8302( 13) - 12/21/00 13:32 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8302 Version: 13 Check-in Date: 21-Dec-2000 13:31:18 1.Proposal Title: Lyman alpha emission in starburst galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Daniel Kunth CNRS, Institute d'Astrophysique de Paris CoI: Dr. Claus Leitherer Space Telescope Science Institute N CoI: Dr. Miguel Mas-Hesse Laboratorio de Astrofisica Espacial y N Fisica Fundamental CoI: Prof. Roberto Terlevich Royal Greenwich Observatory N CoI: Dr. Elena Terlevich Instituto Nacional de Astrofisica Optica y N Electronica CoI: Dr. Guillermo Tenorio-Tagle Instituto Nacional de Astrofisica Optica y N Electronica ------------------------------------------------------------------------------------ 5. Abstract We propose to perform a deep study of Ly-alpha\ emission and destruction in 3 star- forming galaxies. These objects have been already observed with the GHRS and exhibit a variety of situations, with Ly-alpha\ showing P Cyg profiles, secondary emissions or even a deep damped absorption line with no emission. They also span a range of intrinsic properties: IZW18 is a gas-rich, metal deficient dust free dwarf galaxy, Haro 2 has a simple morphology while IRAS 08339+6517 is a luminous IRAS starburst galaxy with more dust and complex Ly- alpha\ profile. The use of STIS will allow for the first time to study the geometrical/kinematical configuration of the ionized and neutral gas across the galaxies nuclear regions and pin point the effects of porosity and the kinematical structure of the ISM, that may play the key roles (in addition to dust) in the detectability of the line. This study will have important impact for cosmology since Ly-alpha\ emitters are nowaday found at high-re dshift. We strongly emphasize that since Ly-alpha\ is primarely a diagnostic of the ISM, a full understanding of how the ISM and Ly-alpha\ are related is a necessary step before we can hope to correlate Ly-alpha\ to the cosmic star-formation rate. Our results will be interpreted against the model of superbubble evolution developed with G. Tenorio Tagle. ------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 2] Observations Description ------------------------ We propose to observe Haro2, IRAS08339+6517, and IZw18 around LyAlpha and HBeta. The galaxies have previously been observed through the GHRS LSA at low and medium dispersion and were imaged from the ground and with HST. LyAlpha emission was detected in Haro2 and IRAS08339+6517, and evidence for spatial structure in optical emission lines was found in all three galaxies. STIS will be used with the G140M and G430L gratings, in combination with the 52x0.5 aperture. The grating and aperture choices were driven by (i) the expected flux levels, (ii) the spatial extension of LyAlpha, and (iii) contamination by geocoronal LyAlpha. The observed flux levels at 1280 Angstrom\ in the GHRS LSA are about 1 - 2 * 10^-14 erg s^-1 cm^-2 AA^-1 for the three galaxies. Inspection of the GHRS spiral search brightness distribution suggests that about 50\ widths smaller than 0.5'' would therefore miss a significant fraction of the emission and the S/N would be become unacceptably low, in particul ar along the spatial direction of the slit. Slit widths larger than 0.5'' would be desirable in terms of S/N but the scientific return would be compromised by decreased spectral resolution and geocoronal LyAlpha contamination. The minimum spectral resolution is expected for a uniform brightness distribution in the slit. For the G140M grating and the 52x0.5 aperture, the resulting dispersion is 1 Angstrom/pixel, still sufficient to resolve the LyAlpha P Cyg profile. In contrast, the 52x2 aperture would degrade the dispersion to 4 Angstrom/pixel, which is unacceptably low. In practice, the emission will be peaked and the effective dispersion will be somewhat higher than for this worst-case assumption. In the absence of better information we conservatively opt for the 0.5'' aperture. This aperture will minimize contamination by geocoronal LyAlpha as well. This line is expected to be strong, and the spectral point spread function around 1200 Angstrom\ is known to be particularly broad. The wavelength of intrinsi c LyAlpha emission in Haro2 and IZ w 18 is shifted by only a few Angstrom\ from the geocoronal line. Cutting the FWHM of the geocoronal line by a factor of four (the 52x0.5 versus 52x2 apertures) will make sure that the scattering wings of geocoronal LyAlpha are not an issue. We can constrain the required S/N from the existing GHRS data. S/N = 15 is adequate to interpret absorption features and the continuum level. On the other hand, detection and interpretation of emission lines are possible at somewhat lower S/N. Therefore it is very likely that LyAlpha can be detected at offset positions even if the flux levels are below the central 1 - 2 * 10^-14 erg s^-1 cm^-2 AA^-1. Exposure times to reach S/N = 15 for a flux of 1 * 10^-14 erg s^-1 cm^-2 AA^-1 at LyAlpha were computed with the ETC. 7500 s each are required for one exposure of Haro2 and IRAS08339+6517 at a central wavelength setting of 1222 Angstrom. 