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    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID 2373c
                                                       Report Date: 09-May-96:17:04
                                                       Version: **********
                                                       Check-in Date: **********

1.Proposal Title:
MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 : CYCLE 1 OBSERVATIONS
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2. Scientific Category   3. Proposal For  4. Proposal Type        5. Continuation ID
GALAXIES & CLUSTERS         GO               2 Long Term yrs         <none>
Sub Category
EVOLUTION/COSMOLOGY
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6. Principal Investigator   Institution                    Country    Telephone
Dr. Alan  Dressler          THE OBSERVATORIES OF THE CAR   USA        818-304-0245
ASTRONOMER
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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.
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8. Scientific Key Words:   GALAXY MORPHOLOGY, EVOLUTION, GALAXY CLUSTER
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9. Est obs time (hours) pri: 11.00    par: 0       10. Num targs pri: 1      par: 0
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11. Instruments requested:  WF/PC
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                                                                  Page   2
I. GENERAL FORM    Proposal 2373c
PI: Dr. Alan  Dressler
Proposal Title:
MORPHOLOGY OF GALAXIES IN CLUSTERS AT Z = 0.5 : CYCLE 1 OBSERVATIONS
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1. Proposers:
Proposers                        Institution                       Country       ESA
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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
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  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 a
 single field in one of the lowest redshifts clusters of our sample, Cl0024-1653,
 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.
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  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.
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  5. Description of special scheduling requirements.
  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.
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  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.
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 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.
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11. Address Information
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
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TARGET LIST    a) Fixed Targets                                                                    ID = 2373c            [  4]
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 1 |     2      |           3           |              4             |  5     |   6    |  7  |              8
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Tar|   Target   |         Target        |            Target          |Coord   | Radial |Acqui|FLX|     Flux data
No |    Name    |       Description     |           Position         |Eqnx    |  Vel.  |Prblm|REF|
   |            |                       |                            |        |        |     |   |
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1   GAL-CLUS-    Z = 0.39 CLUSTER OF     RA= 00H23M56.2S +/-0.1S,     1950.0   Z=0.39
    002400+16530 GALAXIES                DEC= +16D53'19" +/-1"
    0-FLD1
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EXPOSURE LOGSHEET                                                                                  ID = 2373c            [  5]
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 1      |   2   |      3    |  4   |   5   |   6   |    7   |   8   |       9       |10 |   11  |   12    |13 |14|        15
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  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
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1        DEFINE  #           WFC    IMAGE   ALL     #                CR-SPLIT=NO     #   2100S                 #
         MEXP                                                        PRE-FLASH=NO
     Comments: THIS SEQUENCE IS INTENDED TO
               FIT EACH EXPOSURE INTO 1 ORBIT.
               ADJUST EXPOSURE TIME +/- 20
               PERCENT TO ACCOMPLISH. THIS IS
               THE CYCLE 1 VERSION OF THIS
               PROPOSAL: AD 91/04/10
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1.9              GAL-CLUS-   WFC    IMAGE   ALL     F702W            CR-SPLIT=NO     1   700S                  1  CYCLE 1 / 1.9-3
                 002400+1653                                         PRE-FLASH=NO                                 POS TARG 0,0 / 1.9
                 00-FLD1                                                                                          -2
     Comments: THIS LINE ADDED PER SPB REQUEST
               AND WITH OK FROM PI. RAL 28/06/
               91
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2        USE     GAL-CLUS-                          F702W                            9                         1
         MEXP    002400+1653
                 00-FLD1
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3        USE     GAL-CLUS-                          F702W                            8                         1  POS TARG 2,3
         MEXP    002400+1653
                 00-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 PER REQUEST FROM PI.
               RAL - AUG. 1991
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            Summary Form for Proposal 2373c                                                                              [  6]

  Item                          Used in this proposal
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  Configurations                WFC
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  Opmodes                       IMAGE
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  Optional Parameters           CR-SPLIT=NO PRE-FLASH=NO
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  Proposal for                  GO
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  S/C Hours                     11.00
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  Scientific Category           GALAXIES & CLUSTERS
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  Scientific Sub-category       EVOLUTION/COSMOLOGY
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  Special Requirements          CYCLE 1 / 1.9-3; POS TARG 0,0 / 1.9-2; POS TARG 2,3;
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  Spectral Elements             # F702W
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  Target Names                  GAL-CLUS-002400+165300-FLD1
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