! 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