Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4719c Report Date: 09-May-96:19:49 Version: ********** Check-in Date: ********** 1.Proposal Title: MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 - CYCLE 2 DD PROGRAM - CONT OF 2373 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO/DD 2 Long Term yrs 2373 Sub Category GALAXY MORPHOLOGY ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Alan Dressler CARNEGIE OBSERVATORIES USA 818-304-0245 ------------------------------------------------------------------------------------ 7. Abstract We outline a continuing program to study galaxy evolution through the investigation of galaxy morphology as a function of lookback time. The development of disks and bulges, the role of mergers, interactions, and other environmental influences, are expected to be visible over the range 0 < z < 1 as judged by the spectrophotometric evolution already observed over this redshift range. In this Cycle 2 we propose WFC imaging of one new field, the rich cluster A370 at z = 0.37, for which extensive photometry and already exist. Also, we will revisit a Cycle 1 target, the rich cluster CL0939+4713, for a 2-orbit exposure with the F555W filter to complement our 10-orbit exposure in F702W. This will be our first attempt to obtain limited color information to help interpret the morphological classifications we are engaged in. In general, all these data will be used primarily to classify images according to traditional morphological categories and will be used, within the constraints implied by deconvolution techniques, to measure surface brightness distributions and bulge-to-disk ratios. A brief description is given of how the data are applicable to specific questions, like the cause of enhanced starburst activity found for high- z galaxies. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 11.00 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4719c PI: Alan Dressler Proposal Title: MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 - CYCLE 2 DD PROGRAM - CONT OF 2373 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ P.I. Alan Dressler CARNEGIE OBSERVATORIES USA Harvey Butcher KAPTEYN OBSERVATORY NETHERLANDS X Augustus, Jr. Oemler DEPARTMENT OF ASTRONOMY, YALE U. USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. Our original plan was to use the WFC to image 2 fields in each of 8 clusters 0.36 < z < 0.55 over a period of 2 years, fields selected from ground-based CCD images. For each cluster, multicolor photometry for several hundred objects, and low-resolution spectra for 30-50 representative galaxies in the fields covering a magnitude range 19 < m(r) < 23, are available. These fields typically contain field/cluster galaxies in the ratio of 1/2, so the sample covers a wide range of environments. Spectra have been classified according to "activity", as described in the text and the papers cited. The field centers were chosen to maximize the number of "active" galaxies. Following the discovery of SA in the HST-OTA, we requested (and received) 11 hours from our original allocation of 28.5 to image a single cluster (CL0024+1654) in one color. This observation was intended to test the recovery of morphological information on high-redshift galaxies given the degraded imaging performance. We analyzed 3 hours of exposure of these data and concluded that, because of the small core of the PSF, salient features of morphological classification can be extracted with of order 6 hours or greater exposure on clusters at z = 0.4. With our remaining time in Cycle 1, we obtained an exposure of approximately 6 hours on a second cluster CL0939+4713. With the additional 11 hours allocated for Cycle 2, we will increase the integration on CL0024+1654 and add a new cluster CL1446+2621. In this DD proposal of 8 hours we are adding an 8-orbit exposure on the rich cluster A370. These exposures will be coadded from single-orbit exposures, done in a single color with filter F702W, which roughly corresponds to a rest-frame color between B and V. Information on color distributions formed a promising part of our original observing plan, but we were uncertain about ability to restore images of sufficient photometric accuracy through deconvolution. However, our subsequent experience with the LUCY algorithm has convinced us that we should explore the usefulness of multi-color data and test to what extent our conclusions on morphology are color dependent. Hence, this proposal includes a 2-orbit exposure with F555W (rest frame U) on one of our Cycle 1 targets, CL0939+4713. It is important that these additional data on CL0939+4713 be taken at the SAME ORIENT as the original F702W exposures. Also, it is essential that our exposures on A370 be done over a 7 day period in order to deliver the SAME ORIENT so that the frames may be coadded. