Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4014c Report Date: 09-May-96:19:04 Version: ********** Check-in Date: ********** 1.Proposal Title: MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 : CYCLE 1 OBSERVATIONS - PART 2 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO 2 Long Term yrs 2373 Sub Category EVOLUTION/COSMOLOGY ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Alan Dressler THE OBSERVATORIES OF THE CAR USA 818-304-0245 ASTRONOMER ------------------------------------------------------------------------------------ 7. Abstract Our program is intended 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 The approved Cycle I version of this two year program called for imaging with the Wide Field Camera 5 fields in four rich clusters of galaxies at z = 0.35 - 0.55 for which extensive photometry and spectroscopy already exist. The fields included a wide range of environments from the dense cores of clusters to isolated field galaxies. These data were to be used to classify images according to traditional morphological categories and will be used to determine quantitative measures of surface brightness distributions and bulge-to-disk ratios. Due to the SA of the HST optical system, the new goal is to image a single field in one color for three times the exposure (10 hours total) in order to assess the feasibility of these goals with the present performance of the system. ------------------------------------------------------------------------------------ 8. Scientific Key Words: GALAXY MORPHOLOGY, EVOLUTION, GALAXY CLUSTER ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 11.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4014c PI: Dr. Alan Dressler Proposal Title: MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 : CYCLE 1 OBSERVATIONS - PART 2 ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Prof. Harvey Butcher KAPTEYN OBSERVATORY NETHERLANDS X Prof. Augustus, Jr. Oemler DEPARTMENT OF ASTRONOMY, YALE USA UNIVERSITY P.I. Alan Dressler THE OBSERVATORIES OF THE USA CARNEGIE INSTITUTION OF WASHINGTON ------------------------------------------------------------------------------------ 3. Description of proposed observations. The original approved program called for imaging with the WFC of 5 fields in 4 clusters 0.36 < z < 0.55 in the first year of a two-year program. Ground-based CCD images of these fields were used to select a WFC field which includes an area for which multicolor photometry for most objects and low resolution spectroscopy for some objects are already in hand. A typical field will contain 1 contaminating field galaxy for every 2 cluster galaxies, so the sample covers a wide range of environments. The spectra have been classified according to "activity", related to star formation or an active nucleus. We have now chosen another single field in one of the lower redshift clusters of our sample, Cl0939+4712, in order to evaluate the degradation due to SA in the HST optical system, and the ability of deconvolution techniques to recoup some of these losses. The field center has been chosen to maximize the number of "active" galaxies. Observations will be coadded single-orbit exposures of 15,000 s in one broad-band color, roughly corresponding to rest-frame B. This will be directly comparable to morphological classification at low redshift which is traditionally done in this color. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Morphology is the missing component in our attempts to study galaxy evolution for 0 < z < 1. At the distance of our intended targets, 1 arcsecond = 7 1/h kpc, so morphological classification is extremely crude with ground-based seeing of FWHM = 0.5-1.0 arcseconds. No meaningful comparisons can be made with low-z classification systems. The HST with the WFC, with its field of 2.7 x 2.7 arcminutes and 0.1 arcsecond pixels, affords us the only opportunity to fundamentally correct this deficiency. Though not as detailed as the classification of galaxies within the Local Supercluster, where resolutions of order 100 pc can be obtained, imaging with resolutions of order 1 kpc has thus been shown to be sufficient to distinguish between the major classes in the Hubble or de Vaucouleurs schemes. Before the discovery of SA in the HST optical system, it was anticipated that nearly the same resolution of 0.7 1/h kpc could be obtained for galaxies in clusters at z = 0.5. The present plan is to test the degree to which the poorer resolution impacts the program, and to what extent higher S/N ratio imaging combined with deconvolution can restore the original capability. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. 