! File: 2419C.PROP ! Database: PEPDB ! Date: 17-FEB-1994:06:10:20 coverpage: title_1: THE CHRONOLOGY OF THE FORMATION OF THE GALACTIC HALO AND DISK sci_cat: STELLAR POPULATIONS proposal_for: GO pi_title: DR. pi_fname: ROBERT pi_mi: J. pi_lname: ZINN pi_inst: YALE UNIVERSITY pi_country: USA pi_phone: 203-432-3000 keywords_1: GLOBULAR CLUSTERS, POPULATION II hours_pri: 7.39 num_pri: 4 wf_pc: Y funds_amount: 205938 funds_length: 12 funds_date: JUL-91 pi_position: PROFESSOR off_fname: SUZANNE off_lname: POLMAR off_title: DIR.GR&CONTR.ADM off_inst: YALE UNIVERSITY off_addr_1: P.O. BOX 1504A YALE STATION off_city: NEW HAVEN off_state: CT off_zip: 06520 off_country: USA off_phone: 203-432-2460 ! end of coverpage abstract: line_1: Observations with the PC will be used to construct line_2: color-magnitude diagrams that reach more than 2 mag. below line_3: the main-sequence turnoffs in 2 globular clusters. One is line_4: a very metal-poor cluster near the galactic center, and the line_5: other is a metal-rich cluster that belongs to the disk line_6: system. The HST is needed because only it can provide the line_7: high resolution necessary for photometry in the very crowded line_8: fields of these clusters. The ages of the clusters will be line_9: measured from the c-m diagrams using several techniques, and line_10: will be compared with each other and with the ages derived line_11: for other clusters from ground-based observations. The line_12: chronologies of the halo and the disk that result from line_13: these data will constrain theories of galactic evolution, line_14: for they will indicate the time scale of halo formation and line_15: lag-time between halo and disk formation. ! ! end of abstract general_form_proposers: lname: DA COSTA fname: GARY mi: S. inst: YALE UNIVERSITY country: USA ! lname: JANES fname: KENNETH inst: BOSTON UNIVERSITY country: USA ! lname: OLSZEWSKI fname: EDWARD inst: ARIZONA, UNIVERSITY OF country: USA ! lname: CARNEY fname: BRUCE mi: W. inst: NORTH CAROLINA, UNIVERSITY OF country: USA ! lname: CHRISTIAN fname: CAROL inst: UNIVERSITY OF CALIFORNIA AT BERKELEY country: USA ! lname: DEMARQUE fname: PIERRE inst: YALE UNIVERSITY country: USA ! lname: HEASLEY fname: JAMES mi: N. inst: HAWAII, UNIVERSITY OF country: USA ! lname: ZINN fname: ROBERT title: P.I. mi: J. inst: YALE UNIVERSITY country: USA ! lname: SEITZER fname: PATRICK inst: MICHIGAN, UNIVERSIY OF country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: Our program requires accurate photometry of stars in very line_2: crowded regions, which dictates the use of the PC for optimum line_3: image sampling. line_4: The filters of choice are F555W and F785LP, which may be line_5: transformed to the Cousins standard V,I system line_6: for comparisons with previous work on other clusters. Use of line_7: these also minimizes the effect of QEH (quantum efficiency line_8: hysteresis), which is most pronounced near 4000 Angstroms. line_9: To determine the essential absolute calibration, we will conduct line_10: ground-based observations of all of our fields (all four CCDs). line_11: Thus, we will not be only dependent on HST's own absolute calibration line_12: The relative calibration (flat fields) provided by the Institute line_13: will be adequate for our needs. line_14: We require S/N greater than 50 at 2 mag below the expected turnoff line_15: so that we can achieve the required accuracy in these line_16: dense fields. Identical exposures will be taken of a comparison line_17: field near each of these crowded clusters to assess line_18: the amount of field star contamination. line_19: Our exposure times have been computed assuming a preflash level line_20: of 53 electrons. ! question: 4 section: 1 line_1: The HST is needed to resolve and accurately photometer stars at line_2: faint magnitudes in the very crowded fields of the inner halo and