on experience with many excellent photographs and CCD frames of the Crab, we know that ground-based images are inadequate for studying this structure. Because the surface brightnesses are low, deconvolution is difficult and speckle interferometry is impossible. The HST/WFPC2 appears to be the only available instrument that can provide adequate spatial resolution for this type of target. - In addition to high-spatial-resolution images at visual wavelengths, we also need exploratory UV images in order to discover whether UV-bright spots exist in the Crab nebula. UV images made with ASTRO/UIT had exposure times that were too short for this purpose by a factor of the order of 100. The combination of larger collecting area and longer possible exposure time makes HST/WFPC2 more suitable for this purpose. No other existing instrument is adequate. Even with HST/WFPC2, the effective spatial resolution in UV images of the Crab will be about 1", limited by S/N. (The FOC is unsuitable for this purpose because its post-COSTAR field size is too small.) ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. There is no direct special scheduling requirement per se, but we think that the period January -- April is best for this program (in any year). The reason is based on spacecraft orientation, as follows: The Crab Nebula is somewhat larger than the WFPC2 field, and a particular instrument orientation range is desirable in order to image important nebular filaments in all three WFC chips simultaneously. The desired orientation is achieved if the +U3 (anti-solar) axis points approximately toward PA = 90 deg, i.e., if the Sun is due west of the target. Since the Crab Nebula is near the ecliptic, and passes behind the Sun in mid-June, the orientation requirement is satisfied during most of the January- -April time period. As stated in question 3, this "special requirement" is highly desirable but not absolutely essential to the project. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ---- None, so far as we know. ---- ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Two techniques that we hope to employ are worth mentioning (these both appear easy to do): (1) We wish to make sure that each of the three WFC chips includes an important Crab Nebula filament region, all at once. This requires a particular instrument orientation. We hope and expect that this "special requirement" is an easy one, for reasons outlined in questions 3 and 5. (2) Routinely, each 1-to-2 hour WFPC2 image will actually be two or three sub- exposures. We prefer that the instrument be moved slightly (by just a few pixels) between sub-exposures, so that fixed instrument defects do not fall in the same target locations in all of the sub-exposures. ------------------------------------------------------------------------------------ 9. Description of previous HST work. GO 2338, "Spectroscopy of ... Eta Carinae", KD was PI, results will be subm for publ late 1993. GO 2416, "Imagery and spectroscopy of super metal poor galaxies", KD was a CoI. GO 3815, "UV observations of Hubble-Sandage Variables...", KD is a CoI. Observations started but not completed yet. GTO 4831, "Imaging and Spectrophotometry of Seyfert Nuclei", AU is a CoI. GTO 4909, "Polarization Imaging of the Jet in Markarian 463", AU is PI. Publ in AJ 105, 1308 (1993). GO 4356, "Imaging and Spectroscopy in the Crab Nebula", same roster of investigators as this present proposal; obs not done yet. GO 4509, "A Spectroscopic Map of ... Eta Carinae", KD is PI; obs not done yet. ...Note that GO 4356 is Cycle 3 FOS spectroscopy of the