Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5608 Report Date: 18-Jul-95:17:44 Version: ********** Check-in Date: ********** 1.Proposal Title: INTERSTELLAR ABUNDANCES IN THE SMC - IMPLICATIONS FOR QSO ABSORPTION- LINE SYSTEMS AND FOR THE CHEMICAL EVOLUTION OF THE UNIVERSE - CYCLE 4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID INTERSTELLAR MEDIUM GO Sub Category ABSORPTION LINES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Daniel E. Welty UNIVERSITY OF CHICAGO USA (312)702-0599 ------------------------------------------------------------------------------------ 7. Abstract We propose a detailed study of the interstellar (IS) abundances and depletions for one line of sight in the SMC - a nearby low metallicity, low dust-to-gas ratio system where stellar abundance data are also available. We will use the GHRS ECH-B to obtain absorption-line profiles of Zn II, Cr II, Si II, Fe II, Mn II, Mg II, and Al III, to determine both the detailed component structures and the relative abundances of those species in the various components. We will use the derived component structures to obtain similarly detailed abundances for S II, Ni II, and Al II from existing lower resolution short-wavelength IUE spectra (in which severe blending of components has to now prevented accurate abundance determinations). In addition to the intrinsic interest in obtaining detailed IS abundance and depletion data for an external galaxy quite different from our own, such data are needed for interpreting the abundance patterns found in QSO absorption-line systems. A number of the QSOALS examined to date seem to exhibit overall metallicities of about 0.1 x Solar, with some additional depletion of refractory elements. If the pattern of that depletion can be constrained, then the build-up of many elements can be traced, via the QSOALS, from redshifts 3.5 to 0.5 - with significant implications for the formation and evolution of galaxies. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 7.34 par: 0.00 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5608 PI: Daniel E. Welty Proposal Title: INTERSTELLAR ABUNDANCES IN THE SMC - IMPLICATIONS FOR QSO ABSORPTION- LINE SYSTEMS AND FOR THE CHEMICAL EVOLUTION OF THE UNIVERSE - CYCLE 4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Daniel E. Welty 1710 USA J. C. Blades 3470 USA Lewis M. Hobbs 1710 USA James T. Lauroesch 1710 USA Donald G. York 1710 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. The GHRS will be used in echelle mode, using the small science aperture and breaking long exposures into series of 5-minute sub-exposures at several slightly different central wavelengths in order to minimize the effects of magnetic drift and detector non-uniformities. The particular lines to be observed have been selected to cover a range of strengths for species usually dominant in neutral regions (both depleted and undepleted elements); tracers of ionized gas are also included. The range in line strengths is designed to enable both weak and strong components to be reliably identified and separated. The following table lists for each wavelength setting the lines to be observed, their depletion behavior, and their strength in the 3 blended features noted in IUE spectra of HD 5980 by Fitzpatrick & Savage (1983): Strength in blend at Setting Ion Wavelengths depletion? 0/ 140/ 300 km/s (mA) 1) Zn II (2062) undepleted 70/ 40/ - Cr II (2056,2062) quite depleted 15/ 40/ - 2) Fe II (2586) quite depleted 310/1040/ ? Mn II (2593) moderately depleted 80/ 60/ - 3) Fe II (2260) quite depleted (weak; not reported) 4) Mg II (2795,2803) weakly depleted 390/1600/170 5) Al III (1854) (ionized gas) 90/ 150/ - 6) Si II (1808) moderately depleted 110/ 230/ - In order to adequately detect the individual subcomponents of these blends, we will need detection limits (2-sigma) better than about 3 mA for the weak lines (2260, 2056, 2062) and better than about 5 mA for the other, stronger lines. We will thus need S/N = 35-40 for the weak lines and 25-30 for the stronger lines. