8745(  1) - 12/30/99 13:02  - [  1]

    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID:      8745
                                                       Version: 1
                                                       Check-in Date: 30-Dec-1999
                                                                      12:31:29

1.Proposal Title:
Chemistry of Messier 31
------------------------------------------------------------------------------------
2. Proposal For  3. Cycle
AR               9
------------------------------------------------------------------------------------
4. Investigators
                                                                                     Contact?
    PI: Guy Worthey                       Saint Ambrose University

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

Sampling local group spiral M31 from its nucleus to regions where its halo fades to
nothing, stellar color-magnitude diagrams of the brighter giants will be used to
construct histograms of (fraction of stars) as a function of (abundance) at each
radial location. From these abundance distributions the following will be derived:
(1) the overall radial abundance gradient in the disk and spheroid of M31 from
stars, not nebulae, and (2) the simulated all-M31 ``closed box'' abundance
distribution. These data will be far more complete and homogeneous than data
available for the Milky Way. Chemical evolution models will be applied to the data.
If the observed paucity of metal-poor stars in the outer disk of M31 continues to
the M31 outskirts, it will be impossible to reconcile any constant-yield model with
the M31 data, and, by inference, spirals in general.
------------------------------------------------------------------------------------
                                                8745(  1) - 12/30/99 13:02  - [  2]

            Summary Form for Proposal  8745

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