! Proposal 6671, submission 1 ! PI: R. Michael Rich ! Received Wed Feb 28 14:26:14 EST 1996 ! From: rmr@figaro.phys.columbia.edu ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! ! Refer to the HST Phase II Proposal Instructions to fill this out !!!!! version of 2/26 3pm ! 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: Alice Berman ! Phone: 410-338-4462 , E-mail: aberman@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Proposal_Information Title: Deep V,I Photometry for 20 M31 Globular Clusters Proposal_Category: GO Scientific_Category: STELLAR POPULATIONS Cycle: 6 Investigators PI_name: R. Michael Rich PI_Institution: Columbia University CoI_Name: Flavio Fusi Pecci CoI_Institution: Osservatorio Astronomico di Bologna Contact: ! Y or N (designate at most one contact) CoI_Name: George S. Djorgovski CoI_Institution: California Institute of Technology Contact: ! Y or N (designate at most one contact) CoI_Name: Wendy L. Freedman CoI_Institution: Observatories, Carnegie Inst. Washington Contact: ! Y or N (designate at most one contact) CoI_Name: Kenneth J. Mighell CoI_Institution: Columbia University Contact: ! Y or N (designate at most one contact) CoI_Name: Carla Cacciari CoI_Institution: Osservatorio Astronomico di Bologna Contact: ! Y or N (designate at most one contact) CoI_Name: Francesco Ferraro CoI_Institution: Osservatorio Astronomico di Bologna Contact: ! Y or N (designate at most one contact) CoI_Name: Luciana Federici CoI_Institution: Osservatorio Astronomico di Bologna Contact: ! Y or N (designate at most one contact) CoI_Name: Gianluigi Parmeggiani CoI_Institution: Osservatorio Astronomico di Bologna Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose deep photometry (to V=27.5) of a sample of 20 M31 globular clusters in the V, I (F555W, F814W) passbands using WFPC2. The main goals of this project are: (1) to determine the dependence of horizontal branch (HB) luminosity on Fe/H, an important constraint on the absolute and relative ages of Galactic globular clusters. (2) to obtain luminosity functions of the clusters and to correlate these with physical properties, especially the brightest giants as a function of Fe/H. (3) to explore the dependence of HB morphology on various parameters (e.g. metallicity, galactocentric distance, concentration, He abundance, etc.) for essential information they may provide on the formation and early evolutionary phases of galaxies, and on the possible impact of environmental conditions on stellar evolution. Structural parameters (core radii, ellipticities, and surface brightness profiles) will be measured and when combined with Keck measurements of velocity dispersions, used to derive M/L for the sample. Questions ! Free format text (please update) Observing_Description: The sample of 20 clusters has been carefully selected from the brightest clusters to first, sample the range in Fe/H adequately and second, to sample the range in galactocentric distance. All clusters have Fe/H determinations on the scale of Huchra, Brodie, & Kent (1991 ApJ 370, 495) which is tied to the Galactic globular cluster system. As part of another project (Rich et al. 1995 in preparation) images and GASP positions have been obtained for all M31 clusters in the sample of Battistini et al. 1987 A& AS, 67, 447. The proposed targets have all been checked to verify that the background is low and that there are no bright, nearby stars. Our sample spans the range -2 < Fe/H < +0.3; we have several clusters with R>10 kpc and Fe/H~ -1.5 dex, characteristic of the Galaxy's second parameter clusters. Since our main goal is to find V(HB) as a function of Fe/H, we want to sample fully the entire metallicity range. Considering the full range running from -2 to 0.0 dex as consisting of four 0.5 dex wide zones, one would like to populate these with about 5 clusters in each abundance range. No doubt, some clusters will ultimately be excluded because they are strong second parameter clusters, etc. We propose to observe 10 clusters (40 orbits) in each of Cycle 6 and 7. As we describe below, we plan our observations so that the resulting images will be the best that HST can obtain in a reasonable time, thus also providing the community with data of true archival value. We have carefully considered the need for 4 orbits per cluster. Note that the detailed observing plan below is identical to that of Sarajedini et al. who are studying the M33 clusters in V,I. The central goal of this program is quantitative measurement of V(HB) as a function of Fe/H. Note that over the full range of ~ 1.5 dex, a range in V(HB) of 0.3 mag covers the full range of possible slopes. While HB morphology can be discerned with relatively light exposures, systematic errors can occur within 1 mag of the detection limit. The severe crowding of the clusters worsens this (G1 in Figure 1 below is M31's least crowded cluster; and G219 (Fig. 3) is nearly as favorable). We cannot invest the 14,000 sec needed for G351, which has errors that are just barely adequate for this project (note