Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5389 Report Date: 18-Jul-95:17:16 Version: ********** Check-in Date: ********** 1.Proposal Title: THE NATURE OF INTERSTELLAR CLOUD ENVELOPES -- PHYSICAL CONDITIONS AND STRUCTURE ------------------------------------------------------------------------------------ 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 David L. Lambert UNIVERSITY OF TEXAS USA 512-471-7438 ------------------------------------------------------------------------------------ 7. Abstract GHRS/G160M spectra of interstellar CO bands and atomic lines toward two stars will be analyzed to give the column density ratio 12C16O/ 13C16O and excitation temperatures for CO and C I. The ratio of column densities will not, in general, equal the 'true' 12C/13C ratio provided by optical spectroscopy of the CH+ molecular ion. The fractionation of CO is driven in opposite directions by isotopic charge exchange and selective photodissociation. The ratio 12C16O/ 13C16O for a known 12C/13C provides novel information on the physical conditions in a diffuse cloud. These conditions are also obtained from analysis of excitation. Since different probes sample different regions of a cloud, the structure of the cloud is discernible. The proposed experiment has been applied successfully by us to Zeta Oph's diffuse clouds. Now, we propose to use fractionation and excitation as new tools to probe other portions of the Rho Oph Molecular Cloud. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 9.00 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5389 PI: David L. Lambert Proposal Title: THE NATURE OF INTERSTELLAR CLOUD ENVELOPES -- PHYSICAL CONDITIONS AND STRUCTURE ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ David L. Lambert 3550 USA Yaron Sheffer 3550 USA Steven R. Federman 3580 USA Ronald L. Gilliland 3470 USA Jason A. Cardelli 3884 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. Three regions will be observed with the GHRS, grating G160M and the SSA: 1442- 1488A, 1385-1430A, and 1252-1293A. The 1465A observation provides the CO A-X 2-0 and 3-0 bands which are the optimum choice for the 13C16O (and 12C18O and 12C17O) bands. The 1270A observation covering the 10-0 and 11-0 bands provides weak 12C16O bands. It is the ratio of the 13C16O bands from 1465A spectra to the 12C16O bands from the 1270A spectra that provides the 12C16O/13C16O ratio. Furthermore, the 1405A observation includes the 4-0 and 5-0 bands, from which an accurate curve of growth for 13C16O is obtainable. Such a curve of growth allowed us to discern the presence of 12C18O toward Zeta Oph. The 1270A observations also contain a series of C I lines of varying strengths, including those from each level of the ground state, and the 1405 and 1465A spectra have several lines of S I and Ni II. A comparison of the column density from the weakest (unsaturated) lines with the estimates from moderately saturated lines yields a reliable estimate for the Doppler width. Exposure times have been estimated to give a detection limit of 0.3mA for the stars. The chosen limit is roughly 5 or more times smaller the predicted strength of a molecular band and allows detection of the weakest atomic features. As our GTO observations demonstrate, G160M provides adequate resolution if the S/N is sufficiently high. Attaining a S/N of order 500 requires that the observations be structured in such a way as to allow a robust, simultaneous solution for the stellar spectrum and any detector-dependent efficiency variations with wavelength as arise from photocathode granularity. The standard GHRS observing option, FP-SPLIT, allows S/N of a few hundred to be obtained, but can generate problems if the stellar spectrum happens to contain any spectral features with separations comparable to the carrousel stepping (about 5 diodes for FP-SPLIT=STD). To allow a robust separation of the observed spectra into the stellar and detector components, it is better to generate a super-FP-SPLIT in which FP-SPLIT sequences are obtained with wavelength settings incommensurate with structure in the stellar and detector spectra. A simultaneous solution (e.g., with a generalization of the technique given by Bagnuolo and Gies, 1991, ApJ, 376, 266) for the stellar and detector flat-field spectra can yield a S/N very close to that allowed by Poisson statistics (a S/N of 900 out of a Poisson limit of 950 has been demonstrated near 1465A with G160M). Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. In principle, CO is observable from the ground through either the infrared vibration-rotation transitions or the mm/far-ir pure rotation transitions. For clouds like those in front of Zeta Oph, the fundamental V-R transitions at 5 microns should be detectable with the new generation of cryogenic echelle spectrometers such as the one at the IRTF. But 13C16O will be too weak to be detected. The mm also offers little hope of detection of fractionation from the ground; for example, Wilson et al. (1992, A&A, 262, 248) discuss a heroic search for the 13C16O J=1-0 line at 2.7 mm but were able to set the modest limit of 12C16O/13C16O > 60, a factor of ~ 2.5 below our HST measurement of 167. In addition, mm observations sample gas within a large beam and the detected clouds may not correspond to the clouds probed by absorption line spectroscopy. IUE certainly offers access to the A-X bands and the atomic transitions that we shall use, but it does not provide an adequate S/N. With the exception of the recent work on 20 Aql (Hanson et al. 1992, ApJ, 392, 571), no believable 12C16O/13C16O ratios have been provided from IUE. In short, fractionation of CO which can be determined only from HST spectroscopy provides information on physical conditions in a diffuse cloud that cannot be provided from observations of other molecules by ground-based telescopes. Furthermore, the atomic data can only be obtained through ultraviolet observations. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. None. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None. ------------------------------------------------------------------------------------ 9. Description of previous HST work. In anticipation of GTO1065, SV data of the CO A-X 5-0 and 6-0 bands were analyzed in conjunction with Wannier et al.'s (1982, ApJ, 254, 100) measurements of weak 12C16O bands. This analysis gave 12C16O/ 13C16O = 150. GTO observations with G160M yielded a refined value of 167. New results include an estimate of the 12C18O column density and information on excitation temperatures, as well as the first detection of interstellar Co+ and As+. These results are in press in ApJ. GTO1066 has provided echelle spectra of the C2 Mulliken bands and some data on the C2 F-X band with G160M. These data are now being analyzed. Apart from Zeta Oph, the targets for this program are stars low in CO and hence do not appear as targets here. The GHRS SAO and SV echelle data have provided accurate atomic and molecular abundances for the gas toward Xi Per and Zeta Oph. The atomic data reveal the presence of multiple component structure and allow for the quantitative analysis of the effects of differential depletion. The SV echelle data of Zeta Oph have provided the basis for and viability of the science proposed here. Other proposals/programs of the PI and Co-Is are not related to this one. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Adequate computing facilities are available at all participating institutions. We anticipate requesting time at McDonald Observatory to complete the complementary ground-based spectroscopy of the program stars. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: David L. Lambert Category: PI Institution: 3550 Address: Department of Astronomy University of Texas City: Austin State: TX Zip Code: 78712 Country: USA Telephone: 512-471-7438 Telex (or e-mail): DLL@ASTRO.AS.UTEXAS.EDU ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5389 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 HD147933 RHO A; 110 RA = 16H 25M 35.15S +/- 2000 V=-15.0 COMP 1 V=5.02,TYPE=B2IV -OPH-A 0.01S, 1 B-V=+0.24 GSC6794/0549 DEC = -23D 26' 49.8" +/- 2 E(B-V)=0.47 0.15" 3 F-CONT(1270)=4.6+/-0.5E-10 4 F-CONT(1405)=5.4+/-0.5E-10 5 F-CONT(1465)=5.4+/-0.5E-10 Comments: THIS IS THE BRIGHTER MEMBER OF A DOUBLE STAR. SEPARATION IS 3.2" AND BRIGHTNESS DIFFERENCE IS 0.9 MAG. UV FLUXES FROM TD-1 AND GAMMA-PEG (FROM OAO-2). POS. FROM GSC/HIPPARCHOS DATABASE STAR IS SAO NO. 184382. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD148184 CHI A; 110 RA = 16H 27M 1.44S +/- 2000 V=-15.0 1 V=4.42,TYPE=B2IV -OPH 0.01S, 1 B-V=+0.28 GSC6207/1170 DEC = -18D 27' 22.6" +/- 2 E(B-V)=0.53 0.17" 3 F-CONT(1270)=5.2+/-0.7E-10 4 F-CONT(1405)=4.8+/-0.4E-10 5 F-CONT(1465)=4.7+/-0.3E-10 Comments: UV FLUXES FROM OAO-2. POSITION FROM GSC HIPPARCHOS STAR IS SAO NO. 159918. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5389 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE # HRS ACCUM 0.25 # 1.0 FP-SPLIT=STD # 108.8S 100 # STOBSG STEP-PATT=5 20M ------------------------------------------------------------------------------------------------------------------------------------ 2 HD147933 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=5 1 5.0S 10 1 1 ONBOARD ACQ FOR BRIGHT=RETURN 2.1 LOCATE=YES CYCLE 4 / 2.0-9.2 Comments: CENTER IN LSA EXPECT ABOUT 3000 CTS/0.2S STEP ------------------------------------------------------------------------------------------------------------------------------------ 2.1 HD147933 HRS ACQ/ 0.25 MIRROR-A2 SEARCH-SIZE=5 1 5.0S 10 1 1 ONBOARD ACQ FOR PEAKUP 5.1-9.2 ------------------------------------------------------------------------------------------------------------------------------------ 5.1 USE HD147933 G160M X1464.8 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 5.3 USE HD147933 G160M X1466.8 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 5.4 USE HD147933 G160M X1461.0 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 5.5 USE HD147933 G160M X1471.0 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 7 USE HD147933 G160M X1403.1 3 X5 4 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 7.1 USE HD147933 G160M X1405.0 3 X5 4 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 7.2 USE HD147933 G160M X1407.9 3 X5 4 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 9 USE HD147933 G160M X1271.1 3 X5 3 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 9.1 USE HD147933 G160M X1273.0 3 X5 3 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 9.2 USE HD147933 G160M X1275.9 3 X5 3 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 12 HD148184 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=5 1 5.0S 10 1 1 ONBOARD ACQ FOR BRIGHT=RETURN 12.1 LOCATE=YES CYCLE 4 / 12.0- 19.2 Comments: CENTER IN LSA EXPECT ABOUT 3000 CTS/0.2S STEP ------------------------------------------------------------------------------------------------------------------------------------ 12.1 HD148184 HRS ACQ/ 0.25 MIRROR-A2 SEARCH-SIZE=5 1 5.0S 10 1 1 ONBOARD ACQ FOR PEAKUP 15.1-19.2 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5389 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 15.1 USE HD148184 G160M X1464.8 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 15.3 USE HD148184 G160M X1466.8 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 15.4 USE HD148184 G160M X1461.0 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 15.5 USE HD148184 G160M X1471.0 3 X5 5 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 17 USE HD148184 G160M X1403.1 3 X5 4 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 17.1 USE HD148184 G160M X1405.0 3 X5 4 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 17.2 USE HD148184 G160M X1407.9 3 X5 4 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 19 USE HD148184 G160M X1271.1 3 X5 3 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 19.1 USE HD148184 G160M X1273.0 3 X4 3 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ 19.2 USE HD148184 G160M X1275.9 3 X5 3 1 STOBSG ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5389 [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ACQ ACQ/PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FP-SPLIT=STD STEP-PATT=5 SEARCH-SIZE=5 BRIGHT=RETURN LOCATE=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 9.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ABSORPTION LINES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2.1; CYCLE 4 / 2.0-9.2 ONBOARD ACQ FOR 5.1-9.2; ONBOARD ACQ FOR 12.1; CYCLE 4 / 12.0-19.2 ONBOARD ACQ FOR 15.1-19.2; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements # MIRROR-A2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD147933 RHO-OPH-A GSC6794/0549 HD148184 CHI-OPH GSC6207/1170 ------------------------------------------------------------------------------------------------------------------------------------