Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5383 Report Date: 18-Jul-95:17:16 Version: ********** Check-in Date: ********** 1.Proposal Title: THE WOLF-RAYET POPULATION OF GIANT HII REGIONS IN NGC 2403: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 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 Laurent Drissen USA (410) 338 4864 ------------------------------------------------------------------------------------ 7. Abstract Wolf-Rayet (WR) stars, the evolved descendants of the most massive O stars, play a very active role in the ecology of starburst regions by injecting huge amounts of mechanical energy into their surrounding interstellar medium, and by ejecting heavy elements through their powerful winds. The WR population of Giant HII regions (GHRs) has so far been investigated in a very small number of nearby objects. We propose to significantly increase this sample by imaging the four most massive GHRs in the late -type spiral galaxy NGC 2403 with a filter (F439N) centered on the strongest WR emission line, HeII 4686. This will allow for the first time a direct determination of the number of WR stars in GHRs of high metallicity and therefore provide important constraints for evolutionary models of massive stars. We will also obtain narrow-band OIII images to study the effects of WR stars on the morphology of their parent GHR. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 8.89 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5383 PI: Laurent Drissen Proposal Title: THE WOLF-RAYET POPULATION OF GIANT HII REGIONS IN NGC 2403: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Laurent Drissen 3470 USA Michael M Shara 3470 USA Jean-Rene Roy 4638 CANADA Anthony Moffat 4648 CANADA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will image 2 Giant HII regions in NGC 2403 (centered on PC1) with 4 filters: F439W to be used as a reference continuum; F469N centered on the most prominent WR line, HeII 4686; F547M, to eliminate very red stars (such as red supergiants), which could appear brighter in the F469N filter than in F439W; and F502N, to determine the morphology of the gas surrounding the most massive stars. At the same time, the other CCDs (WF2, WF3 and WF4) will image the field of NGC 2403 and detect field WR stars. All images will be obtained with the CR-SPLIT=NO requirement, but multiple exposures with the same filter are requested. All four CCDs will be read out. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The two Giant HII Regions in NGC 2403 included in this proposal have been observed from the ground under very good seeing conditions at the CFHT. Spectra of these targets have already been obtained and show the presence of Wolf-Rayet stars. However, these observations are severely limited by the spatial resolution imposed by the seeing since the WR excess at 4686 A is strongly diluted by the light of other stars. The estimates number of WR stars based on these ground- based data could be in error by large factors. The high resolution provided by HST images (0.1"=1.6 pc at the distance of NGC 2403) is twice as good as the resolution of ground-based imagery in M33, where the on and off-band imaging technique has been succesful in investigating the WR population of NGC 595 and NGC 604. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Not Applicable ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Not Applicable ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Not applicable Page 3 ------------------------------------------------------------------------------------ 9. Description of previous HST work. GO-2441: Search for WR stars in local Group Giant HII Regions, Moffat (PI), Drissen and Shara. GO-2416: Imaging and spectroscopy of super-metal poor galaxies, Roy CoI. GO-3605: UV Spectropolarimetry of AG Car, Drissen (Co-I), GO- 3605: Extreme Stellar Winds and Post Main-Sequence Evolution, Drissen (Co-I) GO- 2472 Binaries in Globular Clusters, Shara (PI) GO-3872 Blue Stragglers in the Cores of Globular Clusters, Shara Although none of the above program are directly related to NGC 2403, most of them aim at studying the properties of massive stars and massive star populuation in starburst regions. GO-2441. PC images of NGC 595 and NGC 604 in M33 and NGC 3603 in the Galaxy were obtained in order to study their Wolf-Rayet population. We were able to determine the number and absolute magnitudes of W-R stars in each region and to obtain a preliminary value of the IMF slope. One paper has been published and one is in preparation. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Drissen and Shara have direct access to STScI computing facilities and expertise. STScI has excellent support facilities, including a library, an extensive computer network, a publications department, and will provide the secretarial support. The PI and co-Is have SUN Sparkstations with 5 Gbyte of disk space available for data reduction; IRAF and STSDas are available at STScI, Montr\'eal and Laval Universities. Summer students are available in Montr\'eal and Laval. ------------------------------------------------------------------------------------ 11. Address Information Name: LAURENT DRISSEN Category: PI Institution: 3470 Address: 3700 San Martin Drive City: Baltimore State: MD Zip Code: 21218 Country: USA Telephone: (410) 338 4864 Telex (or e-mail): drissen@stsci.edu ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5383 [ 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 NGC2403-298 D,203 RA=07H32M17.9S, 1950 V=+165 1 V=23.0 +/- 0.5, TYPE=WR DEC=+65D43'21", REGION, R=15" Comments: THIS IS A CVZ TARGET MAGNITUDE IS FOR FAINTEST WR STAR ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC2403-174 D,203 RA=07H31M56.5S, 1950 V=+79 1 V=23.0 +/- 0.5, TYPE=WR DEC=+65D43'40", REGION, R=15" Comments: THIS IS A CVZ TARGET MAGNITUDE IS FOR FAINTEST WR STAR ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5383 [ 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 NGC2403-298 WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 3 900S 15 1 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC2403-298 WFPC2 IMAGE PC1-FIX F469N CR-SPLIT=NO 5 2200S 10 1 1 CYCLE 4 SAME POS FOR 2-4 AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC2403-298 WFPC2 IMAGE PC1-FIX F547M CR-SPLIT=NO 2 700S 15 1 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC2403-298 WFPC2 IMAGE PC1-FIX F502N 1 1000S 10 1 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC2403-174 WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 3 900S 15 1 2 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC2403-174 WFPC2 IMAGE PC1-FIX F469N CR-SPLIT=NO 5 2200S 10 1 2 CYCLE 4 SAME POS FOR 6-8 AS 5 ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC2403-174 WFPC2 IMAGE PC1-FIX F547M CR-SPLIT=NO 2 700S 15 1 2 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC2403-174 WFPC2 IMAGE PC1-FIX F502N 1 1000S 10 1 2 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5383 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 8.89 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; SAME POS FOR 2-4 AS 1 SAME POS FOR 6-8 AS 5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F439W F469N F547M F502N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2403-298 NGC2403-174 ------------------------------------------------------------------------------------------------------------------------------------