! 5919_v3.prop
! Revised by Ray Lucas, 8 December, 1995.
! Comments added to Exp Log lines and General Form text. Also removed 
! semicolons etc. from special requirements and placed them on separate
! lines for better readability. Also added visit level comments.
! Closed ORIENT range down to exactly 227.32D by making both values in
! the range equal to the same value, which was the same value for the U3
! ORIENT ( PA_V3+180D ) used in the Early Release program 5190 in January
! 1994.
!
! Set all exposure times to 2800s ( equivalent to turning off the EXPAND
! feature for all but the initial exposure of both SUs, which were originally
! 2500s each, but were EXPANDed by TRANS to 2800s each ). This was done to
! try to make SU 01 schedulable and to try to give SU 02 more schedulability
! than the very minimal schedulability it originally had in the flight
! database in the original version of the program. - RAL - 11 December, 1995
!
! Proposal 5919, submission 1
! PI: Francesco Bertola
! Received Tue Mar  7 12:50:15 EST 1995
! From: lbuson@eso.org
! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template
! $Id: 5919,v 4.1 1995/12/11 22:05:26 pepsa Exp $

Proposal_Information                           
              Title:  UV EVOLUTION OF GALAXIES IN A DISTANT
                      CLUSTER
  Proposal_Category:  GO
Scientific_Category:  Galaxies & Clusters
             Cycle:    5

Investigators
     PI_name:         Francesco Bertola
     PI_Institution:  University of Padova

          CoI_Name:   Lucio Buson
   CoI_Institution:   Osservatorio Astronomico di Padova
           Contact:   Y

          CoI_Name:   Cesare Chiosi
   CoI_Institution:   University of Padova
           Contact:   N 

          CoI_Name:   Alan Dressler
   CoI_Institution:   Carnegie Observatories
           Contact:   N 

          CoI_Name:   Augustus Oemler
   CoI_Institution:   Yale University
           Contact:   N 


Abstract:                                
    It is proposed to image in two properly spaced UV passbands
    (rest frame wavelength 1500 Angstrom and 2000 Angstrom) the
    very rich galaxy cluster CL0939+4713 = Abell 851 at a redshift
    of z=0.41. Such a cluster, which represents a lookback time of
    4--5 billion yr in conventional cosmologies, contains a large
    population of galaxies with strong ongoing star formation.
    Moreover, already existing HST images corresponding to a rest
    frame color between Johnson B and V, reveal an abundance of
    late--type galaxies as well as many merging or interacting
    systems. The new UV observations proposed here are primarily
    intended to test the current ideas on the age and metal
    abundance of distant systems. In particular we plan to measure
    at z=0.4 the level of the well--known UV turn--up observed in
    present--day ellipticals and spiral bulges. The level of this
    turn--up is expected to decrease with lookback time. Its
    precise determination at a given z will allow us to put strict
    constraints on the evolutionary history of these galaxies. As
    a by--product it is expected to derive essential clues on the
    nature of a cluster of faint objects surrounding a quasar at
    z=2.055 contained in the field. Since the proposed
    observations will sample a wavelength below the Lyman limit
    for z=2 and z=1.2 respectively, it is expected to see a strong
    drop in flux for these objects depending on their redshift,
    thus possibly confirming their association with the quasar
    itself.

Questions                       

     Observing_Description:
         Cluster galaxies in our proposed field are as bright as V=20,
         but to reach a significant number of detected objects one has
         to go down at least to the characteristic magnitude of the
         luminosity function. As a consequence we have chosen V~23 as
         the limit to which one has to try to get good detections. Our
         estimate of the exposure times comes from the expected
         electrons detected from WFPC-2, as described in Sec. 6 of the
         WFPC-2 Instrument Handbook. On the basis of the model SEDs
         provided in Fig. 2 one can assume that an object at z=0.4
         will show in the observer rest frame a drop (when compared
         to V) of ~3 mag at Lambda~ 3000 Angstrom and a subsequent
         rise of ~1.5 mag at Lambda~ 2000 Angstrom. Even if the lower
         efficiency of the F218W filter will be partially compensated
         by the above rise in UV flux at shorter wavelengths, we
         expect to collect twice the electrons per single orbit
         exposure (~200) in the F300W filter with respect to the
         shorter wavelength F218W filter. As a consequence, we
         estimate that, in order to study at least 30--50 galaxies we
         will need a minimum exposure of 10 orbits in the F218W filter
         and 5 orbits in the F300W filter (15 in total).

   Real_Time_Justification: 
         None.

Calibration_Justification:              
         None.

      Additional_Comments:
         Please use SAME GUIDE STARS for both visits if possible. The
         GROUP 1-2 WITHIN 7 Days may be relaxed for scheduling as long as
         the SAME ORIENT ( and preferably also the SAME GUIDE STARS if 
         possible ) are maintained for both visits. The absolute ORIENT
         value exactly matches that used in the Early Release program 5190
         done in January 1994. This value is U3 ORIENT 227.32D which 
         corresponds to 180D plus the PA_V3 value in the headers of the 
         program 5190 data, e.g. 5190 PA_V3=47.32 and U3 ORIENT = PA_V3+180D,
         so U3 ORIENT for both programs should be 47.32+180 = 227.32D.

