9551(  1) - 12/06/01 12:54  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      9551
                                                       Version: 1
                                                       Check-in Date: 06-Dec-2001
                                                                      11:51:26

1.Proposal Title:
The influence of blending on synthetic model-based interpretation of the HII region
luminosity function
------------------------------------------------------------------------------------
2. Proposal For  3. Cycle
AR               11
------------------------------------------------------------------------------------
4. Investigators
                                                                                     Contact?
    PI: David Thilker                     National Radio Astronomy Observatory
   CoI: Dr. Salman Hameed                 Smith College, Five College Astron. Dept.     N

------------------------------------------------------------------------------------
5. Abstract

The HII region luminosity function (HII LF), as determined from HAlpha photometry,
reflects vital information regarding the process of OB star cluster formation.
Despite a growing collection of published LFs there is still no true consensus on
the detailed form of the LF in spiral galaxies of various Hubble types. Part of the
problem can be traced to lack of uniformity in observations and method of source
photometry, but it also stems from not making optimal use of realistic models for
the HII region population and associated OB clusters. To address these deficiencies,
we are engaged in a joint observational / modeling project to analyze HII LFs for a
complete sample of 175 nearby spirals. Our interpretation of these LFs is founded on
fitting observational data with synthetic HII LFs. We have reached an impass at
which the influence of blending on the LF as a function of spatial resolution must
be quantified at small scales (>~ 15 pc). Without this, we cannot fairly compare
models against our seeing-limited data. We plan to analyze a collection of archival
WFPC2 HAlpha images for 24 spirals taken from our ground-based survey. Using minimal
spanning tree methods, we can characterize the clustering properties of HII regions
on scales smaller than typically resolved from the ground. With this information, we
will implement a blending correction to our synthetic models so they can be compared
directly with our survey observations.
------------------------------------------------------------------------------------
                                                9551(  1) - 12/06/01 12:54  - [  2]

            Summary Form for Proposal  9551

  Item                         Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Proposal Category            AR
------------------------------------------------------------------------------------------------------------------------------------