10550(  2) - 05/12/05 08:17  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      10550
                                                       Version: 2
                                                       Check-in Date: 12-May-2005
                                                                      12:17:12

1.Proposal Title:
The Nature of LSB galaxies revealed by their Globular Clusters
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2. Proposal For  3. Cycle  4. Parallel Pointing Tolerance
GO               14        <none>
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5. Investigators
                                                                                     Contact?
    PI: Dr. Markus Kissler-Patig          European Southern Observatory - Germany
   CoI: Dr. Andres Jordan                 European Southern Observatory - Germany       N
   CoI: Dr. Paul Goudfrooij               Space Telescope Science Institute             N
   CoI: Dr. Martin A. Zwaan               European Southern Observatory - Germany       N

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6. Abstract

Low Surface Brightness (LSB) galaxies encompass many of the extremes in galaxy
properties. Their understanding is essential to complete our picture of galaxy
formation and evolution. Due to their historical under-representation on galaxy
surveys, their importance to many areas of astronomy has only recently began to be
realized. Globular clusters are superb tracers of the formation histories of
galaxies and have been extensively used as such in high surface brightness galaxies.
We propose to investigate the nature of massive LSB galaxies by studying their
globular cluster systems. No globular cluster study has been reported for LSB
galaxies to date. Yet, both the presence or absence of globular clusters set very
strong constraints on the conditions prevailing during LSB galaxy formation and
evolution. Both in dwarf and giant high surface brightness (HSB) galaxies, globular
clusters are known to form as a constant fraction of baryonic mass. Their
presence/absence immediately indicates similarities or discrepancies in the
formation and evolution conditions of LSB and HSB galaxies. In particular, the
presence/absence of metal-poor halo globular clusters infers
similarities/differences in the halo formation and assembly processes of LSB vs. HSB
galaxies, while the presence/absence of metal-rich globular clusters can be used to
derive the occurrence and frequency of violent events (such as mergers) in the LSB
galaxy assembly history. Two band imaging with ACS will allow us to identify the
globular clusters (just resolved at the selected distance) and to determine their
metallicity (potentially their rough age). The composition of the systems will be
compared to the extensive census built up on HSB galaxies. Our representative sample
of six LSB galaxies (cz < 2700 km/s) are selected such, that a large system of
globular clusters is expected. Globular clusters will constrain phases of LSB galaxy
formation and evolution that can currently not be probed by other means. HST/ACS
imaging is the only facility capable of studying the globular cluster systems of LSB
galaxies given their distance and relative scarcity.
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                                                10550(  2) - 05/12/05 08:17  - [  2]

