5892( 5) - 09/05/95 16:54 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5892 Version: 5 Check-in Date: ********** 1.Proposal Title: PHYSICAL CONDITIONS IN THE GALACTIC HALOS OF THE MILKY WAY AND NGC 3067 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Michael Shull University of Colorado, Boulder CoI: Dr. John Stocke University of Colorado, Boulder N CoI: Mr. Steve Penton University of Colorado, Boulder N ------------------------------------------------------------------------------------ 6. Abstract We propose to conduct a detailed GHRS spectroscopic study of the metal absorption lines in the halo gas of the Milky Way and NGC 3067, using the quasar 3C 232 as a background source. Because 3C 232 is the only QSO metal-line system imaged in H I emission for which we can study metal-line ratios in detail, it provides a rare opportunity to measure abundances, grain depletions, and photoionizing radiation fields in halo gas. Discovered in 21-cm and Ca II absorption, the NGC 3067 absorption system has now been studied in 21-cm emission and absorption (VLA, Westerbork) and in UV absorption (IUE, HST/FOS) with 3 components spread over 160 kms. The H I cloud is almost certainly a tidal tail, pulled out of NGC 3067 some (10 kpc)h_75^-1 into the halo. We will measure column densities of Fe I and II, Mg I and II, S II, Mn II, Si II, C IV, Si IV, and perhaps C II and O I. These abundances and the H I emission characteristics can be used to determine metallicities and grain depletions in the halos of NGC 3067 and the Milky Way. The Fe I/Fe II and Mg I/Mg II ionization equilibrium, coupled with H I columns, will be used to set the metagalactic photoionizing radiation field and to model the thermal equilibrium of halo gas. The C IV/Si IV absorption can be used to diagnose the relative effects of photoionization and hot gas in these halo absorption systems. The depletion factors of Si, Mn, and Fe will be used to estimate the amount of grain disruption during the tidal encounter. ------------------------------------------------------------------------------------ 5892( 5) - 09/05/95 16:54 - [ 2] Observations Description ------------------------ Our program requires us to measure a sufficient number of resonance absorption lines of key interstellar species (Mg, Fe, Si, S, Mg, Mn) to obtain abundances and depletion factors in the halos of the Galaxy and NGC 3067. In addition, we need to measure the ionization fractions, Fe I/Fe II and Mg I/Mg II, in order to determine the ionizing radiation field. Finally, to resolve the 3 known velocity components of the NGC 3067 absorption, spread over 160 kms, and to separate some Galactic lines from lines in NGC 3067, we need to make some of our measurements at resolution R = 20,000. The planned observing program consists of two parts. In Part I, we will use grating G270M (5 settings at R = 20,000 and S/N = 10) for the long-wavelength lines (2339 -- 2880 Angstrom) as shown in Figure 3. These observations require 20 orbits and will provide good measurements of Fe I, Fe II, Mg I, Mg II, and Mn II. In Part II, we will use grating G140L (2 settings at R = 2000) for the region 1150 -- 1716 Angstrom. These observations require 6 orbits and will measure Si II, S II, C IV, Si IV, and possibly C II and O I. The target, 3C 232, lies at 33^degrees declination and has a 54-min clear viewing zone per orbit. The GHRS observing times were computed for S/N = 10 (Part I) and S/N = 20 (Part II) breaking up the observing into 20-minute ``FP-split'' segments to handle pattern noise. The two tables below summarize the breakdown of these observations into ``orbits''. In Part I, we have optimized time by fitting the changes in G270M grating setting into some of the orbits (hence the fractional orbit listings). , begincenter TABLE 1: Part I: Wavelength Settings for G 270M , endcenter begincenter begintabularccrrl Setting & Wavelengths & Expo & Orbits & Ions , & (Angstrom) & (min) & & , 1 & 2835 - 2880 & 160 & 4.5 & Mg I , 2 & 2782 - 2828 & 144 & 3.5 & Mg II , 3 & 2577 - 2624 & 140 & 3.5 & Mn II, Fe II , 4 & 2488 - 2535 & 140 & 4.0 & Fe I , 5 & 2339 - 2387 & 180 & 4.5 & Fe II , endtabular endcenter vspace1cm begincenter TABLE 2: Part II: Wavelength Settings for G 140L , endcenter begincenter begintabularccrrl Setting & Wavelengths & Expo & Orbits & Ions , & (Angstrom) & (min) & & , 1 & 1150 - 1436 & 81 & 2 & S II, C II, Si II, O I, Si IV , 2 & 1430 - 1716 & 153 & 4 & Si IV, C IV, Si II, Fe II , endtabular endcenter Real Time Justification ----------------------- None A key question about the extended H I emission and metal-line absorption cloud in the NGC 3067 halo is its tidal origin. We will conduct a ground-based (optical) deep spectroscopic survey searching for galaxies in the field down to B = 19 over a 1^degrees field of view. These observations will be proposed at the WIYN telescope using the HYDRA spectrograph. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5892( 5) - 09/05/95 16:54 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5892( 5) - 09/05/95 16:54 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 3C232 GALAXY,QSO RA = 9H 58M 21.00S +/- 0.04S, J2000 Z=0.533 V=15.78 DEC = 32D 24' 2.3" +/- 0.5", B-V=0.1 PLATE-ID = 01RS Comments: Coordinates are from an inventory GASP measurement by ABerman Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.132 0.0 0.0 0.0 5892( 5) - 09/05/95 16:54 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: 3C232-G270M-2 Wavelength settings Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 3C232 HRS ACQ 2.0 MIRROR-N2 1 13.5S ONBOARD ACQ FOR 2-3 Comments: STEP-TIME=1.5S ------------------------------------------------------------------------------------------------------------------------------------ 2 3C232 HRS ACCUM 2.0 G270M 2835- FP- 6 1849.6S 2880 SPLIT=NO,STEP- PATT=DEF,DOPPLE R=ON ------------------------------------------------------------------------------------------------------------------------------------ 3 3C232 HRS ACCUM 2.0 G270M 2782- FP- 5 2148.8S 2828 SPLIT=NO,STEP- PATT=DEF,DOPPLE R=ON ------------------------------------------------------------------------------------------------------------------------------------ 5892( 5) - 09/05/95 16:54 - [ 6] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: 3C232-G270M-2 Wavelength settings Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 4 3C232 HRS ACQ 2.0 MIRROR-N2 1 13.5S ONBOARD ACQ FOR 5-6 Comments: STEP-TIME=1.5S ------------------------------------------------------------------------------------------------------------------------------------ 5 3C232 HRS ACCUM 2.0 G270M 2577- FP- 5 1795.2S 2624 SPLIT=NO,STEP- PATT=DEF,DOPPLE R=ON ------------------------------------------------------------------------------------------------------------------------------------ 6 3C232 HRS ACCUM 2.0 G270M 2339- FP- 6 2148.8S 2387 SPLIT=NO,STEP- PATT=DEF,DOPPLE R=ON ------------------------------------------------------------------------------------------------------------------------------------ 5892( 5) - 09/05/95 16:54 - [ 7] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: 3C232-G270M-1 Wavelength Settings Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 7 3C232 HRS ACQ 2.0 MIRROR-N2 1 13.5S ONBOARD ACQ FOR 8 Comments: STEP-TIME=1.5S ------------------------------------------------------------------------------------------------------------------------------------ 8 3C232 HRS ACCUM 2.0 G270M 2488- FP- 5 2094.4S 2535 SPLIT=NO,STEP- PATT=DEF,DOPPLE R=ON ------------------------------------------------------------------------------------------------------------------------------------ 5892( 5) - 09/05/95 16:54 - [ 8] Summary Form for Proposal 5892 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FP-SPLIT=NO STEP-PATT=DEF DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-3 ONBOARD ACQ FOR 5-6 ONBOARD ACQ FOR 8 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G270M ------------------------------------------------------------------------------------------------------------------------------------ Target Names 3C232 ------------------------------------------------------------------------------------------------------------------------------------