7279( 4) - 02/08/99 17:21 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7279 Version: 4 Check-in Date: 08-Feb-1999 17:20:46 1.Proposal Title: THE IMPACT OF CLUSTER SUBSTRUCTURE ON GALAXIES: A CASE STUDY IN ABELL 2125 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Frazer Owen National Radio Astronomy Observatory CoI: William Keel University of Alabama N CoI: Michael Ledlow New Mexico State University N CoI: Glenn Morrison University of New Mexico N CoI: Victor Andersen University of Alabama N ------------------------------------------------------------------------------------ 5. Abstract We propose to image three regions of the Butcher-Oemler (BO) cluster, A2125 (z=0.247), to better understand the BO effect. VLA data show that, as well as a large blue-galaxy fraction (0.19) for its redshift, it has an unprecedented number of radio galaxies (30 with confirmed redshifts), evenly split between old stellar populations and starbursting galaxies. There is also optical and X-ray evidence that a cluster- cluster merger is underway. A prominent radial ``filament'' is rich in both blue galaxies and radio sources. This combination, of unusually low redshift and radio activity suggesting that we are seeing a BO ``event'' soon after the fact, makes this cluster especially attractive in trying to distinguish various physical mechanisms at work in producing blue galaxies in rich clusters, and in tracing the links between events on cluster scales with the response within individual galaxies. We propose to image the core and filament regions of the cluster in WFPC2 filters F450W and F675W (1) to look for color and morphological evidence of the dominant mechanism among the competing theories for the BO effect and (2) to understand the origin of the enhanced radio activity. Enhancement of AGN in the substructure region would suggest that the environment is affecting the galaxy on very small nuclear scales. For star-forming galaxies, the color distribution can discriminate among several proposed mechanisms for producing a blue excess during cluster mergers. ------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 2] Observations Description ------------------------ We need to see the color distribution across each galaxy, as well as searching for signs of tidal interaction between neighboring galaxies. Based on our ground-based surface photometry, and guided by cycle 4 imaging of galaxies in Cl 0939+4713 (provided by Alan Dressler), we estimate that each field needs a total exposure of 3000s (F450W) and 1800s (F675W) to reach adequate signal/noise for color mapping across much of a typical spiral disk (the limiting factor for our application). These passbands are picked to represent rather closely U and V in the emitted frame. We have selected three fields within Abell 2125 for imaging with WFPC2. One includes the central (triple) galaxy and encompasses 7 detected radio galaxies, which we will take to represent the initial cluster population of red galaxies before infall of the new neighbors. Two more fields will cover almost all the bright galaxies (among which are eleven radio sources) in the southwest filament. This is where we particularly want to study the pattern of star formation and interactions. The selected fields are shown in Fig. 2, at the optimal camera orientations. Our orientation tolerances are not terribly strict, +/- 20^degrees or so, and this close to the northern ecliptic pole they do not impose very strong scheduling constraints. Real Time Justification ----------------------- No special requirements. Spectra have very recently been obtained for about 200 galaxies in the A2125 field (using the fiber spectrograph on the WIYN telescope) by a group led by Bill Oegerle and including the P.I. of this proposal. When these data have been reduced, we should have a detailed velocity field for A2125 which will further clarify the nature of any on-going cluster- cluster merger in A2125. We have already measured redshifts from the KPNO 4- meter for 35 radio galaxies, as shown in Fig. 1, and done the deep VLA observations for cluster selection. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2125- CLUSTER OF GALAXIES, RA=15H 41M 05.1S +/- 1", 2000 z=0.246 V = 16.5 CORE RICH CLUSTER, BCM, DEC=+66D 16' 37.1" +/- 1", PLATE B-V = 1.4 INTERACTING GALAXY -ID=01FX 2 ABELL2125- CLUSTER OF GALAXIES, RA=15H 40M 19.6S +/- 1", 2000 z=0.246 V = 17.3 SOUTH RICH CLUSTER, DEC=+66D 12' 29.0" +/- 1", PLATE B-V = 1.2 INTERACTING GALAXY -ID=01FX 3 ABELL2125- CLUSTER OF GALAXIES, RA=15H 39M 59.0S +/- 1", 2000 z=0.246 V = 17.3 SOUTHWEST RICH CLUSTER, DEC=+66D 10' 34.2" +/- 1", PLATE B-V = 1.2 INTERACTING GALAXY -ID=01FX 7279( 4) - 02/08/99 17:21 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 15D TO 50D 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 ABELL2125-C WFPC2 IMAGE WFALL-F F814W 1 2700. S POS TARG +35, +35 ORE IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2125-C WFPC2 IMAGE WFALL-F F606W 1 2700. S SAME POS AS 1 ORE IX ------------------------------------------------------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENT 150D TO 170D On Hold Comments: Additional Comments: schedule either visit 2 or 3; two are listed because there are two disjoint acceptable ORIENT ranges Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2125-S WFPC2 IMAGE WFALL-F F814W 1 2700. S POS TARG +45, +33 OUTH IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2125-S WFPC2 IMAGE WFALL-F F606W 1 2700. S SAME POS AS 1 OUTH IX ------------------------------------------------------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 6] Visit: 03 Visit Priority: Visit Requirements: ORIENT 160D TO 170D On Hold Comments: Additional Comments: schedule either visit 2 or 3; two are listed because there are two disjoint acceptable ORIENT ranges Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2125-S WFPC2 IMAGE WFALL-F F814W 1 2700. S POS TARG +35, +35 OUTH IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2125-S WFPC2 IMAGE WFALL-F F606W 1 2700. S SAME POS AS 1 OUTH IX ------------------------------------------------------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 7] Visit: 04 Visit Priority: Visit Requirements: ORIENT 45D TO 80D On Hold Comments: Additional Comments: schedule one of visits 4, 5, and 6; there are three disjoint acceptable ORIENT ranges Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2125-S WFPC2 IMAGE WFALL-F F814W 1 2700. S OUTHWEST IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2125-S WFPC2 IMAGE WFALL-F F606W 1 2700. S SAME POS AS 1 OUTHWEST IX ------------------------------------------------------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 8] Visit: 05 Visit Priority: Visit Requirements: ORIENT 160D TO 180D On Hold Comments: Additional Comments: schedule one of visits 4, 5, and 6; there are three disjoint acceptable ORIENT ranges Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2125-S WFPC2 IMAGE WFALL-F F814W 1 2700. S OUTHWEST IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2125-S WFPC2 IMAGE WFALL-F F606W 1 2700. S SAME POS AS 1 OUTHWEST IX ------------------------------------------------------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 9] Visit: 06 Visit Priority: Visit Requirements: ORIENT 270D TO 300D On Hold Comments: Additional Comments: schedule one of visits 4, 5, and 6; there are three disjoint acceptable ORIENT ranges Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ABELL2125-S WFPC2 IMAGE WFALL-F F814W 1 2700. S POS TARG +5, +5 OUTHWEST IX ------------------------------------------------------------------------------------------------------------------------------------ 2 ABELL2125-S WFPC2 IMAGE WFALL-F F606W 1 2700. S SAME POS AS 1 OUTHWEST IX ------------------------------------------------------------------------------------------------------------------------------------ 7279( 4) - 02/08/99 17:21 - [ 10] Summary Form for Proposal 7279 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFALL-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 15D TO 50D POS TARG +35, +35 SAME POS AS 1 ORIENT 150D TO 170D POS TARG +45, +33 ORIENT 160D TO 170D ORIENT 45D TO 80D ORIENT 160D TO 180D ORIENT 270D TO 300D POS TARG +5, +5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ABELL2125-CORE ABELL2125-SOUTH ABELL2125-SOUTHWEST ------------------------------------------------------------------------------------------------------------------------------------