7511( 2) - 05/08/97 09:22 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7511 Version: 2 Check-in Date: 08-May-1997 09:20:26 1.Proposal Title: Spectroscopy of the interstellar medium in the Magellanic Bridge ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle INTERSTELLAR MATTER GO 7 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Francis Keenan The Queen's University of Belfast CoI: Philip Dufton The Queen's University of Belfast N CoI: Neil McErlean The Queen's University of Belfast N CoI: Robert Rolleston The Queen's University of Belfast N CoI: Kenneth Sembach Johns Hopkins University Y ------------------------------------------------------------------------------------ 6. Abstract Our optical observations of two B-type stars in the Magellanic Bridge, a region of material between the Large and Small Magellanic Clouds (LMC, SMC), reveal strong interstellar Ca II K absorption arising from the Bridge gas. We now propose to obtain medium resolution STIS spectra of the ultraviolet interstellar lines toward both of the stars. The proposed observations will provide an opportunity to investigate the physical conditions within the Bridge gas, and to determine the chemical composition of important elements such as C, N, O, Mg, Si, S, and Fe. These abundances will be compared with those found for the LMC and SMC, which will allow us to investigate if the Bridge gas originated in the SMC, as current theory suggests. The presence of young B-type stars in the Bridge implies that star formation is still occurring in this region. It has been suggested that the formation mechanism is similar to that believed to be responsible for some of the young B-type stars found in the halo of our Galaxy, namely collisions between cloudlets within high-velocity clouds (HVCs). To investigate this, we will compare our derived physical conditions for the Bridge gas with those found for halo HVCs. We will also search for cloudlet structure in the Bridge gas, through the identification of multicomponents in the interstellar line profiles; such cloudlets have already been found by us in an HVC. ------------------------------------------------------------------------------------ 7511( 2) - 05/08/97 09:22 - [ 2] Observations Description ------------------------ We will use the E140M grating of STIS to observe the wavelength region between 1150 A and 1700 A toward two stars in the Magellanic Bridge, DI1388 and DGIK975. The data will have a two pixel (FWHM) resolution of ~6.5 km/sec and S/N > 10 per resolution element over much of the bandpass (S/N > 7 for DGIK975). We will use the 0.2"x0.06" aperture to attain the highest resolution available with the E140M grating Real Time Justification ----------------------- None Calibration Justification ------------------------- None Additional Comments ------------------- Ten CVZ orbits were awarded by the TAC. Due to RPS2 CVZ scheduling constraints for these targets, it is necessary to drop the CVZ requirement for one object (target number 2). If this target can be observed in the CVZ, then the exposures should be modified as detailed in the comments under the appropriate visit, and the CVZ flag added as a visit level special requirement. ------------------------------------------------------------------------------------ Data Distribution Media: DAT Blocking Factor: 10 Ship To: Kenneth Sembach*Dept. of Physics and Astronomy*The Johns Hopkins University*Bloomberg 133*Baltimore, MD 21218 Ship Via: Email: sembach@sundoggie.pha.jhu.edu ------------------------------------------------------------------------------------ 7511( 2) - 05/08/97 09:22 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DI1388 STAR RA=02H 57M 11.94S +/- 0.03S, J2000 V = 14.39 DEC=-72D 52' 54.6" +/- 0.4", B-V = -0.25 PLATE-ID=00RE TYPE=B0V Comments: Coords are from GSC. 2 DGIK975 STAR RA=04H 19M 58.63S +/- 0.02S, J2000 V = 15.05 DEC=-73D 52' 25.8" +/- 0.3", B-V = -0.19 PLATE-ID=00RF TYPE=B0V Comments: Coordinates are from GSC. 7511( 2) - 05/08/97 09:22 - [ 4] Visit: 01 Visit Requirements: CVZ On Hold Comments: Additional Comments: RPS2 shows only very small window in the CVZ. If object cannot be observed in CVZ, exposure 3 should be modified as described in the comments below, and the CVZ flag added to the visit level requirements for this visit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DI1388 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.3 S ONBOARD ACQ FOR 2 CD P Comments: Expect approx 20,000 cnts in 3x3 checkbox. Imaging ETC used with GAIN=4 e-/ADU, CR-SPLIT=1, 1x1 binning, and B1V Kurucz model. ------------------------------------------------------------------------------------------------------------------------------------ 2 DI1388 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3.0 S ONBOARD ACQ FOR 3 CD K 6 Comments: Expect about 28,000 cnts/pix after scaling for aperture throughput. Spectroscopic ETC used with GAIN=4, CR-SPLIT=1,1x1 binning, amd B1V Kurucz model. ------------------------------------------------------------------------------------------------------------------------------------ 3 DI1388 STIS/F ACCUM 0.2X0.0 E140M 1425 4 109 M UV-MAM 6 A Comments: Exposure covers 1122A-1710A. Nominal default setting. IF non-CVZ, then modify to 1 iteration of 38M and add 4th exposure with same settings for 4 iterations of 50M. ------------------------------------------------------------------------------------------------------------------------------------ 7511( 2) - 05/08/97 09:22 - [ 5] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: RPS2 shows no scheduling windows in the CVZ. If object can be observed in CVZ, exposures 3-4 should be modified as described in the comments below, and the CVZ flag added to the visit level requirements for this visit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DGIK975 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.4 S ONBOARD ACQ FOR 2 CD P Comments: Expect approx 20,000 cnts in 3x3 checkbox. Imaging ETC used with GAIN=4 e-/ADU, CR-SPLIT=1, 1x1 binning, and B1V Kurucz model. ------------------------------------------------------------------------------------------------------------------------------------ 2 DGIK975 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 5.0 S ONBOARD ACQ FOR 3-4 CD K 6 Comments: Expect about 26,000 cnts/pix after scaling for aperture throughput. Spectroscopic ETC used with GAIN=4, CR-SPLIT=1,1x1 binning, amd B1V Kurucz model. ------------------------------------------------------------------------------------------------------------------------------------ 3 DGIK975 STIS/F ACCUM 0.2X0.0 E140M 1425 1 37 M UV-MAM 6 A Comments: Exposure covers 1122A-1710A. Nominal default setting. IF CVZ, then modify to 4 iterations of 109M. ------------------------------------------------------------------------------------------------------------------------------------ 4 DGIK975 STIS/F ACCUM 0.2X0.0 E140M 1425 4 50 M UV-MAM 6 A Comments: Exposure covers 1122A-1710A. Nominal default setting. If CVZ, then omit this exposure (but only omit if CVZ flag and exposure 3 have been modified accordingly). ------------------------------------------------------------------------------------------------------------------------------------ 7511( 2) - 05/08/97 09:22 - [ 6] Summary Form for Proposal 7511 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MATTER ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names DI1388 DGIK975 ------------------------------------------------------------------------------------------------------------------------------------