7986(  1) - 04/16/98 14:08  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      7986
                                                       Version: 1
                                                       Check-in Date: 16-Apr-1998
                                                                      14:05:17

1.Proposal Title:
Feeding the Nucleus: a Study of Double- Barred Galaxies
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2. Proposal For  3. Cycle
AR               7
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4. Investigators
                                                                                     Contact?
    PI: Linda S. Sparke                   University of Wisconsin-Madison
   CoI: Peter Erwin                       University of Wisconsin-Madison               N
   CoI: John S. Gallagher                 University of Wisconsin-Madison               N

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5. Abstract

About half of all spiral and S0 galaxies are barred: recent observations show that
the main bar often harbors one, and sometimes two, smaller ``nuclear bars''. The
inner bars appear to be dynamically distinct, rotating faster than the outer main
bars. Fast-rotating bars form only in dynamically cold disks, so the presence of an
inner bar indicates that disk material is present right into the center. The complex
time-varying gravitational field of a multiply-barred galaxy sweeps gas in towards
the center, or causes it to build up in a circumnuclear ring. The development of the
central regions of a galaxy must depend on how much material accumulates there with
``no place to go''; nuclear bars must strongly influence the flow of gas in the
innermost kiloparsec of disk galaxies, and merit detailed study to determine their
physical and evolutionary characteristics. We propose to investigate central
structures in nearby barred galaxies, including some of the best examples of double
bars, using archival WFPC2 and NICMOS images. Since nuclear bars have physical sizes
<< 1 kpc, they can be detected from the ground but not properly resolved. We will
measure bar amplitudes and isophotal shapes, map dust lanes which reveal gas flow,
and make color maps for most of our galaxies. We will investigate the influence of
central bars on the nuclear region, as revealed by the presence of circumnuclear
rings, regions of intense star formation, nuclear star clusters, or bright compact
nuclei.
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  Data Distribution

  Media:           ELECTRONIC
  Blocking Factor: 10
  Ship To:         PI_Address
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                                                7986(  1) - 04/16/98 14:08  - [  2]

            Summary Form for Proposal  7986

  Item                         Used in this proposal
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  Proposal Category            AR
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