5887( 0) - 07/18/95 18:28 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5887 Version: ********** Check-in Date: ********** 1.Proposal Title: The Depletion Behavior of Chromium Relative to Zinc in the Magellanic Clouds ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Katherine Roth Space Telescope Science Institute CoI: J. Chris Blades Space Telescope Science Institute N CoI: Claus Leitherer Space Telescope Science Institute N ------------------------------------------------------------------------------------ 6. Abstract Observations of singly ionized zinc and chromium in the ISM primarily trace the depletion characteristics of metals in H I gas. Zn II does not deplete onto dust grains, and can provide an accurate metallicity measure. Conversely, Cr II is readily removed from the gas phase, and the Cr/Zn column density ratio provides a sensitive measure of dust destruction and contributing physical conditions within the absorbing material. In this proposal we are seeking time to use the GHRS ECH-B to measure the Cr/Zn ratio in Magellanic Cloud gas using four background sources. We will use these measurements to help interpret values obtained in high redshift (0.6 <= z <= 3) damped Lyman-Alpha systems which to date have only been compared to published Galactic values toward two stars, namely Zeta Ophiuchi and Chi Persei. From an archive study of 10 Galactic stars we have just finished, we have discovered that these 2 stars are not typical: rather, there is a much larger spread in the Cr/Zn ratio than previously thought, thus complicating but not invalidating comparison with high- redshift systems. Our proposed determination of Cr/Zn in two external galaxies known to have different extinction curves than the Milky Way will be used to construct a valid extragalactic baseline against which the Galactic and QSO observations can be compared. ------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 2] Observations Description ------------------------ We are proposing ECH-B observations through the small science aperture of Zn II Lambda 2026 and Mg I Lambda 2026 in order 28 and of Cr II LambdaLambda 2056,2062 and Zn II Lambda 2063 in order 27. We have calculated exposure times based on the values found in the GHRS Instrument Handbook 5.0 (Figures 8-4 and 8-6, Table 8-4), and Figure 5 of GHRS Instrument Science Report \#62. For ECH- B-28, we use a sensitivity S_lambda=3.04*10^11, mLambda=56750 for a blaze function sensitivity of 0.76, and a post-costar SSA/LSA transmission factor of 0.575 to derive an effective sensitivity of S_lambda^ eff=1.328times10^11 counts s^-1 diode^-1 (erg s^-1 cm^-2 AA^-1)^-1. For ECH-B-27 these values are 4.29times10^11, 55680, 0.74, and 0.575 for an S_lambda^ eff=1.825times10^11. In all calculations we have assumed an average D2 dark count rate of 0.011 counts diode^-1 s^-1. vspace*0.1in For our LMC targets, one of us (CL) has measured accurate fluxes at Lambda 2050 based on low-resolution FOS spectra of 7times10^-13 and 2.3times10^-13 erg s^-1 cm^-2 AA^ -1 for Sk -69 175 and Sk -68 33, respectively. These spectra indicate no problems due to narrow stellar line contamination, and also reveal interstellar Zn II and Cr II absorption is present. Images obtained of these fields verify that these are single stars, and we expect no difficulty with the standard 11+8 minute SSA target acquisition. Our SMC stars were selected for similar reasons, and we have estimated the flux at Lambda 2050 based on the spectral types (Garmany et al.\ 1987, AJ, 93, 1070) to be 4times10^-13 erg s^-1 cm^-2 AA^-1. We have calculated exposure times and orbits based on the requirement that we achieve a S/N ratio diode^-1 of 15. At a resolution of R=80,000 (Delta v=3.75 km s^-1 diode^-1, DeltaLambda=0.026 Angstrom\ diode^- 1), this would allow for a 2Sigma detection limit of 3.5 mAngstrom in one diode. For comparison, the S/N per diode in Figure 2 ranges from ~ 20 to >= 100. All orbits assumed a target visibility of 59 minutes (96 minutes target visibility in the CVZ), a 12 minute guide star acquisition and 6 minute reacquisition (no reacquisition in our CVZ observation) an 11+8 minute SSA target acquisition and peakup, a 3 minute SPYBAL per grating setting (2 per object), and 20-24 minute FPSPLITs with a 4 minute overhead. In the table below we summarize the resulting observation parameters. vspace*0.2in begincenter begintabularlccccccc multicolumn8cObservations Summary, ,-0.1in underlineStar & multicolumn3c *0.3inECH-B-28 *0.3in& multicolumn3c *0.3inECH-B-27 *0.3in& underlineOrbits, & Counts^ a & Delta t^ b & S/N & Counts^ a & Delta t^ b & S/N &, ,-0.1in Sk - 69 175 & 0.093 & 60 & 17 & 0.128 & 