Fixed_Targets                           
  Target_Number: 1
    Target_Name: ABELL851
    Description: CLUSTER OF GALAXIES, Rich Cluster
       Position: RA=9H 39M 48.0S +/- 0.1S, DEC=+47D 12' 41.0" +/- 1" 
        Equinox: 1950.0
        RV_or_Z: Z=0.41
           Flux: SURF(V)=23.0 +/- 1.0, B-V=1.3 +/- 0.3  
       Comments: The field contains many faint galaxies in the range 21< V <25.

Visits                                  
      Visit_Number: 1
Visit_Requirements: ORIENT 227.32D TO 227.32D
    Visit_Comments: Make use of the SAME GUIDE STARS for both visits, if
                    possible. Do both visits at the SAME ORIENT. GROUP 1-2
                    WITHIN 7 Days requirement may be relaxed for scheduling
                    as long as SAME ORIENT ( and also SAME GUIDE STARS if
                    possible ) maintained for both visits.
        
     Exposure_Number: 1                  
         Target_Name: ABELL851    
              Config: WFPC2
              Opmode: IMAGE
            Aperture: WFALL-FIX
          Sp_Element: F218W
          Wavelength: 2159
 Optional_Parameters: CR-SPLIT=NO   
Number_of_Iterations: 1
   Time_Per_Exposure: 2800S 
Special_Requirements: POS TARG +10,+10
                      MIN DUR 2500S
                      END ORBIT 
            Comments: WFALL-FIX with POS TARG +10,+10 places Fixed Target List 
                      coordinate position ~at apex of the WFPC2 pyramid.
         
     Exposure_Number: 2                 
         Target_Name: ABELL851    
              Config: WFPC2
              Opmode: IMAGE
            Aperture: WFALL-FIX
          Sp_Element: F218W
          Wavelength: 2159
 Optional_Parameters: CR-SPLIT=NO   
Number_of_Iterations: 4
   Time_Per_Exposure: 2800S 
Special_Requirements: SAME POS AS 1
                      MIN DUR 2800S
                      END ORBIT 
            Comments: Do at WFALL-FIX with POS TARG +10,+10 as in first
                      exposure of this visit. 

     Exposure_Number: 3                  
         Target_Name: ABELL851   
              Config: WFPC2
              Opmode: IMAGE
            Aperture: WFALL-FIX
          Sp_Element: F300W
          Wavelength: 2911
 Optional_Parameters: CR-SPLIT=NO 
Number_of_Iterations: 3
   Time_Per_Exposure: 2800S 
Special_Requirements: SAME POS AS 1
                      MIN DUR 2800S
                      END ORBIT 
            Comments: Do at WFALL-FIX with POS TARG +10,+10 as in first
                      exposure of this visit.
 
      Visit_Number: 2
Visit_Requirements: SAME ORIENT AS 1
                    GROUP 1-2 WITHIN 7D  
    Visit_Comments: Make use of the SAME GUIDE STARS for both visits, if
                    possible. Do both visits at the SAME ORIENT. GROUP 1-2
                    WITHIN 7 Days requirement may be relaxed for scheduling
                    as long as SAME ORIENT ( and also SAME GUIDE STARS if
                    possible ) maintained for both visits.
      
     Exposure_Number: 1                  
         Target_Name: ABELL851    
              Config: WFPC2
              Opmode: IMAGE
            Aperture: WFALL-FIX
          Sp_Element: F218W
          Wavelength: 2159
 Optional_Parameters: CR-SPLIT=NO 
Number_of_Iterations: 1
   Time_Per_Exposure: 2800S 
Special_Requirements: POS TARG +10.5,+10.5
                      MIN DUR 2500S
                      END ORBIT 
            Comments: WFALL-FIX with POS TARG +10.5,+10.5 places Fixed Target 
                      List coordinate position ~0.5 arcsec from apex of WFPC2
                      pyramid in both x and y.
                      
     Exposure_Number: 2                 
         Target_Name: ABELL851    
              Config: WFPC2
              Opmode: IMAGE
            Aperture: WFALL-FIX
          Sp_Element: F218W
          Wavelength: 2159
 Optional_Parameters: CR-SPLIT=NO 
Number_of_Iterations: 4
   Time_Per_Exposure: 2800S 
Special_Requirements: SAME POS AS 1
                      MIN DUR 2800S
                      END ORBIT 
            Comments: Do at WFALL-FIX with POS TARG +10.5,+10.5 as in first
                      exposure of this visit.

     Exposure_Number: 3                  
         Target_Name: ABELL851   
              Config: WFPC2
              Opmode: IMAGE
            Aperture: WFALL-FIX
          Sp_Element: F300W
          Wavelength: 2911
 Optional_Parameters: CR-SPLIT=NO 
Number_of_Iterations: 2
   Time_Per_Exposure: 2800S 
Special_Requirements: SAME POS AS 1
                      MIN DUR 2800S
                      END ORBIT 
            Comments: Do at WFALL-FIX with POS TARG +10.5,+10.5 as in first
                      exposure of this visit.

Data_Distribution                       

         Medium:        6250BPI         
Blocking_Factor:        10            

        Ship_To:        PI_Address      
                                        
       Ship_Via:        UPS