6438( 7) - 12/09/98 15:46 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6438 Version: 7 Check-in Date: 30-Nov-1998 13:15:04 1.Proposal Title: DUST STRUCTURE IN BACKLIT GALAXIES ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 6 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: William C. Keel University of Alabama CoI: Raymond White, III University of Alabama N ------------------------------------------------------------------------------------ 5. Abstract Pairs of overlapping galaxies offer an unusually direct way to measure the extinction within the disk of spiral galaxies, which has implications for M/L ratios, star-formation histories, and the role of galaxy obscuration in statistics of high-redshift objects. Ground-based data have allowed us to measure the extinction in several backlit spirals, as averaged over regions of hundreds of parsecs. WFPC2 imaging of three of our best candidates in B and I bands will allow us to measure the dust clumping on finer scales than possible from the ground, and to establish whether the relatively flat reddening curves we have found are indeed the product of clumping. Together with scheduled ISO observations, we should be able to establish the clumping spectrum of dust over a very wide range of scales, which is crucial to modelling the effects of dust on the emergent radiation from spiral galaxies. ------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 2] Observations Description ------------------------ Each pair fits comfortably within the WFPC2 field, and the overlap region always fits on a single chip. We place these regions on WF3 to keep the surface -brightness sensitivity of larger pixels than in PC1, and to include as much of the surrounding galaxy pair as possible. We select passbands which give a long wavelength baseline and avoid strong emission lines, as was done with B and I bands for the ground-based observations. For the WFPC2, F450W and F814W were chosen for their appropriate locations and wide bandwidths (in the interest of throughput). Exposure-time estimates use the mean measured surface brightness in B and I in the overlap regions, known from ground-based observations. All the regions are well within the B=25 per square arcsecond isophote, with B surface brightness typically 23.5-24 per square arcsecond (1-1.5 scale lengths inside the reference isophote). We expect S/N ratio of ~ 7 (or better) per pixel so we can be sure of detecting even marginally resolved clouds of high optical depth (i.e. optically thick covering only a fraction of a single pixel). CR splits are especially important to avoid losing dust features under a cosmic ray. Using the WFPC2 sensitivity and filter curves from the instrument manual, we need typically 45 minutes total in F450W and 25 minutes in F814W (in practice two orbits per target). AM1316-241 and AM0500-620 have reasonably symmetric spirals in front of well-behaved elliptical galaxies, and are both in our ISO target lists. NGC 3314 is an almost perfect superposition of an Sc galaxy in front of an Sb, giving a unique chance to trace dust in the inner parts of a spiral now that we can interplate its structure guided by a K ground -based image. We note that one of our best target pairs, AM0500-620, spends substantial time in the continuous-viewing zone, so that opportunities for improved efficiency may exist (though we do not require CVZ time for scientific reasons). Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3314 GALAXY, CLUSTER OF RA=10H 37M 13.14S +/-0.04S, DEC= 2000 V=2763 V = 13.5+/-0.5 GALAXIES, GALAXY PAIR -27D 41' 05.9" +/-0.5", PLATE- SURF(B) = 24.0+/-0.5 ID=00GU Comments: Overlapping (noninteracting) galaxy pair in Abell 1060; orientation restrictions are to keep a 13.5-mag GSC star off WF3 and on WF2 or WF4 for scattered-light control. 2 AM1316-241 GALAXY, INTERACTING RA=13H 19M 32.31S +/- 0.16S, 2000 V=9700 V = 15.0+/-0.5 GALAXY, SPIRAL, DEC=-24D 29' 10.2" +/- 2.0", SURF(B) = 24.0+/-0.5 ELLIPTICAL PLATE-ID=02J5 Comments: Overlapping spiral/elliptical galaxy pair; orientation restrictions are to avoid the outer end of the spiral falling on PC1 and losing surface-brightness sensitivity (the outer edge of the elliptical would be acceptable on PC1). 3 AM0500-620 GALAXY, INTERACTING RA=05H 00M 34.11S +/-0.28S, DEC= 2000 V = 15.5+/-0.5 GALAXY, SPIRAL, -62D 04' 08.0" +/- 2.0", PLATE- SURF(B) = 24.5+/-0.5 ELLIPTICAL ID=00MU Comments: Overlapping spiral/elliptical galaxy pair 6438( 7) - 12/09/98 15:46 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENTation 350D TO 40D On Hold Comments: Additional Comments: Schedule either visit 1 or 2 (multiple orient ranges acceptable) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3314 WFPC2 IMAGE WF3-FIX F450W 1 120 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3314 WFPC2 IMAGE WF3-FIX F814W 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3314 WFPC2 IMAGE WF3-FIX F814W 1 2000 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3314 WFPC2 IMAGE WF3-FIX F450W 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENTation 260D TO 310D On Hold Comments: Additional Comments: Schedule either visit 1 or 2 (two orient ranges acceptable) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3314 WFPC2 IMAGE WF3-FIX F450W 1 120 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3314 WFPC2 IMAGE WF3-FIX F814W 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3314 WFPC2 IMAGE WF3-FIX F814W 1 2000 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3314 WFPC2 IMAGE WF3-FIX F450W 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 6] Visit: 03 Visit Priority: Visit Requirements: Orientation 193D to 103D 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 AM1316-241 WFPC2 IMAGE WF3-FIX F450W 1 120 S POS TARG +10.0,+10.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 AM1316-241 WFPC2 IMAGE WF3-FIX F814W 1 60 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 AM1316-241 WFPC2 IMAGE WF3-FIX F814W 1 2000 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 AM1316-241 WFPC2 IMAGE WF3-FIX F450W 1 2600 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 7] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 AM0500-620 WFPC2 IMAGE WF3-FIX F450W 1 120 S ------------------------------------------------------------------------------------------------------------------------------------ 2 AM0500-620 WFPC2 IMAGE WF3-FIX F814W 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 3 AM0500-620 WFPC2 IMAGE WF3-FIX F814W 1 2000 S ------------------------------------------------------------------------------------------------------------------------------------ 4 AM0500-620 WFPC2 IMAGE WF3-FIX F450W 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 8] Visit: 51 Visit Priority: Visit Requirements: ORIENTation 350D TO 40D ORIENTation 269D TO 310D On Hold Comments: Additional Comments: Replacement for observations lost to guide-star failure; schedule either visit 51 or 52 (two orient ranges acceptable) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3314 WFPC2 IMAGE WF3-FIX F814W 1 2400 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3314 WFPC2 IMAGE WF3-FIX F450W 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 9] Visit: 52 Visit Priority: Visit Requirements: ORIENTation 269D TO 310D On Hold Comments: Additional Comments: Replacement for observations lost to guide-star failure; schedule either visit 51 or 52 (two orient ranges acceptable) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3314 WFPC2 IMAGE WF3-FIX F814W 1 2400 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3314 WFPC2 IMAGE WF3-FIX F450W 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 6438( 7) - 12/09/98 15:46 - [ 10] Summary Form for Proposal 6438 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENTation 350D TO 40D ORIENTation 260D TO 310D Orientation 193D to 103D POS TARG +10.0,+10.0 SAME POS AS 1 ORIENTation 350D TO 40D ORIENTation 269D TO 310D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F450W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC3314 AM1316-241 AM0500-620 ------------------------------------------------------------------------------------------------------------------------------------