! Proposal 6229, submission 1 ! PI: TRAUGER, JOHN ! Received Fri Apr 7 20:36:05 EDT 1995 ! From: krs@ls3.jpl.nasa.gov Proposal_Information Title: STELLAR POPULATIONS IN THE MAGELLANIC CLOUDS Proposal_Category: GTO/WF2 Scientific_Category: STELLAR POPULATIONS Cycle: 5 Investigators PI_name: John Trauger PI_Institution: JET PROPULSION LABORATORY CoI_Name: Jay Gallagher CoI_Institution: University of Wisconsin CoI_Name: Jon Holtzman CoI_Institution: Lowell Observatory CoI_Name: Jeremy Mould CoI_Institution: Mount Stromlo Observatory Questions Observing_Description: Color-magnitude diagrams are well established as powerful tools for investigating galactic stellar populations. In cases such as the LMC and SMC where HST allows observations to be made to well below the oldest main sequence turnoff, we can recover information about the form of the stellar IMF and the history of star formation (e.g., Mighell \& Butcher 1992, AA, 255, 26). In Cycle 4 the WFPC2 IDT obtained a CMD which is reasonably complete to V=27 (M_V=8) for an outer disk field in the LMC. These data demonstrate that this region has experienced episodic star forming events which appear as three well-defined main sequence turn-offs which are separated by gaps. This behavior is consistent with star formation ceasing for extended times. We also have obtained the first reliable stellar LF for the lower main sequence in another galaxy, which we are now analyzing (c.f., Bessell \& Stringfellow 1993, ARAA, 31, 433). The objectives of the Cycle 5 GTO program is to obtain high quality photometric data in the F555W and F814W filters for more fields in the LMC with the goal of testing the uniformity of stellar populations in the LMC. In all cases we will make more effective use of the PC by centering on a small star cluster of the type which abound in the Magellanic Clouds (e.g., Hodge 1980, AJ, 85, 423; Hodge 1986, PASP, 98, 1113). The target clusters have been selected to be compact and relatively sparse so that we will not experience significant contamination in the surrounding WF fields. Based on our experience in Cycle 4 we will reach to about M_V=8 in the crowded bar and somewhat fainter in the outer LMC disk and SMC fields. Target areas were chosen in consultation with Paul Hodge. In the bar the PC will be placed on the star cluster Hodge-Sextans 275 while the WFs sample the surrounding rich star fields. We selected this location to avoid obvious areas of recent star formation. In the outer LMC disk we will observe the cluster Hodge 2164-10 which is in an area with a well-defined background of of fainter stars. The SMC field is near the star cluster Bruck 83 which is slightly east of the SMC bar and away from areas of active star formation. Real_Time_Justification: Calibration_Justification: Additional_Comments: Abstract: The Magellanic Clouds (MC) are the nearest major galaxies and therefore afford unique opportunities for studies of stellar populations and star formation histories through observations of color-magnitude diagrams (CMDs; e.g. Bertelli et al. 1992, ApJ, 388, 400). In this program we extend HST WFPC2 studies of low mass stars in the LMC through observations of a field in the dense stellar bar and a second field in the outer disk. In the SMC we will observe a field near the bar, but in a region where the depth of the SMC is not likely to be large (Hodge, private communication). The resulting CMDs will be modelled using isochrones such as those by Bergbusch & Vandenberg (1992, ApJS, 81, 163) to recover the lower stellar IMF and to search for the signatures of episodic star formation in these galaxies. Fixed_Targets Target_Number: 1 Target_Name: HS-275 Alternate_Names: Description: GALAXY Position: RA=5H 24M 21.0S +/- 0.010S, DEC=-69D 46' 27" +/- 0.10" Equinox: J2000 Rv_or_z: Flux: Comments: Target_Number: 2 Target_Name: HODGE-10 Alternate_Names: Description: GALAXY Position: RA=5H 58M 21.15S +/- 0.010S, DEC=-68D 21' 19.5" +/- 0.10" Equinox: J2000 Rv_or_z: Flux: Comments: Target_Number: 3 Target_Name: BRUCK-83 Alternate_Names: Description: GALAXY Position: RA=0H 55M 30.44S +/- 0.010S, DEC=-73D 04' 22.3" +/- 0.10" Equinox: J2000 Rv_or_z: Flux: Comments: Visits Visit_Number: 01 Visit_Requirements: ORIENT 15D TO 75D Exposure_number: 10 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO, ATD-GAIN=15 Number_of_iterations:1 Time_Per_Exposure: 200S Special_Requirements:NO SPLIT Exposure_number: 20 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1000S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 21 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1100S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 25 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1400S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 26 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 30 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO, ATD-GAIN=15 Number_of_iterations:1 Time_Per_Exposure: 200S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 40 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1100S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 41 Target_Name: HS-275 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Visit_Number: 02 Visit_Requirements: Exposure_number: 10 Target_Name: HODGE-10 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO, ATD-GAIN=15 Number_of_iterations:1 Time_Per_Exposure: 100S Special_Requirements:NO SPLIT Exposure_number: 11 Target_Name: HODGE-10 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1000S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 12 Target_Name: HODGE-10 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 20 Target_Name: HODGE-10 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO, ATD-GAIN=15 Number_of_iterations:1 Time_Per_Exposure: 100S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 21 Target_Name: HODGE-10 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 22 Target_Name: HODGE-10 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Visit_Number: 03 Visit_Requirements: Exposure_number: 10 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO, ATD-GAIN=15 Number_of_iterations:1 Time_Per_Exposure: 300S Special_Requirements:NO SPLIT Exposure_number: 20 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1000S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 21 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1000S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 25 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 26 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1600S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 30 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO, ATD-GAIN=15 Number_of_iterations:1 Time_Per_Exposure: 200S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 40 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1200S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 41 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 45 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1300S Special_Requirements:SAME POS AS 10 NO SPLIT Exposure_number: 46 Target_Name: BRUCK-83 Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Optional_Parameters: CR-SPLIT=NO Number_of_iterations:1 Time_Per_Exposure: 1600S Special_Requirements:SAME POS AS 10 NO SPLIT Data_Distribution Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS Recipient_Email: