8270( 6) - 02/08/00 14:15 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8270 Version: 6 Check-in Date: 08-Feb-2000 14:15:02 1.Proposal Title: Proper Motion of the Leo II Dwarf Spheroidal ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle SNAP 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Michael Siegel The University of Virginia CoI: Dr. Steven Majewski University of Virginia, Department of N Astronomy CoI: Dr. Kyle Cudworth Yerkes Observatory, University of Chicago N ------------------------------------------------------------------------------------ 5. Abstract We propose to continue our investigation into the proper motion of distant satellites of the Milky Way with a series of HST snapshots around faint galaxies within our Leo II astrometric field. We will determine a proper motion for Leo II by combining images from 111 Palomar 200" photographic plates taken by Baade between 1950-1959 with the HST snapshots. Only with the fine pixel scale of HST can we realistically hope to match the exquisite Baade images, which were all taken on the very best nights from a decade of Baade's allotment of about forty 200arcsecond nights a year. As part of Siegel's Ph.D. thesis, our project on Leo II will: (1) Determine the proper motion of Leo II with respect to the extra-galactic reference frame, allowing a measurement of the orbital properties of Leo II from 3-D space velocity (1) Develop techniques (of growing importance with the declining availability of photographic cameras and plates) for the astrometric combination of WFPC2 data with older plate material to derive high-precision proper motions. (2) Determine the proper motion for an object at the greatest Galactocentric distance yet attempted, which will provide significant leverage in determining the mass of the Galaxy. (3) Provide a list of proper-motion selected stars for future refinement of the proper motion and parallax of Leo II with the Space-Interferometry Mission. ------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 2] Observations Description ------------------------ We plan to observe two fields in the Leo II galaxy with the F555W filter. Exposure times of 300 seconds will give us excellent signal to noise at the limiting magnitude of Baade's plates (22-22.5). We will use Baade's first epoch plates and our own 4-meter data to catalogue the galaxies in the Leo II field. We will then identify two HST pointings that will sample the maximum number of compact background galaxies for the absolute reference frame. Each field should be observed in visits of 3-4 images. Each visit should be dithered slightly from its predecessors. The observation blocks do not have to be done consecutively and can be scheduled in any suitable open area of HST time. Including overhead, each visit will last 29-37 minutes. We conservatively expect to determine accurate positions for any individual frame to 1/10 of a pixel, which corresponds to 0."01 on the Wide Field cameras, 0."005 on the Planetary Camera. The most optimistic measure would be 1/20 of a pixel, or 0."005/0."003 on WF/PC CCD's respectively. Figure 1 show how the expected proper motion precision with the Wide Field varies as the number of exposures taken for our most conservative and most optimistic estimate of our centroiding ability. We find that approximately five observation visits in each field will allow the proper motion of Leo II to be determined to the precision of 5 mas/century. Obviously, the more blocks that can be worked into the schedule, the better the solution. The right axis shows the corresponding velocity errors for the proper motion errors. Obtaining a large number of images is crucial to understanding systematic errors in the CCD data. Any tilt of the chip with respect to the optical axis or any CCD or filter non-flatness will cause systematic centroiding errors that need to be accounted for. Evaluation of ground-based data reveals that a number of images over a range of spatial displacements should allow us to map the WFPC2 CCD+F555W combination. The combination of two separate reductions for the two different fields will allow a check on internal consistency. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LEOII-A GALAXY RA=11H 13M 29.20S +/- 0.10S, 2000.0 V=+76 SURF(V) = 23.91+/-0.18 DEC=+22D 9' 16.0" +/- 0.10" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 2 LEOII-B GALAXY RA=11H 13M 29.20S +/- 0.10S, 2000.0 V=+76 SURF(V) = 23.91+/-0.18 DEC=+22D 11' 01.0" +/- 0.10" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 3 LEOII-C GALAXY RA=11H 13M 29.20S +/- 0.10S, 2000.0 V=+76 SURF(V) = 23.91+/-0.18 DEC=+22D 7' 31.0" +/- 0.10" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 4 LEOII-D GALAXY RA=11H 13M 36.80S +/- 0.10S, 2000.0 V=+76 SURF(V) = 23.91+/-0.18 DEC=+22D 9' 16.0" +/- 0.10" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 5 LEOII-E GALAXY RA=11H 13M 21.60S +/- 0.10S, 2000.0 V=+76 SURF(V) = 23.91+/-0.18 DEC=+22D 9' 16.0" +/- 0.10" Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0 0.0 0.0 8270( 6) - 02/08/00 14:15 - [ 4] Visit: 01 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 LEOII-A WFPC2 IMAGE WF3 F555W DITHER-TYPE=LINE, 1 200 S DITHER-LINE-STEPS=4, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 5] Visit: 02 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 LEOII-A WFPC2 IMAGE WF3 F439W DITHER-TYPE=LINE, 1 400 S DITHER-LINE-STEPS=3, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 6] Visit: 03 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 LEOII-B WFPC2 IMAGE WF3 F555W DITHER-TYPE=LINE, 1 200 S DITHER-LINE-STEPS=6, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 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 LEOII-B WFPC2 IMAGE WF3 F439W DITHER-TYPE=LINE, 1 400 S DITHER-LINE-STEPS=4, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 8] Visit: 05 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 LEOII-C WFPC2 IMAGE WF3 F555W DITHER-TYPE=LINE, 1 200 S DITHER-LINE-STEPS=6, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 9] Visit: 06 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 LEOII-C WFPC2 IMAGE WF3 F439W DITHER-TYPE=LINE, 1 400 S DITHER-LINE-STEPS=4, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 10] Visit: 07 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 LEOII-D WFPC2 IMAGE WF3 F555W DITHER-TYPE=LINE, 1 200 S DITHER-LINE-STEPS=6, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 11] Visit: 08 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 LEOII-D WFPC2 IMAGE WF3 F439W DITHER-TYPE=LINE, 1 400 S DITHER-LINE-STEPS=4, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 12] Visit: 09 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 LEOII-E WFPC2 IMAGE WF3 F555W DITHER-TYPE=LINE, 1 200 S DITHER-LINE-STEPS=6, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 13] Visit: 10 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 LEOII-E WFPC2 IMAGE WF3 F439W DITHER-TYPE=LINE, 1 400 S DITHER-LINE-STEPS=4, DITHER-LINE-SPACING=0.3 ------------------------------------------------------------------------------------------------------------------------------------ 8270( 6) - 02/08/00 14:15 - [ 14] Summary Form for Proposal 8270 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters DITHER-TYPE=LINE DITHER-LINE-STEPS=4 DITHER-LINE-SPACING=0.3 DITHER-LINE-STEPS=3 DITHER-LINE-STEPS=6 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category SNAP ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names LEOII-A LEOII-B LEOII-C LEOII-D LEOII-E ------------------------------------------------------------------------------------------------------------------------------------