5954( 13) - 11/20/95 08:25 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5954 Version: 13 Check-in Date: ********** 1.Proposal Title: The Exceptionally Bright, Compact Starburst Galaxy 0833+652 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Carmelle Robert Universite Laval CoI: Timothy M. Heckman John Hopkins University N CoI: Claus Leitherer Space Telescope Science Institute Y CoI: Michael Dahlem Space Telescope Science Institute N CoI: Gerhardt Meurer John Hopkins University N ------------------------------------------------------------------------------------ 6. Abstract Starburst galaxies are ideal laboratories to study both the physics of massive stars and processes important in galaxy formation and evolution. Observations of these galaxies at UV wavelengths are crucial to our understanding of the starburst phenomenon, because only in this spectral regime can we directly observe the spectroscopic signatures of the hot, massive stars that power the emission at other wavebands. UV signatures from hot, massive stars are mainly broad spectral features formed in the hot star winds. The study of the stellar populations based on UV spectral synthesis requires therefore a high quality UV spectrum (S/N >~ 30, spectral resolution ~ 200-300 km s^-1), which is only possible with the HST spectrographs. We have selected the exceptionally bright, compact starburst galaxy 0833+652 to study the morphology of star-forming regions, from a WFPC2 image, and to quantify the massive star population of a starburst by performing the UV synthesis of a GHRS spectrum. We will compare the new results with those obtained for 4 other starburst galaxies also observed by us during previous HST cycles. We believe that a large sample of starbursts with different properties must be studied in the UV before answering important specific questions related to the formation and evolution of galaxies. ------------------------------------------------------------------------------------ 5954( 13) - 11/20/95 08:25 - [ 2] Observations Description ------------------------ We require an image of the UV continuum with WFPC2 in the F28.3 (PC1) mode, using the F218W filter (Lambda moyen = 2174 A, Delta Lambda = 373.4 A). (Note that the FOC was not chosen here because of its dynamical limitations for high surface brithness objects.) In the PC1, the pixel size is 0.044'', the pixel format is 800*800, and the field of view is 35''*35'' (slightly larger than the 10''*20'' IUE aperture through which the UV fluxes have been measured). This field should contain the whole galaxy for which low surface brightness contours extend to 20'' in the optical (Margon et al. 1988, ApJ 334, 597). The image will be use to delineate the size and morphology of the starburst, as seen in the UV near 1500 A. The F218W is centered at a longer wavelength than the wavelengths selected to collect the GHRS spectra. The WFPC2 F218W filter offers advantages, i.e. negligeable red leak and a relatively higher efficiency, compared to the shorter wavelength filters. Furthermore, based on the low- resolution IUE spectrum of Margon et al. (1988) the change of the flux between 1500 and 2200 A is less than a factor two. The WFPC2 image will be valuable in its own right, as it will reveal the intrinsic structure of the starburst. It is also essential as a prelude to spectroscopy. It will allow us at a later date to automatically position the GHRS large science aperture (LSA) for optimum efficiency and insure that there is no chance that the onboard target acquisition algorithm becomes confused by a complex UV morphology. One orbit is requested for the image. For our bright starburst (V ~ 13; Margon et al. 1988) the F218W filter should allow us to obtain S/N > 10 in the nuclear region after one orbit (which corresponds to ~ 60 minutes at DEC = 65 deg). The observation will be separated in multiple exposures (CR split) to allow for the removal of the cosmic rays. The main portion of the proposal involves the acquisition of the GHRS spectra. We will obtain spectra of the brightest region of the galaxy selected according to the WFPC2 image. We will use the LSA and the G140L grating at two different settings, covering the wavelength ranges from about 1200 to 1500 A and about 1480 to 1780 A. The use of the LSA (1.74'') is a compromise between our desires to detect as much of the light as possible from the starburst and to obtain adequate spectral resolution. Assuming that the concentration of light within the LSA is intermediate between a point source and uniform illumination, we estimate that the spectral resolution will be ~ 1.5 A. This resolution is required to study the stellar wind line profiles, i.e. to clearly discriminate between stellar wind lines, stellar photospheric and interstellar absorption lines, and nebular emission lines. The G140L short wavelength setting will be primarily used to measure the Ly_alpha line, stellar lines of NV 1240 and SiIV 1400, and interstellar lines such as SII, SiII, OI, CI and CII. The long wavelength spectrum will covers stellar features of CIV 1550, HeII 1640, and NIV 1718, and more interstellar lines of SiII, FeII and AlII. The main goal of this project is to use the stellar features (from stellar photospheres and stellar winds) to constrain the massive star population of the starburst. Ly_alpha may also reveal some information about the presence of an older population of stars. The interstellar lines will also be used to study the ionization conditions and kinematics of the starburst interstellar medium. In order to model the wind line profiles, we estimate that S/N ~ 30 diode^-1 is required in the GHRS spectra. Note that if the spectral resolution is about 2 diodes (due to the spatial extent of the starburst) then S/N per resolution element will even be larger. Radio maps of 0833+652 show that 80 percent of the emission arrises in a point source no larger than a few arcsec in size. Since the nonthermal radio source in well-studied starbursts like M82 and NGC253 seem to reliably trace the star-formation region, we