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The lines for the desired species all lie in the UV; high resolution and sensitivity are essential. Eighteen short-wavelength IUE spectra exist for HD 5980 - which was one reason for its selection for this study - so that decent S/N should be achievable below about 2100 Angstroms. There are only two relatively poor long-wavelength IUE spectra, however. It is the lack of adequate spectral resolution, however, that has prevented determination of accurate abundances for the various types of regions inferred to be present along these lines of sight, due to the presence of multiple, closely spaced components. Although Wayte (1990) did not observe this star, his 5 km/s Ca II data toward other LMC and SMC stars give an indication of the IS component structure present that cannot be distinguished in the existing IUE data, but which will be distinguished at the 3.5 km/s resolution of ECH-B (see also Fig. 4). The lines to be observed span a range in strength, depletion, and environment, and should provide sufficient information for determining both the detailed component structure of this line of sight and the abundances of the various species in each of those distinct components. The Zn II and Cr II lines near 2060, which give direct, initial estimates for the metallicity and depletion, are being observed in a number of QSOALS. The other species are needed for detailed comparisons with depletion and nucleosynthesis patterns. Knowledge of the detailed component structure should enable us to derive similarly detailed column densities for species from the lower resolution (but adequate S/N) short-wavelength IUE data (e.g., Ni II, S II, Al II). Some useful information on the detailed component structure could be obtained from high-resolution ground-based observations of Na I and Ca II, but those are generally trace ionization states in neutral regions, and also are typically not strong enough to reveal some of the weaker components. For the lines to be observed, the blended features observed in existing IUE spectra range in strength from about 20 to 1600 mA - so that we will need a sensitivity of about 3 mA (2-sigma) for accurate delineation of the weakest individual components in the weakest lines (Zn II and Cr II are critical). The following table uses fluxes from low-resolution IUE spectra, the OTA + GHRS + ECH system sensitivities from the GHRS manual, a factor 2/3 to account for the loss of throughput through the SSA, a factor 0.9 to account for 10% background time, and the effects of the echelle blaze function. HD 5980 is among the brightest SMC stars in the UV, and there are short-wavelength IUE spectra of decent S/N available. wavelength 2060 2590 2260 2800 1855 1808 flux (erg/cm2 s A) 1.3e-12 7.1e-13 8.5e-13 6.3e-13 1.6e-12 1.8e-12 sensitivity 4.5e+11 1.2e+12 8.5e+11 1.2e+12 1.6e+11 1.1e+11 blaze factor 0.70 0.80 0.95 0.95 0.85 0.97 count rate (/min diode) 14.7 24.5 24.7 25.9 7.8 6.9 exp. time (min) 100 60 60 40 60 90 total counts 1474 1472 1483 1034 470 622 S/N 38 38 39 32 22 25 2-sigma eq. width (mA) 2.7 3.3 2.9 4.4 4.2 3.6 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The SMC star to be observed, HD 5980, is an eclipsing binary, and should be observed at maximum brightness to maximize the S/N. The period is 19.266 +/- 0.003 days; the reference date for zero phase is JD = 2443158.771; the primary and secondary minima are at phases 0.00 and 0.36, respectively; each minimum lasts about 2 days. The observations should thus be obtained between phases 0.05 and 0.31 or between phases 0.41 and 0.95. We also plan to obtain a single WFPC2 image of the field prior to the spectroscopic observations, in order to assure a successful acquisition in the GHRS SSA (there may be a close companion). Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. We will use the calibrated science data provided by STScI. Those data will be analyzed using absorption-line profile-fitting software developed and extensively used for the analysis of similar optical and UV data (including GHRS ECH-B and G160M data from Cycle 1). We will determine self-consistent models for the component structures of this line of sight by comparing the structures derived from both weak and strong, and both depleted and undepleted species (Zn II, Cr II, Mn II, Fe II, Mg II), and using Al III to trace ionized regions. Only the strongest components will be detected in the weakest lines; lines of increasing strength will reveal weaker and weaker components. The derived component structure will then be used to model the lower resolution short-wavelength IUE data for other dominant H I region species (Si II, S II, Ni II, Al II, and perhaps O I, N I, and C II). The resulting set of abundance patterns for the different components (regions) will be compared with abundances inferred from SMC stars and nebulae to determine depletions, which will then be compared with depletion patterns