8709( 2) - 03/21/00 09:31 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8709 Version: 2 Check-in Date: 21-Mar-2000 09:29:43 1.Proposal Title: UV Light from Old Stellar Populations: A Census of UV Bright Stars in `Blue Tail' Globular Clusters ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Francesco Ferraro Osservatorio Astronomico di Bologna CoI: Prof. Robert W. O'Connell University of Virginia N CoI: Dr. Ben Dorman Raytheon STX N CoI: Dr. Barbara Paltrinieri Istituto di Astronomia---Universita La N Sapienza, Roma CoI: Prof. Robert T. Rood University of Virginia N CoI: Prof. Roberto Buonanno Osservatorio Astronomico di Roma N CoI: Dr. Carla Cacciari Osservatorio Astronomico di Bologna N ------------------------------------------------------------------------------------ 5. Abstract We propose observations of UV-bright stars in 7 Galactic Globular Clusters (GGCs). These will complement data obtained during Cycles 5 and 6. Our goals are multifold: (a) to observe the morphology in the faint blue tails (BTs) of GGC horizontal branches (HBs); (b) to explore the relationship between the HB mass distribution in BT clusters to the clusters' structural and dynamical properties; (c) to gain further samples of Blue Straggler Stars and the long-sought Cataclysmic Variables in GGC cores; and (d) to obtain relatively large samples of post main sequence stars. All the targets have a BT which reaches at least to or beyond the turnoff in V; the actual extent can only be determined from the uncrowded UV observations. Our observations will allow a number of studies which cannot be done using ground-based observations: (a) and (b) will indirectly probe the mass loss process close to the tip of the red giant branch (RGB), which our data (from previous cycles) suggest to be often multimodal; (c) provides a complete survey of these peculiar UV stellar types, along with their radial distributions, will provide fundamental data for internal cluster dynamics. The observations will add to an archive of HST\ data on GGC's optimized for the study of hot stellar populations. This data set, beyond the study of GGCs, will be fundamental to the understanding of the origin of UV light from elliptical galaxies. ------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 2] Observations Description ------------------------ We will image fields in the cluster centers in the F160BW, F255W, F336W ultraviolet passbands. A short exposure in the Visual band F555W is also required to provide a long wavelength baseline for the HB observations and to allow the calculation of integrated 16 -V and 25-V colors. The V observations will also allow the detection of spurious cool sources arising from the redleak in the F336W passband. Short F814W exposure are required to get the properties of the giants in the metal rich clusters. NGC 4833 and NGC 6752 are in the sky region of CVZ (96 minutes of visibility). For the clusters in our program each orbit will have about 53 minutes of visibility. We propose to spend 3 or 4 orbits for each cluster except for NGC 6752, for which only one orbit is required. For NGC 4833, the extra time afforded by CVZ orbits is needed for longer UV exposures due to the higher reddening toward that cluster. We require exposures which give high photometric accuracy for EHB stars down to the faint end of the BT and BSS at the turnoff luminosity level. Exposure times were calculated using the WFPC2 Exposure Time Calculator provided by STScI on WWW and checked against the results we obtained in previous cycles. The exposure time criteria are: beginitemize em filters F555W: S/N=25-30 at V ~ V_0( TO)+2 mag for a G0 star, except for the most reddened cluster M62 where only 1 mag below the TO is reached at this S/N ratio em filter F336W: S/N=25-30 at V ~ V_0( TO)+1 mag level for an F0 star in NGC 4833, M2, M12; and for a A0 stars in M62. S/N=20 in NGC 6388 and NGC 6441 for B0 star at the TO level. These criteria ensure that some of the brighter CVs will be measurable. em filters F255W, F160W: S/N=25-30 at V ~ V_0( TO) mag level for an B0 star. For F160BW our previous exposures show visible aberration. The variable PSF and lack of crowding in the far-UV may allow accurate and efficient measurement with aperture photometry, so we have reduced the effective ``sharpness'' for this filter. For M62, NGC 6388, & N6441 we have not requested F160BW because the exposure times required to get adequate S/N are prohibitive. enditemize All exposures will be split into 4 separate images, shifted by 1.67 pixel, for the twofold purpose of mapping the PSF for a better photometric accuracy. The observations will consist of 2 sets of CR-SPLIT images with a POS-TARG repositioning halfway through the program of exposures in order to minimize overhead. The V and I exposures will be subdivided into sets of sub-exposures short enough to avoid severe blooming from the brightest (V ~ 13) M0 giants, which would introduce some degree of incompleteness and limit accuracy especially in the very crowded central regions. In each field, a few very short V and I exposures will also be taken for non-saturated photometry of the brightest part of the CM diagram. Real Time Justification ----------------------- NGC 6752 and NGC 4833 are Continuous Viewing Zone targets. We wish to take advantage of CVZ orbits in order to increase the efficiency of our program, albeit at some loss of flexibility as to scheduling. Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC6218 Stellar Cluster, RA=16H 47M 14.5S +/- 0S, DEC=- 2000 V = 18.00 Globular Cluster 01D 56' 52.00" +/-0" E(B-V) = 0.18 Comments: Above Flux value refers to the central magnitude of the cluster for ACQ purpose only. For individual stars see observing description. 2 NGC6266 Stellar Cluster, RA=17H 01M 12.6S +/- 0S, DEC=- 2000 V = 15.19 Globular Cluster 30D 06' 44.00" +/-0" E(B-V) = 0.50 Comments: Above Flux value refers to the central magnitude of the cluster for ACQ purpose only. For individual stars see observing description. 3 NGC7089 Stellar Cluster, RA=21H 33M 29.3S +/- 0S, DEC=- 2000 V = 15.78 Globular Cluster 00D 49' 23.00" +/-0" E(B-V) = 0.02 Comments: Above Flux value refers to the central magnitude of the cluster for ACQ purpose only. For individual stars see observing description. 4 NGC6752 Stellar Cluster, RA=19H 10M 51.8S +/- 0S, DEC=- 2000 V = 15.20 Globular Cluster 59D 58' 55.00" +/-0" E(B-V) = 0.04 Comments: Above Flux value refers to the central magnitude of the cluster for ACQ purpose only. For individual stars see observing description. 