5919( 4) - 12/11/95 17:14 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5919 Version: 4 Check-in Date: ********** 1.Proposal Title: UV EVOLUTION OF GALAXIES IN A DISTANT CLUSTER ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Francesco Bertola University of Padova CoI: Lucio Buson Osservatorio Astronomico di Padova Y CoI: Cesare Chiosi University of Padova N CoI: Alan Dressler Carnegie Observatories N CoI: Augustus Oemler Yale University N ------------------------------------------------------------------------------------ 6. 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. ------------------------------------------------------------------------------------ 5919( 4) - 12/11/95 17:14 - [ 2] Observations 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. ------------------------------------------------------------------------------------ Data Distribution Media: 6250BPI Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5919( 4) - 12/11/95 17:14 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL851 CLUSTER OF GALAXIES, RA=9H 39M 48.0S +/- 0.1S, 1950.0 Z=0.41 SURF(V)=23.0 +/- 1.0 Rich Cluster DEC=+47D 12' 41.0" +/- 1" B-V=1.3 +/- 0.3 Comments: The field contains many faint galaxies in the range 21< V <25. 5919( 4) - 12/11/95 17:14 - [ 4] Visit: 01 Visit Requirements: ORIENT 227.32D TO 227.32D On Hold Comments: Additional 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. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL851 WFPC2 IMAGE WFALL- F218W 2159 CR-SPLIT=NO 1 2800S POS TARG +10,+10 MIN DUR 2500S END ORBIT FIX Comments: WFALL-FIX with POS TARG +10,+10 places Fixed Target List coordinate position ~at apex of the WFPC2 pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL851 WFPC2 IMAGE WFALL- F218W 2159 CR-SPLIT=NO 4 2800S SAME POS AS 1 MIN DUR 2800S END ORBIT FIX Comments: Do at WFALL-FIX with POS TARG +10,+10 as in first exposure of this visit. ------------------------------------------------------------------------------------------------------------------------------------ 3 ABELL851 WFPC2 IMAGE WFALL- F300W 2911 CR-SPLIT=NO 3 2800S SAME POS AS 1 MIN DUR 2800S END ORBIT FIX Comments: Do at WFALL-FIX with POS TARG +10,+10 as in first exposure of this visit. ------------------------------------------------------------------------------------------------------------------------------------ 5919( 4) - 12/11/95 17:14 - [ 5] Visit: 02 Visit Requirements: SAME ORIENT AS 1 GROUP 1-2 WITHIN 7D On Hold Comments: Additional 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. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL851 WFPC2 IMAGE WFALL- F218W 2159 CR-SPLIT=NO 1 2800S POS TARG +10.5,+10.5 MIN DUR 2500S END FIX 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. ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL851 WFPC2 IMAGE WFALL- F218W 2159 CR-SPLIT=NO 4 2800S SAME POS AS 1 MIN DUR 2800S END ORBIT FIX Comments: Do at WFALL-FIX with POS TARG +10.5,+10.5 as in first exposure of this visit. ------------------------------------------------------------------------------------------------------------------------------------ 3 ABELL851 WFPC2 IMAGE WFALL- F300W 2911 CR-SPLIT=NO 2 2800S SAME POS AS 1 MIN DUR 2800S END ORBIT FIX Comments: Do at WFALL-FIX with POS TARG +10.5,+10.5 as in first exposure of this visit. ------------------------------------------------------------------------------------------------------------------------------------ 5919( 4) - 12/11/95 17:14 - [ 6] Summary Form for Proposal 5919 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 227.32D TO 227.32D POS TARG +10,+10 MIN DUR 2500S END ORBIT SAME POS AS 1 MIN DUR 2800S END ORBIT SAME ORIENT AS 1 GROUP 1-2 WITHIN 7D POS TARG +10.5,+10.5 MIN DUR 2500S END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F218W F300W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ABELL851 ------------------------------------------------------------------------------------------------------------------------------------