7374( 9) - 11/02/00 05:58 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7374 Version: 9 Check-in Date: 02-Nov-2000 05:57:30 1.Proposal Title: Probing Low Density Cluster Environments at Moderate-to-High Redshifts ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Piero Rosati European Southern Observatory - Germany CoI: Colin Norman Johns Hopkins University N CoI: Chris Mihos Johns Hopkins University N CoI: Mark Dickinson Space Telescope Science Institute N CoI: Mauro Giavalisco Observatories Carnegie Institute of N Washington CoI: Duccio Macchetto Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract Recent HST WFPC2 images of rich clusters at moderate-to-high redshifts have revealed that morphological information is a crucial ingredient in understanding the physical processes responsible for the evolution of the galaxy population in clusters. However, HST observations have been targeted mostly to optically selected very rich systems or very luminous X-ray selected clusters. Therefore, studies have been made only on very massive, centrally condensed systems which represent only a limited, rare subsample of the cluster population. This may lead to a somewhat distorted view of the observed evolutionary properties. We therefore propose to obtain deep images of 6 clusters extracted from a new, deep X-ray selected sample, at moderate redshift (0.2-0.6) and moderate-low X-ray luminosity, to quantify galaxy morphology and measure the merger/interaction rate in different physical conditions. By combining these observations with those of other clusters that HST has already observed, we will obtain a more meaningful data set covering the complete range of the intracluster medium properties over a substantial look-back time. In addition, complementary ground-based and X-ray observation will provide galaxy colors and spectra, as well as dynamical/thermal state of the intracluster gas and cluster masses. With these essential ingredients we will be able to test models of cluster galaxy evolution and in particular establish the role of environmental effects on the evolution of structure and stellar population. ------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 2] Observations Description ------------------------ We propose to use WFPC2 with the F702W passband to image 6 clusters of galaxies with redshifts in the range 0.2<~ z<~ 0.6. We have chosen the above passband for the following reasons: (a) even at the highest redshift of our sample, the 4000 Angstrom break is entirely blueward of the passband, allowing the elliptical galaxies to be observed with optimum sensitivity; (b) for moderately blue galaxies it offers the highest throughput among the WFPC2 filters. We believe that the 6 clusters proposed span the physical parameter space described above (Fig.1) in such a way that we can fully achieve our scientific objectives. The aim of our program is to study the morphologies of the cluster members, reaching 2 mag fainter than L_*. This is motivated by the need to study the galaxy population at the faint-end of the luminosity function. As described below, at redshift z~ 0.5, this implies a limiting surface brightness of ~ 27.7 (at the 3Sigma level). In the F702W passband this is accomplished with ~ 2.5 hours of total integration, or about 4 orbits (~eq 4* 40 min) and 3 orbits for the brightest, low-redshift targets (in the target list, V is roughly the mag of the brightest cluster memember). Since we need to discriminate the galaxy morphologies in terms of the light profiles of their ``bulges'' and ``disks'', we require a signal-to-noise ratio high enough to measure the surface brightness of the isophotes at sufficiently large radii. An elliptical galaxy 2 mag fainter than L_* at z=0.5 is observed with apparent magnitudes m_702~ 23 (for q_0=0.5). In order to determine the light profile to a typical angular scale of 1.5" (~ 3*r_e), assuming an r^1/4 law, we derive a surface brightness of 27.7 mag/arcsec^2. Using the sky brightness in the F702W passband from the WFPC2 manual as well as the value of the dark current rate and read-out noise, we