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 0,0 and those in exposure log line 3 are all to be done at POS TARG 2,3. The SAME ORIENT should be used for all of the exposures in lines 1-3. Exposure log line 4 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 1-3, but not necessarily at the SAME ORIENT as the other ( science ) exposures in 1-3. Half of this program was done on another cluster, 0024+1653, but all observations were not taken together and cannot be done for some time due to nearly mutually exclusive guide star availability and target visibility problems. The STScI Director therefore approved our request to conclude our Cycle 1 test by using another of the clusters which we had previously deferred to Cycle 2. From CCD images of low-z cluster spirals we simulated HST observations and concluded that, for clusters at z = 0.4, exposures of 15,000 s (6 x 2500 s single-orbit) exposures would be required for a S/N = 20, necessary even for rudimentary classification. We have arrived at these numbers by obtaining CCD images of spiral galaxies in low-redshift clusters and using them to simulate exposures with the HST WFC, taking into account telescope and detector efficiency, dark current, readout noise, resolution, and sampling. However, these simulations did not take into account the poorer optical performance of HST. In light of this, we have obtained computer simulations done by William Keel for HST imaging projects of Windhorst et al. that make use of a V=20 mag spiral at z = 0.3. From these tests we expect that the gross features like spiral structure should be discernible in an exposure of approximately 30,000 s in a cluster at z = 0.40, particularly if a fair fraction of the light is in point sources (H-II regions) and sufficient S/N ratio is reached to allow successful deconvolution. We have not included the possibility that evolution may make such features easier to detect. We will propose further cluster observaions in Cycle 2 or abandon the program for the present depending on the the results of this test. ------------------------------------------------------------------------------------ 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 be 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. Of course, deconvolution techniques will play a major role in the processing of these data. ------------------------------------------------------------------------------------ 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. ------------------------------------------------------------------------------------ 11. Address Information Page 4 Name: ALAN DRESSLER Category: PI Institution: THE OBSERVATORIES OF THE CARNEGIE Address: 813 SANTA BARBARA ST. City: PASADENA State: CA Zip Code: 91101 Country: USA Telephone: 818-304-0245 Telex (or e-mail): 1561318 OCIW UT ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4014c [ 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- Z = 0.40 CLUSTER OF RA= 09H39M48.0S +/-0.1S, 1950.0 Z=0.40 093942+4713- GALAXIES DEC= +47D12'21.0" +/-1" FLD1 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC188PSF-1 PSF STAR FIELD RA=00H 47M 32S +/-0.5S, 2000 DEC= +85D 14' 58" +/-1", ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4014c [ 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 ALL F702W CR-SPLIT=NO 1 700S 1 CYCLE 1 / 1-4 093942+4713 PRE-FLASH=NO POS TARG 0,0 / 1-2 -FLD1 GROUP 1-4 WITHIN 7D SAME ORIENT FOR 2- 3 AS 1 Comments: THIS SHORT-EXPOSURE LINE ADDED PER SPB REQUEST AND WITH OK FROM PI TO GO 2373 AND DUPLICATED FOR SAME PURPOSE HERE. SAME ORIENT FOR 1-3. RAL 18/12/91 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-CLUS- WFC IMAGE ALL F702W CR-SPLIT=NO 5 2200S 1 093942+4713 PRE-FLASH=NO -FLD1 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-CLUS- WFC IMAGE ALL F702W CR-SPLIT=NO 5 2200S 1 POS TARG 2,3 093942+4713 PRE-FLASH=NO -FLD1 Comments: OFFSET 2 ARCSEC IN RA AND 3 ARCSEC IN DEC TO REMOVE POSSIBLE EFFECTS ASSOCIATED WITH INDIVIDUAL PIXELS AND POINT SPREAD FUNCTIONS. THIS LINE ADDED TO GO 2373 PER REQUEST FROM PI AND DUPLICATED HERE. RAL - 18/12/91 ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC188PSF-1 WFC IMAGE ALL F702W CR-SPLIT=NO 2 40S 1 CYCLE 1 PRE-FLASH=YES POS TARG 0,0 Comments: SHORT EXPOSURE OF NGC188 AT POS TARG 0,0 FOR DETERMINATION OF PSF OVER WIDE FIELD IN F702W. EXPOSURE TIME MAY HAVE TO BE REVISED. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4014c [ 7] 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 EVOLUTION/COSMOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 1 / 1-4; POS TARG 0,0 / 1-2; GROUP 1-4 WITHIN 7D; SAME ORIENT FOR 2-3 AS 1; POS TARG 2,3; CYCLE 1; POS TARG 0,0; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-CLUS-093942+4713-FLD1 NGC188PSF-1 ------------------------------------------------------------------------------------------------------------------------------------