! File: 4953C.PROP ! Database: PEPDB ! Date: 23-FEB-1994:12:10:46 coverpage: title_1: QSO ABSORPTION SYSTEM SNAP SHOT SURVEY-PART 3 OF 3: CYCLE 3 HIGH sci_cat: QUASARS & AGN sci_subcat: QUASAR ABSORPTION proposal_for: SNAP cont_id: 4396 pi_fname: DAVID pi_mi: R. pi_lname: TYTLER pi_inst: 1560 pi_country: USA hours_pri: 75.00 num_pri: 128 fos: Y funds_amount: 1 funds_length: 24 ! end of coverpage abstract: line_1: A snap shot survey with the HST FOS can readily provide a wealth line_2: of information on four different types of QSO absorption systems, all of which line_3: have strong spectral signatures. Lyman limit systems include a large fraction line_4: of all metal line systems which arise in galaxy halos, plus those line_5: intergalactic clouds with the largest HI column densities. Damped Lyman-alpha line_6: systems probably arise in galactic disks. They are 10 times rarer, but they line_7: have the largest column densities, and are the most interesting of systems. line_8: Strong Associated CIV systems arise in high ionization gas which is physically line_9: connected to the individual QSOs, as do the ejected Broad Absorption Line line_10: systems. We show that we can readily produce samples of each of these four line_11: types of systems which are twice the size of the existing samples. line_12: These systems sample gas in a wide variety of environments: intergalactic line_13: clouds, galactic halos, galactic disks, the neighbourhood of the QSO, and gas line_14: ejected from the QSOs. The follow-up potential is enormous. All of the rarer line_15: types of system will each be studied in detail in future. We will learn about line_16: the origin, redshift evolution, ionization, and the metal abundances of line_17: absorption systems. A quick look at many targets, providing a primary sample line_18: for follow-up investigations, is an optimal way to spend HST time prior to line_19: COSTAR. ! ! end of abstract general_form_proposers: lname: TYTLER fname: DAVID title: PI inst: 1560 - UNIVERSITY OF CALIFORNIA, SAN DIEGO country: USA ! lname: BOWEN fname: DAVID mi: V inst: 3470 - STSCI country: USA esa: Y ! lname: FAN fname: XIAOMING inst: 1560 - UNIVERSITY OF CALIFORNIA, SAN DIEGO country: USA ! lname: LANZETTA fname: KENNETH inst: 1560 - UNIVERSITY OF CALIFORNIA, SAN DIEGO country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: SUBMISSION line_2: The parent program, ID=4396 is being submitted in three parts, with line_3: 30, 34, 32 targets grouped by RA respectively. line_5: The parts differ only in their targets. Otherwise they are identical, line_6: both in the type of observations, and in the accompanying text. line_8: MULTIPLE VISITS TO SOME TARGETS line_9: For some targets we wish to use more than one FOS grating. Since 30 min of line_10: spacecraft time (Tsc) have been used by the time the observation with line_11: the first grating is complete, we treat each grating as a totally separate line_12: observation, each with its own acquisition. An individual target appears line_13: only once in the fixed target list, and all observations of that target are line_14: planced in the same part of the proposal. Ron Downes has approved of this. line_16: PRIORITY line_17: We hasve been informed by Larry Perto and Ralf Dettmar line_18: that priority is not considered at the time of scheduling for line_19: snaps, so we have not assigned indvidual priorities, and we have labled line_20: all observations as PRIORITY=1, even though some observations are of more line_21: interest to us. ! question: 3 section: 2 line_1: SCIENCE GOALS line_2: The mail goal is to discover QSO absorption line systems, especially those at line_3: low redshifts. We are most interested in the following: line_4: 1. Associated CIV systems which have zabs differing by less than 5000km/s from line_5: zem, and rest frame equivalent widths Wr >1A. line_6: 2. Damped systems with Wr>10A line_7: 3. Lyman limit systems with tau>1. line_8: 4. BAL systems at low zem. line_10: Secondary goals include the study of emission lines, QSO continuua, especially line_11: in the far uv. We also expect to detect a few low zabs intervening CIV system line_12: with Wr>1A. line_14: TARGET SELECTION line_15: Targets were taken from the 5th Veron catalogue, or from Hewitt and Burbidge, line_16: plus a few other unpublished QSOs. They were selected to satisfy the above line_17: science goals. WARNING: Some targets were deliberately selected because they line_18: are especially likely to show absorption, or not to show absorption. line_19: They should not be used to determine the frequency of occurence of systems. ! question: 3 section: 3 line_1: REMOVAL OF DUPLICATES line_2: We have attempted to remove all duplicates located in the file line_3: observer/completed_observations AEC.CATALOGUE in February 1993. We have also line_4: removed observations which produced duplications when our TA Ray Lucas ran line_5: a duplicate search on RPSS format target lies. We have checked that the listed line_6: duplication programs are active. The submitted observations should be completely line_7: free of duplicates. line_9: Nolan Walborn informs me that our observations which are assigned high priority line_10: snap shot time will take preference over cycle 3 observations which are line_11: supplemental, but both high and medium priority cycle 3 observations take line_12: preference over our observations,because some of each will definately get done. line_14: There are four possible types of duplication. line_16: 1. Another program is requesting observations with the same grating, with line_17: similar or longer exposure times. line_18: (a) We will not observe if their time is high or medium priority. line_19: (b) We will observe if their time is supplemental. line_21: 2. We request G160L and other proposals request both G130H and G190H, line_22: or they request one of the two gratings and data with the other already line_23: exist. ! question: 3 section: 4 line_1: (a) We will not observe if their time is high or medium priority. line_2: (b) We will observe if their time is supplemental. line_4: 3. We request G160L and other programs are requesting observations with either line_5: G130H or G190H but not both, and data with the other grating does not exist. line_6: (a) We will decide on an object by object basis. Usually we would not want a line_7: G160L if a G130H has been scheduled, but we would want the G160L if there line_8: is no G130H. line_10: 4. We request G130H or G190H and other programs are requesting observations line_11: with G160L. line_12: (a) We will decide on an object by object basis. line_14: 5. We assume that other proposals will always request similar or longer line_15: exposure times. We did not find any exceptions to this. line_17: TARGET POSITIONS line_18: All targets have been GASPED. Expected position errors are about 0.75 arcsec line_19: rms. We list nominal errors of 0.1s and 1.0" for all targets on the line_20: fixed_targets form. All positions are J2000. ! question: 3 section: 5 line_1: TARGET MAGNITUDES line_2: We give V magnitudes for all objects. These are usually from the 5th edition of line_3: the Veron catalogue. line_5: TARGET NAMES line_6: We name each target by its 1950 position: hhmm+ddmm. Such names are essential line_7: for easy identification of objects in published literature. We precess back line_8: from the gasped J2000 positions to get 1950 positions for the names. Note that line_9: these names differ slightly from the HB names which are 1950 hhmm+ddD where line_10: D=truncated decimal degrees = mm/60. e.g. our name 1234+4511 is 1234+451 in HB, line_11: and 1234+4512 is 1234+452 in HB. line_13: SPACECRAFT TIME PER OBSERVATION line_14: A major constraint on this program is that the total spacecraft time (Tsc) per line_15: observation be as short as possible. Duccio Machetto has informed us in writing line_16: that there is no upper limit on Tsc per target, but that we should do line_17: everything possible to minimize times to make it more likely that targets will line_18: be observed. We have taken this constraint very seriously. line_20: We talked at length with Larry Petro, Ralf Dettmar and Melissa McGraph, and line_21: indirectly with Ron Downes about line_22: the likelihood that an observation would be made as a function of the Tsc. line_23: There is no detailed information on this, nor is any available. It was felt ! question: 3 section: 6 line_1: that the likelihood should be similar for times in the range 30-35min (approx), line_2: but will fall fast by 40min (approx). Duccio Machetto said that the likelihood line_3: distribution was roughly exponential. We have spent many hours attempting to line_4: get clarification on the accuracy of this statment and the numerical values, line_5: (e.g. the Tsc at which the likelihood that a target with a random sky position line_6: could be observed is 50% of that for a target with