! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6604,v 8.1 1996/03/20 15:49:42 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6604,v 8.1 1996/03/20 15:49:42 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Landis ! Phone: 410-338-4560 , E-mail: landis@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0543.walker.prop ! Date generated: Fri Dec 22 15:58:40 EST 1995 ! Proposal_Information ! Section 4 Title: Photometry of the Oldest Field Populations in the Magellanic Clouds Proposal_Category: GO Scientific_Category: STELLAR POPULATIONS Cycle: 6 Investigators PI_name: Alistair Walker PI_Institution: Cerro Tololo Inter-American Observatory CoI_Name: Paul Hodge CoI_Institution: Department of Astronomy, University of Washington Contact: ! Y or N (designate at most one contact) CoI_Name: Mario Mateo CoI_Institution: Department of Astronomy, University of Michigan Contact: ! Y or N (designate at most one contact) CoI_Name: Edward Olszewski CoI_Institution: Steward Observatory, University of Arizona Contact: ! Y or N (designate at most one contact) CoI_Name: Robert Schommer CoI_Institution: Cerro Tololo Inter-American Observatory Contact: ! Y or N (designate at most one contact) CoI_Name: Nicholas Suntzeff CoI_Institution: Cerro Tololo Inter-American Observatory Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to obtain deep V (F555W) and I (F814W) images for one field in the Large Magellanic Cloud (LMC), one field in the Small Magellanic Cloud (SMC), and for the old SMC cluster NGC 121. These observations will allow us to measure ages and population densities of the oldest field stars (t > 5Gyr) in the Magellanic Clouds (MC), and place into context the ages of formation of the Galaxy and the two MC's. In our own Galaxy, the oldest nearby stars appear to belong to two subsystems: an initial population represented by a flattened spheroid with a small amount of rotation, and a non-rotating spherical population which may be a few Gyr younger than the first population. A third old population, the ``metal-weak old disk'', also may exist. In the outer regions of the MC's where we would expect to find populations analogous to the Galactic Population II, we see something much different: a field population that is dominated by stars with Fe/H~ -0.6 and t~ 8Gyr, with small admixtures of a very old metal-poor population analogous to the Galactic halo and a younger (t ~ 5Gyr) system (in the LMC). We propose to measure the ages of the oldest MC field populations and the oldest SMC cluster to compare with the ages of the oldest components of our Galactic halo and disk. The observations will be interpreted using synthetic color-magnitude diagrams and luminosity functions to develop a model for the star formation history in both the MC's over the first 10 Gyr. Questions ! Free format text (please update) Observing_Description: We propose to observe one LMC field (requires four HST pointings) and two SMC fields (one requires four pointings, the other, NGC 121, requires a single pointing with the cluster centered on the PC) with the HST WFPC2 instrument and F555W and F814W (VI equivalent) filters. We will observe each of the ``four-pointing'' fields as: 4*500s V + 4*600s I. (LMC, in some cases 3*600 + 1*500 I), 4*600s V and I (SMC). This requires two orbits per pointing, thus 16 orbits total. For the single NGC 121 field we will observe as: 4*400s + 6*40s (V) and 4*500s + 4*20s (I). This also requires 2 orbits. The grand total number of orbits requested is therefore 18. This work will complement our cluster and field star photometry in the LMC bar obtained with HST (N. Suntzeff, PI, Cycle 5 proposal 5916). We have calculated the estimated exposure times as follows: The average magnitude for the LMC horizontal branch is V ~ 19.3 and for the SMC V ~ 19.7 (Walker 1991, IAU Symposium 108). The difference in magnitude between the horizontal branch and the main-sequence turnoff for a typical Galactic globular cluster is Delta V(TO -HB) = 3.55 +/- 0.09 (Buonanno et al 1989, A&A, 216, 80). We estimate that we must reach 2.0 magnitudes below the turnoff with <0.1 accuracy in (V-I) to measure a reliable age and to allow modelling of multiple populations. Thus we need to reach V = 24.85 for the LMC and V = 25.25 for the SMC. Using the WFPC2 Exposure Time Calculator, we find we will reach S/N = 13 in 600s in I and S/N = 14 in 500s in V for V = 24.85, and S/N = 10 and 11 respectively at V = 25.25, for a main sequence MC star. With four exposures per color, we will achieve Sigma (V) = 0.035 and Sigma (V-I) = 0.055 in the LMC, and Sigma(V) = 0.045, Sigma (V-I) = 0.07 in the SMC. For NGC 121 we have slightly shorter exposures, hence Sigma (V) = 0.05, Sigma (V-I) = 0.08. According to information in the WFPC2 Instrument handbook, a 500s exposure with the F555W filter will saturate at V ~ 18.3. For the sparse MC field regions there will be no difficulty in