6428( 3) - 02/13/96 10:54 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6428 Version: 3 Check-in Date: 13-Feb-1996 10:52:06 1.Proposal Title: The nature of the density cusp in the core of Ursa Minor ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle GALAXIES & CLUSTERS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Paolo Battinelli Osservatorio Astronomico di Roma CoI: Serge Demers Departement de Physique, Universite de N Montreal CoI: Michael Irwin Royal Greenwich Observatory N ------------------------------------------------------------------------------------ 6. Abstract The determination by Hargreaves et al. (1994, MNRAS 271, 639) of a mass-to-light ratio of M/L = 59 for the core of Ursa Minor and the recent finding by Demers et al. (1995, MNRAS 274,491) of a central cusp in the stellar surface density profile strongly suggest the presence of a black hole in Ursa Minor. Thus, we plan to use the WFPC2 to determine the stellar surface density profile of the central part of the core of Ursa Minor so to obtain a very precise definition of the cusp. This is crutial for a reliable estimate of the central mass. Ursa Minor observations will be compared to black hole models of Quinlan et al. (1995, ApJ 440, 554) to obtain the parameters of the black hole and also to set limits on the properties of the core of Ursa Minor. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to image the innermost part of Ursa Minor using the WFPC2 V (F606W) filter. Placing the target close to the center of the WF3 we could estimate the stellar surface density (along two perpendicular directions) up to 100'' from the Ursa Minor center, a distance fully encompassing the cusp found by Demers et al. (1995). The small number of foreground stars in the Ursa Minor direction (~ 5 stars/arcmin^2 at V_lim=29 from Ratnatunga & Bahcall 1985, ApJS 59, 63) makes observations in a second filter not needed. Real Time Justification ----------------------- None None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6428( 3) - 02/13/96 10:54 - [ 2] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6428( 3) - 02/13/96 10:54 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DDO199 GALAXY,DWARF RA=15H 8M 41.15S +/- 10",DEC=67D J2000 V = 17+/-1 SPHEROIDAL, 12' 36" +/- 10" 6428( 3) - 02/13/96 10:54 - [ 4] Visit: 01 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 DDO199 WFPC2 IMAGE WF3-FIX F606W ATD-GAIN=15 1 1300S ------------------------------------------------------------------------------------------------------------------------------------ 5 DDO199 WFPC2 IMAGE WF3-FIX F606W ATD-GAIN=15 1 1100S ------------------------------------------------------------------------------------------------------------------------------------ 10 DDO199 WFPC2 IMAGE WF3-FIX F606W ATD-GAIN=15 2 1200S ------------------------------------------------------------------------------------------------------------------------------------ 6428( 3) - 02/13/96 10:54 - [ 5] Summary Form for Proposal 6428 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names DDO199 ------------------------------------------------------------------------------------------------------------------------------------