calculate that surface brightness fluctuations of ~ 27.7 mag/arcsec^2 (at the 3-Sigma level) are reached in about 2.5 hours of integration. This includes the additional noise from cosmic ray events. To avoid contamination from the earth limb, which could be substantial in the F702W passband, we assume that the visibility period is limited to 40 minutes (this is based on previous observations, Giavalisco et al. GO #5970). Thus, the requested exposure times translates into 4 orbits per field. This allows us to obtain 8 exposures of 20 minutes each, sufficient for an efficient cosmic ray removal. Real Time Justification ----------------------- None We have already obtained deep V and I photometry and spectroscopic optical data for the proposed sample. Over the past 3 years, 29 nights of imaging and 19 of spectroscopy have been allocated for this project on 2-4m class telescopes at KPNO, CTIO and ESO. We still have an on-going and successful spectroscopic follow-up program which has been aimed so far at measuring cluster redshifts. We plan to extend the spectroscopic study for the HST subsample to more cluster members (>15) in order to obtain velocity dispersions, to map the star formation activity and to correlate the spectral energy distribution with the morphoplogy of the galactic population. In addition, we have ROSAT-PSPC X-ray data as part of the original selection process. Calibration Justification ------------------------- Additional Comments ------------------- Coordinates for all targets do not correspond to specific objects, however they are accurate (GSS) coordinates which optimize the position of the clusters in the WFPC2 aperture for the given ORIENT range. There is a bug in RPS2 dealing with dithered observations using WFPC2 with the CR-SPLIT and DITHER-TYPE=LINE parameters. >>> Please make sure that observations are implemented as desired. Sometimes it was not possible to fill up completely the unused visibility within some orbits (typically 3-8 mins). >>> Please try to fill up these gaps by extending the exposure time when possible ------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 3] Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS- CLUSTER OF GALAXIES, RA=16H 33M 42.80S +/- 0.1S, J2000 V = 20+/-0.5 163340+57143 POOR CLUSTER DEC=57D 14' 05.0" +/- 0.5", 3 PLATE-ID=00T2 2 GAL-CLUS- CLUSTER OF GALAXIES, RA=7H 20M 20.50S +/- 0.1S, J2000 R = 20+/-0.5 072015+71321 POOR CLUSTER DEC=71D 32' 26.0" +/- 0.5", 8 PLATE-ID=01KS 3 GAL-CLUS- CLUSTER OF GALAXIES, RA=8H 41M 11.50S +/- 0.1S, J2000 R = 21+/-0.5 084106+64222 POOR CLUSTER DEC=64D 22' 28.0" +/- 0.5", 7 PLATE-ID=01JR 4 GAL-CLUS- CLUSTER OF GALAXIES, RA=8H 48M 48.50S +/- 0.1S, J2000 R = 22+/-0.5 084847+44562 HIGH REDSHIFT CLUSTER DEC=44D 56' 29.0" +/- 0.5", 1 PLATE-ID=036M 5 GAL-CLUS- CLUSTER OF GALAXIES, RA=2H 18M 20.40S +/- 0.1S, DEC=- J2000 R = 22+/-0.5 021816- HIGH REDSHIFT CLUSTER 73D 56' 08.0" +/- 0.5", PLATE- 735626 ID=04BU 6 GAL-CLUS- CLUSTER OF GALAXIES, RA=3H 37M 45.30S +/- 0.1S, DEC=- J2000 R = 22+/-0.5 033745- HIGH REDSHIFT CLUSTER 25D 22' 58.0" +/- 0.5", PLATE- 252217 ID=027X 7 GAL-CLUS- CLUSTER OF GALAXIES, RA=8H 48M 48.7S +/- 0.1S, J2000 R = 22+/-0.5 084847+44562 HIGH REDSHIFT CLUSTER DEC=44D 54' 43" +/-0.5", PLATE- 1-NEW ID=036M 7374( 9) - 11/02/00 05:58 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 280D TO 10D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-16 WFPC2 IMAGE WF3-FIX F702W DITHER-TYPE=LINE,CR-SPLIT=NO, 2 1200 S 3340+571433 DITHER-LINE-STEPS=2 Comments: Observation pattern: two exposures at each of the two pointings of the dither pattern. The SAM displayed in the middle of the 2nd orbit in the RPS2 Analysis Report is wrong. Please make sure observations are implemented correctly. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 185D TO 260D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-07 WFPC2 IMAGE WF3-FIX F702W DITHER-TYPE=LINE,CR-SPLIT=NO, 2 1200 S 2015+713218 DITHER-LINE-STEPS=2 Comments: Observation pattern: two exposures at each of the two pointings of the dither pattern. The SAM displayed in the middle of the 2nd orbit in the RPS2 Analysis Report is wrong. Please make sure observations are implemented correctly. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 271D TO 300D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-08 WFPC2 IMAGE WF3-FIX F702W DITHER-TYPE=LINE,CR-SPLIT=NO, 2 1200 S 4106+642227 DITHER-LINE-STEPS=3 Comments: Observation pattern: two exposures at each of the three pointings of the dither pattern ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 8] Visit: 04 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-08 WFPC2 IMAGE WF2-FIX F702W CR-SPLIT=NO 2 1200 S 4847+445621 Comments: Observation pattern: two exposures at same position. ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS-08 WFPC2 IMAGE WF2-FIX F702W DITHER-TYPE=BOX,CR-SPLIT=NO 2 1200 S 4847+445621 Comments: Two exposures at each of the four pointings of the dither pattern starting at the same position as 1. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 9] Visit: 05 Visit Priority: Visit Requirements: ORIENT 223D TO 245D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-02 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT=NO 2 1200 S 1816-735626 Comments: Observation pattern: two exposures at the same position. ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS-02 WFPC2 IMAGE WF3-FIX F702W DITHER-TYPE=BOX,CR-SPLIT=NO 2 1200 S 1816-735626 Comments: Two exposures at each of the four pointings of the dither pattern starting at the same position as 1. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 10] Visit: 06 Visit Priority: Visit Requirements: ORIENT 340D TO 15D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-03 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT=NO 2 1100 S 3745-252217 Comments: Observation pattern: two exposures at the same position. ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS-03 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT=NO,DITHER-TYPE=BOX 2 1100 S 3745-252217 Comments: Two exposures at each of the four pointings of the dither pattern starting at the same position as 1. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 11] Visit: 54 Visit Priority: Visit Requirements: ORIENT 102D TO 110D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-08 WFPC2 IMAGE WFALL F702W CR-SPLIT=NO 2 1200 S 4847+445621 -NEW Comments: Observation pattern: two exposures at same position. ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS-08 WFPC2 IMAGE WFALL F702W DITHER-TYPE=BOX,CR-SPLIT=NO 2 1200 S 4847+445621 -NEW Comments: Two exposures at each of the four pointings of the dither pattern starting at the same position as 1. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 12] Visit: 56 Visit Priority: Visit Requirements: ORIENT 340D TO 15D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS-03 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT=NO 2 1100 S 3745-252217 Comments: Observation pattern: two exposures at the same position. ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS-03 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT=NO,DITHER-TYPE=BOX 2 1100 S 3745-252217 Comments: Two exposures at each of the four pointings of the dither pattern starting at the same position as 1. ------------------------------------------------------------------------------------------------------------------------------------ 7374( 9) - 11/02/00 05:58 - [ 13] Summary Form for Proposal 7374 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3-FIX WF2-FIX WFALL ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters DITHER-TYPE=LINE CR-SPLIT=NO DITHER-LINE-STEPS=2 DITHER-LINE-STEPS=3 DITHER-TYPE=BOX ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 280D TO 10D ORIENT 185D TO 260D ORIENT 271D TO 300D ORIENT 223D TO 245D ORIENT 340D TO 15D ORIENT 102D TO 110D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-CLUS-163340+571433 GAL-CLUS-072015+713218 GAL-CLUS-084106+642227 GAL-CLUS-084847+445621 GAL-CLUS-021816-735626 GAL-CLUS-033745-252217 GAL-CLUS-084847+445621-NEW ------------------------------------------------------------------------------------------------------------------------------------