Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2340c Report Date: 09-May-96:17:02 Version: ********** Check-in Date: ********** 1.Proposal Title: IMAGING AND SPECTROSCOPY 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 Dr. Kris Davidson MINNESOTA, UNIVERSITY OF USA 612-624-5711 DR. ------------------------------------------------------------------------------------ 7. Abstract The Crab Nebula is the only young SNR (i.e., composed mainly of SN ejecta) whose condensations are resolvable by ST while also being "easily" observable in the UV. Moreover,it is now thought to represent an important SN mass range, and at the same time the Crab's chemical composition is poorly understood. V spectral data is essential for understanding the Crab, while high-spatial-resolution studies of its condensations will also be useful for producing more reliable ionization models in order to study it composition and its dynamics. We propose a detailed set of observations with the WFC, and FOC, partly to obtain useful data soon and partly to enable planning of future, more sophisticated UV spectroscopy. The WFC is to study density gradients and local structure in the condensations and also to provide accurate positions for possible future FOS work. The FOC is to make images of UV emission lines, for composition with visual- wavelength structure and also for possible future planning. ------------------------------------------------------------------------------------ 8. Scientific Key Words: SUPERNOVA, SUPERNOVA REMNANT, CRAB NEBULA, ABUNDANCE, NUCLEOSYNTHESIS, MORPHOLOGY ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 12.40 par: 0 10. Num targs pri: 9 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOC WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2340c PI: Dr. Kris Davidson Proposal Title: IMAGING AND SPECTROSCOPY IN THE CRAB NEBULA ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr. Minas Kafatos GEORGE MASON UNIVERSITY USA Dr. Gordon M Macalpine MICHIGAN, UNIVERSITY OF USA Dr. Alan Uomoto JOHNS HOPKINS UNIVERSITY USA Dr. Andrew S Wilson MARYLAND, UNIVERSITY OF USA P.I. Kris Davidson MINNESOTA, UNIVERSITY OF USA Dr. Richard Bc Henry OKLAHOMA, UNIVERSITY OF USA Dr. Robert A Fesen DARTMOUTH COLLEGE USA Dr. Robert P Kirshner CFA USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. WFC: We will image the OIII, H-alpha, NII, and SII emission lines in 2 WFC fields in the Crab using narrow filters and about 20 m per exposure. We also plan continuum exposures in two of the fields to assess the degree of non-thermal structure associated with the thermal filaments. A third intermediate field will be done with one filter for additional coverage and astrometry. We have optimized the fields to have maximum expectation of excluding the 3 brightest stars in the region without any special requirement on ST orientation, but this detail is not critical to the project. FOC/48, 44" field: This is essential for imaging the brightest UV emission lines in selected parts of the Crab. (WFC readout noise is too large for this low UV surface brightness object.) The 3 most promising filamentary regions have been selected for this purpose. We will use filter F175W to detect CIII] 1908 emission and F150W to detect the sum of CIII] 1908 plus CIV 1549 and HeII 1640. (F195W is unsuitable because its visual- wavelength transmission is too high.) The exposure times are about 30 minutes each. A shorter exposure with F275W will be used to determine UV continuum for subtraction. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. WFC: Models suggest characteristic size scales of 0.1 to 0.4 arcsec for the thermal-gas structure, and ground-based images appear consistent with this idea. The Crab obviously cannot be done by speckle techniques. Therefore, only HST can provide images to resolve the ionization and gas-dynamical structure. Excellent measures of the filament proper motions are also attainable from the WFC images. FOC/48: We know that major spatial variations in spectra occur in the Crab, probably due to composition gradients. Bright spots in the UV carbon lines are expected to occur, and if they do occur then we need to see the UV in order to detect them for future UV and visual-wavelength spectroscopy. The FOC is the only instrument that can detect the carbon UV lines at the expected surface brightnesses. (WFC won't work for this; readout noise makes it impossible.) Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Since surface brightnesses of emission lines in the Crab Nebula span a very large range, S/N ratios depend on location. In general, the surface brightness is low enough to be difficult for both the WFC and the FOC. We have adjusted our exposure times to give excellent S/N and high spatial resolution on the few brightest condensations, and useful S/N on a reasonably large fraction of the Crab filaments. Spatial resolution will be S/N limited for the fainter filaments in the WFC images and for all structure in the FOC images. Refs. to fluxes in the Crab are given in (e.g.) Ann.Revs.Astron.Ap. 23, 119, Ap.J. 228, 179 (visual- wavelength) and Ap.J. 253, 696 (UV). WFC: Fairly bright filaments have apparent intensities of the order of 1.E-14 erg cm-2 s-1 arcsec-2 in each of the brightest visual-wavelength emission lines. The peak QT-factors for appropriate WFC filters are slightly less than 0.1, implying somewhat more than 100 cts/pixel in 20- minutes, for S/N = about 7. For fainter filaments the S/N-limited resolution may be degraded to 0.2 arcsec. Since we must sample several physically different emission lines, 20 minutes per field is appropriate for exploratory purposes. FOC: IUE data suggest that we can expect about 1.E-14 erg cm-2 s-1 arcsec-2 in the CIII] 1908 line (e.g.) in a bright condensation. With F175W, of the order of 360 cts per arcsec2 will be obtained in a 30-minute exposure. But the non- thermal continuum background will be comparable; therefore the S/N ratio in one arcsec2 would be 10-15 if continuum subtraction (based on F275W exposure) were perfect. So a realistic S/N in the net CIII]-emission image is between 5 and 10 for 1 arcsec2, which will therefore be the effective resolution for the assumed emission brightness. A few condensations may be considerably brighter. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. A WFC image of the Crab will contain structure across most of the WFC field, and is more complicated than an image even of a cluster of localized objects. Moreover, the intersection of radial velocities in the Crab within the available WFC narrow emission-line filter bands will create additional complexity in the data analysis. Image resolution will be position-dependent (because it is S/N- limited in some of the filaments). The FOC images will not be quite as complicated, but will have to be linearly combined in order to produce separate CIII], (CIV+HeII), and UV-continuum maps of the localized FOC fields. Davidson, Uomoto, Fesen, and Wilson will concentrate on data reduction. Using the WFC images, emission-line surface brightnesses will be measured at high resolution, leading to estimates of local column thickness and densities of ions as functions of location within individual condensations. Astrometry will be done on stars in the WFC fields and precise locations of gaseous condensations will be determined -- both for future spectroscopy and also to measure the nebular expansion rate. The FOC ultraviolet images will allow maps of (CIV + HeII) and CIII] emission- line brightnesses to be made. These will be compared with ground-based visual- wavelength spectroscopy of the same regions. If UV-bright spots are discovered in the FOC images, ground-based spectra of those locations will be obtained using, for example, the McGraw-Hill 2.4-m telescope. Henry, MacAlpine, Kafatos and Kirshner will concentrate on the spectroscopic implications of the FOC data. MacAlpine's photoionization codes will be used to produce realistic models of thermal condensations, taking local morphology indicated in the WFC images into account. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: KRIS DAVIDSON Category: PI Institution: UNIVERSITY OF MINNESOTA Address: 116 CHRUCH ST. S.E. City: MINNEAPOLIS State: MN Zip Code: 55455 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2340c [ 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- INTERSTELLAR MEDIUM; RA= 05H 34M 32.72S +/- 2000 V=0 1 SURF(V) = 21 +/- 2 WFCC1 CRAB- SUPERNOVA REMNANT; 0.07S, 2 SURF-LINE(5007) = 1.0 +/- 1.0 E-14 NEBULA M1 CENTRAL FIELD DEC=+22D 01' 04.00" +/- 1" 3 SURF-LINE(6563) = 1.0 +/- 1.0 E-14 4 SURF-LINE(6583) = 1.0 +/- 1.0 E-15 5 SURF-LINE(6724) = 0.7 +/- 0.7 E-15 6 SURF-LINE(3727) = 5.0 +/- 5.0 E-15 7 W-LINE(5007) = 1.0 +/- 0.0 8 W-LINE(6563) = 1.0 +/- 0.0 9 W-LINE(6583) = 1.0 +/- 0.0 Comments: EMISSION LINES SPAN +/- 1500 KM/S IN 10 W-LINE(6724) = 1.0 +/- 0.0 RADIAL VELOCITY IN EACH PART OF FIELD. SURFACE BRIGHTNESS SPANS A LARGE RANGE OF VALUES. FLUXES QUOTED HERE REFER TO A TYPICAL MODERATE FILAMENT. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC1952- INTERSTELLAR MEDIUM; RA= 05H 34M 33.44S +/- 2000 V=0 1 SURF(V) = 21 +/- 2 WFCS1 CRAB- SUPERNOVA REMNANT; 0.07S, 2 SURF-LINE(5007) = 1.0 +/- 1.0 E-14 NEBULA M1 SOUTH-1 FIELD DEC=+22D 00' 12.00" +/- 1" 3 SURF-LINE(6563) = 1.0 +/- 1.0 E-14 4 SURF-LINE(6583) = 1.0 +/- 1.0 E-15 5 SURF-LINE(6724) = 0.7 +/- 0.7 E-15 6 SURF-LINE(3727) = 5.0 +/- 5.0 E-15 7 W-LINE(5007) = 1.0 +/- 0.0 8 W-LINE(6563) = 1.0 +/- 0.0 9 W-LINE(6583) = 1.0 +/- 0.0 Comments: EMISSION LINES SPAN +/- 1500 KM/S IN 10 W-LINE(6724) = 1.0 +/- 0.0 RADIAL VELOCITY IN EACH PART OF FIELD. SURFACE BRIGHTNESS SPANS A LARGE RANGE OF VALUES. FLUXES QUOTED HERE REFER TO A TYPICAL MODERATE FILAMENT. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC1952- INTERSTELLAR MEDIUM; RA= 05H 34M 28.84S +/- 2000 V=0 1 SURF(V) = 21 +/- 2 WFCN1 CRAB- SUPERNOVA REMNANT; 0.07S, 2 SURF-LINE(5007) = 1.0 +/- 1.0 E-14 NEBULA M1 NORTH-1 FIELD DEC=+22D 02' 44.00" +/- 1" 3 SURF-LINE(6563) = 1.0 +/- 1.0 E-14 4 SURF-LINE(6583) = 1.0 +/- 1.0 E-15 5 SURF-LINE(6724) = 0.7 +/- 0.7 E-15 6 SURF-LINE(3727) = 5.0 +/- 5.0 E-15 7 W-LINE(5007) = 1.0 +/- 0.0 8 W-LINE(6563) = 1.0 +/- 0.0 9 W-LINE(6583) = 1.0 +/- 0.0 Comments: EMISSION LINES SPAN +/- 1500 KM/S IN 10 W-LINE(6724) = 1.0 +/- 0.0 RADIAL VELOCITY IN EACH PART OF FIELD. SURFACE BRIGHTNESS SPANS A LARGE RANGE OF VALUES. FLUXES QUOTED HERE REFER TO A TYPICAL MODERATE FILAMENT. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC1952- INTERSTELLAR MEDIUM; RA= 05H 34M 32.80S +/- 2000 V=0 1 SURF(V) = 21.1 +/- 0.8 FOC01 CRAB- SUPERNOVA REMNANT; 0.07S, 2 SURF-LINE(1908) = 1.0 +/- 0.8 E-14 NEBULA M1 NORTH LOOP DEC=+22D 02' 11.00" +/- 1" 3 SURF-LINE(1548) = 1.0 +/- 0.8 E-14 4 SURF-CONT(1800) = 0.6 +/- 0.3 E-17 5 W-LINE(1908) = 1.0 +/- 0.0 6 W-LINE(1548) = 1.0 +/- 0.0 ------------------------------------------------------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2340c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC1952- INTERSTELLAR