the width of the RGB at the level of the HB). We want the errors on the faint side of the HB to be <0.1 mag and we want the faint side to be well detected, to avoid systematic errors that could pull the mean V(HB) off of its true magnitude. Artificial star tests on our G1 frames show that <1 mag above the frame limit, stars are recovered systematically 0.1 to 0.2 mag too bright, with the problem more severe in crowded regions. We do not want to make such large corrections to our data, and we want the HB to lie at least 1.5 mag (or more) above the plate limit, providing a buffer against this effect. Reductions of G1 show that the HB of M31 globular clusters is found at V~ 25.3. Since we are interested in defining the entire HB, including the blue end, we consider V=25.6 to be the target magnitude of the HB. At V=25.6, a 5000s exposure yields S/N 25 at V=25.6; a 5000s exposure with F814W results in S/N 20 at I=25.6; the red HB has (V-I)=0.5 to 1.0, and will therefore be observed at comparable S/N in I and V. The clusters are extremely crowded, so the PC must be used for imaging; the crowding also requires longer exposures to reach the target S/N. M31 is available for 53 min/orbit. A visit consists of 480s for guide star acquisition + 2400s CR-SPLIT F814W exposure + 300s overhead. During Earth occultation we will offset the field slightly to improve sampling and to completely remove hot pixels. The next orbit is a 360s guide star reaquisition, followed by a 2500s CR-SPLIT F814W + 300s overhead. Orbits 3 and 4 are identical to the second orbit, so that the V band (F555W) imaging receives 300s more (a total of 5400s). We may choose to break the long exposures into 2 shorter non CR-split exposures, but to make a slight offset during the readout of the first exposure; this will depend on our final optimal observing strategy. Real_Time_Justification: George Djorgovski has agreed to use the Hires echelle spectrograph on the W.M. Keck 10m telescope to measure velocity dispersions for all the clusters observed in this program. The high S/N of the echelle data should yield dispersions of unprecedented quality. The Palomar 60-inch is available for V,I imaging of Galactic globular clusters, if needed. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number:1 Target_Name:M31-G76 Alternate_Names:Bo338 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 40M 58.83S +/- 0.05S, DEC=+40D 35' 46.94" +/- 0.5" ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=14.28, B-V=0.82 ! Include at least V and B-V Comments: Target_Number:2 Target_Name:M31-G64 Alternate_Names:Bo12 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 40M 32.419S +/- 0.05S, DEC=41D 21' 43.82" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.08, B-V=0.78 ! Include at least V and B-V Comments: Target_Number:3 Target_Name:M31-G87 Alternate_Names:Bo27 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 41M 14.467S +/- 0.05S, DEC=40D 55' 50.233" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.08, B-V=0.78 ! Include at least V and B-V Comments: Target_Number:4 Target_Name:M31-G287 Alternate_Names:Bo233 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 44M 42.0673S +/- 0.05S, DEC=41D 43' 54.153" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.76, B-V=0.89 ! Include at least V and B-V Comments: Target_Number:5 Target_Name:M31-G11 Alternate_Names:Bo293 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 44M 42.0673S +/- 0.05S, DEC=41D 43' 54.153" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=16.36, B-V=0.60 ! Include at least V and B-V Comments: Target_Number:6 Target_Name:M31-G119 Alternate_Names:Bo58 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 41M 52.96S +/- 0.05S, DEC=40D 47' 09.049" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.02, B-V=0.80 ! Include at least V and B-V Comments: Target_Number:7 Target_Name:M31-G33 Alternate_Names:Bo311 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 39M 33.678S +/- 0.05S, DEC=40D 31' 13.56" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.48, B-V=0.90 ! Include at least V and B-V Comments: Target_Number:8 Target_Name:M31-G319 Alternate_Names:Bo384 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 46M 21.913S +/- 0.05S, DEC=40D 16' 59.47" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.76, B-V=0.89 ! Include at least V and B-V Comments: Target_Number:9 Target_Name:M31-G322 Alternate_Names:Bo386 Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 46M 26.98S +/- 0.05S, DEC=42D 01' 52.55" +/- 0.5", ! PLATE-ID=0000 Equinox:J2000 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.61, B-V=0.75 ! Include at least V and B-V Comments: Target_Number:10 Target_Name:M31-G327 Alternate_Names: Description:EXT-CLUSTER, Globular Cluster Position:RA=0H 46M 49.49S +/- 0.05S, DEC=42D 44' 47.33" +/- 0.5", ! PLATE-ID=0000 Equinox:1950.0 RV_or_Z: RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch:1982 Annual_Parallax: Flux:V=15.76, B-V=0.89 ! Include at least V and B-V Comments: ! 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