40 & 17 & 3, Sk -68 73 & 0.031 & 160 & 15 & 0.042 & 120 & 15 & hspace*0.065in4^ c, Sk 157 & 0.053 & 88 & 15 & 0.073 & 64 & 16 & 4, Sk 94 & 0.053 & 88 & 15 & 0.073 & 64 & 16 & 4, multicolumn8l a: counts diode^-1 s^-1, multicolumn8l b: exposure time (minutes), multicolumn8l c: CVZ orbits, endtabular endcenter Real Time Justification ----------------------- We have flagged the LMC star Sk -68 73 for continuous viewing zone observations. The LMC and SMC provide only limited CVZ opportunities; for example, there were only 3 CVZ opportunities at this position last year for a total of 69 hours. For this reason we are not requesting CVZ status for all our targets. However, the measured FOS flux at 2050 Angstrom\ for this object (2.3times10^-13) is sufficiently faint that we feel the extra efficiency afforded by the CVZ is necessary in this case. We have 4 nights observing time with the CTIO 4-m echelle spectrograph in November of this year with which we will obtain high signal-to-noise spectra of Ti II and Ca II of several stars in both the Large and Small Magellanic Clouds at comparable resolution to the proposed HST GHRS observations. Ti II and Ca II are both also heavily depleted onto dust grains in H I regions, although Ca II is additionally complicated by recombination of Ca III in hotter material (T >= 10,000 K). By comparing the relative depletions of these ions to Zn II and Cr II we can better understand the physical processes and dust destruction mechanisms within the intervening gas. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 Sk-68D73 EXT-MEDIUM, HI Cloud, RA = 05H 22M 59.87S +/- 0.1S, 2000 V = 11.46 B-V = +0.27 F(2050) = 2.3 E-13 High Velocity Cloud, DEC = -68D 01' 46.7" +/- 0.1", E(B-V) = 0.23 F(5160) = 5.4 E-12 Halo, IGM; EXT-STAR, PLATE-ID=05ZW Wolf Rayet Comments: spectral type Ofpe/WN9 2 Sk-69D175 EXT-MEDIUM, HI Cloud, RA = 05H 31M 25.66S +/- 0.1S, 2000 V = 11.90 B-V = -0.07 F(2050) = 7.0 E-13 High Velocity Cloud, DEC = -69D 05' 38.6" +/- 0.1", Halo, IGM; EXT-STAR, PLATE-ID=05ZW Wolf Rayet Comments: spectral type Ofpe/WN9 3 Sk157 EXT-MEDIUM, HI Cloud, RA = 01H 15M 51.91S +/- 0.1S, 2000 V = 12.12 B-V = -0.16 F(2050) = 4 E-13 High Velocity Cloud, DEC = -73D 20' 48.7" +/- Halo, IGM; EXT-STAR, 0.1",PLATE-ID=06B1 Wolf Rayet Comments: spectral type O9.5III 4 Sk94 EXT-MEDIUM, HI Cloud, RA = 01H 01M 07.72S +/- 0.1S, 2000 V = 12.36 B-V = -0.15 F(2050) = 4 E-13 High Velocity Cloud, DEC = -71D 59' 58.6" +/- Halo, IGM; EXT-STAR, 0.1",PLATE-ID=06B1 Wolf Rayet Comments: spectral type B2Iab 5887( 0) - 07/18/95 18:28 - [ 5] Visit: 01 Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 101 Sk-68D73 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 1.8S ONBOARD ACQ FOR 102 Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 102 Sk-68D73 HRS ACQ/PEA 0.25 MIRROR-N2 1 5S ONBOARD ACQ FOR 103-106 KUP Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 103 WAVE HRS ACCUM SC2 ECH-B28 2025.5- SPYBAL = YES 1 DEF 2029.5 Comments: WAVECAL for Zn II, Mg I ------------------------------------------------------------------------------------------------------------------------------------ 104 Sk-68D73 HRS ACCUM 0.25 ECH-B28 2025.5- FP-SPLIT = TWO, 19 598.4S 2029.5 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 11x2(27.2) s; Zn II, Mg I; expect total S/N = 15.5 per diode ------------------------------------------------------------------------------------------------------------------------------------ 105 WAVE HRS ACCUM SC2 ECH-B27 2055.6- SPYBAL = YES 1 DEF 2065.7 Comments: WAVECAL for Zn II, Cr II ------------------------------------------------------------------------------------------------------------------------------------ 106 Sk-68D73 HRS ACCUM 0.25 ECH-B27 2055.6- FP-SPLIT = TWO, 14 598.4S 2065.7 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 11x2(27.2)s; Zn II, Cr II; expect total S/N = 16.2 per diode ------------------------------------------------------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 6] 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 ------------------------------------------------------------------------------------------------------------------------------------ 201 Sk-69D175 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 1.8S ONBOARD ACQ FOR 202 Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 202 Sk-69D175 HRS ACQ/PEA 0.25 MIRROR-N2 1 5S ONBOARD ACQ FOR 203-206 KUP Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 203 WAVE HRS ACCUM SC2 ECH-B27 2055.6- SPYBAL = YES 1 DEF 2065.7 Comments: WAVECAL for Zn II, Cr II ------------------------------------------------------------------------------------------------------------------------------------ 