6096( 11) - 09/05/96 10:31 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6096 Version: 11 Check-in Date: 05-Sep-1996 10:27:50 1.Proposal Title: NGC 2363: ANATOMY OF A TWO-STAGE STARBURST ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Stellar Populations GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: LAURENT DRISSEN UNIVERSITE LAVAL CoI: Jean-Rene Roy Universite Laval N CoI: Carmelle Robert Universite Laval N ------------------------------------------------------------------------------------ 6. Abstract This proposal aims at identifying the massive star content of NGC 2363, the archetype of a whole class of small but powerful young starbursts with blowout like- properties. NGC 2363 is a large and very luminous metal-poor giant H II region located at the soutwestern end of the magellanic galaxy NGC 2366. It presents an unusual combination of kinematical features, the most outstanding being low- intensity, broad spectral components (FWHM = 2400 kms) in the bright nebular lines H Alpha\ and O III. These features, detected over a spatial extent of 500 pc, betray very high velocity gas and mimic, at a smaller scale, galactic superwinds of large starburst galaxies. Ground-based imagery suggests that two clusters of massive stars, of different ages, ionize the gas and supply the kinetic energy to the nebula. Identifying the stellar content of NGC 2363 is an essential step in trying to unveal its powerhouse and to understand the intriguing origin of the very high- velocity nebular gas. We propose to obtain optical images and high quality UV spectra of the two ionizing clusters in NGC 2363. The images will be used to assess the starburst history by studying the morphology of the clusters, locating and counting individual Wolf-Rayet and Red Supergiant stars and to determine the spatial extent of the He^++ zone. The continuum slope and the profiles of the UV stellar lines will be analyzed using the most up-to-date population synthesis models to quantify the global characteristics of the upper IMF. ------------------------------------------------------------------------------------ Observations Description ------------------------ noindent a) Imagery: The target (NGC 2363; total extent of clusters + nebular core = 25 '') will be centered on the PC1 CCD. Based on the WFPC2 handbook, as well as our previous experience with our Cycle 4 observations of NGC 2403 (same distance modulus as NGC 2363), the following exposure times are necessary to (1) detect the faintest WR and RSG stars (v ~ 24), and (2) determine the morphology of the He^++ and H^+ zones : F439W: 40 min; F547M: 25 min; F469N: 180 min; F656N: 20 min Assuming a 59-min orbital visibility outside the CVZ, 6 orbits are necessary. b) UV spectroscopy: NGC 2363 has been observed with IUE. However, because of the large IUE aperture, the spectra are largely dominated by the nebular component, thus drowning the stellar line profiles. Very little information on the stellar population is available, even in the high-dispersion spectra (S/N ~ 10). Only HST-FOS observations with the 1.0-aperture will allow us to analyze separately the stellar populations of the two clusters with high S/N ratio, high resolution and with little contamination from nebular lines. The lines used for the population synthesis (SiIV 1400, CIV 1550) are covered by the G130H grating of the FOS. After having obtained the images, we will determine the position of a relatively bright star in the field to be used for target acquisition, as well as offsets from this star to the two clusters. The offset star will be acquired using ACQ/BIN, and a non-critical peak-up in the 0.3 aperture; the telescope will then be slewed to the brightest cluster, using the offset determined from the WFPC2 images. After having obtained the spectrum of the first cluster, a slew will be performed to move the telescope to the second cluster; The offset star will be centered once again to minimize centering errors for the second target. Finally, HST wil be slewed to the position of the second cluster and spectra will be obtained. From our experience with the modeling of UV lines in starburst regions, we need S/N ~ 30 per resolution element (2.23 Angstrom \\\\\\\\ for the G130H, extended source). From the IUE spectra of NGC 2363, we get F_1400 = 5 * 10^-15 and 1 * 10^- 14 erg/s/cm^2/Angstrom\\\\\\\\ for clusters B and A, respectively. According to the FOS manual, N_Lambda = 2.28 * 10^12 F_Lambda (Lambda Delta Lambda) E_Lambda T_Lambda. Hence, for the FOS/BL with the G130H grating and the 0.86'' aperture, we get N_Lambda = 0.075 Counts/s/diode for cluster A at 1450 Angstrom . To get a S/N of 30, we need 105 minutes of integration. For cluster B, 170 minutes are necessary. Assuming an orbit visibility of 59 minutes, a total of 7 orbits are necessary to perform the UV spectroscopy of the two clusters. Real Time Justification ----------------------- In order to determine the location of the FOS apertures, the WFPC2 images should be obtained at least a few weeks before the FOS observations. NGC 2363 is in the CVZ. However, there is no scientific reason to observe the target continuously. NGC 2363 has already been extensively studied from the ground and with IUE (by ourselves and other teams). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Laurent Drissen (PI), Departement de Physique, Universite Laval, Pavillon Vachon, Ste-Foy, Quebec, G1K 7P4 Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6096( 11) - 09/05/96 10:31 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2363 EXT-CLUSTER, OB RA=07H 23M 25.4S,DEC=69D 17' 1950 V=+200 V = 16 Association 30",REGION,R=15" B-V = 0 2 NGC2363- STAR RA=07H 28M 46.4909S +/- 2000.0 V = 17 OFFSET 0.01S,DEC=69D 12' 38.04" +/- B-V = 0.0 0.1" 3 NGC2363-A EXT-CLUSTER, OB RA-OFF=-3.936S+/- 0.02S,DEC-OFF= 2000 V=+200 V = 18.0 Association -76.06"+/- 0.1",FROM 2 B-V = 0.0 4 NGC2363-B EXT-CLUSTER, OB RA-OFF=-3.015S+/- 0.02S,DEC-OFF= 2000 V=+200 V = 19.0 Association -75.347"+/- 0.1",FROM 2 B-V = 0.0 5 CP1-NGC2363- STAR, RA=07H 28M 46.4909S +/- J2000.0 V = 17 OFFSET 0.01S,DEC=69D 12' 38.04" +/- B-V = 0.0 0.1",PLATE-ID=01KS 6 CP1-NGC2363- EXT-CLUSTER,OB RA-OFF=-3.936S+/- 0.02S,DEC-OFF= J2000 V = 200 V = 18.0 A ASSOCIATION, -76.06"+/- 0.1",FROM 5 B-V = 0.0 7 CP1-NGC2363- EXT-CLUSTER,OB RA-OFF=-3.015S+/- 0.02S,DEC-OFF= J2000 V = 200 V = 19.0 B ASSOCIATION, -75.347"+/- 0.1",FROM 5 B-V = 0.0 6096( 11) - 09/05/96 10:31 - [ 2] 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 NGC2363 WFPC2 IMAGE PC1-FIX F439W 1 1700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC2363 WFPC2 IMAGE PC1-FIX F439W CR-SPLIT=NO 1 700 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC2363 WFPC2 IMAGE PC1-FIX F547M 1 1700 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC2363 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 1 900 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC2363 WFPC2 IMAGE PC1-FIX F656N CR-SPLIT=NO 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC2363 WFPC2 IMAGE PC1-FIX F469N CR-SPLIT=NO 1 2000 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC2363 WFPC2 IMAGE PC1-FIX F469N 3 45 M ------------------------------------------------------------------------------------------------------------------------------------ 6096( 11) - 09/05/96 10:31 - [ 3] Visit: 02 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 NGC2363-OFF FOS/BL ACQ/BIN 4.3 MIRROR 1 95 S ONBOARD ACQ FOR 2 SET ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC2363-OFF FOS/BL ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.11,SCAN-STEP-Y=0.11 1 3.2 S ONBOARD ACQ FOR 3-4 SET K ,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC2363-A FOS/BL ACCUM 1.0 G130H 1 980 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC2363-A FOS/BL ACCUM 1.0 G130H 2 2650 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC2363-OFF FOS/BL ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.11,SCAN-STEP-Y=0.11 1 3.2 S ONBOARD ACQ FOR 6-7 SET K ,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC2363-B FOS/BL ACCUM 1.0 G130H 1 1750 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC2363-B FOS/BL ACCUM 1.0 G130H 3 2650 S ------------------------------------------------------------------------------------------------------------------------------------ 6096( 11) - 09/05/96 10:31 - [ 4] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: This is a repeat of visit 2 which failed. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CP1-NGC2363 FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP-X=3.33,SCAN-STEP-Y=1.23 1 6 S ONBOARD ACQ FOR 2 -OFFSET K ,SEARCH-SIZE-X=2,SEARCH-SIZE-Y=6 ------------------------------------------------------------------------------------------------------------------------------------ 2 CP1-NGC2363 FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 6 S ONBOARD ACQ FOR 3 -OFFSET K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 CP1-NGC2363 FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 6 S ONBOARD ACQ FOR 4 -OFFSET K ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 4 CP1-NGC2363 FOS/BL ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.11,SCAN-STEP-Y=0.11 1 60 S ONBOARD ACQ FOR 5-6 -OFFSET K ,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ 5 CP1-NGC2363 FOS/BL ACCUM 1.0 G130H 1 980 S -A ------------------------------------------------------------------------------------------------------------------------------------ 6 CP1-NGC2363 FOS/BL ACCUM 1.0 G130H 2 2650 S -A ------------------------------------------------------------------------------------------------------------------------------------ 15 CP1-NGC2363 FOS/BL ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.11,SCAN-STEP-Y=0.11 1 3.2 S ONBOARD ACQ FOR 16-17 -OFFSET K ,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 ------------------------------------------------------------------------------------------------------------------------------------ 16 CP1-NGC2363 FOS/BL ACCUM 1.0 G130H 1 1750 S -B ------------------------------------------------------------------------------------------------------------------------------------ 17 CP1-NGC2363 FOS/BL ACCUM 1.0 G130H 3 2650 S -B ------------------------------------------------------------------------------------------------------------------------------------ 6096( 11) - 09/05/96 10:31 - [ 5] Summary Form for Proposal 6096 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/BINARY ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO SEARCH-SIZE-Y=4 SEARCH-SIZE-X=4 SEARCH-SIZE-Y=6 SEARCH-SIZE-Y=2 SEARCH-SIZE-Y=3 SCAN-STEP-Y=0.11 SCAN-STEP-X=0.11 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Stellar Populations ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3-4 ONBOARD ACQ FOR 6-7 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 4 ONBOARD ACQ FOR 5-6 ONBOARD ACQ FOR 16-17 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F439W F547M F656N F469N MIRROR G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2363 NGC2363-OFFSET NGC2363-A NGC2363-B CP1-NGC2363-OFFSET CP1-NGC2363-A CP1-NGC2363-B ------------------------------------------------------------------------------------------------------------------------------------