  Observations Description
  ------------------------

     Requirements to meet the Scientific Objectives: To meet goals our scientific
     goals we need a representative sample of globular clusters in each galaxy. The
     number of globular clusters is known to scale with galaxy luminosity (i.e.
     roughly constant specific frequency SN, defined as the number of globular
     clusters per unit MV = ?15 of the galaxy) with some dependence on galaxy type.
     The SN of LSB galaxies is unknown, but we conservatively assume it is low, i.e.
     in the regime of late-type galaxies, SN~1. In our selected galaxies (L??0.5
     mag), we expect between 50 and several 100 globular clusters. Thus, an adequate
     minimum number of several tens of globular clusters in each of the two broad
     sub-populations is met by sampling the GCLF up to a magnitude or more past the
     turn-over (Mg(TO)~?6.8 mag). To derive colors with the required accuracy (~0.1
     mag or better, see Fig. 1), we aim at a S/N~10 at these magnitudes (Mg~?5.5 mag
     or g~25.0 to 26.5 given the distance of our targets). Any general conclusions
     on the formation and evolution of LSB galaxies must be supported by the study
     of a minimum sample of massive LSB galaxies. We restrict ourselves in this
     study to LSB galaxies selected by their rotational velocity (measured through
     the 21-cm velocity width W20) to have masses roughly of the Milky Way or above.
     This ensures that these systems should have enough globular cluters for our
     analysis. The sample was further selected to span a range of total luminosities
     around L?, as well as about 2 magnitudes in surface brightness. Finally, we
     applied a distance cut-off ((m ? M)~32.5, 2500 km/s) to ensure that star
     clusters are still resolved in the ACS images. ACS deep wide-field Imaging in
     two Colors: ACS deep wide-field images in Sloan g (F475W) and Sloan i (F775W)
     will be used to investigate the globular cluster systems of LSB galaxies. The
     Sloan bandpasses were chosen to optimize sensitivity for globular clusters type
     objects and to provide a long color baseline for high sensitivity to
     metallicity and some sensitivity to age (e.g. the mean color difference between
     metal-poor [Fe/H]~?1.5 dex, and metal-rich [Fe/H]~?0.5 dex globular clusters
     will be (g ? i)~0.3 mag; the mean difference in magnitude between a 13 Gyr and
     a 4 Gyr population will be around g ~1 mag). The globular cluster
     identification will be performed both through colors (chosen to allow
     discrimination of stars and OB associations), and the fact that most globular
     clusters will still be barely resolved at the chosen distances. We will line
     dither to facilitate cosmic ray removal and increase effective spatial
     resolution. Our strategy, recipes and data reduction scripts were confirmed on
     the large dataset of ACS Virgo globular clusters study (Jordan et al. 2004).
     The requirement of resolving the globular clusters sets the upper distance to
     our targets, which in turn defines the visual peak magnitude of the GCLF to be
     probed and the limiting magnitude to be reached at a S/N~10: g~26.5 and i~25.5.
     This goal can be reached in 1100s and 650s, respectively, according to the ACS
     exposure time calculator (varying by ?10% depending the star clusters
     age/metallicicty, i.e. spectral type). Assuming 1 target acquisition, the g-
     band time split into 3 dithered exposures, the i-band split into 2, we arrive
     at a total duration of ~52 min per galaxy, i.e. both exposures fit in 1 HST
     orbit (assuming our worst case: DEC 0 deg, 2-gyro mode). Galaxy Sample
     Selection: Our goal is to meet the criteria listed in the above section while
     selecting a representative sample of massive LSB galaxies. LSB galaxies much
     more luminous than L? are very rare (i.e. not typical/representative), while
     LSB galaxies significantly fainter than MB > ?18 mag are not expected to host
     significant globular cluster populations (see above). Thus, we focus here on
                                                10550(  2) - 05/12/05 08:17  - [  3]

     LSB galaxies with luminosities around L?. Among these, we selected 6 galaxies
     as a minimum number spanning the typical ranges of surface brightness, H I
     mass, MHI/LB ratios found in LSB galaxies. The galaxies were selected following
     the above criteria from the catalogs of Bothun et al. (1985) and O?Neil et al.
     (2004). Their work is largely based on the Uppsala General Catalog (UGC, Nilson
     1973) which we went back to in order to select the galaxies in size and to
     compute the photographic surface brightness (?mpg ). Absolute magnitudes (MB0)
     were derived with the most recent data compiled in the Nasa Extragalactic
     Database (NED), using the Schlegel et al. (1998) reddening maps. All galaxies
     were further visually inspected on Digital Sky Survey (DSS) images. The six
     selected galaxies are: Name MB0 ?mpg H I W20 rad.vel. [mag] [mag] [km/s] [km/s]
     UGC 477 -19.0 26.3 246 2649 UGC 3459 -19.9 25.8 311 2475 UGC 3587 -19.0 25.5
     220 1267 UGC 6138 -18.5 25.9 224 2574 UGC 11131 -19.4 24.0 206 1803 UGC 11651 -
     18.7 26.5 276 1525

  Real Time Justification
  -----------------------


  Calibration Justification
  -------------------------


  Additional Comments
  -------------------

     none
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                                                10550(  2) - 05/12/05 08:17  - [  4]

TARGET LIST    Fixed Targets
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Tar|   Target   |         Target        |            Target              |Coord   | Radial |             Flux data
No |    Name    |       Description     |           Position             |Eqnx    |  Vel.  |
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1   UGC-00477    GALAXY, LSB             RA=00H46M13.1000S +/- 1",        J2000             V = 13.4
                                         DEC=+19D29'24.00" +/- 1"
    Coordinate Source: Other_Source: NED
    Comments: This object was generated by the targetselector and
              retrieved from the NED database.

2   UGC-03459    GALAXY, LSB             RA=06H23M59.9000S +/- 1",        J2000             V = 12.9
                                         DEC=+04D42'39.00" +/- 1"
    Coordinate Source: Other_Source: NED
    Comments: This object was generated by the targetselector and
              retrieved from the NED database.

3   UGC-03587    GALAXY, LSB             RA=06H53M54.8000S +/- 1",        J2000             V = 12.3
                                         DEC=+19D17'59.00" +/- 1"
    Coordinate Source: Other_Source: NED
    Comments: This object was generated by the targetselector and
              retrieved from the NED database.

4   UGC-06138    GALAXY, LSB             RA=11H04M39.7000S +/- 1",        J2000             V = 14.1
                                         DEC=+27D43'26.00" +/- 1"
    Coordinate Source: Other_Source: NED
    Comments: This object was generated by the targetselector and
              retrieved from the NED database.

5   UGC-11131    GALAXY, LSB             RA=18H10M22.6000S +/- 1",        J2000             V = 12.5
                                         DEC=+01D35'33.00" +/- 1"
    Coordinate Source: Other_Source: NED
    Comments: This object was generated by the targetselector and
              retrieved from the NED database.

6   UGC-11651    GALAXY, LSB             RA=20H57M15.4000S +/- 1",        J2000             V = 12.8
                                         DEC=+25D57'53.00" +/- 1"
    Coordinate Source: Other_Source: NED
    Comments: This object was generated by the targetselector and
              retrieved from the NED database.

                                                10550(  2) - 05/12/05 08:17  - [  5]

Patterns
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Pattern_Number: 1

                    Primary_Pattern                   Secondary_Pattern
Pattern_Type        ACS-WFC-DITHER-LINE
Pattern_Purpose     DITHER
Number_Of_Points    3
Point_Spacing       0.17
Line_Spacing        <none>
Coordinate_Frame    POS-TARG
Pattern_Orient      47.23
Angle_Between_Sides <none>
Center_Pattern      NO

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Pattern_Number: 2

                    Primary_Pattern                   Secondary_Pattern
Pattern_Type        ACS-WFC-DITHER-LINE
Pattern_Purpose     DITHER
Number_Of_Points    2
Point_Spacing       0.145
Line_Spacing        <none>
Coordinate_Frame    POS-TARG
Pattern_Orient      47.23
Angle_Between_Sides <none>
Center_Pattern      NO

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                                                10550(  2) - 05/12/05 08:17  - [  6]

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


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
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1    UGC-00477   ACS/WFC  ACCUM   WFC       F475W            CR-SPLIT=NO                    1   404 S      PATTERN 1 1
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2    UGC-00477   ACS/WFC  ACCUM   WFC       F775W            CR-SPLIT=NO                    1   405 S      PATTERN 2 2
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
UGC-00477           1     ACS/WFC  ACCUM   WFC      F475W          1            none         none       none       1       N/A
UGC-00477           1     ACS/WFC  ACCUM   WFC      F475W          2            none         none       none       1       N/A
UGC-00477           1     ACS/WFC  ACCUM   WFC      F475W          3            none         none       none       1       N/A
UGC-00477           2     ACS/WFC  ACCUM   WFC      F775W          1            none         none       none       1       N/A
UGC-00477           2     ACS/WFC  ACCUM   WFC      F775W          2            none         none       none       1       N/A
                                                10550(  2) - 05/12/05 08:17  - [  7]

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


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    UGC-03459   ACS/WFC  ACCUM   WFC       F475W            CR-SPLIT=NO                    1   400 S      PATTERN 1 1
------------------------------------------------------------------------------------------------------------------------------------
2    UGC-03459   ACS/WFC  ACCUM   WFC       F775W            CR-SPLIT=NO                    1   400 S      PATTERN 2 2
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
UGC-03459           1     ACS/WFC  ACCUM   WFC      F475W          1            none         none       none       1       N/A
UGC-03459           1     ACS/WFC  ACCUM   WFC      F475W          2            none         none       none       1       N/A
UGC-03459           1     ACS/WFC  ACCUM   WFC      F475W          3            none         none       none       1       N/A
UGC-03459           2     ACS/WFC  ACCUM   WFC      F775W          1            none         none       none       1       N/A
UGC-03459           2     ACS/WFC  ACCUM   WFC      F775W          2            none         none       none       1       N/A
                                                10550(  2) - 05/12/05 08:17  - [  8]

Visit: 03
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    UGC-03587   ACS/WFC  ACCUM   WFC       F475W            CR-SPLIT=NO                    1   404 S      PATTERN 1 1
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2    UGC-03587   ACS/WFC  ACCUM   WFC       F775W            CR-SPLIT=NO                    1   405 S      PATTERN 2 2
------------------------------------------------------------------------------------------------------------------------------------

Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
UGC-03587           1     ACS/WFC  ACCUM   WFC      F475W          1            none         none       none       1       N/A
UGC-03587           1     ACS/WFC  ACCUM   WFC      F475W          2            none         none       none       1       N/A
UGC-03587           1     ACS/WFC  ACCUM   WFC      F475W          3            none         none       none       1       N/A
UGC-03587           2     ACS/WFC  ACCUM   WFC      F775W          1            none         none       none       1       N/A
UGC-03587           2     ACS/WFC  ACCUM   WFC      F775W          2            none         none       none       1       N/A
                                                10550(  2) - 05/12/05 08:17  - [  9]

Visit: 04
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    UGC-06138   ACS/WFC  ACCUM   WFC       F475W            CR-SPLIT=NO                    1   406 S      PATTERN 1 1
------------------------------------------------------------------------------------------------------------------------------------
2    UGC-06138   ACS/WFC  ACCUM   WFC       F775W            CR-SPLIT=NO                    1   407 S      PATTERN 2 2
------------------------------------------------------------------------------------------------------------------------------------

Sub Exposures
------------------------------------------------------------------------------------------------------------------------------------
Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
UGC-06138           1     ACS/WFC  ACCUM   WFC      F475W          1            none         none       none       1       N/A
UGC-06138           1     ACS/WFC  ACCUM   WFC      F475W          2            none         none       none       1       N/A
UGC-06138           1     ACS/WFC  ACCUM   WFC      F475W          3            none         none       none       1       N/A
UGC-06138           2     ACS/WFC  ACCUM   WFC      F775W          1            none         none       none       1       N/A
UGC-06138           2     ACS/WFC  ACCUM   WFC      F775W          2            none         none       none       1       N/A
                                                10550(  2) - 05/12/05 08:17  - [ 10]

Visit: 05
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    UGC-11131   ACS/WFC  ACCUM   WFC       F475W            CR-SPLIT=NO                    1   400 S      PATTERN 1 1
------------------------------------------------------------------------------------------------------------------------------------
2    UGC-11131   ACS/WFC  ACCUM   WFC       F775W            CR-SPLIT=NO                    1   400 S      PATTERN 2 2
------------------------------------------------------------------------------------------------------------------------------------

Sub Exposures
------------------------------------------------------------------------------------------------------------------------------------
Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
UGC-11131           1     ACS/WFC  ACCUM   WFC      F475W          1            none         none       none       1       N/A
UGC-11131           1     ACS/WFC  ACCUM   WFC      F475W          2            none         none       none       1       N/A
UGC-11131           1     ACS/WFC  ACCUM   WFC      F475W          3            none         none       none       1       N/A
UGC-11131           2     ACS/WFC  ACCUM   WFC      F775W          1            none         none       none       1       N/A
UGC-11131           2     ACS/WFC  ACCUM   WFC      F775W          2            none         none       none       1       N/A
                                                10550(  2) - 05/12/05 08:17  - [ 11]

Visit: 06
     Visit Priority:      <none>
     Visit Requirements:  <none>
     On Hold Comments:    <none>
     Additional Comments: <none>


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|          |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    UGC-11651   ACS/WFC  ACCUM   WFC       F475W            CR-SPLIT=NO                    1   406 S      PATTERN 1 1
------------------------------------------------------------------------------------------------------------------------------------
2    UGC-11651   ACS/WFC  ACCUM   WFC       F775W            CR-SPLIT=NO                    1   407 S      PATTERN 2 2
------------------------------------------------------------------------------------------------------------------------------------

Sub Exposures
------------------------------------------------------------------------------------------------------------------------------------
Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
UGC-11651           1     ACS/WFC  ACCUM   WFC      F475W          1            none         none       none       1       N/A
UGC-11651           1     ACS/WFC  ACCUM   WFC      F475W          2            none         none       none       1       N/A
UGC-11651           1     ACS/WFC  ACCUM   WFC      F475W          3            none         none       none       1       N/A
UGC-11651           2     ACS/WFC  ACCUM   WFC      F775W          1            none         none       none       1       N/A
UGC-11651           2     ACS/WFC  ACCUM   WFC      F775W          2            none         none       none       1       N/A
                                                10550(  2) - 05/12/05 08:17  - [ 12]

            Summary Form for Proposal  10550

  Item                         Used in this proposal
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  Apertures                    WFC
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  Configurations               ACS/WFC
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  Opmodes                      ACCUM
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  Optional Parameters          CR-SPLIT=NO
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  Proposal Category            GO
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  Special Requirements         PATTERN 1 1 PATTERN 2 2
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  Spectral Elements            F475W F775W
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  Target Names                 UGC-00477 UGC-03459 UGC-03587 UGC-06138 UGC-11131 UGC-11651
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