Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3857c Report Date: 09-May-96:18:53 Version: ********** Check-in Date: ********** 1.Proposal Title: MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 - CONT OF 2373 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO 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. We propose in Cycle 2 to continue our efforts by imaging with the Wide Field Camera two additional fields containing rich clusters of galaxies at z = 0.5 for which extensive photometry and spectroscopy already exist. The fields include a range of environments, from the dense cores of clusters to isolated field galaxies. 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 3857c PI: Alan Dressler Proposal Title: MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 - 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. From our revised Cycle 1 allocation we have acquired 3 hrs on cluster CL0024+1654 and 6 hours on Cl0939+4713. These observations demonstrate that morphological information can be extracted from high-redshift galaxies despite the degraded imaging performance of HST. The 20% of the light concentrated in the small PSF core has made it possible to assess the salient features of morphological classification like bulge-to-disk ratio and strong spiral structure with of order 6 hours of exposure on clusters at z = 0.4. With our time in Cycle 2, we have scheduled approximately 6 hours on a third cluster CL1446+2621 and an additional 3 hours on CL0024+1654. 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 though minor part of our original observing plan, but the prospect of restoring images of high photometric accuracy through deconvolution is sufficiently daunting that we will not attempt this unless experiments by others confirm its feasibility. We have included exposures of NGC 188 in order to build up a library of PSF's over the field with filter F702W. It is important that our exposures be done over a 7 day period per target in order to deliver the SAME ORIENT so that the frames may be coadded. We also request that a set of the PSF exposures of NGC 188 be grouped within the same 7 days in which each target is observed. 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 6 orbits of data on Cl0024+1654 and 10 orbits on CL0939+4713 (Cycle 1), we have confirmed the results of these simulations that useful morphological data can be extracted, even with the SA problem, due to the non-negligible power in the core of the PSF. In these data we clearly see thin disks and unresolved point-like structures in galaxies with V = 21. At this time, our plan is to compromise between even better data and some range of cluster environments, by choosing to use our 22 allocated hours to image 3 different clusters at roughly 6 hours each. NOTE: With the approval of the STScI, this program has now been revised to include 2 of a total of 10 hours of Director's Discretionary time which was awarded us in late Spring of 1992. With this extra 2 hours, we have increased our exposure time on the target GAL-CLUS-1446+2621 by increasing the number of exposures to 5 in both Exposure Log lines 4 and 5. The remaining 8 hours of Director's Discretionary time is being used to study the cluster Abell 370 in a separate Director's Discretionary ( GO/DD ) proposal, also in Cycle 2. Page 4 ------------------------------------------------------------------------------------ 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. The exposures in exposure log line 1 and 1.5 are all to be done at POS TARG +10,-10 and those in exposure log line 2 are all to be done at POS TARG +12,-7. The SAME ORIENT should be used for all of the exposures in lines 1 through 2. Exposure log line 3 is for two short exposures of NGC 188 in order to determine PSFs across the field of all 4 chips. They should be done within the same week as exposure lines 1 through 2, but not necessarily at the SAME ORIENT as the other ( science ) exposures in 1 through 2. The same instructions apply to the next set of lines, but SPB says no single shorter exp is needed. Do all exposures within 7 days. The exposures in exposure log line 4 are all to be done at POS TARG +10,-10 and those in exposure log line 5 are all to be done at POS TARG +12,-7. The SAME ORIENT should be used for all of the exposures in lines 4 and 5. Exposure log line 6 is for two short exposures of NGC 188 in order to determine PSFs across the field of all 4 chips. They should be done within the same week as exposure lines 4 and 5, but not necessarily at the SAME ORIENT as the other ( science ) exposures in 4 and 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 +12,-7 is intended to roughly duplicate the old Cycle 1 usage, POS TARG 2,3. 