line_3: disk clusters. Several of our team members have used some of line_4: the best ground-based instruments (i.e., 4m telescopes and CCD line_5: detectors) to construct color-magnitude diagrams for clusters line_6: in similar fields. The experiences of these observers indicate that line_7: it is impossible, even when operating under ideal conditions, to do line_8: precise photometry at the levels required for accurate measurements line_9: of the relative and absolute ages of the clusters in our program. line_10: For example, Da Costa and Sarajedini (in prep) line_11: observed the inner halo cluster, N6541, with a CCD detector under line_12: good conditions. Their color magnitude diagram failed, however, line_13: to provide any information on the cluster's age, for at the radius line_14: where image crowding allowed stars fainter than the turnoff to be line_15: measured precisely, the c-m diagram was completely dominated by line_16: stars of the rich galactic field background. Measurements nearer line_17: the cluster center are required, and they can only be obtained with line_18: the greater resolution of the HST. For each of the line_19: clusters, we will also take identical exposures of a nearby line_20: comparison field, which will provide an estimate of line_21: the contamination in the cluster field and the means to remove line_22: it statistically. ! question: 5 section: 1 line_1: In our calculations of exposure time, we have adopted the mean line_2: efficiency of the of the 4 PC chips that was given in the latest line_3: WF/PC manual (May 89), a preflash of 53 electrons (Lauer 1989, PASP line_4: 101, 445, and the spectral energy distribution of a G0 star. line_5: We then multiplied these times by factors of 5 and 10, line_6: respectively, for F555W and F785LP to account for the image line_7: degradation of the HST and the lower than expected red response. line_8: The exposure times were calculated to yield S/N>50 at line_9: 2 mag below the main-sequence turnoff, whose magnitude was line_10: estimated by adding 3.5 to the observed V mag. of the horizontal line_11: branch. For each cluster, we will take identical exposures of line_12: a nearby comparison field, which will provide an estimate of the line_13: field star contamination in the cluster field and the means to line_14: remove it statistically. In addition, we will determine the line_15: the zero-points of the HST observations from ground-based line_16: photometry in these comparisons fields. Our target list is line_17: setup so that the comparison field will be observed immediately line_18: before the cluster field. Any residual images generated by previous line_19: observations or by the ones of the comparison field will be line_20: removed by purging after the last exposure of the comparison line_21: field. ! question: 7 section: 1 line_1: The HST observations will be reduced by several subgroups of our line_2: team who already have considerable experience with reducing CCD line_3: photometry of globular clusters (Da Costa and Zinn at Yale; line_4: Seitzer at Michigan; Heasley at Hawaii, Christian at Berkeley, line_5: Janes at B.U.; Carney at UNC; Olsewski at Arizona). The photometry line_6: will be reduced using point-spread function fitting techniques line_7: that take into account the complexities of HST images and their line_8: variations across the field of view. We are in the process of line_9: obtaining ground-based V and I and F555W and F785LP photometry in line_10: each of our clusters and their comparison fields so that we will line_11: (i) not have to rely on the HST calibrations for the zero-points of line_12: the observations and (ii) have precise photometry of the horizontal line_13: branch (HB) stars in each cluster. line_14: Our clusters dating techniques will relie heavily on line_15: differential comparisons between the target clusters