MEDIUM; RA= 05H 34M 29.70S +/- 2000 V=0 1 SURF(V) = 19.8 +/- 0.5 FOC02 CRAB- SUPERNOVA REMNANT; 0.07S, 2 SURF-LINE(1908) = 1.0 +/- 0.8 E-14 NEBULA M1 BRIGHT FILAMENT WSW DEC=+22D 00' 35.00" +/- 1" 3 SURF-LINE(1548) = 1.0 +/- 0.8 E-14 4 SURF-CONT(1800) = 2.0 +/- 0.8 E-17 5 W-LINE(1908) = 1.0 +/- 0.0 6 W-LINE(1548) = 1.0 +/- 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC1952- INTERSTELLAR MEDIUM; RA= 05H 34M 34.20S +/- 2000 V=0 1 SURF(V) = 20.5 +/- 0.6 FOC03 CRAB- SUPERNOVA REMNANT; 0.07S, 2 SURF-LINE(1908) = 1.0 +/- 0.8 E-14 NEBULA M1 BRIGHT FILAMENT SE DEC=+21D 59' 50.00" +/- 1" 3 SURF-LINE(1548) = 1.0 +/- 0.8 E-14 4 SURF-CONT(1800) = 1.1 +/- 0.5 E-17 5 W-LINE(1908) = 1.0 +/- 0.0 6 W-LINE(1548) = 1.0 +/- 0.0 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2340c [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 DEFINE NGC1952- WFC IMAGE ALL # PRE-FLASH=YES 1 1M # # POS TARG 0,0 WFCC1 WFCC1 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 12 DEFINE NGC1952- WFC IMAGE ALL # PRE-FLASH=YES 1 1M # # POS TARG 0,0 WFCS1 WFCS1 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 13 DEFINE NGC1952- WFC IMAGE ALL # PRE-FLASH=YES 1 1M # # POS TARG 0,0 WFCN1 WFCN1 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 14 DEFINE NGC1952- FOC/48 IMAGE 512X102 # PIXEL=50X25 1 1M # # FOC01 FOC01 4 ------------------------------------------------------------------------------------------------------------------------------------ 15 DEFINE NGC1952- FOC/48 IMAGE 512X102 # PIXEL=50X25 1 1M # # FOC02 FOC02 4 ------------------------------------------------------------------------------------------------------------------------------------ 16 DEFINE NGC1952- FOC/48 IMAGE 512X102 # PIXEL=50X25 1 1M # # FOC03 FOC03 4 ------------------------------------------------------------------------------------------------------------------------------------ 111 USE F664N X15 7 3 3 WFCC1 4 5 ------------------------------------------------------------------------------------------------------------------------------------ 112 USE F656N X15 7 3 3 WFCC1 4 ------------------------------------------------------------------------------------------------------------------------------------ 114 USE F502N X15 7 2 3 WFCC1 ------------------------------------------------------------------------------------------------------------------------------------ 121 USE F664N X30 7 3 2 WFCS1 4 5 ------------------------------------------------------------------------------------------------------------------------------------ 122 USE F656N X24 7 3 2 WFCS1 4 ------------------------------------------------------------------------------------------------------------------------------------ 123 USE F547M X20 7 1 2 WFCS1 Comments: S/N IS FOR 1 PIXEL WITH SURF(V)=21, CRAB AVERAGE. CONTINUUM IS BRIGHTER THAN SURF(V)=21 IN PARTS OF FIELD. ------------------------------------------------------------------------------------------------------------------------------------ 124 USE F502N X30 7 2 2 WFCS1 ------------------------------------------------------------------------------------------------------------------------------------ 125 USE F658N X30 7 3 2 WFCS1 4 ------------------------------------------------------------------------------------------------------------------------------------ 126 USE F673N X30 7 3 2 WFCS1 4 5 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2340c [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 131 USE F664N X20 7 3 1 WFCN1 4 5 ------------------------------------------------------------------------------------------------------------------------------------ 132 USE F656N X20 7 3 1 SAME POS FOR 132- WFCN1 4 136 AS 131 ------------------------------------------------------------------------------------------------------------------------------------ 133 USE F547M X15 7 1 2 WFCN1 ------------------------------------------------------------------------------------------------------------------------------------ 134 USE F502N X20 7 2 1 WFCN1 ------------------------------------------------------------------------------------------------------------------------------------ 135 USE F658N X20 7 3 1 WFCN1 4 ------------------------------------------------------------------------------------------------------------------------------------ 136 USE F673N X20 7 3 2 WFCN1 4 5 ------------------------------------------------------------------------------------------------------------------------------------ 141 USE F175W X30 12 4 3 FOC01 Comments: S/N IS PER SQ ARCSEC FOR EMISSION LINE IMAGE AFTER CONTINUUM SUBTRACTION. ------------------------------------------------------------------------------------------------------------------------------------ 142 USE F150W X30 12 3 3 FOC01 Comments: S/N IS PER SQ ARCSEC FOR EMISSION LINE IMAGE AFTER CONTINUUM SUBTRACTION. ------------------------------------------------------------------------------------------------------------------------------------ 143 USE F275W X10 15 4 3 FOC01 Comments: S/N IS FOR 1 SQ ARCSEC, NEEDED FOR SUBTRACTION IN LINE EMISSION IMAGES. ------------------------------------------------------------------------------------------------------------------------------------ 151 USE F175W X30 12 4 2 FOC02 Comments: S/N IS PER SQ ARCSEC FOR EMISSION LINE IMAGE AFTER CONTINUUM SUBTRACTION. ------------------------------------------------------------------------------------------------------------------------------------ 152 USE F150W X30 12 3 2 FOC02 Comments: S/N IS PER SQ ARCSEC FOR EMISSION LINE IMAGE AFTER CONTINUUM SUBTRACTION. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2340c [ 9] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 153 USE F275W X10 25 4 2 FOC02 Comments: S/N IS FOR 1 SQ ARCSEC, NEEDED FOR SUBTRACTION IN LINE EMISSION IMAGES. ------------------------------------------------------------------------------------------------------------------------------------ 161 USE F175W X30 12 4 1 FOC03 Comments: S/N IS PER SQ ARCSEC FOR EMISSION LINE IMAGE AFTER CONTINUUM SUBTRACTION. ------------------------------------------------------------------------------------------------------------------------------------ 162 USE F150W X30 12 3 1 FOC03 Comments: S/N IS PER SQ ARCSEC FOR EMISSION LINE IMAGE AFTER CONTINUUM SUBTRACTION. ------------------------------------------------------------------------------------------------------------------------------------ 163 USE F275W X10 20 4 1 FOC03 Comments: S/N IS FOR 1 SQ ARCSEC, NEEDED FOR SUBTRACTION IN LINE EMISSION IMAGES. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2340c [ 10] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC FOC/48 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PRE-FLASH=YES CR-SPLIT=NO PIXEL=50X25 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 12.40 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category SN & SNR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0,0 SAME POS FOR 132-136 AS 131 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements # F664N F656N F502N F547M F658N F673N F175W F150W F275W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1952-WFCC1 CRAB-NEBULA M1 NGC1952-WFCS1 NGC1952-WFCN1 NGC1952-FOC01 NGC1952-FOC02 NGC1952-FOC03 ------------------------------------------------------------------------------------------------------------------------------------