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 set of specific ORIENT angles requested for the exposures of the first target, GAL-CLUS-0024+1653-FLD1A (Exposure Log lines 1 through 2), with one angle being specified in the special requirements on Exposure Log line 1, and acceptable alternate ORIENT angles which are 90 degrees apart with a range +/- 5 degrees being specified in the comments section of Exposure Log line 1. 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 as whichever of the angles is used for the first exposure. NOTE ALSO THAT SPB HAS SAID THAT EXPOSURE LOG LINE 1 SHOULD BE USED FOR THE INITIAL ACQUISITION, AND IT HAS BEEN MADE SHORTER BY 100S, BY STSCI, FOR THAT REASON. THIS ONLY APPLIES TO THE FIRST TARGET, GAL-CLUS-0024, AND NOT TO THE SECOND, GAL-CLUS-1446, SINCE SPB DID NOT THINK THERE WOULD BE A PROBLEM WITH THE ACQUISITION TIME FITTNG ALONG WITH THE SCIENCE EXPOSURE IN THE FIRST ORBIT FOR THAT TARGET. ------------------------------------------------------------------------------------ 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. We have used our exposures of NGC-188 to produce PSF models for use in Lucy deconvolution that have significantly improved our ability to classify these distant galaxies. Page 5 ------------------------------------------------------------------------------------ 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 Carnegie Observatories and Yale which includes a variety of I/O devices and access to BITNET and other communication networks. ------------------------------------------------------------------------------------ 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 = 3857c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 RA= 00H24M00.3S +/-0.1S, 1950.0 Z=0.40 0024+1653- DEC= +16D53'10.0" +/-1" FLD1A Comments: CLUSTER OF GALAXIES AT Z=0.40. ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS- F,404 RA= 14H47M16.5S +/-0.1S, 1950.0 Z=0.37 1446+2621 DEC= +26D20'20.0" +/-1" Comments: CLUSTER OF GALAXIES AT Z=0.37. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC188PSF-1 C,202 RA=00H 47M 32S +/-0.5S, 2000 DEC= +85D 14' 58" +/-1", Comments: NGC 188 PSF STAR FIELD #1 FROM WF/PC GTO COORDS. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC188PSF-4 C,202 RA=00H 46M 51S +/-0.5S, 2000 DEC= +85D 15' 33" +/-1", Comments: NGC 188 PSF STAR FIELD #4 FROM WF/PC GTO COORDS. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3857c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 / 1-6 0024+1653- FIX PRE-FLASH=NO POS TARG +10,-10 FLD1A GROUP 1-3 WITHIN 7D ORIENT 196D +/- 5D / 1-2 Comments: WFC OFFSET ANGLE = 45.3 DEGREES SAME ORIENT FOR SKY POSITION ANGLE OF FIELD: 1.5-2 AS 1 331D. ORIENT ANGLES OF 16D +/- 5D, 106D +/- 5D, 286D +/- 5D ALSO ACCEPTABLE. ------------------------------------------------------------------------------------------------------------------------------------ 1.5 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 2 2200S 1 POS TARG +10,-10 0024+1653- FIX PRE-FLASH=NO FLD1A ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 3 2200S 1 POS TARG +12,-7 0024+1653- FIX PRE-FLASH=NO FLD1A Comments: OFFSET 2 ARCSEC IN RA AND 3 ARCSEC IN DEC TO REMOVE POSSIBLE EFFECTS ASSOCIATED WITH INDIVIDUAL PIXELS AND POINT SPREAD FUNCTIONS. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC188PSF-1 WFC IMAGE WFALL- F702W CR-SPLIT=NO 2 40S 1 POS TARG +10,-10 FIX PRE-FLASH=YES Comments: SHORT EXPOSURE OF NGC188 AT POS TARG +10,-10 FOR DETERMINATION OF PSF OVER WIDE FIELD IN F702W. EXPOSURE TIME MAY HAVE TO BE REVISED. ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 5 2200S 1 POS TARG +10,-10 1446+2621 FIX PRE-FLASH=NO ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-CLUS- WFC IMAGE WFALL- F702W CR-SPLIT=NO 5 2200S 1 POS TARG +12,-7 1446+2621 FIX PRE-FLASH=NO ORIENT 305.356D +/ - 0.01D Comments: OFFSET 2 ARCSEC IN RA AND 3 ARCSEC IN DEC TO REMOVE POSSIBLE EFFECTS ASSOCIATED WITH INDIVIDUAL PIXELS AND POINT SPREAD FUNCTIONS. ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC188PSF-4 WFC IMAGE WFALL- F702W CR-SPLIT=NO 2 40S 1 POS TARG +10,-10 FIX PRE-FLASH=YES Comments: SHORT EXPOSURE OF NGC188 AT POS TARG +10,-10 FOR DETERMINATION OF PSF OVER WIDE FIELD IN F702W. EXPOSURE TIME MAY HAVE TO BE REVISED. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3857c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO PRE-FLASH=NO PRE-FLASH=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 11.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category GALAXY MORPHOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 2 / 1-6; POS TARG +10,-10; GROUP 1-3 WITHIN 7D; ORIENT 196D +/- 5D / 1-2; SAME ORIENT FOR 1.5-2 AS 1; POS TARG +12,-7; ORIENT 305.356D +/- 0.01D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-CLUS-0024+1653-FLD1A GAL-CLUS-1446+2621 NGC188PSF-1 NGC188PSF-4 ------------------------------------------------------------------------------------------------------------------------------------