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. For our original proposal we used CCD images of low-z cluster spirals to simulate HST observations and concluded that 20,000 s (8 x 2500 s single-orbit) exposures were desireable for satisfactory classification. We have obtained CCD images of spiral galaxies in a low-redshift cluster and used them to simulate exposures with the WFC, taking into account telescope and detector efficiency, dark current, readout noise, resolution, and sampling. From our 5 orbits of data on Cl0024+1654 (Cycle 1), and 10 orbits on CL0939+4713, we demonstrated that useful morphological data can be extracted, even with the SA problem, thanks to the significant power in the core of the PSF. In these data we clearly see thin disks and and unresolved point-like structures in galaxies with V = 21. We have chosen not to pursue even better S/N ratio data, but rather to use the balance of our time to image 2 other clusters (and to increase the exposure on CL0024+1654), so that we will have roughly 5 hours for each of 4 fields, thereby covering the minimum range of environments. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Do all exposures PER TARGET within 7 days in this program. For the first set, do the following: Do all exposures within 7 days. Exposure line 1 should be done first according to SPB, and the multiple exposures in lines 2 and 3 can follow as schedulable. The exposures in exposure log lines 1 and 2 are all to be done at POS TARG +10,-10 and those in exposure log line 3 are all to be done at POS TARG +11,-8. The SAME ORIENT should be used for all of the exposures in lines 1-3. Similar instructions apply to the next set of lines: The exposures in lines 4 and 5 can be done as schedulable within 7 days. The exposure in exposure log line 4 is to be done at POS TARG +10,-10 and the one in exposure log line 5 is to be done at POS TARG +11,-8. The SAME ORIENT should be used for both of the exposures in lines 4-5. NOTE: In the discussion above, and on the exposure logsheet lines, POS TARG +10,-10 is intended to roughly duplicate the old POS TARG 0,0 used in the Cycle 1 versions of this program, and POS TARG +11,-8 is intended to roughly duplicate the old Cycle 1 usage, POS TARG 1,2. These changes were made because the STScI redefined the coordinate system and apertures for the WF/PC. The aperture WFALL-FIX is used to tie the aperture center to the same reference point over time in case the WFALL aperture center location is shifted for any reason by STScI. ALSO, NOTE THE FOLLOWING: There is a specific ORIENT angle requested for the exposures of the second target, GAL-CLUS-093942+4713-FLD1 ( Exposure Log lines 4-5 ), with the angle being specified in the special requirements on Exposure Log line 4. So, there is both a specific ORIENT requirement for this target, and a requirement that all other data for it be taken at the SAME ORIENT. This is being done to match data in a different filter which was done in Proposal 4014. Specifically, the U3 ORIENT angle for the special requirement on Exp Log line 4 is 137.32D, and this is intended to match the ORIENT used in SUs 01 and 02 of GO 4014. This also corresponds to the V3 Position Angle of 317.32 used in 4014. ( V3 POS ANGLE - 180D = U3 ORIENT angle for special reqs. ) So, 317.32D - 180D = 137.32D = ORIENT for Exp Log lines 4-5. Note, however, that in this proposal, the coords for Cl 0939 have been moved 9 arcsec North of those used in GO 4014, at the request of the PI. Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. In order to accomplish our scientific objectives we must develop methods of moving from images to parametrized data. Traditionally this has been accomplished by using the image processing capabilities of the human eye plus brain, in order to assign morphological classes, estimate bulge-to-disk ratios, and describe distributions of color, dust, non-axisymmetric structures, etc. These classifications are semi-quantitative at best, and useful results regarding the evolution of galaxy morphology will depend on having an equivalent sample of observations at low redshift for which the same subjective criteria can be applied. With this in mind, Dressler has begun to obtain CCD images of low