8246( 3) - 07/15/99 15:48 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8246 Version: 3 Check-in Date: 16-Feb-1999 14:26:47 1.Proposal Title: The youngest massive star clusters in the SMC as clues to star formation in the early Universe ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: M. Heydari-Malayeri Observatoire de Paris CoI: Dr. Michael R. Rosa Space Telescope European Coordinating N Facility, European Southern Observatory CoI: Dr. Daniel Schaerer Observatoire de Midi-Pyrenees N CoI: Dr. Hans Zinnecker Potsdam Astrophysical Institute N CoI: Dr. Lise Deharveng Observatoire de Marseille N CoI: Dr. Vassilis Charmandaris Observatoire de Paris N ------------------------------------------------------------------------------------ 5. Abstract High resolution imaging with WFPC2 has recently allowed us to resolve two very tight clusters of newly born massive stars in the Small Magellanic Cloud (N81, N88A; STScI Press Release 25-98, 23 July 1998). These are the youngest massive stars accessible to direct observations at ultraviolet and optical wavelengths. Situated in an extremely rare category of \h2 regions in the Magellanic Clouds (only 5\frac to 10\frac across and of very high excitation), these stars should rank among the hottest ones in these galaxies. Although color- magnitude diagrams yield valuable information, follow-up STIS observations of so identified hot star candidates are imperative for obtaining spectral types and stellar parameters and establishing the H-R diagrams. Comparison with models will allow us to derive the evolutionary state of the stars and clarify the nature of the most intriguing ones. In particular, one of the stars is a Wolf-Rayet candidate, which is an extremely rare kind of massive star in the metal-poor SMC. If confirmed by the planned spectroscopy, this finding will be important for stellar evolutionary models. Since the SMC is the most metal- poor galaxy observable with very high angular resolution, the proposed observations will provide valuable templates for studying star formation in the very distant metal-poor galaxies which populate the early Universe. ------------------------------------------------------------------------------------ 8246( 3) - 07/15/99 15:48 - [ 2] Observations Description ------------------------ We will to observe the brightest massive star candidates in N81 and N88A using the gratings G430L (CCD) in the visible and G140L (MAMA) in the UV. The former grating will give us the spectral features necessary for spectral classification, and the latter one is intended for deriving the wind properties and physical parameters as explained in Section 2. The position for the offset star is from the DSS. The relative positions (offsets) of the target stars as well as all photometry are from our Cyc 6 WFPC2 data, cross-checked against the DSS grid (cf. Heydari-Malayeri et al. 1999, Astron.Astrophys, in press; available from http://wwwusr.obspm.fr/~heydari/projects/N81 ) We used the STIS Exposure Time Calculator to predict exposure times, as well as the STIS Target ACQ calculator and the on-line Phase II documentation and advisories. For all targets we adopted a Kurucz O5V to B1V spectral ranges and the LMC extinction law with E(B-V)=0.1 and 0.65 for N81 and N88A respectively. The exposure times are calculated to get a S/N = 30 for 1550 A region in G140L and for the central region of G430L (CR-split) in the 52*0.2 slit. Brighter stars are assumed to be closer to the B1V type, fainter ones closer to O5. On the FUV MAMA data we will be able to bin by 2-4 pixels, further increasing the S/N if necessary for faint features. Reduced resolution and improved S/N are sufficient in both spectral domains to obtain the information required, namely the relative strenght of (broadened) wind emission lines (or P Cygni profiles) and H and He emission and absorption features. We take the stars one by one, since roll constraining (i.e. aligning with 2 or more stars) does not pay off considering the scheduling restrictions involved and the overhead incurred anyway for short exposures. All stars of a given cluster are well within 1' radius, and therefore accessible without change of guide stars. We acquire an offset star outside the crowded and nebulous region and rely on the offsets measured on our WFPC2 Stroemgren filter images, registered against the DSS/GS. We have separated CCD and MAMA science exposures into separate visits. Real Time Justification ----------------------- None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8246( 3) - 07/15/99 15:48 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SMC-N81-13 EXT-STAR, Supergiant O RA=01H 09M 16.0830S +/- 0.23S, J2000 V = 16.65 DEC=-73D 11' 29.111" +/- 1", B-V = -0.10 PLATE-ID=06B1 E(B-V) = 0.1 TYPE=B1V Comments: OFFSET STAR FOR ACQ OF N81 SOURCES 2 SMC-N81-01 EXT-STAR, Supergiant O RA-OFF=-3.0148S +/- 0.007S, DEC- J2000 V = 14.38 OFF=-9.173" +/- 0.01", FROM 1 B-V = -0.11 E(B-V) = 0.1 3 SMC-N81-02 EXT-STAR, Supergiant O RA-OFF=-3.0385S +/- 0.007S, DEC- J2000 V = 14.87 OFF=-8.929" +/- 0.01", FROM 1 B-V = -0.08 E(B-V) = 0.1 4 SMC-N81-11 EXT-STAR, Supergiant O RA-OFF=-2.3431S +/- 0.007S, DEC- J2000 V = 15.74 OFF=-4.21" +/- 0.01", FROM 1 B-V = -0.10 E(B-V) = 0.1 5 SMC-N81-03 EXT-STAR, Supergiant O RA-OFF=-2.7253S +/- 0.007S, DEC- J2000 V = 16.42 OFF=-9.237" +/- 0.01", FROM 1 B-V = 0.00 E(B-V) = 0.01 6 SMC-N81-04 EXT-STAR, Supergiant O RA-OFF=-3.233S +/- 0.007S, DEC- J2000 V = 17.41 OFF=-9.199" +/- 