11000 s are needed for IZw18. A second exposure at the same position and with the same aperture will be tak en with the G430L grating. The pur pose is to correlate the locations of the LyAlpha and Balmer-line emission. The exposure times are negligibly low: a 5 minute exposure is perfectly adequate to analyze the emission lines. This is significant, as this allows us to combine the CCD and MAMA exposures in the same orbit without violating the 30 min maximum rule for the CCD exposure. The spectral resolution with G430L+52x0.5 will be degraded in comparison with the point source case but a resolution of 10 Angstrom\ or better is sufficient for Balmer-line flux measurements. Our observing strategy is as follows: We will perform a standard target acquisition on the galaxy nucleus. Imagery suggests simple morphology and no significant spatial offset between the optical and UV brightness peak. Then a brief G430L spectrum will be taken, followed by the G140M exposure at 1222 Angstrom. Three orbits are required to obtain exposure times of 7500 and 300 s for G140M and G430L, respectively. Four orbits are necessary for the longer exposure in IZw18. The obse r vations will be performed at a fixed orientation. A second orientation with an angular offset of 90^degrees will be done for Haro2 with the same exposure time. Therefore the total number of orbits per galaxy are 6 (Haro2), 3 (IRAS08339+6517), and 4 (IZw18). The grand total is 13 orbits. Real Time Justification ----------------------- Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 IRAS08339+65 GALAXY, STARBURST RA=08H 38M 23.2S +/- 0.1S, J2000 F(1250)=1.0e-14 17 DEC=65D 7' 15.0" +/- 1.0" V = 14.2 Coordinate Source: Comments: Flux from existing GHRS spectrum 2 IZW18 GALAXY, STARBURST RA=09H 34M 2.0S +/- 0.1S, J2000 F(1250)=1.2e-14 DEC=55D 14' 27.4" +/- 1.0" V = 16.1 Coordinate Source: Comments: Flux from existing GHRS spectrum 3 HARO2 GALAXY, STARBURST RA=10H 32M 31.8S +/- 0.1S, J2000 F(1250)=2.0e-14 DEC=54D 24' 35.0" +/- 1.0" V = 13.4 Coordinate Source: Comments: Flux from existing GHRS spectrum 4 CP1-HARO2 GALAXY, STARBURST RA=10H 32M 31.8S +/- 0.1S, J2000 F(1250)=2.0e-14 DEC=54D 24' 3.5" +/- 1.0" V = 13.4 Coordinate Source: Comments: Flux from existing GHRS spectrum. Updated coordinates for visit 04 observations. 8302( 13) - 12/21/00 13:32 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 216D TO 220D On Hold Comments: Additional Comments: Orientation +180 deg also ok Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 IRAS08339+6 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=11, 1 2 S 517 CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 20 IRAS08339+6 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=3 1 5 M 517 CD ------------------------------------------------------------------------------------------------------------------------------------ 30 IRAS08339+6 STIS/F ACCUM 52X0.5 G140M 1222 1 22 M MAX DUR 517 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 IRAS08339+6 STIS/F ACCUM 52X0.5 G140M 1222 1 50 M MAX DUR 517 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 IRAS08339+6 STIS/F ACCUM 52X0.5 G140M 1222 1 50 M MAX DUR 517 UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 309D TO 311D ORIENT 129D TO 131D On Hold Comments: Additional Comments: Orientation +180 deg also ok Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 IZW18 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=11, 1 4 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 20 IZW18 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=3 1 5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 30 IZW18 STIS/F ACCUM 52X0.5 G140M 1222 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 IZW18 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 IZW18 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 60 IZW18 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 195D TO 199D On Hold Comments: Additional Comments: Orientation +180 deg also ok Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HARO2 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=11, 1 8 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 20 HARO2 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=3 1 5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 30 HARO2 STIS/F ACCUM 52X0.5 G140M 1222 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 HARO2 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 HARO2 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 8] Visit: 04 Visit Priority: Visit Requirements: ORIENT 104D TO 106D ORIENT 284D TO 286D On Hold Comments: Additional Comments: Orientation +180 deg also ok Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 CP1-HARO2 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=11, 1 8 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 20 CP1-HARO2 STIS/C ACCUM 52X0.5 G430L 4300 CR-SPLIT=3 1 5 M CD ------------------------------------------------------------------------------------------------------------------------------------ 30 CP1-HARO2 STIS/F ACCUM 52X0.5 G140M 1222 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 CP1-HARO2 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 CP1-HARO2 STIS/F ACCUM 52X0.5 G140M 1222 1 53 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8302( 13) - 12/21/00 13:32 - [ 9] Summary Form for Proposal 8302 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE CHECKBOX=11 DIFFUSE-CENTER=FLUX-CENTROID CR-SPLIT=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 216D TO 220D MAX DUR ORIENT 309D TO 311D ORIENT 129D TO 131D ORIENT 195D TO 199D ORIENT 104D TO 106D ORIENT 284D TO 286D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names IRAS08339+6517 IZW18 HARO2 CP1-HARO2 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 1222 ------------------------------------------------------------------------------------------------------------------------------------