redshift clusters 0.02 < z < 0.04 in seeing of FWHM < 1 arcsecond. With suitable processing, such data can be used to simulate the HST observations (similar sampling, S/N, and resolution) in order to provide calibration images. Thus, although the criteria will remain subjective in this initial step, it can be applied so that redshift is the only significant variable, and a good assessment of differential morphology can be made. Our early comparison of our first HST images to convolved ground-based images for low-redshift confirms this approach as instructive in assessing morphology, even with the SA problem. With the point spread functions we obtained with our most recent data on CL0939+4713, we were highly successful in deconvolving the images with the LUCY algorithm. This had the primary effect of removing the scattered light of the PSF halos (due to spherical aberration) which were hampering somewhat our efforts at morhpological classification. ------------------------------------------------------------------------------------ 9. Description of previous HST work. We are presently involved in analyzing our first WFC images, of cluster CL0024+1654 and CL0939+4713, as described in the above text. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Dressler and Oemler each have access to a MicroVAX computer with image display capability. Each MicroVAX is part of a VAX system, supplied and maintained individually by MWLCO and Yale which includes a variety of I/O devices and access to BITNET and other communication networks. Both now also have and are using SUN workstations to process and analyze the WFC data. ------------------------------------------------------------------------------------ 11. Address Information Name: ALAN DRESSLER Category: PI Institution: CARNEGIE OBSERVATORIES Address: 813 SANTA BARBARA ST. City: PASADENA State: CA Zip Code: 91101 Country: USA Telephone: 818-304-0245 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4719c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS- F,404,411 RA= 02H37M21.3S +/-0.1S, 1950.0 Z=0.37 ABELL370- DEC= -01D47'15.5" +/-1" FLD1A ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS- F,404 RA= 09H39M48.0S +/-0.1S, 1950.0 Z=0.40 093942+4713- DEC= +47D12'30.0" +/-1" FLD1 Comments: COORDS ARE 9 ARCSEC NORTH OF THOSE USED IN GO 4014. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4719c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 1 2100S 1 CYCLE 2 / 1-3 ABELL370- FIX PRE-FLASH=NO POS TARG +10,-10 FLD1A GROUP 1-3 WITHIN 7D SAME ORIENT FOR 2- 3 AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 3 2200S 1 POS TARG +10,-10 ABELL370- FIX PRE-FLASH=NO FLD1A ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 4 2200S 1 POS TARG +11,-8 ABELL370- FIX PRE-FLASH=NO FLD1A Comments: OFFSET 1 ARCSEC IN RA AND 2 ARCSEC IN DEC TO REMOVE POSSIBLE EFFECTS ASSOCIATED WITH INDIVIDUAL PIXELS AND POINT SPREAD FUNCTIONS. ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-CLUS- WFC IMAGE WFALL- F555W CR-SPLIT=0.5 1 2000S 1 CYCLE 2 / 4-5 093942+4713 FIX CR- POS TARG +10,-10 -FLD1 TOLERANCE=0.0 GROUP 4-5 WITHIN PRE-FLASH=NO 7D ORIENT 137.32D +/- 0.01D Comments: THIS ORIENT IS INTENDED TO SAME ORIENT FOR 5 DUPLICATE THE ORIENT USED IN SU AS 4 01 AND 02 OF GO 4014, AND CORRESPONDS TO A V3 POS ANGLE OF 317.32. TARGET POSITION IS 9 ARCSEC NORTH OF THAT USED IN GO 4014. ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-CLUS- WFC IMAGE WFALL- F555W CR-SPLIT=0.5 1 2000S 1 POS TARG +11,-8 093942+4713 FIX CR- -FLD1 TOLERANCE=0.0 PRE-FLASH=NO Comments: OFFSET 1 ARCSEC IN RA AND 2 ARCSEC IN DEC TO REMOVE POSSIBLE EFFECTS ASSOCIATED WITH INDIVIDUAL PIXELS AND POINT SPREAD FUNCTIONS. MUST BE DONE AT SAME ORIENT AS EXP LOG LINE 4, ABOVE. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4719c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO PRE-FLASH=NO CR-SPLIT=0.5 CR-TOLERANCE=0.0 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO/DD ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 11.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category GALAXY MORPHOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 2 / 1-3; POS TARG +10,-10; GROUP 1-3 WITHIN 7D; SAME ORIENT FOR 2-3 AS 1; POS TARG +11,-8; CYCLE 2 / 4-5; GROUP 4-5 WITHIN 7D; ORIENT 137.32D +/- 0.01D; SAME ORIENT FOR 5 AS 4; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-CLUS-ABELL370-FLD1A GAL-CLUS-093942+4713-FLD1 ------------------------------------------------------------------------------------------------------------------------------------