0.01", FROM 1 B-V = 0.07 E(B-V) = 0.1 7 SMC-N81-08 EXT-STAR, Supergiant O RA-OFF=-3.2475S +/- 0.007S, DEC- J2000 V = 17.84 OFF=-11.098" +/- 0.01", FROM 1 B-V = 0.15 E(B-V) = 0.1 8 SMC-N88-28 EXT-STAR, Supergiant O RA=01H 24M 22.4028S +/- 0.23S, J2000 V = 17.28 DEC=-73D 09' 43.787" +/- 0.1", B-V = -0.46 PLATE-ID=02I5 E(B-V) = 0.65 9 SMC-N88-55 EXT-STAR, Supergiant O RA-OFF=-13.2502S +/- 0.007S, DEC J2000 V = 16.57 -OFF=37.153" +/- 0.01", FROM 8 B-V = 0.00 E(B-V) = 0.65 10 SMC-N88-38 EXT-STAR, Supergiant O RA-OFF=-11.2513S +/- 0.007S, DEC J2000 V = 16.94 -OFF=22.683" +/- 0.01", FROM 8 B-V = -0.22 E(B-V) = 0.65 11 SMC-N88-71 EXT-STAR, Supergiant O RA-OFF=-17.3277S +/- 0.007S, DEC J2000 V = 16.46 -OFF=28.163" +/- 0.01", FROM 8 B-V = 0.09 E(B-V) = 0.65 8246( 3) - 07/15/99 15:48 - [ 4] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: CCD ACQ AND LIST OF STARS IN G430L Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 SMC-N81-13 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2 S ONBOARD ACQ FOR 12-18 CD P Comments: ACQ ETC EXP TIME 0.5S * 4 ------------------------------------------------------------------------------------------------------------------------------------ 12 SMC-N81-13 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 13 SMC-N81-01 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 0.4 M CD ------------------------------------------------------------------------------------------------------------------------------------ 14 SMC-N81-02 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 0.6 M CD ------------------------------------------------------------------------------------------------------------------------------------ 15 SMC-N81-11 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 1.5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 16 SMC-N81-03 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 2 M CD ------------------------------------------------------------------------------------------------------------------------------------ 17 SMC-N81-04 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 7 M CD ------------------------------------------------------------------------------------------------------------------------------------ 18 SMC-N81-08 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 12.5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 8246( 3) - 07/15/99 15:48 - [ 5] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: CCD ACQ AND LIST OF STARS IN G140L (FUV MAMA) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 SMC-N81-13 STIS/C ACQ F28X50L MIRROR 1 1 S ONBOARD ACQ FOR 22-24 CD P ------------------------------------------------------------------------------------------------------------------------------------ 22 SMC-N81-13 STIS/F ACCUM 52X0.5 G140L 1425 1 43 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 23 SMC-N81-04 STIS/F ACCUM 52X0.5 G140L 1425 1 54 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 24 SMC-N81-08 STIS/F ACCUM 52X0.5 G140L 1425 2 54 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8246( 3) - 07/15/99 15:48 - [ 6] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: CCD ACQ AND LIST OF STARS IN G140L (FUV MAMA) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 31 SMC-N81-13 STIS/C ACQ F28X50L MIRROR 1 1 S ONBOARD ACQ FOR 32-35 CD P ------------------------------------------------------------------------------------------------------------------------------------ 32 SMC-N81-01 STIS/F ACCUM 52X0.5 G140L 1425 1 8 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 33 SMC-N81-11 STIS/F ACCUM 52X0.5 G140L 1425 1 20 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 34 SMC-N81-02 STIS/F ACCUM 52X0.5 G140L 1425 1 12 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 35 SMC-N81-03 STIS/F ACCUM 52X0.5 G140L 1425 1 54 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8246( 3) - 07/15/99 15:48 - [ 7] Visit: 04 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: STARS IN SMC N88 (CCD G430L) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 41 SMC-N88-28 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 5 S ONBOARD ACQ FOR 42-44 CD P Comments: ACQ ETC EXP TIME 0.54S * 4 ------------------------------------------------------------------------------------------------------------------------------------ 42 SMC-N88-55 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 10 M CD ------------------------------------------------------------------------------------------------------------------------------------ 43 SMC-N88-38 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 10 M CD ------------------------------------------------------------------------------------------------------------------------------------ 44 SMC-N88-71 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=2 1 10 M CD ------------------------------------------------------------------------------------------------------------------------------------ 8246( 3) - 07/15/99 15:48 - [ 8] Summary Form for Proposal 8246 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 12-18 ONBOARD ACQ FOR 22-24 ONBOARD ACQ FOR 32-35 ONBOARD ACQ FOR 42-44 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names SMC-N81-13 SMC-N81-01 SMC-N81-02 SMC-N81-11 SMC-N81-03 SMC-N81-04 SMC-N81-08 SMC-N88-28 SMC-N88-55 SMC-N88-38 SMC-N88-71 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 1425 ------------------------------------------------------------------------------------------------------------------------------------