204 Sk-69D175 HRS ACCUM 0.25 ECH-B27 2055.6- FP-SPLIT = TWO, 12 217.6S 2065.7 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 4x2(27.2) s; Zn II, Cr II; expect total S/N = 17.0 per diode ------------------------------------------------------------------------------------------------------------------------------------ 205 WAVE HRS ACCUM SC2 ECH-B28 2025.5- SPYBAL = YES 1 DEF 2029.5 Comments: WAVECAL for Zn II, Mg I ------------------------------------------------------------------------------------------------------------------------------------ 206 Sk-69D175 HRS ACCUM 0.25 ECH-B28 2025.5- FP-SPLIT = TWO, 17 217.6S 2029.5 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 4x2(27.2) s; Zn II, Mg I; expect total S/N = 17.0 per diode ------------------------------------------------------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 301 Sk157 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 1.8S ONBOARD ACQ FOR 302 Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 302 Sk157 HRS ACQ/PEA 0.25 MIRROR-N2 1 5S ONBOARD ACQ FOR 303-306 KUP Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 303 WAVE HRS ACCUM SC2 ECH-B28 2025.5- SPYBAL = YES 1 DEF 2029.5 Comments: WAVECAL for Zn II, Mg I ------------------------------------------------------------------------------------------------------------------------------------ 304 Sk157 HRS ACCUM 0.25 ECH-B28 2025.5- FP-SPLIT = TWO, 26 217.6S 2029.5 STEP-PATT = DEF, SPYBAL = NO Comments: Exposure time = 4x2(27.2)s; Zn II, Mg I; expect total S/N = 15.3 per diode ------------------------------------------------------------------------------------------------------------------------------------ 305 WAVE HRS ACCUM SC2 ECH-B27 2055.6- SPYBAL = YES 1 DEF 2065.7 Comments: WAVECAL for Zn II, Cr II ------------------------------------------------------------------------------------------------------------------------------------ 306 Sk157 HRS ACCUM 0.25 ECH-B27 2055.6- FP-SPLIT = TWO, 18 217.6S 2065.7 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 4x2(27.2); Zn II, Cr II; Expect total S/N = 15.3 per diode ------------------------------------------------------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 8] Visit: 04 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 ------------------------------------------------------------------------------------------------------------------------------------ 401 Sk94 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 1.8S ONBOARD ACQ FOR 402 Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 402 Sk94 HRS ACQ/PEA 0.25 MIRROR-N2 1 5S ONBOARD ACQ FOR 403-406 KUP Comments: STEP-TIME = 0.2S ------------------------------------------------------------------------------------------------------------------------------------ 403 WAVE HRS ACCUM SC2 ECH-B28 2025.5- SPYBAL = YES 1 DEF 2029.5 Comments: WAVECAL for Zn II, Mg I ------------------------------------------------------------------------------------------------------------------------------------ 404 Sk94 HRS ACCUM 0.25 ECH-B28 2025.5- FP-SPLIT = TWO, 26 217.6S 2029.5 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 4x2(27.2)s; Zn II, Mg I; expect total S/N = 15.3 per diode ------------------------------------------------------------------------------------------------------------------------------------ 405 WAVE HRS ACCUM SC2 ECH-B27 2055.6- SPYBAL = YES 1 DEF 2065.7 Comments: WAVECAL for Zn II, Cr II ------------------------------------------------------------------------------------------------------------------------------------ 406 Sk94 HRS ACCUM 0.25 ECH-B27 2055.6- FP-SPLIT = TWO, 18 217.6S 2065.7 STEP-PATT = 7, SPYBAL = NO Comments: Exposure time = 4x2(27.2); Zn II, Cr II; Expect total S/N = 15.3 per diode ------------------------------------------------------------------------------------------------------------------------------------ 5887( 0) - 07/18/95 18:28 - [ 9] Summary Form for Proposal 5887 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SPYBAL = YES SPYBAL = NO STEP-PATT = 7 FP-SPLIT = TWO STEP-PATT = DEF ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ONBOARD ACQ FOR 102 ONBOARD ACQ FOR 103-106 ONBOARD ACQ FOR 202 ONBOARD ACQ FOR 203-206 ONBOARD ACQ FOR 302 ONBOARD ACQ FOR 303-306 ONBOARD ACQ FOR 402 ONBOARD ACQ FOR 403-406 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 ECH-B28 ECH-B27 ------------------------------------------------------------------------------------------------------------------------------------ Target Names Sk-68D73 WAVE Sk-69D175 Sk157 Sk94 ------------------------------------------------------------------------------------------------------------------------------------