observed in the Galaxy. If the depletion patterns observed in the SMC (a lower metallicity, lower dust-to-gas ratio system) are similar to those observed in the Galaxy, then separation of depletion and nucleosynthetic effects in QSOALS abundances should be more secure. ------------------------------------------------------------------------------------ 9. Description of previous HST work. 3993, 2251, 4798, "The Properties of Single Interstellar Clouds" (Cycle 1) PI = Hobbs; with Morton, Spitzer, Welty, York 3472, 4826, "The Properties of Single Interstellar Clouds" (Cycle 2) PI = Hobbs; with Morton, Spitzer, Welty, York 3482, "Variable Infalling Material on Beta Pictoris" (Cycle 2) PI = Vidal-Madjar; with Hobbs and others 4510, "The Evolution of Boron" (Cycle 3) PI = Duncan; with Hobbs and others Blades is PI or co-I on the following: 2553, 3755, "Absorption Cross-Sections of Nearby Galaxies" (1 and 2) 2563, 3853, 4016, 4022, "Supernova Intensive Study" (1 and 2) 2638, "Near-UV Spectrum of 0215+015" (1; ToO) 2644, 3676, "Environments of Starburst Galaxies" (1 and 2) 3525, "ISM of Nearby Galaxies Using SN as Probes" (2; ToO) 3761, "UV Spectroscopy of CO in Seyfert Galaxies" (2) Blades is also a part of several GTO/FOC programs (1235,3179; 1259,3231; 1263; 1265,3747,4075) and the GTO/HRS program 1306 The "Single IS Clouds" program(s) have some common goals, in that they use the echelle to determine detailed component structures for a number of elements for a set of 12 Galactic lines of sight - in order to obtain temperatures, densities, abundances, and sizes of individual IS clouds. We have received almost all of the Cycle 1 data, but none of the Cycle 2 data; reductions of the data in hand are proceding. Some initial results are the discovery of IS Tin, which with the abundances of several other heavy elements has clarified the pattern of depletion in the Galactic ISM; a detailed study of the line of sight to 23 Ori; an examination of collisionally ionized gas at high velocities in several lines of sight; and a study of the relative abundances of lightly depleted elements in individual clouds. (The latter three are in preparation.) "Heavy Elements in the Interstellar Medium: Copper, Germanium, Gallium, Krypton, and Tin", Welty, Hobbs, Morton, Spitzer, & York, poster paper given at The First Symposium on the Infrared Cirrus and Diffuse Interstellar Clouds, Tucson, AZ, April 1993 "The Interstellar Abundances of Tin and Four Other Heavy Elements", Hobbs, Welty, Morton, Spitzer, & York, ApJ, in press, 1993 "Interstellar Mg II and C IV Absorption toward Mrk 205 by NGC 4319: An 'Optically-Thick' QSO Absorption System", Bowen, & Blades, ApJ, 403, L55, 1993 "Imaging of Four Planetary Nebulae in the Magellanic Clouds Using the HST FOC", Blades et al, ApJ, 398, L41, 1992 "Preliminary Analysis of an Ultraviolet HST FOC Image of the Center of M31", King et al, ApJ, 397, L35, 1992 "Discovery of an Optical Synchrotron Jet in 3C 264", Crane et al, ApJ, 402, L37, 1993 Blades has also collaborated on 12 additional FOC papers Page 5 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). We will have access to the necessary computational resources and software at Chicago. ------------------------------------------------------------------------------------ 11. Address Information Name: DANIEL E. WELTY Category: PI Institution: 1710 Address: University of Chicago Astronomy and Astrophysics Center 5640 S. Ellis Ave. City: Chicago State: IL Zip Code: 60637 Country: USA Telephone: (312)702-0599 Telex (or e-mail): welty@oddjob.uchicago.edu ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5608 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC346-E-REF J,701,702, RA = 00H 59M 29.5S +/- 1.3", 2000 V = 182 1 V=11.7 +/- 0.1 D,202 DEC = -72D 10' 20.8" +/- 1 B-V=-0.22 +/- 0.01 1.3" 2 E(B-V)=0.07 +/- 0.01 4 F-CONT(2260) = 8.5 +/- 0.1 E-13 5 F-CONT(2590) = 7.1 +/- 0.1 E-13 6 F-CONT(2800) = 6.3 +/- 0.1 E-13 Comments: FLUX IS FOR HD5980 (BRIGHTEST STAR IN FIELD); This may be a CVZ target ------------------------------------------------------------------------------------------------------------------------------------ 2 HD5980 SK78 B,103, RA = 00H 59M 26.66S +/- 2000 V = 182 1 V=11.7 +/- 0.1 H,508,509,510,506 1.2", 1 B-V=-0.22 +/- 0.01 DEC = -72D 09' 55.3" +/- 2 E(B-V)=0.07 +/- 0.01 1.2" 4 F-CONT(1808) = 1.8 +/- 0.1 E-12 5 F-CONT(1855) = 1.6 +/- 0.1 E-12 6 F-CONT(2060) = 1.3 +/- 0.1 E-12 7 F-CONT(2260) = 8.5 +/- 0.1 E-13 8 F-CONT(2590) = 7.1 +/- 0.1 E-13 9 