9044( 4) - 06/01/01 12:51 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9044 Version: 4 Check-in Date: 01-Jun-2001 12:50:00 1.Proposal Title: The Stellar Population of UGCA 292, An Extreme Low Metallicity Galaxy ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Liese van Zee Dominion Astrophysical Observatory CoI: Dr. Robbie Dohm-Palmer University of Michigan N CoI: Dr. Lisa Young New Mexico Institute of Mining and N Technology ------------------------------------------------------------------------------------ 5. Abstract As the third lowest metallicity galaxy known, UGCA 292 provides a unique opportunity to investigate the evolutionary status of extremely metal--poor, gas--rich, star-- forming galaxies. UGCA 292 is sufficiently nearby (3.1 Mpc), that it is possible to resolve the stellar population with HST. The proposed observations will enable us to investigate the stellar population of this relatively unevolved galaxy to determine if the low metallicity and high gas mass fraction are indicative of a newly formed galaxy. The detection of an intermediate age stellar population in UGCA 292 will definitively prove that it is possible to have galaxies which are gas--rich and metal--poor, yet have extended star formation histories. Alternatively, the lack of an intermediate age stellar population in UGCA 292 will support the hypothesis that there is no single epoch of galaxy formation, and that some low mass galaxies have delayed formation for almost a Hubble time. ------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 2] Observations Description ------------------------ We propose to obtain WFPC2 images of UGCA 292, a nearby metal--poor galaxy. Our main objective is to detect the horizontal branch (HB) and red clump (RC) stars in UGCA 292 in order to determine if this metal--poor galaxy has intermediate (> 1 Gyr) and old (> 9 Gyr) stellar populations. Detection of HB and RC stars will ensure that we will also have a complete census of the massive core He- burning stars, which are as bright or brighter than the red clump. We have used the WFPC2 ETC to estimate the exposure times to detect M_V=0 and M_V=1 in the F555W filter at the distance of UGCA 292. For an estimated distance of 3.1 Mpc, 5 orbits will achieve a S/N of approximately 10 at M_V=0. Thus we will detect the red clump, but will likely not be complete. Team member Dohm-Palmer has experience measuring and correcting for this incompleteness (Dohm-Palmer et al. 1997a). In addition to the F555W filter, we require images in F814W. The ETC, as well as our own experience with previous WFPC2 data, indicates this filter will need about twice the exposure time as the F555W filter to reach similar detection limits. Thus, we request a total of 15 orbits to determine the star formation history of this extremely low metallicity galaxy. The STIS coordinated parallels will be taken in two filters. Half of the images will use the 50CCD clear filter, and the other half will use the F28X50LP filter. This will provide an indication of the color of the objects detected, which will be crucial for determining membership of stars to the host galaxy. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UGCA292 GALAXY, DWARF COMPACT RA=12H 38M 39.8S +/- 0.5S, J2000 V = 16 DEC=32D 45' 55.59" +/- 0.5", PLATE-ID=01PQ Coordinate Source: GUIDE_STAR_CATALOG 9044( 4) - 06/01/01 12:51 - [ 4] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: The orientation requirements were chosen to avoid bright stars in the STIS field. When observations are scheduled, please be sure there are no bright stars in the STIS field.( orient values removed when stis observation were removed. If stis observations are to be put back in, the so do orient requirements. -wj) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 UGCA292 WFPC2 IMAGE WF3 F555W 1 2600 S ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 5] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 UGCA292 WFPC2 IMAGE WF3 F555W 1 2600 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 6] Visit: 03 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 UGCA292 WFPC2 IMAGE WF3 F555W 1 2600 S POS TARG 0.5, 0.5 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 7] Visit: 04 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 UGCA292 WFPC2 IMAGE WF3 F555W 1 2600 S POS TARG 0.5, 0 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 8] Visit: 05 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 UGCA292 WFPC2 IMAGE WF3 F555W 1 2600 S POS TARG 0, 0.5 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S SAME POS AS 10 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 9] Visit: 06 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S POS TARG 0.25, 0 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 10] Visit: 07 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S POS TARG 0.5, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 11] Visit: 08 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S POS TARG 0.25, 0.5 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 12] Visit: 09 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S POS TARG 0, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 13] Visit: 10 Visit Priority: Visit Requirements: SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 UGCA292 WFPC2 IMAGE WF3 F814W 1 2600 S POS TARG 0.25, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ 9044( 4) - 06/01/01 12:51 - [ 14] Summary Form for Proposal 9044 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SAME POS AS 10 SAME ORIENT AS 01 POS TARG 0.25, 0.25 POS TARG 0.5, 0.5 POS TARG 0.5, 0 POS TARG 0, 0.5 POS TARG 0.25, 0 POS TARG 0.5, 0.25 POS TARG 0.25, 0.5 POS TARG 0, 0.25 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names UGCA292 ------------------------------------------------------------------------------------------------------------------------------------