and other line_16: clusters of the same metal abundance that can be adequately observed line_17: from the ground. We will also measure the relative ages of line_18: clusters of different metal abundances (our targets and clusters line_19: with ground-based observations), which, for example, will line_20: indicate whether the disk began to form at the same time as the line_21: halo. We must first know the relative distances of the clusters line_22: which we will determine from the latest results for the line_23: variation in HB luminosity with metal abundance and from fitting ! question: 7 section: 2 line_1: the ms to subdwarfs of the same abundance and known parallax. line_2: Several members of our team are working on the luminosity of the line_3: HB (Carney, Demarque, Janes, Zinn), and we are in close contact line_4: with W. van Altena who has GTO time with the HST to measure line_5: to measure the parallaxes of subdwarfs. Since the absolute ages line_6: of the clusters provide extremely important information (e.g. line_7: the duration of halo formation and the minimum age of the line_8: universe), we will spend considerable effort analyzing and line_9: reducing the uncertainties in their distances and chemical line_10: compositions and in the theoretical isochrones used in the age line_11: determinations. The metal abundances of our targets are being line_12: remeasured from new low-dispersion spectroscopic and photometric line_13: observations (Da Costa and Zinn) and where possible from new line_14: high dispersion spectroscopy of red giants (Carney). More data line_15: on the O/Fe ratio and its variation with [Fe/H] and possibly line_16: galactocentric distance is being obtained (Carney) from line_17: measurements of a sample of subdwarfs, which includes the ones line_18: that will be used in the ms fitting to derive distances and line_19: also others whose orbits take them far from the solar line_20: neighborhood. For the theoretical calculations and advice on line_21: their use, we will draw on the wide experience and expertise line_22: in stellar physics at Yale's Center for Solar and Space Research line_23: (team member Demarque is director), which conducts research, ! question: 7 section: 3 line_1: under NASA contract, on stellar evolution, pulsation, rotation, line_2: convection, and MHD. Members of CSSR have recently completed line_3: programs for calculating opacities for any particular chemical line_4: composition, the evolution of stars with rotating interiors, line_5: and for converting isochrones and luminosity functions to any line_6: particular photometric system. In summary, we will approach line_7: the dating problem in a series of steps that are designed to line_8: yield the maximum amount of information while introducing as line_9: little uncertainty as possible. We already have considerable line_10: experience with these methods, the input data for the clusters line_11: and the theoretical calculations of isochrones, and we are line_12: currently investigating each of these areas so that the best line_13: data and theory will be used. ! question: 8 section: 1 line_1: We request that sheduling take care to avoid that residual line_2: images from previous PC observations do not contaminate our line_3: frames. Our fields are chosen to avoid, as much as possible, line_4: the generation of residual images by our exposures. ! question: 9 section: 1 line_1: N/A ! question: 10 section: 1 line_1: The computational, image display, and software resources line_2: available at Yale, Boston University, North Carolina, Hawaii, line_3: Arizona, and Michigan will be used for the data reduction and line_4: analysis. The resources of Yale's Center for Solar and Space line_5: Research will be used for the computation of new stellar line_6: evolutionary tracks and isochrones. The ground-based support line_7: observations