Crab Nebula, part of the same overall project as this proposal. Page 4 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). In most cases, the normal computer and data-analysis facilities, etc. GMM is obtaining relevant ground-based spectroscopy of the Crab the the McGraw-Hill Observatory (in which both Michigan and Dartmouth are participants), and we hope that additional ground-based imaging can be obtained there also, in support of the HST imaging proposed here. Students from some of our institutions will be involved in the data reduction and analysis, but we don't know the details yet because they depend on the availability of appropriate students. ------------------------------------------------------------------------------------ 11. Address Information Name: KRIS DAVIDSON Category: PI Institution: 2710 Address: ASTRONOMY DEPT. UNIVERSITY OF MINNESOTA 116 CHURCH ST. SE City: MINNEAPOLIS State: MN Zip Code: 55455 Country: USA Telephone: 612-624-5711 Telex (or e-mail): KD@EA.SPA.UMN.EDU ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5354 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1952- G,506,922,925,926,927 RA = 5H 34M 29.2S +/- 0.1S, J2000 1 SURF(V) = 20.0 +/- 1.0 BRTFIL DEC = +22D 00' 50.0" +/- 2 SURF-LINE(6563) = 1.0 +/- 0.7 E-15 CRAB_NEBULA- 1.0" 3 W-LINE(6563) = 5.0 +/- 1.0 BRTFIL 4 SURF-LINE(5007) = 2.0 +/- 1.3 E-15 5 W-LINE(5007) = 5.0 +/- 1.0 6 SURF-LINE(1640) = 1.0 +/- 0.5 E-15 7 W-LINE(1640) = 5.0 +/- 1.0 8 SURF-CONT(3000) = 2.5 +/- 1.5 E-17 Comments: BRT FILAMENT REGION IN CRAB NEB, TO BE IMAGED IN WF3; WF2 AND WF4 WILL IMAGE OTHER FILAMENTS. EMISSION-LINE BRIGHTNESSES REFER TO SMALL GAS CONDENSATIONS. EMISSION LINES 6584 AND 6724 ARE ABOUT AS BRIGHT AS 6563. VALUE FOR 1640 HERE IS REALLY THE SUM OF EMIS LINES 1549+1640+ 1908, IN A VERY BRT BLOB. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5354 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 DEFINE NGC1952- WFPC2 IMAGE WF3-FIX # CR-SPLIT=NO 1 2000S 10 2 # CYCLE 4 / 11-13 TRIPLE- BRTFIL CLOCKS=YES 3 GROUP 11-13 NO GAP IM 4 ORIENT 87D +/- 8D 5 / 11-13 POS TARG -0.6,-0.6 Comments: ORIENT REQ ENSURES THAT IMPORTANT FILAMENTS ARE IMAGED IN WF2, WF4 AS WELL AS WF3. THIS SPEC REQ IS NOT DIFFICULT, SEE QUESTIONS 3 AND 5 IN THE GENERAL FORM. SEE ALSO COMMENT FOR LINE 12. ------------------------------------------------------------------------------------------------------------------------------------ 12 DEFINE NGC1952- WFPC2 IMAGE WF3-FIX # CR-SPLIT=NO 1 2300S 10 2 # POS TARG -0.6, - TRIPLE- BRTFIL CLOCKS=YES 3 0.6 IM 4 5 Comments: LINES 11,12,13 ARE ALIKE EXCEPT FOR THEIR POS TARG VALUES. THIS PROCEDURE IS A FANCIER FORM OF CR-SPLIT. S/N REFERS TO ONE PIXEL, ONE EXP. SEE COMMENTS FOR LINE 11. ------------------------------------------------------------------------------------------------------------------------------------ 13 DEFINE NGC1952- WFPC2 IMAGE WF3-FIX # CR-SPLIT=NO 2 2300S 10 2 # POS TARG +0.6,+0.6 TRIPLE- BRTFIL CLOCKS=YES 3 IM 4 5 Comments: SEE COMMENTS FOR LINES 11 AND 12. ------------------------------------------------------------------------------------------------------------------------------------ 101 USE F656N 1 TRIPLE- IM Comments: H-ALPHA EMISSION LINE IMAGE ------------------------------------------------------------------------------------------------------------------------------------ 102 USE F658N 3 TRIPLE- IM Comments: [NII] EMISSION LINE IMAGE ------------------------------------------------------------------------------------------------------------------------------------ 103 USE F502N 3 TRIPLE- IM Comments: [OIII] EMISSION