6807( 10) - 01/10/97 11:52  - [  0]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      6807
                                                       Version: 10
                                                       Check-in Date: 10-Jan-1997
                                                                      11:49:52

1.Proposal Title:
The spatial distribution of dust extinction through spiral disks
------------------------------------------------------------------------------------
2. Scientific Category   3. Proposal For  4. Cycle
GALAXIES & CLUSTERS         GO               6
------------------------------------------------------------------------------------
5. Investigators
                                                                                     Contact?
    PI: HANS-WALTER RIX                   STEWARD OBSERVATORY

------------------------------------------------------------------------------------
6. Abstract

I propose WFPC2 imaging in V and I of a special galaxy pair (UGC 5041) in which the
light of an early-type galaxy is seen through the disk of a foreground spiral. These
systems provide an excellent opportunity to map with high spatial resolution the
dust extinction, tau_Lambda(\vecR), light passing through a galaxy disk. Knowing the
extinction distribution within galaxies is important (1) for interpreting the broad-
band colors of galaxies, (2) for the statistics of gravitationally lensed objects
and (3) for estimating the total hydrogen content of the damped LyAlpha absorber
population. Ground-based observations of these two galaxy pairs indicate optical
depths, averaged over (600 pc)^2 resolution elements, of tau_ V=0.3-1.2. However,
each 1^ resolution element is much larger than the width of dust lanes seen in more
nearby galaxies and therefore it contains areas of both much larger and much smaller
optical depth. The proposed HST observations provide the unprecedented opportunity
to probe the dust extinction over a contiguous area with a resolution (~ 60pc)
comparable to the width of the prominent dust lanes. Consequently, the data would
provide a greatly improved estimate of which portion of a spiral galaxy disk is
opaque (Tau_Lambda>> 1) or transparent (Tau_Lambda<< 1). Compared to ground-based
observations, the high resolution WFPC2 observations will also increase the contrast
of the small dust lanes and patches by nearly two orders of magnitude.
------------------------------------------------------------------------------------
  Data Distribution

  Media:           8MM
  Blocking Factor: 10
  Ship To:         PI_Address
  Ship Via:        UPS
  Email:                                                              ,
------------------------------------------------------------------------------------

                                                6807( 10) - 01/10/97 11:52  - [  1]

TARGET LIST    a) Fixed Targets
------------------------------------------------------------------------------------------------------------------------------------
Tar|   Target   |         Target        |            Target              |Coord   | Radial |             Flux data
No |    Name    |       Description     |           Position             |Eqnx    |  Vel.  |
------------------------------------------------------------------------------------------------------------------------------------
1   UGC5041      Galaxy                  RA=09H 27M 53.01S +/- 1S,        J2000             V = 13.4
                                         DEC=32D 39' 04.9" +/- 1", PLATE-                   B-V = 0.5
                                         ID=01RX

                                                6807( 10) - 01/10/97 11:52  - [  2]

Visit: 01
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1        UGC5041     WFPC2  IMAGE   WF3-FIX F814W            CR-SPLIT=NO                       1   500 S
------------------------------------------------------------------------------------------------------------------------------------
2        UGC5041     WFPC2  IMAGE   WF3-FIX F814W            CR-SPLIT=NO                       1   500 S
------------------------------------------------------------------------------------------------------------------------------------
3        UGC5041     WFPC2  IMAGE   WF3-FIX F814W            CR-SPLIT=NO                       1   500 S
------------------------------------------------------------------------------------------------------------------------------------
4        UGC5041     WFPC2  IMAGE   WF3-FIX F814W            CR-SPLIT=NO                       1   10 M
------------------------------------------------------------------------------------------------------------------------------------
                                                6807( 10) - 01/10/97 11:52  - [  3]

Visit: 02
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exposure|   Target  |Instr | Oper. | Aper  |Spectral|Central|             Optional            |Num|  Time |       Special
 Number |    Name   |Config| Mode  |or FOV |Element |Waveln.|            Parameters           |Exp|       |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1        UGC5041     WFPC2  IMAGE   WF3-FIX F555W            CR-SPLIT=NO                       1   500 S
------------------------------------------------------------------------------------------------------------------------------------
2        UGC5041     WFPC2  IMAGE   WF3-FIX F555W            CR-SPLIT=NO                       1   500 S
------------------------------------------------------------------------------------------------------------------------------------
3        UGC5041     WFPC2  IMAGE   WF3-FIX F555W            CR-SPLIT=NO                       1   500 S
------------------------------------------------------------------------------------------------------------------------------------
4        UGC5041     WFPC2  IMAGE   WF3-FIX F555W            CR-SPLIT=NO                       1   10 M
------------------------------------------------------------------------------------------------------------------------------------
                                                6807( 10) - 01/10/97 11:52  - [  4]

            Summary Form for Proposal  6807

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Configurations               WFPC2
------------------------------------------------------------------------------------------------------------------------------------
  Opmodes                      IMAGE
------------------------------------------------------------------------------------------------------------------------------------
  Optional Parameters          CR-SPLIT=NO
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            GO
------------------------------------------------------------------------------------------------------------------------------------
  Scientific Category          GALAXIES & CLUSTERS
------------------------------------------------------------------------------------------------------------------------------------
  Spectral Elements            F814W F555W
------------------------------------------------------------------------------------------------------------------------------------
  Target Names                 UGC5041
------------------------------------------------------------------------------------------------------------------------------------