Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5423 Report Date: 18-Jul-95:17:21 Version: ********** Check-in Date: ********** 1.Proposal Title: THE TUCANA DWARF SPHEROIDAL GALAXY ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO Sub Category STELLAR POPULATIONS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Patrick O. Seitzer 2660 USA 313-936-1741 ------------------------------------------------------------------------------------ 7. Abstract WFPC2 images of the core of the recently discovered Tucana dwarf spheroidal galaxy will be used to construct a color magnitude diagram that shows for the first time the horizontal branch magnitude and morphology of this system. An accurate distance modulus of this isolated Local Group member will be determined as well. All other galaxies of this class are satellites of much larger parent galaxies, such as the eight known systems around our Galaxy and the three systems around M31. In addition, the internal abundance dispersion of Tucana can be determined from the width of the giant branch at a faint enough level to be free from AGB star contamination. We will compare these characteristics with those of other known dwarf spheroidal galaxies, and determine what is unique about this isolated Local Group system. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 11.80 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5423 PI: Patrick O. Seitzer Proposal Title: THE TUCANA DWARF SPHEROIDAL GALAXY ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Patrick O. Seitzer 2660 USA Russell Lavery 1662 USA Alistair Walker 4720 USA Nicholas Suntzeff 4720 USA Gary Da Costa ANGLO-AUSTRALIAN OBSERVATORY AUSTRALIA ------------------------------------------------------------------------------------ 3. Description of proposed observations. First, for each filter (F555W and F814W) we will first do a series of short exposures for comparison with groundbased calibration and photometry of the brighter stars. Next, we will do a series of long 1800 second exposures offsetting between them to provide a check on photometric errors. We prefer that the entire sequence be taken at the same pointing to ensure that the short and long exposures in both filters have the stars in the same place on the PC. Hence, we have specified SEQ NO GAP ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Both the CTIO and AAO 4 meter reflectors (the largest telescopes in the southern hemisphere) equipped with CCD cameras have been used to observe Tucana. In several observing seasons we have reached the limit of groundbased studies of this system. Accurate photometry at the expected V magnitude of the horizontal branch (V = 25.3) is considerably beyond the capability of these telescopes even in the best seeing. The problem is not only the faintness of the stars we are interested in, but also the crowding and confusion. Even in sub arc second seeing the images of stars at V=25.3 will be blended with brighter stars. The full resolution of the PC is required to obtain the accurate photometry necessary to address the problems set forth here. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. None. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. Seitzer and Da Costa are both Co-Is in GO proposal 2419 "The Chronology of the Formation of the Galatic Halo and Disk". Zinn is PI of that proposal and the Co- Is are Carney, Christian, Da Costa, Demarque, Heasley, Janes, Olszewski and Seitzer. It is not directly scientifically related to the present proposal. This is a Cycle 1 proposal. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Computing resources will be made available at all of our institutions (Michigan, DTM, CTIO, and the AAO) for the reduction of this data. Should additional ground based data be required, the University of Michigan will provide telescope time on its Curtis Schmidt telescope at CTIO, and access to larger instruments at CTIO and the AAO will be sought through normal TAC procedures. ------------------------------------------------------------------------------------ 11. Address Information Page 3 Name: Patrick Seitzer Category: PI Institution: 2660 Address: Dept. of Astronomy University of Michigan 830 Dennison Building City: Ann Arbor State: MI Zip Code: 48109 Country: USA Telephone: 313-936-1741 Telex (or e-mail): seitzer@astro.lsa.umich.edu ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5423 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 TUCANA 049V E,308 PLATE-ID=049V, 2000.0 1 SURF(V) = 24.5 +/- 1.0 RA = 22H 41M 48.030S +/- 2 B-V = 0.8 +/- 0.2 0.2S, DEC = -64D 25' 16.22" +/- 0.5" ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5423 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 TUCANA WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 3 180.00S 3 1 1 CYCLE 4/1-4 180.00S GROUP 1-4 NO GAP POS TARG 0.0,0.0 SAME POS FOR 2-4 AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 TUCANA WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 4 1800.00 10 1 1 1800.00S ------------------------------------------------------------------------------------------------------------------------------------ 3 TUCANA WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 3 180.00S 3 1 1 180.00S ------------------------------------------------------------------------------------------------------------------------------------ 4 TUCANA WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 7 1800.00 10 1 1 1800.00S ------------------------------------------------------------------------------------------------------------------------------------ 12 TUCANA WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 4 1800.00 10 1 1 CYCLE 4/12-13 1800.00S GROUP 12-13 NO GAP POS TARG 0.86, 0.86 SAME POS FOR 13 AS 12 ------------------------------------------------------------------------------------------------------------------------------------ 13 TUCANA WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 8 1800.00 10 1 1 1800.00S ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5423 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 11.80 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4/1-4; GROUP 1-4 NO GAP; POS TARG 0.0,0.0; SAME POS FOR 2-4 AS 1 CYCLE 4/12-13; GROUP 12-13 NO GAP; POS TARG 0.86, 0.86; SAME POS FOR 13 AS 12 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names TUCANA 049V ------------------------------------------------------------------------------------------------------------------------------------