that are necessary for this project will be made line_8: with the telescopes of Yale, Arizona, and Hawaii. line_9: Graduate students will take part in the data line_10: reduction and the theoretical computations. ! !end of general form text general_form_address: lname: ZINN fname: ROBERT mi: J. title: DR. category: PI inst: YALE UNIVERSITY addr_1: DEPT. OF ASTRONOMY addr_2: 260 WHITNEY AVE. addr_3: P.O. BOX 6666 city: NEW HAVEN state: CT zip: 06511 country: USA ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: NGC6293-COMPARISON-FIELD descr_1: STAR CLUSTER; GLOBULAR CLUSTER; BLANK SKY descr_2: STELLAR POPULATION pos_1: PLATE-ID = 067P, pos_2: RA = 17H 09M 11.198S +/- 2", pos_3: DEC = -26D 34' 10.65" +/- 2" equinox: 2000.0 fluxnum_1: 1 fluxval_1: V = 21.8 , TYPE = G0 ! targnum: 2 name_1: NGC6293 descr_1: STAR CLUSTER; GLOBULAR CLUSTER descr_2: STELLAR POPULATION pos_1: PLATE-ID = 067P, pos_2: RA = 17H 10M 10.724S +/- 2", pos_3: DEC = -26D 35' 24.21" +/- 2" equinox: 2000.0 fluxnum_1: 1 fluxval_1: V = 21.8 , TYPE = G0 ! targnum: 3 name_1: NGC6352-COMPARISON-FIELD descr_1: STAR CLUSTER; GLOBULAR CLUSTER; BLANK SKY descr_2: STELLAR POPULATION pos_1: PLATE-ID = 0689, pos_2: RA = 17H 24M 26.213S +/- 2", pos_3: DEC = -48D 21' 53.39" +/- 2" equinox: 2000.0 fluxnum_1: 1 fluxval_1: V = 20.9 , TYPE = G0 ! targnum: 4 name_1: NGC6352 descr_1: STAR CLUSTER; GLOBULAR CLUSTER descr_2: STELLAR POPULATION pos_1: PLATE-ID = 0689, pos_2: RA = 17H 25M 28.270S +/- 2", pos_3: DEC = -48D 25' 37.55" +/- 2" equinox: 2000.0 fluxnum_1: 1 fluxval_1: V = 20.9 , TYPE = G0 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 sequence_1: DEFINE VSQ targname: # config: PC opmode: IMAGE aperture: ALL sp_element: F555W num_exp: # time_per_exp: 10S s_to_n: # fluxnum_1: 1 priority: 1 param_1: PURGE=NO, param_2: CR-SPLIT=NO, param_3: SUM=1X1, param_4: READ=YES, param_5: PRE-FLASH=YES, param_6: CLOCKS=YES req_1: CYCLE 1; ! linenum: 2.000 sequence_1: DEFINE ISN targname: # config: PC opmode: IMAGE aperture: ALL sp_element: F785LP num_exp: # time_per_exp: 10S s_to_n: # fluxnum_1: 1 priority: 1 param_1: CR-SPLIT=NO, param_2: SUM=1X1, param_3: READ=YES, param_4: PRE-FLASH=YES, param_5: CLOCKS=YES, param_6: PURGE=NO req_1: CYCLE 1; ! linenum: 3.000 sequence_1: USE VSQ targname: NGC6293-COMPARISON-FIELD num_exp: 3 time_per_exp: X60 s_to_n: 36.5 req_2: SEQ 3-8 NO GAP; req_3: POS TARG 0.0,0.0; ! linenum: 4.000 sequence_1: USE ISN targname: NGC6293-COMPARISON-FIELD num_exp: 3 time_per_exp: X190 s_to_n: 35.6 req_3: POS TARG 0.0,0.0; ! linenum: 5.000 sequence_1: USE VSQ targname: NGC6293 num_exp: 2 time_per_exp: X60 s_to_n: 36.5 req_3: POS TARG 0.0,0.0; ! linenum: 6.000 sequence_1: USE ISN targname: NGC6293 num_exp: 2 time_per_exp: X190 s_to_n: 35.6 req_3: POS TARG 0.0,0.0; ! linenum: 7.000 sequence_1: USE VSQ targname: NGC6293 num_exp: 2 time_per_exp: X60 s_to_n: 36.5 req_3: POS TARG -1.5,-1.5; ! linenum: 8.000 sequence_1: USE ISN targname: NGC6293 num_exp: 2 time_per_exp: X190 s_to_n: 35.6 req_3: POS TARG -1.5,-1.5; ! linenum: 9.000 sequence_1: USE VSQ targname: NGC6352-COMPARISON-FIELD num_exp: 3 time_per_exp: X30 s_to_n: 40.4 req_2: SEQ 9-14 NO GAP; req_3: POS TARG 0.0,0.0; ! linenum: 10.000 sequence_1: USE ISN targname: NGC6352-COMPARISON-FIELD num_exp: 3 time_per_exp: X100 s_to_n: 35.7 req_3: POS TARG 0.0,0.0; ! linenum: 11.000 sequence_1: USE VSQ targname: NGC6352 num_exp: 2 time_per_exp: X30 s_to_n: 40.4 req_3: POS TARG 0.0,0.0; ! linenum: 12.000 sequence_1: USE ISN targname: NGC6352 num_exp: 2 time_per_exp: X100 s_to_n: 35.7 req_3: POS TARG 0.0,0.0; ! linenum: 13.000 sequence_1: USE VSQ targname: NGC6352 num_exp: 2 time_per_exp: X30 s_to_n: 40.4 req_3: POS TARG -1.5,-1.5; ! linenum: 14.000 sequence_1: USE ISN targname: NGC6352 num_exp: 2 time_per_exp: X100 s_to_n: 35.7 req_3: POS TARG -1.5,-1.5; ! ! end of exposure logsheet ! No scan data records found