6412( 9) - 08/19/96 17:04 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6412 Version: 9 Check-in Date: 19-Aug-1996 17:01:52 1.Proposal Title: Ionization of C IV High Velocity Clouds in the Galactic Halo ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle INTERSTELLAR MEDIUM GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: KEN SEMBACH THE JOHNS HOPKINS UNIVERSITY CoI: Blair Savage University of Wisconsin - Madison N CoI: Limin Lu California Institute of Technology N ------------------------------------------------------------------------------------ 6. Abstract Understanding the origin and properties of the high velocity cloud (HVC) system in the Milky Way has been a persistent problem for more than half a century. However, significant advances in studying HVCs have been made with the Hubble Space Telescope, and it is now possible to determine abundances and ionization properties of some HVCs through diagnostic line ratios at ultraviolet wavelengths. We recently discovered a pair of highly ionized HVCs in a Cycle 4 investigation of the C IV halo gas absorption toward the AGN Markarian 509. The HVCs are unique in their ionization properties for Galactic HVCs; they have been detected only in C IV and their general absorption properties more closely resemble those of the high ionization quasar metal line absorption systems than those for most interstellar clouds found in the Milky Way disk or halo. We request GHRS intermediate resolution observations of the strong resonance lines of C II and Si II-III-IV to study the ionization processes in the C IV HVCs toward Mrk 509. When combined with our existing C IV, N V, and Si II data, the proposed observations will allow us to distinguish between different ionization mechanisms believed to be operating in the Galactic halo. The results of this investigation have implications for the origin of the HVCs, the ionization of gas at large distances from the Galactic plane, and the relationship between Milky Way halo gas and gas in the halos of galaxies at high redshifts. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain GHRS G160M observations of the interstellar lines in the 1200, 1330, and 1400 A spectral regions of Markarian 509. The large science aperture observations are designed to produce S/N = 10 per resolution element at a resolution (FWHM) of 16-18 km/sec. The strong spectral lines to be studied include C II 1334, Si II 1190, 1193, Si III 1206, and Si IV 1393, 1400. Strong lines of N I and S III will also be covered by the observations. Real Time Justification ----------------------- No special scheduling requirements are necessary. Calibration Justification ------------------------- No special calibration requirements are necessary. Additional Comments ------------------- No additional comments at this time. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6412( 9) - 08/19/96 17:04 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MRK509 Galaxy, Seyfert RA = 20H 44M 9.75S +/- 0.1S, DEC J2000 Z = V = 13.0 = -10D 43' 24.53" +/- 1.0", 0.0355 F-CONT(1200)=7.0+/-2.0e-14 PLATE-ID=00E1 F-CONT(1330)=6.0+/-2.0e-14 F-CONT(1400)=4.9+/-2.0e-14 Comments: Fluxes from FOS G130H spectrum of Mrk 509 (1993). 6412( 9) - 08/19/96 17:04 - [ 2] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Number exposures beginning with 1. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MRK509 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=3 1 7.2 S ONBOARD ACQ FOR 2-5 Comments: STEP-TIME=0.8 seconds. This worked fine before in GO program #3463. ------------------------------------------------------------------------------------------------------------------------------------ 2 MRK509 HRS ACCUM 2.0 G160M 1198.0 FP-SPLIT=FOUR,COMB=FOUR, 2 1523.2 STEP-PATT=DEF,CENSOR=YES Comments: N I, Si II, Si III, S III ------------------------------------------------------------------------------------------------------------------------------------ 3 MRK509 HRS ACCUM 2.0 G160M 1198.0 FP-SPLIT=FOUR,COMB=FOUR, 2 1523.2 STEP-PATT=DEF,CENSOR=YES Comments: N I, Si II, Si III, S III ------------------------------------------------------------------------------------------------------------------------------------ 4 MRK509 HRS ACCUM 2.0 G160M 1319.2 FP-SPLIT=FOUR,COMB=FOUR, 3 1196.8 STEP-PATT=DEF,CENSOR=YES Comments: Si II, C II, C II* ------------------------------------------------------------------------------------------------------------------------------------ 5 MRK509 HRS ACCUM 2.0 G160M 1400.0 FP-SPLIT=FOUR,COMB=FOUR, 4 1305.6 STEP-PATT=DEF,CENSOR=YES Comments: Si IV ------------------------------------------------------------------------------------------------------------------------------------ 6412( 9) - 08/19/96 17:04 - [ 3] Summary Form for Proposal 6412 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 CENSOR=YES STEP-PATT=DEF COMB=FOUR FP-SPLIT=FOUR ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names MRK509 ------------------------------------------------------------------------------------------------------------------------------------