Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5309 Report Date: 18-Jul-95:17:07 Version: ********** Check-in Date: ********** 1.Proposal Title: Star Formation and the Massive Star Population in Blue Compact Dwarf Galaxies: Cycle4Medium ------------------------------------------------------------------------------------ 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 Deidre A. Hunter Lowell Observatory USA 602-774-3358 ------------------------------------------------------------------------------------ 7. Abstract Blue Compact Dwarf galaxies are tiny galaxies that are dominated by intense, compact star-forming regions that contain thousands of massive OB and Wolf-Rayet stars. Thus, they present a different and extreme environment for star formation compared to the Milky Way and other nearby galaxies for the examination of the star formation process. The IMF of the massive stars in these enigmatic galaxies, in fact, is controversial. Global properties and models have been interpretted as showing considerable variation in the IMF with the metallicity of the system, while other studies argue that the IMF is fairly normal. We will resolve this issue by resolving one BCD into individual massive stars for the first time. The galaxy, IZW18, is renowned for its low abundances. We will use UVI-equivalent colors to construct color-magnitude diagrams and luminosity functions for the massive stars and F469N to identify evolved Wolf-Rayet stars. We will also examine the images in order to determine the numbers, physical sizes, and distributions of the star-forming regions. Halpha images will be used to examine the effect of the extreme concentration of massive stars on their environment. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 9.82 par: 0.00 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5309 PI: Deidre A. Hunter Proposal Title: Star Formation and the Massive Star Population in Blue Compact Dwarf Galaxies: Cycle4Medium ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Harley A. Thronson Univ. of Wyoming USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will obtain F336W, F555W, F814W, F469N, and F656N images of one blue compact dwarf galaxy, IZw18. The observations for the broad-band filters include short and long exposures in order to cover an apparent magnitude of V=19 to 26. These will enable us to examine the OB star population (V=21 is M_V=-10). The F469N filter will be used to identify Wolf-Rayet stars, and high resolution Halpha images will be used to examine the structure of the star-forming regions. The exposures of the narrow-band filters are as long as are feasible, since they will be photon-starved for any reasonable exposure time. The long exposures are multiples in order to permit CR removal. They should not be split further. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. IZW18 is not resolved on ground-based images. With HST we will for the first time measure the brightnesses of individual stars and locate them for future spectroscopy with HST in order to test statements in the literature that this type of galaxy has an abnormal IMF. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. None. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. We require flat fields for F336W, F555W, F814W, F469N, and F656N. We expect the first 3 to be done as part of the standard calibration, but F469N and F656N may not be. Thus, they need to be scheduled for calibration as well. We also require photometric calibration of the 3 broad-band filters, but, again, we would expect this to be done as part of the standard proceedure. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None. ------------------------------------------------------------------------------------ 9. Description of previous HST work. DAH is a member of the WFPCI team and has worked on the stellar photometry of R136 (Campbell et al. 1992, AJ, 104, 1721). DAH has also been involved in a GO program to examine superstar clusters in irregular galaxies (in preparation). ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Computing facilities and software for data analysis, access to telescopes for any ground-based support that might be necessary. ------------------------------------------------------------------------------------ 11. Address Information Page 3 Name: Deidre A. Hunter Category: PI Institution: Lowell Observatory Address: 1400 W. Mars Hill Rd. City: Flagstaff State: AZ Zip Code: 86001 Country: USA Telephone: 602-774-3358 Telex (or e-mail): dah@lowell.edu ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5309 [ 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 IZW18 E,307 RA = 09H 30M 30.4S +/- 0.1S, 1950 1 V=21, TYPE=O DEC = +55D 27' 46" +/- 2" 1 E(B-V)=0 2 V=25.6, TYPE=O 2 E(B-V)=0 Comments: V=21 is the maximum expected. V=25.6 is the minimum for S/N=10. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5309 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 2 IZW18 WFPC2 IMAGE PC1-FIX F336W CR-SPLIT=NO 3 1400S 10 2 1 CYCLE 4 / 2-8 2 ------------------------------------------------------------------------------------------------------------------------------------ 4 IZW18 WFPC2 IMAGE PC1-FIX F555W CR-SPLIT=NO 3 2200S 10 2 1 SAME POS FOR 4-8 2 AS 2 GROUP 2-8 WITHIN 7D ------------------------------------------------------------------------------------------------------------------------------------ 6 IZW18 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 3 2200S 10 2 1 2 ------------------------------------------------------------------------------------------------------------------------------------ 7 IZW18 WFPC2 IMAGE PC1-FIX F469N CR-SPLIT=NO 3 2300S 10 1 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 8 IZW18 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 3 1400S 10 1 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5309 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 9.82 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 / 2-8 SAME POS FOR 4-8 AS 2; GROUP 2-8 WITHIN 7D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F336W F555W F814W F469N F656N ------------------------------------------------------------------------------------------------------------------------------------ Target Names IZW18 ------------------------------------------------------------------------------------------------------------------------------------