5 NGC4833 Stellar Cluster, RA=12H 59M 35.0S +/- 0S, DEC=- 2000 V = 8.35 Globular Cluster 70D 52' 29.00" +/-0" E(B-V) = 0.32 Comments: Above Flux value refers to the integrated magnitude of the cluster for ACQ purpose only. For individual stars see observing description. 8709( 2) - 03/21/00 09:31 - [ 4] Visit: 01 Visit Priority: Visit Requirements: 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 NGC6218 WFPC2 IMAGE PC1-FIX F160BW CR-SPLIT=0.5 1 1800 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6218 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 70 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6218 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 35 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6218 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6218 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15 1 500 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6218 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6218 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=0.5 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC6218 WFPC2 IMAGE PC1-FIX F255W 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC6218 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 1 S ------------------------------------------------------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 5] Visit: 02 Visit Priority: Visit Requirements: 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 NGC6266 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=NO 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6266 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6266 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=NO 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6266 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6266 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=NO 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6266 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 1000 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6266 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 200 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC6266 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 280 S ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC6266 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 280 S ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC6266 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 2 S ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC6266 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,CR-SPLIT=NO 1 140 S ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC6266 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,CR-SPLIT=0.5 1 280 S ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC6266 WFPC2 IMAGE PC1-FIX F814W ATD-GAIN=15,CR-SPLIT=0.5 1 2 S ------------------------------------------------------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 6] Visit: 03 Visit Priority: Visit Requirements: 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 NGC7089 WFPC2 IMAGE PC1-FIX F160BW CR-SPLIT=0.5 1 1800 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7089 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 70 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7089 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 35 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC7089 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC7089 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15 1 500 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7089 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC7089 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=0.5 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC7089 WFPC2 IMAGE PC1-FIX F255W 1 600 S ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC7089 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 1 S ------------------------------------------------------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 7] Visit: 04 Visit Priority: Visit Requirements: CVZ 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 NGC6752 WFPC2 IMAGE PC1-FIX F160BW CR-SPLIT=0.5 1 800 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC6752 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=0.5 1 800 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC6752 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=NO 1 400 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC6752 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 520 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC6752 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 260 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC6752 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 20 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC6752 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 0.2 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC6752 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC6752 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 30 S ------------------------------------------------------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 8] Visit: 05 Visit Priority: Visit Requirements: CVZ 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 NGC4833 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=0.5 1 1800 S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4833 WFPC2 IMAGE PC1-FIX F255W CR-SPLIT=NO 1 900 S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4833 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4833 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=NO 1 700 S ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC4833 WFPC2 IMAGE PC1-FIX F336W ATD-GAIN=15,CR-SPLIT=0.5 1 100 S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC4833 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 140 S ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC4833 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=NO 1 70 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC4833 WFPC2 IMAGE PC1-FIX F555W ATD-GAIN=15,CR-SPLIT=0.5 1 4 S ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC4833 WFPC2 IMAGE PC1-FIX F160BW CR-SPLIT=0.5 1 2800 S ------------------------------------------------------------------------------------------------------------------------------------ 8709( 2) - 03/21/00 09:31 - [ 9] Summary Form for Proposal 8709 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.5 ATD-GAIN=15 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160BW F555W F336W F255W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC6218 NGC6266 NGC7089 NGC6752 NGC4833 ------------------------------------------------------------------------------------------------------------------------------------