8314( 4) - 08/26/99 12:38 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8314 Version: 4 Check-in Date: 18-Feb-1999 08:50:57 1.Proposal Title: Star Clusters of NGC 6822 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Paul Hodge University of Washington CoI: Prof. Eugene Magnier University of Washington N CoI: Andrew Dolphin University of Washington N CoI: Rupali Chandar The Johns Hopkins University N ------------------------------------------------------------------------------------ 5. Abstract We propose to obtain BVI photometry of four fields in the irregular Local Group galaxy NGC 6822. The chosen fields include star clusters of a variety of ages and we will study the CMDs of both the clusters and the surrounding field stars. Our goals are: (1) to measure the oldest population of stars in the field to answer the question of when star formation commenced in this galaxy; (2) to ascertain the nature of the star formation history of the galaxy; and (3) to look for evidence of a halo population of old stars. ------------------------------------------------------------------------------------ 8314( 4) - 08/26/99 12:38 - [ 2] Observations Description ------------------------ We propose to observe 4 fields centered on selected open clusters in NGC 6822 with the WFPC-2. We will observe each cluster with 3 filters, F439W, F555W, and F814W. Our goal is to obtain photometry down to 25th magnitude. We require three filters to make accurate determinations of the extinction for each cluster. The extinction is not expected to be large, nor is it expected to vary significantly in the small area of a single field, but an accurate determination is necessary to obtain accurate colors of the main sequence. We will use two orbits for each pointing. The total exposure times listed below will be split between two exposures so that we may remove cosmic rays. We have used the WWW Exposure Time Calculator to determine the necessary exposure times. For the F439W filter, we will need a total exposure time of 1500 seconds, resulting in a signal-to-noise ratio of 8 for a 25th magnitude star. For the F555W filter, we will need a total exposure time of 1200 seconds, reaching a signal-to-noise ratio of 20 for the same 25th magnitude star. For the F814W filter, we will also request a 1200 second exposure for a similar limit. We have investigated the overhead times needed and find that these exposures will fit within the two orbits per pointing. Real Time Justification ----------------------- None. None. Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8314( 4) - 08/26/99 12:38 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6822-C1 EXT-CLUSTER, Open RA=19H 44M 31.4S +/- 0.1S, DEC= J2000 V=-56 V = 20.675+/-0.048 Cluster -14D 48' 0.7" +/- 1.0" B-V = 0.135+/-0.056 Comments: The V magnitude and B-V color under flux refer to the magnitude and color of the brightest star in the field which is likely to be a cluster member. 2 NGC6822-C12 EXT-CLUSTER, Open RA=19H 44M 54.7S +/- 0.1S, DEC= J2000 V=-56 V = 21.192+/-0.049 Cluster -14D 45' 39.5" +/- 1.0" B-V = -0.010+/-0.071 Comments: The V magnitude and B-V color under flux refer to the magnitude and color of the brightest star in the field which is likely to be a cluster member. 3 NGC6822-C18 EXT-CLUSTER, Open RA=19H 45M 4.0S +/- 0.1S, DEC= - J2000 V=-56 V = 21.081+/-0.045 Cluster 14D 46' 34.8" +/- 1.0" Comments: The V magnitude under flux refers to the magnitude the brightest star in the field which is likely to be a cluster member. 4 NGC6822-C25 EXT-CLUSTER, Open RA=19H 45M 17.0S +/- 0.1S, DEC= J2000 V=-56 V = 21.748+/-0.051 Cluster -14D 46' 21.4" +/- 1.0" B-V = 0.566+/-0.098 Comments: The V magnitude and B-V color under flux refer to the magnitude and color of the brightest star in the field which is likely to be a cluster member. 8314( 4) - 08/26/99 12:38 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 170D TO 345D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6822-C1 WFPC2 IMAGE PC1-FIX F439W 1 1500 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6822-C1 WFPC2 IMAGE PC1-FIX F555W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6822-C1 WFPC2 IMAGE PC1-FIX F814W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 8314( 4) - 08/26/99 12:38 - [ 5] Visit: 02 Visit Priority: Visit Requirements: ORIENT 75D TO 105D ORIENT 180D TO 195D ORIENT 210D TO 245D ORIENT 270D TO 340D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6822-C12 WFPC2 IMAGE PC1-FIX F439W 1 1500 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6822-C12 WFPC2 IMAGE PC1-FIX F555W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6822-C12 WFPC2 IMAGE PC1-FIX F814W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 8314( 4) - 08/26/99 12:38 - [ 6] Visit: 03 Visit Priority: Visit Requirements: ORIENT 30D TO 195D ORIENT 270D TO 315D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6822-C18 WFPC2 IMAGE PC1-FIX F439W 1 1500 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6822-C18 WFPC2 IMAGE PC1-FIX F555W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6822-C18 WFPC2 IMAGE PC1-FIX F814W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 8314( 4) - 08/26/99 12:38 - [ 7] Visit: 04 Visit Priority: Visit Requirements: ORIENT 45D TO 90D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6822-C25 WFPC2 IMAGE PC1-FIX F439W 1 1500 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6822-C25 WFPC2 IMAGE PC1-FIX F555W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6822-C25 WFPC2 IMAGE PC1-FIX F814W 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 8314( 4) - 08/26/99 12:38 - [ 8] Summary Form for Proposal 8314 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 170D TO 345D ORIENT 75D TO 105D ORIENT 180D TO 195D ORIENT 210D TO 245D ORIENT 270D TO 340D ORIENT 30D TO 195D ORIENT 270D TO 315D ORIENT 45D TO 90D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F439W F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6822-C1 NGC6822-C12 NGC6822-C18 NGC6822-C25 ------------------------------------------------------------------------------------------------------------------------------------