8180( 6) - 08/10/99 10:48 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8180 Version: 6 Check-in Date: 07-Apr-1999 12:18:09 1.Proposal Title: The Lyman continuum radiation from galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Jean-Michel Deharveng Laboratoire d'Astronomie Spatiale CoI: Dr. Bruno Milliard Laboratoire d'Astronomie Spatiale N CoI: Dr. Daniel Kunth Institut d'Astrophysique N ------------------------------------------------------------------------------------ 5. Abstract The amount of ionizing radiation released into the intergalactic medium by star formation is a poorly known but crucial parameter. This parameter would tell how the galaxies can complement the contribution of quasars for ionizing the IGM, especially at the epoch of re-ionization when the number density of quasars appears to decline. Direct measurements of the Lyman continuum radiation from galaxies are difficult and scarce. Indirect evaluations using models or theoretical arguments are plagued by the uncertainties on the Lyman continuum (Lyc) escape fraction. We would like to take advantage of the ultraviolet sensitivity of the G140L grating of STIS to detect (or set significant upper limit on) the Lyc radiation of star-forming galaxies in the redshift range 0.35 -- 0.6. We have selected 4 objects with an H Beta flux (or equivalent) that warrants the detection of a Lyc escape fraction as low as 5 percent. Following TAC's recommendations, we plan to observe three of these o bjects. ------------------------------------------------------------------------------------ 8180( 6) - 08/10/99 10:48 - [ 2] Observations Description ------------------------ The flux selection is at the heart of the proposal. It is crucial, if the Lyc radiation is not detected, to have a significant upper limit on the escape fraction; by significant we mean at least 5 percent. An HBeta flux f (in ergs cm^-2 s^-1) imply a total number of ~ 2 * 10^12 f Lyman continuum photons (in photons cm^-2 s^-1) and, under current conditions (Leitherer et al. 1995) and assuming a Lyc escape fraction x percent, an observed flux of 0.1 x f / (1+z) (in ergs cm^-2 s^-1 A^-1) at the Lyman limit. Using this relation and the exposure time calculator we found that a 5 percent Lyc escape fraction can be reached at a spectral resolution of 15 A and signal to noise ratio of 3 with an object of H Beta flux of 5 * 10^-16 ergs cm^-2 s^-1 and redshift 0.5 in about 3 orbits. Targets were searched according to this criterion. The exposure time calculator was run with their specific fluxes and redhsifts; all three targets have similar exposure times. We plan to use the slit 52X 0.5 in order to minimise Ly alpha geocoronal contamination. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8180( 6) - 08/10/99 10:48 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CFRS22.0274 GALAXY, HIGH REDSHIFT RA=22H 18M 4.07S +/- 2", DEC=00D J2000 Z = V = 21.6+/-0.5 GALAXY 21' 32" +/- 2" 0.5057 F-LINE(3727)=5.9+/-1e-16 2 FOCA-279 GALAXY, HIGH REDSHIFT RA=15H 40M 31.24S +/- 2", J2000 Z = V = 19.3+/-0.5 GALAXY DEC=34D 45' 37" +/- 2", PLATE- 0.534 F-CONT(2000)=11+/-5e-17 ID=01RV 3 FOCA-498 GALAXY, HIGH REDSHIFT RA=15H 40M .27S +/- 2", DEC=34D J2000 Z = V = 19.6+/-0.5 GALAXY 28' 15.5" +/- 2", PLATE-ID=01RV 0.434 F-CONT(2000)=11+/-5e-17 8180( 6) - 08/10/99 10:48 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 100D TO 120D 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 CFRS22.0274 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 4 M ONBOARD ACQ FOR 2, 3, 4 CD P DIFFUSE-CENTER=FLUX-CENTROID, CHECKBOX=9 ------------------------------------------------------------------------------------------------------------------------------------ 2 CFRS22.0274 STIS/F ACCUM 52X0.5 G140L 1425 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 CFRS22.0274 STIS/F ACCUM 52X0.5 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 CFRS22.0274 STIS/F ACCUM 52X0.5 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8180( 6) - 08/10/99 10:48 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENT 170D TO 190D 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 FOCA-279 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 2 M ONBOARD ACQ FOR 2, 3, 4 CD P DIFFUSE-CENTER=FLUX-CENTROID, CHECKBOX=9 ------------------------------------------------------------------------------------------------------------------------------------ 2 FOCA-279 STIS/F ACCUM 52X0.5 G140L 1425 1 35 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 FOCA-279 STIS/F ACCUM 52X0.5 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 FOCA-279 STIS/F ACCUM 52X0.5 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8180( 6) - 08/10/99 10:48 - [ 6] Visit: 03 Visit Priority: Visit Requirements: ORIENT 170D TO 190D 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 FOCA-498 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 2 M ONBOARD ACQ FOR 2, 3, 4 CD P DIFFUSE-CENTER=FLUX-CENTROID, CHECKBOX=9 ------------------------------------------------------------------------------------------------------------------------------------ 2 FOCA-498 STIS/F ACCUM 52X0.5 G140L 1425 1 35 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 FOCA-498 STIS/F ACCUM 52X0.5 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 FOCA-498 STIS/F ACCUM 52X0.5 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8180( 6) - 08/10/99 10:48 - [ 7] Summary Form for Proposal 8180 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE DIFFUSE-CENTER=FLUX-CENTROID CHECKBOX=9 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 100D TO 120D ONBOARD ACQ FOR 2, 3, 4 ORIENT 170D TO 190D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names CFRS22.0274 FOCA-279 FOCA-498 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------