Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3051c Report Date: 09-May-96:17:52 Version: ********** Check-in Date: ********** 1.Proposal Title: HELIUM IN THE EARLY UNIVERSE ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID QUASARS & AGN SAT/FOS Sub Category QUASAR EMISSION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone E. margaret Burbidge UC, SAN DIEGO USA (619) 534-4477 ------------------------------------------------------------------------------------ 7. Abstract We will use the FOS to measure the strength of the He I lambda 584 line in the UV in a QSO which has a good probability of having light at that wavelength. We will test the ability of the FOS to detect weak emission lines against a background of weak absorption lines in a faint object with the degraded performance due to the slit losses, decreased resolution, possible increased scattered light and greater than expected particle-induced background. From this line we will determine the relative abundance of Helium in the early universe. ------------------------------------------------------------------------------------ 8. Scientific Key Words: UV SPECTROSCOPY, QUASAR, EMISSION LINE PROFILE, ABUNDANCE EVOLUTION, ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 1.71 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 3051c PI: E. margaret Burbidge Proposal Title: HELIUM IN THE EARLY UNIVERSE ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Edward Beaver UC, SAN DIEGO USA E. Margaret Burbidge UC, SAN DIEGO USA Bruce Margon WASHINGTON, UNIVERSITY OF USA J. Roger P. Angel ARIZONA, UNIVERSITY OF USA Frank Bartko MARTIN MARIETTA CORPORATION USA Arthur F. Davidsen JOHNS HOPKINS UNIVERSITY USA Richard J. Harms APPLIED RESEARCH CORPORATION USA Ralph Bohlin SPACE TELESCOPE SCIENCE USA INSTITUTE Holland C. Ford SPACE TELESCOPE SCIENCE USA INSTITUTE Page 3 ------------------------------------------------------------------------------------ 2. Scientific Justification. Observations of 0150-202 will characterize the ability of the FOS to measure weak emission lines in faint objects as well as making a determination of the cosmic abundance of Helium at a look back time of more than 75% of the age of the universe. We will make this determination by comparing the strength of the He I lambda 584 recombination line with the strengths of other emission lines we will measure from the ground. This UV emission line has never been measured, and measurements of this line and He II lambda 304 are important HST goals. Additionally, we may be able to set constraints on the ionization level of the intergalactic medium of the early universe, a major indicator of the constituent parts of the early universe. Determining the initial cosmic Helium abundance can in principle refine our estimate of the baryon number of the universe. 0150 is the best object (see below) available to us within the proposed restrictions in right ascension which will enable us to perform this test. The FOS ability to measure emission lines differs from predicted in several ways. First, much less light gets through the aperture. Second, any (unresolved) absorption, although decreased in depth is broadened by a significant amount. Finally, all measurements of faint objects are increased in difficulty because the FOS background is approximately .01 c/s/d, considerably greater than predicted based on ground based calibrations. This is approximately 15% of the count rated expected for the object itself. The signal-to-noise per diode for a 6000s exposure will be approximately 20, assuming that the 1.0 arc sec diameter FOS aperture transmits 34.3% of the incident light. We have also included a short exposure with the 4.3 arc second aperture to obtain an accurate flux for the scientific analysis. This will also be useful for testing the predicted light loss through the 1.0 arc second aperture. Because of these problems, we do not feel that measurement of weak emission lines in a low-redshift, bright QSO is an adequate test of FOS performance for these difficult measurements. The bright objects are unaffected by background and will not have any absorption lines confusing the emission lines, whereas He I and He II will always occur in the Lyman alpha forest of absorption lines. Several brighter objects are available in our GTO program, but these are at 12 hours right ascension, and thus unavailable for the SAT program. Of those which are available, the combination of brightness, redshift (lower redshift objects will have much lower FOS efficiency at He I) and lack of obvious features indicating a cutoff in the UV spectrum caused by a lower redshift Lyman limit absorption make this the best candidate known to us for this test. This observation will also test the ability of the FOS to detect UV absorption in an object with relatively low signal-to-noise. With this test, we will first determine whether the FOS can detect a weak emission line, superposed on absorption lines, in the face of degraded spectral resolution, in an object, which, while brighter than many proposed targets, is still faint enough for a meaningful test. Second we can test deconvolution techniques for the emission and absorption on data of relatively low signal-to- noise. Third, we can split the observation into pieces to test the accuracy of the (highly orbital position dependant) particle induced background subtraction. It may also allow us to test for other effects, such as an increase in sky background near the limb of the earth. Because the particle induced background is significant for this object, this will be a critical test of the ability of the FOS to observe faint objects. ------------------------------------------------------------------------------------ 3. Description of proposed observations. This proposal contains 1 object which will be observed with G160L and the red detector of the FOS. S/N will be 20 per diode allowing us to detect a weak emission line. A very short exposure will be used to measure the absolute flux. All exposures are cycle 0. Page 4 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The main point of this program is to determine the effects of the actual HST and FOS performance on the abilities of the FOS to carry out some of its unique observations. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The signal-to-noise calculation assumed transmission through the 1.0 arc second diameter of 34.3% and a total HST+FOS efficiency of 2.5% with G160L at 1838 Angstroms. The particle-induced background is assumed to be 0.01 c/s/d. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. The OV prerequisite programs for all observations are: Prop ID 2188, 2189, 1441, 1442, and 1443 The SV prerequisite program for all observations is: Prop ID 2195 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. To characterize the performance of the HST + FOS, we will measure the flux in a weak emission line, superposed on absorption, in the total observation as well as in shorter segments of the total integration. We will compare the flux levels in portions to check the particle-induced background subtraction. We will do spectral deconvolution to determine the effect of the decreased spectral resolution of the FOS on our observations. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. We will schedule ground-based observations at Lick Observatory as close to the HST observations in time as possible in order to check FOS fluxes and obtain other data for science analysis. ------------------------------------------------------------------------------------ 11. Address Information Name: E. MARGARET BURBIDGE Category: PI Institution: UC, SAN DIEGO Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ Name: ROSS D. COHEN Category: CON Institution: UNIVERSITY OF CALIFORNIA, SAN DIE Address: CASS DEPT., C-011 City: LA JOLLA State: CA Zip Code: 92093 Country: USA Telephone: (619) 534-2664 Telex (or e-mail): FAX: (619) 534-6316 ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 3051c [ 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 UM675 0150- QUASAR RA = 01H 52M 27.291S +/- 2000 Z=2.15 1 V=17.1 +/- 0.5 202 1.0", DEC = -20D 01' 07.29" +/- 1.0", PLATE-ID = 05XZ ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3051c [ 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 UM675 FOS/RD ACQ/ 4.3 MIRROR BRIGHT=700000 1 22S 1 1 ONBOARD ACQ FOR 2- BINARY 4 CYCLE 0 / 1-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 ^ ^ ACQ ^ ^ 1 22S 1 ^ ------------------------------------------------------------------------------------------------------------------------------------ 3 ^ ^ ACCUM 4.3 G160L 1600 STEP- 1 100S 4 ^ PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 4 ^ ^ ACCUM 1.0 G160L 1600 STEP- 1 6000S 20 ^ PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3051c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ^ ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT STEP-PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Proposal for SAT/FOS ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 1.71 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category QUASARS & AGN ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category QUASAR EMISSION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-4; CYCLE 0 / 1-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR ^ G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names UM675 0150-202 ------------------------------------------------------------------------------------------------------------------------------------