9830( 3) - 05/20/03 10:14 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9830 Version: 3 Check-in Date: 20-May-2003 10:12:27 1.Proposal Title: A New Member of the Local Group? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 12 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Prof. Gregory D. Bothun University of Oregon CoI: Dr. Karen L O'Neil NRAO, Green Bank N CoI: Dr. Mario L. Mateo University of Michigan N ------------------------------------------------------------------------------------ 5. Abstract An August 2002 detection at 21-cm of a previously undetected low surface brightness galaxy yielded a radial velocity of -360 km/s. As the galaxy is located in the opposite part of the sky as the Virgo cluster, its seems quite likely that this velocity places it squarely in the Local Group (LG). The characteristics of this galaxy, if its at a distance of 1-2 Mpc, are such that it easily could have escaped detection from previous searches. Its optical surface brightness is low and its integrated blue magnitude would lie in the range -6.5 to -8.0. The total H I mass is less than 3 x 10^5 solar masses. The H I profile is relatively low S/N and distorted, with a signal that is spread out over about 80 km/s. much larger than the internal velocity dispersion of the galaxy. This is likely the result of an interaction (most probably with M31). With the efficiency of the ACS, we can easily detect the TRGB population in this object using V and I observations in 2 orbits. The goal here is to provide confirming evidence that this object is indeed a member of the LG by obtaining its distance via the now well calibrtated TRGB method using V-I as the filter system. If indeed in the LG (which seems likely) it would also represent a new kind of dwarf galaxy as its considerably more compact than other LG dwarfs of similar absolute magnitude. ------------------------------------------------------------------------------------ 9830( 3) - 05/20/03 10:14 - [ 2] Observations Description ------------------------ We have been assigned two orbits to image this object. On the first visit we request 2 separate F606 W exposures of 900 seconds each. On the second visit, we request a single 1800 second exposure using the F814 W filter. All of these exposure times are well below the visibility window of the target per orbit. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9830( 3) - 05/20/03 10:14 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 P6-6 GALAXY RA=23H21M31.0S +/- 0.1", J2000 V = 18.0 DEC=+08D56'21.0" +/- 0.1" Coordinate Source: Other_Source: O'Neil etal 1997 9830( 3) - 05/20/03 10:14 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE On Hold Comments: Additional Comments: F606 V-band image Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 P6-6 ACS/WF ACCUM WFCENTE F606W 1 900 S C R ------------------------------------------------------------------------------------------------------------------------------------ 2 P6-6 ACS/WF ACCUM WFCENTE F606W 1 900 S C R ------------------------------------------------------------------------------------------------------------------------------------ 9830( 3) - 05/20/03 10:14 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE SCHED 30% On Hold Comments: Additional Comments: I-band Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 P6-6 ACS/WF ACCUM WFCENTE F814W 1 1800 S C R ------------------------------------------------------------------------------------------------------------------------------------ 9830( 3) - 05/20/03 10:14 - [ 6] Summary Form for Proposal 9830 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE PCS MODE FINE SCHED 30% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names P6-6 ------------------------------------------------------------------------------------------------------------------------------------