6668( 4) - 12/09/98 15:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6668 Version: 4 Check-in Date: 09-Dec-1998 15:12:06 1.Proposal Title: Star Formation and Galaxy Morphologies in Distant, X-ray Luminous Clusters of Galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 6 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Megan Donahue Space Telescope Science Institute CoI: John Stocke University of Colorado N CoI: Gerry Luppino Institute for Astronomy N CoI: Isabella Gioia Institute for Astronomy N ------------------------------------------------------------------------------------ 5. Abstract Distant rich clusters of galaxies are natural laboratories for studying galaxy evolution because they provide large galaxy samples at fixed redshifts. Spectacular WFPC images of distant clusters of galaxies have revealed surprisingly complex galaxy morphologies and much higher interaction rates than in present-day clusters. We propose to obtain rest-frame U images of three distant (z=0.55-0.83) X-ray- selected, X-ray-luminous clusters of galaxies. With rest-frame B images from Cycle 5, we will be able to derive galaxy colors and color gradients. This data will distinguish young and old stellar populations, resolve galaxy ``train wrecks'', assess the colors of disk and bulges, and distinguish ram-pressure vs. merger induced star formation. We will compare the star formation in these galaxy clusters with that in low-z clusters of similar X-ray luminosity, distant optically-selected clusters, and field galaxies of similar redshift from the Hubble Deep Survey. Since intracluster medium (ICM) evolution plays at le ast a partial role in many models of galaxy evolution, these observations will test those models. Our ground-based and ROSAT and ASCA observations will supply cluster velocity dispersions, ICM morphology, temperatures and metallicities, as well as gas and cluster masses to characterize the intergalactic environment of these distant galaxies. Since at least two of these clusters are lensing background galaxies, these observations will provide morphology and color information for normal galaxies at even higher redshifts. ------------------------------------------------------------------------------------ 6668( 4) - 12/09/98 15:13 - [ 2] Observations Description ------------------------ We request 3 orbits to augment our Cycle 5 request to complete rest-frame B- band imaging of these clusters (see Duplications). The rest of our request, as limited by the Cycle 6 TAC, will be devoted to acquire rest- frame U-band images for only one cluster at redshifts 0.83. We will construct a single image of the cluster, at rest-wavelength U. We have chosen filters to enhance the contrast for photon wavelengths shorter than 4000Angstrom, while maximizing the number of counts. These filters will also be used by the Hubble Deep Field, thus facilitating direct comparison to the HDF galaxy sample. The orbit estimations were done assuming limiting magnitudes of m(U_rest) = 26.8 mag arcsec^-2 (z=0.8) in the F606W filter, and a required S/N=8-10 in 1 arcsec^2. This will produce observations similar to those acquired by Dressler et al. with the WF. We assumed sky ~ 27 mag pix^-1, dark counts 0.035 s^-1 pix^-1 and read noise of 5.2e^- pix^-1, and the handbook QT integral for the individual filters. Each orbit was assumed to have 45 minutes of visibility. Our results are tabulated below. Sky noise exceeds read noise in exposures exceeding 3-5 minutes, so the exposure during each orbit can be CR-SPLIT. Since we will have plenty of exposures, we have chosen not to CR-SPlIT the exposures so that we do not lose the overhead time. Filter& m_zero & Limit & Limit & Sky & Sky & SNR & Orbits , & & mag/pix & /s/pix & mag/pix & /s/pix (1"x1") F606W & 25.05 & 31.8 & 2.0(-3) & 27.0 & 0.166 & 8 & 10 We will dither the pointing between orbits 5 and 6 to remove hot pixels and improve spatial sampling. Real Time Justification ----------------------- We will have Cycle 5 images of rest-frame B-band images of all 3 clusters. We have ASCA X-ray spectra for MS0451-03 (Donahue 1995, submitted) and MS1137+66 (Donahue et al. in prep.), as well as ROSAT PSPC images and spectra (Donahue & Stocke, 1995, ApJ, 449, 554), and a concurrent ASCA AO4 proposal for MS1137+66. X-ray spectra allow the determination of an overall gas temperature and iron abundance. We have deep ROSAT HRI (High Resolution Imager) observations for all clusters. (The most distant 2 are given priority A in AO6, MS0451-03 was observed in AO5). Xray HRI maps will allow the quanitification of structure in the cluster potential on scales of 30 h_50^-1 kpc. MS0451-03 now has 50 member redshifts, obtained by the CNOC collaboration, and MS1137+66 has 10 from our CFHT observations. We are planning to obtain stackrel>~ 30 redshifts for each of the remaining two clusters with Keck. A lens has been discovered in MS0451- 03 (Luppino & Gioia 1995). Luppino & Kaiser (1995) have looked for weak gravitationa l lensing on a deep I-band image of MS1137+66, and have measured a clear shear signal at the 6Sigma level -- the first detection of lensing at such a high redshift. Similarly deep data does not yet exist for MS1137+66, but will be obtained this Spring with the Keck telescope. High resolution 20 cm radio continuum maps have been made of all three clusters with the VLA's B configuration deep enough to detect typical, low- luminosity cluster radio galaxies, and several head-tail radio galaxies have been discovered in each clusters. Several radio galaxies are detected in each cluster with morphologies and luminosities similar to those found in nearby rich clusters. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6668( 4) - 12/09/98 15:13 - [ 3] Data Distribution Paper Products: Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6668( 4) - 12/09/98 15:13 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MS1137+66 CLUSTER OF GALAXIES RA=11H 37M 36.2S +/- 5", DEC=66D B1950 Z = 0.78 SURF(I) = 25 24' 56.9" +/- 5" 6668( 4) - 12/09/98 15:13 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: This target was observed in Cycle 5, program 5987. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2700 S ------------------------------------------------------------------------------------------------------------------------------------ 2 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6668( 4) - 12/09/98 15:13 - [ 6] Visit: 02 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 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2700 S POS TARG 10, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 MS1137+66 WFPC2 IMAGE WF3 F606W 1 2800 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6668( 4) - 12/09/98 15:13 - [ 7] Summary Form for Proposal 6668 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SAME POS AS 1 POS TARG 10, 0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names MS1137+66 ------------------------------------------------------------------------------------------------------------------------------------