! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6352,v 6.1 1995/12/22 23:59:58 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6352,v 6.1 1995/12/22 23:59:58 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: van Orsow ! Phone: 410-338-4568 , E-mail: vanorsow@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0921.ferguson.prop ! Date generated: Fri Dec 22 18:59:36 EST 1995 ! Proposal_Information ! Section 4 Title: Dwarf Elliptical Galaxy Snapshot Survey Proposal_Category: SNAP Scientific_Category: STELLAR POPULATIONS Cycle: 6 Investigators PI_name: Henry Ferguson PI_Institution: Space Telescope Science Institute CoI_Name: Bryan Miller CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Brad Whitmore CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Massimo Stiavelli CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) Snapshot images in V and I will be obtained for 30 dwarf elliptical galaxies. This survey will provide important information on the globular cluster systems of such galaxies and the properties of their cores and nuclei. The data will provide a straightforward indication of whether dE's are true low-luminosity ellipticals, or simply dwarf irregulars that have lost their gas. The images will be searched for evidence that the nuclei formed recently, and for the existence of dust or low levels of star formation in the more extended dE envelopes. Comparison of this data set to HST images of luminous elliptical galaxies and their globular cluster systems should provide valuable clues to the formation of galaxies and their globular cluster systems. The data will be non-proprietary. Questions ! Free format text (please update) Observing_Description: We propose a snapshot survey of 30 galaxies from a dE sample of roughly 1000. As the database will be of immediate use in a variety of comparative studies to other HST data, we will waive our proprietary rights. Our optimum exposure sequence is two exposures of 230 sec each in F555W, and one exposure of 350 seconds in F814W. The total time per target will be 29 minutes including guide-star acquisition and instrument overheads. Fine lock is required for guiding. Shorter exposure times can be used for smaller observing windows; however windows shorter than 20 minutes are not useful due to our requirement for fine lock and good cosmic ray removal. As a primary goal is a first statistical assessment of the globular cluster dE population, we have chosen a large sample of potential targets and modest exposure times per galaxy. For a distance modulus of 31.7 (the largest of the dwarfs in our sample, for H_0 = 75 km s^-1 Mpc^-1), exposure times to reach S/N = 10 at the peak of the luminosity function (M_V = -7) are 300 sec in F814W. This program is thus ideal for a snapshot survey. The major sources of background in order of importance are (1) cosmic rays, (2) background galaxies, and (3) the dE galaxy itself. With three short exposures, even in different bands, we expect virtually no contamination from cosmic rays. Background galaxies are a much more important source of false detections. Typical effective radii of the dE galaxies in our sample are 15". At V=25, there are roughly 7 * 10^4 galaxies per square degree. Thus, within 15", we expect 4 background galaxies. At this magnitude faint galaxies are still in general well resolved by HST, with median half-light radii of 0.15 arcsec (Griffiths et al. 1994). In contrast, globular clusters at the Virgo Cluster distance are barely resolved, with r_e ~ 0.04" (Whitmore et al. 1995). Thus most background galaxies can be identified by morphology, as has proved to be the case with existing data. Colors will provide additional discrimination, but the median colors of galaxies at I ~ 25 is similar to that of globular clusters, so this must be used with care. If necessary, statistical corrections can be made to the measured values of S_N based on the number of globular- cluster like objects seen in archival blank-field observations. These corrections will dominate the uncertainties for galaxies fainter than M_B = -15 if is less than 1. However, we do not wish to bias our sample by selecting only high-luminosity dE's, as that presupposes that is independent of luminosity. We note that a globular cluster population the size of that in the Fornax dSph would be detectable at the 2-sigma level with only a statistical correction for background galaxies. The smooth background of the dE galaxy itself increases the exposure time to detect an unresolved source. For galaxies fainter than M_V = -14.5 even the central surface brightnesses are fainter than the sky background, so globular clusters can be detected all the way in to the center. For galaxies at the bright end of our sample (M_V = -17), central surface brightnesses are still considerably fainter than in the central regions of M87 surveyed by Whitmore et al. (1995). The expected globular cluster populations are high enough at M_B = -17 that the loss of the central few arcseconds will not significantly affect the determination of S_N. Real_Time_Justification: None. None. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: Target_Name: Alternate_Names: Description: Position: ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 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: ! Include at least V and B-V Comments: Solar_System_Targets ! Section 5.2 Target_Number: Target_Name: Description: Level_1: ! Satellite of Sun Level_2: ! Satellite of Level_1 Level_3: ! Satellite of Level_2 Ephem_Uncert: ! Needed for REQ EPHEM CORR sp req Acq_Uncert: ! Needed for SAVE and USE OFFSET sp reqs Window: Flux: ! Include at least V and B-V Comments: Generic_Targets ! Section 5.3 Target_Number: Target_Name: Description: Criteria: Flux: Comments: Scan_Data ! Appendix B Scan_Number: FGS_Scan: Cont_or_Dwell: Dwell_Points: Dwell_Secs: Scan_Width: Scan_Length: Sides_Angle: Number_Lines: Scan_Rate: First_Line_PA: Scan_Frame: Length_Offset: Width_Offset: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 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