Tsc = 30min.) but without line_7: success. As we increase Tsc, the scientific returns increase rapidly, but the line_8: chance that the observation will be made decreases, so we are forced to line_9: compromise. The exposure submitted times are in most cases less than optimal line_10: from a scientific point perspective, but they are long enough that all line_11: observations will achieve their scientific goals. If necessary we could line_12: reduce most observations by several minutes each. We will do this if the line_13: observations with the longest Tsc are not being done. line_15: We also note that the Tsc that we calculate, using the formulae in line_16: ``Instructions for ...RPSS Resource Estimator V2.1, Nov 1992'' p.3 will not be line_17: the same as the times used when the observations are first entered into the line_18: schedule, which themselves will differ from the times on the final schedule. line_20: As the number of snap opportunities declines, the relative number of line_21: short and long gaps may change, and it is not obvious that the longest line_22: gaps will decline the most. ! question: 3 section: 7 line_1: SPACECAFT TIMES OF THE INDIVIDUAL OBSERVATIONS line_2: We calculate spacecrate times (Tsc) using the formulae in line_3: ``Instructions for ...RPSS Resource Estimator V2.1, Nov 1992'' p.3. line_4: The overhead times for our FOS ACQ/PEAK spatial scans are all line_5: 0.7Ns +4.5 min = 6.6 minutes, since we use only three (Ns=3) dwell points. line_6: The RPSS Resource Estimator makes two mistakes with spatial scans. line_7: It includes the exposure times for only one of the three exposures, and so line_8: underestimates the exposure times by 2x8.4sec for FOS/BL and 2x3.6sec for line_9: FOS/RD. Secondly it gives overhead times of 0.467h for FOS/BL and 0.485h for line_10: FOS/RD, both of which are wrong. line_12: We will monitor the rate at which targets are observed as a function of Tsc. line_13: If we find that those longer time are not being schedued, we will reduce their line_14: times. line_16: GUIDING line_17: All obsevations are to be made with coarse tracking. line_19: INSTRUMENT MODES line_20: All observations are with the FOS/RD (G160L or G130H) or FOS/BL (G190H or line_21: G270H). All observations will be done in ACCUM mode, using the automatic line_22: onboard GIM correction, which is expected to be standard for all observations line_23: by the end of March 1993. ! question: 3 section: 8 line_1: line_2: The phase I proposal included a discussion of only the G130L grating. We have line_3: since calculated that the same science goals are often much better met with line_4: the GxxxH gratings, which we now specify. This has been approved by Nolan line_5: Walborn. line_7: APERTURE line_8: Only one aperture, the 4.3 arcsecond, will be used for all observations, line_9: including all steps of the FOS/ACQ/PEAK. line_11: While high resolution is desirable, it is not of paramount importance here, and line_12: the advantages are out weighted by two problems with the smaller apertures. line_13: (1) It takes significantly longer to center in the smaller apertures. A line_14: ACQ/BINARY, which will center in the 4.3 or 1.0 apeture, has 9.2 min overhead, line_15: plus 0.5-1.0 min exposure, significantly longer than the 6.6 min for our chosen line_16: ACQ/PEAK into the 4.3 aperture. ACQ/PEAK into the 1.0 takes even longer: 30.3 line_17: min overhead alone for a standard centering (3x1 with 4.3, then 2x6 with 1.0, line_18: and 3x3 with 0.5), or 19.5 omitting the 3x3 into the 0.5 aperture, which will line_19: only center to within 0.5. line_20: (2) At 1200A the 1.0 transmits only 51% of the flux admitted by the 4.3. ! question: 3 section: 9 line_1: TARGET ACQUISITIONS line_3: All targets will be acquired with the FOS ACQ/PEAK. We did carefully consider line_4: using blind acquisition in during the preparation of phase II, and concluded line_5: that it was acceptable but not very advantageous. line_6: We will not use FOS/BINARY because it has a longer overhead line_7: than the ACQ/PEAK, which we now discuss. line_9: ACQ/PEAK: Exposure times and choice of mirror line_11: We will use FOS ACQ/PEAK for most acquisitions. All our ACQ/PEAK are done with line_12: the FOS mirror, and we use the detector (RD or BL) which will be used for the line_13: main object exposure. Exposure times are from FOS Instrument Handbook, line_14: Version 2.0, April 1992, page 32, Table 2.1.2. Our targets have 13.86