F-CONT(2800) = 6.3 +/- 0.1 E-13 Comments: ECLIPSING BINARY; PERIOD=19.266+/-0.003 DAYS; PHASE=0 AT JD=2443158.771; MINIMA AT PHASE 0.0 AND 0.36; MINIMA LAST ABOUT 2 DAYS; MEMBER NGC346 IN SMC; This may be a CVZ target ------------------------------------------------------------------------------------------------------------------------------------ 3 SK108 B,103, RA = 01H 03M 25.25S +/- 2000 V = 135 1 V=12.3 +/- 0.1 GSC9138- H,508,509,510 1.0", 1 B-V=-0.23 +/- 0.01 01898 R31 DEC = -72D 06' 43.0" +/- 2 E(B-V)=0.07 +/- 0.02 1.0" 4 F-CONT(1808) = 1.3 +/- 0.1 E-12 5 F-CONT(2060) = 7.9 +/- 0.1 E-13 6 F-CONT(2260) = 5.7 +/- 0.1 E-13 7 F-CONT(2590) = 4.7 +/- 0.1 E-13 8 F-CONT(1250) = 3.0 +/- 0.1 E-12 9 F-CONT(1320) = 2.5 +/- 0.1 E-12 Comments: This may be a CVZ target ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5608 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 101 SK108 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN 1 7.5S 1 1 CYCLE 4 SEARCH-SIZE=5 ONBOARD ACQ FOR LOCATE=YES 102 Comments: STEP-TIME=0.3S; EXPECT 14000 COUNTS IN STEP-TIME ------------------------------------------------------------------------------------------------------------------------------------ 102 SK108 HRS ACQ/ 2.0 MIRROR-N2 1 30.6S 1 1 CYCLE 4 PEAKUP ONBOARD ACQ FOR 103-209 Comments: STEP-TIME=0.3S ------------------------------------------------------------------------------------------------------------------------------------ 103 SK108 HRS IMAGE 2.0 MIRROR-N2 NX=16 1 384.0S 1 1 CYCLE 4 NY=16 Comments: STEP-TIME=1.5S ------------------------------------------------------------------------------------------------------------------------------------ 201 SK108 HRS ACCUM 2.0 ECH-B 1806.7 FP-SPLIT=DSFOUR 5 25.72M 22 4 1 CYCLE 4 STEP-PATT=9 128.6M STEP-TIME=0.2 COMB=FOUR Comments: FIVE SETS OF 4x6.43-MIN FP- SPLIT EXPOSURES; S/N IS PER HALF DIODE; Si II 1808.0126 ------------------------------------------------------------------------------------------------------------------------------------ 204 SK108 HRS ACCUM 2.0 ECH-B 2059.95 FP-SPLIT=DSFOUR 5 21.28M 27 5 1 CYCLE 4 STEP-PATT=7 106.4M STEP-TIME=0.2 COMB=FOUR Comments: FIVE SETS OF 4x5.32-MIN FP- SPLIT EXPOSURES; S/N IS PER HALF DIODE; AIR WAVELENGTHS; Cr II 2055.596, 2061.575; Zn II 2062.005 ------------------------------------------------------------------------------------------------------------------------------------ 205 SK108 HRS ACCUM 2.0 ECH-B 2258.6 FP-SPLIT=DSFOUR 3 21.8M 29 6 1 CYCLE 4 STEP-PATT=7 65.4M STEP-TIME=0.2 COMB=FOUR Comments: THREE SETS OF 4x5.45-MIN FP- SPLIT EXPOSURES; S/N IS PER HALF DIODE; AIR WAVELENGTHS; Fe II 2260.0808 ------------------------------------------------------------------------------------------------------------------------------------ 207 SK108 HRS ACCUM 2.0 ECH-B 2590.8 FP-SPLIT=DSFOUR 3 20.0M 29 7 1 CYCLE 4 STEP-PATT=7 60.0M STEP-TIME=0.2 COMB=FOUR Comments: THREE SETS OF 4x5-MIN FP-SPLIT EXPOSURES; S/N IS PER HALF DIODE; AIR WAVELENGTHS; Fe II 2585.8763; Mn II 2593.724 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5608 [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 208 SK108 HRS ACCUM 2.0 G160M 1252.0 FP-SPLIT=DSFOUR 2 20.0M 44 8 1 CYCLE 4 STEP-PATT=5 40.0M STEP-TIME=0.2 COMB=FOUR Comments: TWO SETS OF 4x5-MIN FP-SPLIT EXPOSURES; S/N IS PER HALF DIODE; S II 1250, 1253, 1259; Mg II 1239, 1240; Si II 1260 ------------------------------------------------------------------------------------------------------------------------------------ 209 SK108 HRS ACCUM 2.0 G160M 1316.0 FP-SPLIT=DSFOUR 2 20.0M 44 9 1 CYCLE 4 STEP-PATT=5 40.0M STEP-TIME=0.2 COMB=FOUR Comments: TWO SETS OF 4x5-MIN FP-SPLIT EXPOSURES; S/N IS PER HALF DIODE; O I 1302; Si II 1304; Ni II 1317 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5608 [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAKUP IMAGE ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=5 LOCATE=YES NX=16 NY=16 FP-SPLIT=DSFOUR STEP-PATT=9 STEP-TIME=0.2 COMB=FOUR STEP-PATT=7 STEP-PATT=5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 7.34 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ABSORPTION LINES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; ONBOARD ACQ FOR 102 ONBOARD ACQ FOR 103-209 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 ECH-B G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC346-E-REF HD5980 SK78 SK108 GSC9138-01898 R31 ------------------------------------------------------------------------------------------------------------------------------------