believe that the bulk of the UV flux detected by IUE will be encompassed by the LSA. To be conservative, we assume here that about half of the IUE UV light goes into the LSA. Therefore, based on an IUE flux of 3.5 and 3.0 * 10^-14 erg cm^-2 s^-1 A^-1 at 1350 and 1630 A, respectively, the exposure time is about 1 hour and 4 hours for the short and long wavelength spectrum. Considering the guide star acquisition, target acquisition and the overheads, about 380 minutes, which corresponds to 4 orbits in the CVZ, are required for the spectroscopy. Although the FOS offers a better efficiency at longer wavelengths, other of its caracteristics (i.e. smaller science aperture, reduced efficiency at shorter wavelengths, and longer delay for the target acquisition) do not prove it to be better suited for our purposes. Real Time Justification ----------------------- Our galaxy is located in the CVZ. This makes extremely good use of the telescope time for the spectroscopic part of our project. (Note that CVZ time is not requested for the imaging part since we must see the image before the spectroscopy can be done.) Ground-based images and spectra in the optical will be obtained. For example, an H_alpha image will be used to explore the presence of superwinds due to the massive star population. High S/N spectra in the optical will be used to get information on the physical conditions and chemical abundances of the starburst. 0833+652 has been detected by the Einstein satellite. We will propose follow-up ROSAT HRI observations at higher spatial resolution to search for the origin of the X-ray emission ( i.e. supernova remnants or massive X-ray binaries in the nucleus versus extended emission from a shocked superwind). The new UV data are also to be compared with a HUT spectrum (of resolution of 3-4 A in a large 12'' aperture) scheduled for January 1995 (Leitherer & Heckman). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5954( 13) - 11/20/95 08:25 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5954( 13) - 11/20/95 08:25 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL- GALAXY, STARBURST, RA=8H 38M 23.45S +/- 0.3S, J2000 V=+5700 V=13+/-1 083824+65071 NUCLEUS DEC=+65D 7' 15.0" +/- 5", PLATE- E(B-V)=0.55+/-0.05 5 ID=01JR F(1500)=3.5+/-0.5E-14 2 GAL- GALAXY, STARBURST, RA=8H 33M 56.9S +/- 0.06S, B1950 V=+5700 V=14.5 083824+65071 NUCLEUS DEC=+65D 17' 45.0" +/- 1" E(B-V)=0.55+/-0.05 5-UPD F(1500)=3.5+/-0.5E-15 5954( 13) - 11/20/95 08:25 - [ 5] 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 GAL- WFPC2 IMAGE PC1 F218W 2 60S 083824+6507 15 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL- WFPC2 IMAGE PC1 F218W 1 900S 083824+6507 15 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL- WFPC2 IMAGE PC1 F218W 1 900S POSition TARGet 0.5,0.5 083824+6507 15 ------------------------------------------------------------------------------------------------------------------------------------ 5954( 13) - 11/20/95 08:25 - [ 6] Visit: 02 Visit Requirements: CVZ On Hold Comments: Additional Comments: Has been updated from early acq data visits 1,3 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL- FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP- 1 1S ONBOARD ACQ FOR 2 083824+6507 K Y=1.23 SEARCH- 15-UPD SIZE-X=1 SEARCH -SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL- FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP- 1 1S ONBOARD ACQ FOR 3 083824+6507 K X=0.61 SCAN- 15-UPD STEP-Y=0.61 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL- FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP- 1 2S ONBOARD ACQ FOR 4-10 083824+6507 K X=0.29 SCAN- 15-UPD STEP-Y=0.29 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL- FOS/BL ACQ 4.3 MIRROR 1 180S 083824+6507 15-UPD ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE HRS ACCUM SC2 G140L 1350 1 60S SEQ 6 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 6 GAL- HRS ACCUM 2.0 G140L 1350 FP-SPLIT=NO 1 4240S 083824+6507 15-UPD ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE HRS ACCUM SC2 G140L 1610 1 60S SEQ 8 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 8 GAL- HRS ACCUM 2.0 G140L 1610 FP-SPLIT=NO 1 4640S 083824+6507 15-UPD ------------------------------------------------------------------------------------------------------------------------------------ 9 GAL- HRS ACCUM 2.0 G140L 1610 FP-SPLIT=NO 1 4640S 083824+6507 15-UPD ------------------------------------------------------------------------------------------------------------------------------------ 10 GAL- HRS ACCUM 2.0 G140L 1610 FP-SPLIT=NO 1 4640S 083824+6507 15-UPD ------------------------------------------------------------------------------------------------------------------------------------ 5954( 13) - 11/20/95 08:25 - [ 7] Visit: 03 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 GAL- WFPC2 IMAGE PC1 F218W 2 60S 083824+6507 15 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL- WFPC2 IMAGE PC1 F218W 1 900S 083824+6507 15 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL- WFPC2 IMAGE PC1 F218W 1 900S POSition TARGet 0.5,0.5 083824+6507 15 ------------------------------------------------------------------------------------------------------------------------------------ 5954( 13) - 11/20/95 08:25 - [ 8] Summary Form for Proposal 5954 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/PEAK ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.23 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-X=0.61 SCAN-STEP-Y=0.61 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 SCAN-STEP-X=0.29 SCAN-STEP-Y=0.29 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=3 FP-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POSition TARGet 0.5,0.5 CVZ ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 4-10 SEQ 6 NON-INT SEQ 8 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F218W MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-083824+650715 GAL-083824+650715-UPD WAVE ------------------------------------------------------------------------------------------------------------------------------------