LINE IMAGE ------------------------------------------------------------------------------------------------------------------------------------ 104 USE F673N 3 TRIPLE- IM Comments: [SII] EMISSION LINE IMAGE ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5354 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 111 NGC1952- WFPC2 IMAGE WF3-FIX F547M CR-SPLIT=NO 2 800S 16 1 4 CYCLE 4 / 111-114 BRTFIL CLOCKS=YES GROUP 111-114 NO GAP ORIENT 87D +/- 8D / 111-114 POS TARG -0.6,-0.6 Comments: SEE COMMENT FOR LINE 11. LINES 111-114 ARE ALIKE EXCEPT FOR POS TARG -- THEY ARE LIKE A CR- SPLIT WITH A SLIGHT INSTRUMENT MOVEMENT BETWEEN SUB-EXPOSURES. ------------------------------------------------------------------------------------------------------------------------------------ 114 NGC1952- WFPC2 IMAGE WF3-FIX F547M CR-SPLIT=NO 2 1000S 16 1 4 POS TARG +0.6,+0.6 BRTFIL CLOCKS=YES Comments: SEE COMMENTS FOR LINE 111. ------------------------------------------------------------------------------------------------------------------------------------ 201 NGC1952- WFPC2 IMAGE WF3-FIX F170W CR-SPLIT=NO 1 2000S 5 1 2 CYCLE 4 / 201-204 BRTFIL SUM=2X2 GROUP 201-204 NO CLOCKS=YES GAP ORIENT 87D +/- 8D / 201-204 POS TARG -0.6,-0.6 Comments: UV EMIS LINES IMAGED IN LINES 201-202. FOR UV IMAGING HERE, S TO N REFERS TO 1 ARCSEC, NOT 1 PIXEL. LINES 201 AND 202 ARE ALIKE EXCEPT POS TARG, SEE COMMENTS FOR LINES 111 AND 11. ------------------------------------------------------------------------------------------------------------------------------------ 201.5 NGC1952- WFPC2 IMAGE WF3-FIX F170W CR-SPLIT=NO 1 2300S 5 1 2 POS TARG -0.6,-0.6 BRTFIL SUM=2X2 CLOCKS=YES Comments: UV EMIS LINES IMAGED IN LINES 201-202. FOR UV IMAGING HERE, S TO N REFERS TO 1 ARCSEC, NOT 1 PIXEL. LINES 201 AND 202 ARE ALIKE EXCEPT POS TARG, SEE COMMENTS FOR LINES 111 AND 11. ------------------------------------------------------------------------------------------------------------------------------------ 202 NGC1952- WFPC2 IMAGE WF3-FIX F170W CR-SPLIT=NO 2 2300S 5 1 2 POS TARG +0.6,+0.6 BRTFIL SUM=2X2 CLOCKS=YES Comments: SEE COMMENTS FOR LINE 201. ------------------------------------------------------------------------------------------------------------------------------------ 203 NGC1952- WFPC2 IMAGE WF3-FIX F300W CR-SPLIT=NO 1 1000S 20 1 2 POS TARG -0.6,-0.6 BRTFIL SUM=2X2 CLOCKS=YES Comments: UV CONTINUUM IMAGED IN LINES 203-204. SEE COMMENTS FOR LINE 201. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5354 [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 204 NGC1952- WFPC2 IMAGE WF3-FIX F300W CR-SPLIT=NO 1 1000S 20 1 2 POS TARG +0.6,+0.6 BRTFIL SUM=2X2 CLOCKS=YES Comments: SEE COMMENTS FOR LINE 203. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5354 [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO CLOCKS=YES SUM=2X2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 11.79 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category SN & SNR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 / 11-13; GROUP 11-13 NO GAP; ORIENT 87D +/- 8D / 11-13; POS TARG -0.6,-0.6 POS TARG -0.6, -0.6 POS TARG +0.6,+0.6 CYCLE 4 / 111-114; GROUP 111-114 NO GAP; ORIENT 87D +/- 8D / 111-114; CYCLE 4 / 201-204; GROUP 201-204 NO GAP; ORIENT 87D +/- 8D / 201-204; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements # F656N F658N F502N F673N F547M F170W F300W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1952-BRTFIL CRAB_NEBULA-BRTFIL ------------------------------------------------------------------------------------------------------------------------------------