tying stars of magnitude 18--20 into our ground-based photometry. However for the crowded NGC 121 field we will take some short exposures in order to facilitate a tie-in with the ground- based observations. We will take exposures of 6*30s in V and 4*20s in I, which will saturate at about V ~ 15.2. We will avoid a moderately bright (14 mag.) star near NGC 121. We (AW,NS,RS,EO) have been granted 4 nights on the CTIO 4-m and 4 nights on the CTIO 1.5-m with SITe 2048 direct CCD during November and December 1995 for a program entitled ``Photometric Investigation of Magellanic Cloud Field Populations''. This program is aimed at producing accurate photometry in 30x30'\ square fields in positions containing the proposed HST fields. The areas are extensive enough to accumulate significant samples even for stars in relatively short-lived evolutionary phases, and will complement the deeper, but much smaller field, HST images. We will observe using CTIO's copies of the HST F555W and F814W filters, plus a DDO51 to identify foreground G--K dwarfs. This work will also provide local standards so that the HST and ground-based photometry can be correctly tied together. We (EO, RS, NS) have extensive observations (photometry, abundances, radial velocities) for LMC red giant branch (RGB) stars in seven one -degree fields. The most complete of these is near NGC 2257 (r = 8.4degrees), where in addition proper motions are available (Lin et al 1995). This region also has extensive photometry for the field RR Lyraes (Nemec et al., 1985; Walker 1988). The proposed HST observations will provide deeper and more accurate photometry in the magnitude range V = 22-25, at and below the MS turn-offs for older populations. This accurate photometry is crucial when trying to disentangle mixed populations that have differing ages and metallicities. As described in the scientific justification, we estimate how many stars are near the old-population turn- off (V = 21.75--22.5, B-V = 0.2--0.6) by scaling from CTIO 4m V, B-V photometry by one of us (NS). For a single WFPC2 pointing there are ~ 26 such stars. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: LMC-062630-644500 Alternate_Names: Description: Unidentified, Blank Field Position: RA=06H 26M 30.0S +/- 0.1S, ! Most common specification format is DEC=-64D 45' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=00MS ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 2 Target_Name: LMC-062930-640200 Alternate_Names: Description: Unidentified, Blank Field Position: RA=06H 29M 30.0S +/- 0.1S, ! Most common specification format is DEC=-64D 02' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=00MS ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 3 Target_Name: LMC-063600-640600 Alternate_Names: Description: Unidentified, Blank Field Position: RA=06H 36M 00.0S +/- 0.1S, ! Most common specification format is DEC=-64D 06' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=00MS ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 4 Target_Name: LMC-062806-650800 Alternate_Names: Description: Unidentified, Blank Field Position: RA=06H 28M 06.0S +/- 0.1S, ! Most common specification format is DEC=-65D 08' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=00MS ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 5 Target_Name: SMC-004600-703500 Alternate_Names: Description: Unidentified, Blank Field Position: RA=00H 46M 00.0S +/- 0.1S, ! Most common specification format is DEC=-70D 35' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=015Q ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 6 Target_Name: SMC-004612-704700 Alternate_Names: Description: Unidentified, Blank Field Position: RA=00H 46M 12.0S +/- 0.1S, ! Most common specification format is DEC=-70D 47' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=015Q ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 7 Target_Name: SMC-004900-704800 Alternate_Names: Description: Unidentified, Blank Field Position: RA=00H 49M 00.0S +/- 0.1S, ! Most common specification format is DEC=-70D 48' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=015Q ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 8 Target_Name: SMC-004900-703300 Alternate_Names: Description: Unidentified, Blank Field Position: RA=00H 49M 00.0S +/- 0.1S, ! Most common specification format is DEC=-70D 33' 00.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=015Q ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Target_Number: 9 Target_Name: NGC121 Alternate_Names: Description: Ext-Cluster, Globular cluster Position: RA=00H 26M 48.9S +/- 0.1S, ! Most common specification format is DEC=-71D 32' 12.0" +/- 0.1", ! RA=0H 0M 0.00S +/- 0S, ! PLATE-ID=015Q ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V=24 B-V=0.5 ! Include at least V and B-V Comments: Flux refers to the faintest stars which we wish to accurately measure ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN