5983( 9) - 02/15/96 14:10 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5983 Version: 9 Check-in Date: 15-Feb-1996 13:54:02 1.Proposal Title: Circumstellar Disks in Young Nebulous Clusters ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Karl Stapelfeldt Jet Propulsion Laboratory CoI: John Trauger Jet Propulsion Laboratory N CoI: Michael Werner Jet Propulsion Laboratory N CoI: Raghvendra Sahai Jet Propulsion Laboratory N ------------------------------------------------------------------------------------ 6. Abstract Recent WFPC2 images of the Orion nebula region have revealed several disklike circumstellar dust clouds seen in absorption against background nebula light. The sizes and ages of these clouds closely match those expected for circumstellar disks with ongoing planet formation. Observations with the refurbished HST offer a new and unprecedented opportunity to study the frequency, size, morphology, optical depth, and lifetimes of these solar nebula analogs; so far, only the M42 Orion region is scheduled for an HST study. We propose an imaging survey of the circumstellar material of young solar type stars in six other nebulous clusters. In four nearby clusters associated with H II regions (NGC 1972, NGC 2024, NGC 2264, S 155), we will search for disks seen in silhouette and as externally ionized rims of HAlpha emission. In two nearby clusters possessing bright reflection nebulosity (NGC 7023 and NGC 1432), we will search for disks in silhouette against the background continuum. The goal of our circumstellar census is to discover and characterize disks of different ages (a few Myrs toward the H II regions, 80 Myrs towards the reflection nebulae), and thereby constrain the disk evolution processes which profoundly affect theories of the origin of the solar system. ------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 2] Observations Description ------------------------ At HAlpha, the maximum optical depth in the M42 circumstellar oval is 1.5. To meaningfully constrain the disk dissipation timescale by detecting more tenuous disks, we must design the observations to be sensitive to much smaller optical depths. We have chosen Tau= 0.1 as the desired sensitivity of the survey; for a single WF pixel, this limit corresponds to a dust mass of only 10^-2 Earth masses at the distance of NGC 1972 and NGC 2024. To achieve this limit, the background nebular light must be measured at a signal to noise of 3/Tau= 30. For the WFPC2 Orion observations, a signal to noise of 80 was obtained for HAlpha in an unremarkable part of the nebula in the WF cameras with 350 seconds of integration. This sensitivity limit can be scaled to other H II regions using the tabulation of HAlpha surface brightnesses given by Fich, Treffers, and Dahl (1990). Relative to M42, the latter reference gives the following surface brightnesses for our program objects: NGC 1972 (S279), 0.018; NGC 2024 (S277), 0.015; NGC 2264 (S273), 0.007; and S155, 0.014. These brightnesses will require 2100 second HAlpha exposures in order to achieve the target signal to noise ratio. A matching continuum exposure is required for each field in order to clearly identify the location of stars in the HAlpha image. Using the F814W filter and an exposure time of 120 seconds, a limiting magnitude I= 24 can be achieved. We plan to conduct both the HAlpha and continuum exposures for each field within a single orbit. In the reflection nebulae we must observe in a broadband continuum filter to achieve the target signal to noise of 30. The widest available filter for WFPC2 is F606W; in a 2000 sec exposure, the desired S/N can be obtained with this filter for a surface brightness of 20.5 mag per square arcsecond. This surface brightness is available for 2 fields in NGC 7023 (Witt and Schild 1986) and 3 fields in NGC 1432 / Pleiades (Cottrell and Witt 1983). There is an additional challenge in these observations which is not present in the case of the H II regions: by observing the nebulosity in a broadband filter, most of the stars we observe will be saturated. The objects we have selected for study are generally well-known young clusters with nebulosity. NGC 2264 is is associated with the cone nebula; NGC 2024 lies in the horsehead nebula region. S 155 is an H II region in Cepheus for which an associated young cluster has recently been found (Moreno-Corral et al. 1993). More than 100 young low mass stars are concentrated within S155 in a region 3^primex2^ square, making this an ideal field for an HST study. We anticipate that many interesting objects will be discovered during this proposed survey of young nebulous clusters. Most of the areal coverage will be accomplished with the Wide Field Cameras, and we anticipate that selected targets will warrant follow-up observations at higher resolution using the Planetary Camera or the FOC. Given the strong possibility that most of our Cycle 5 data would not be available in time to propose follow-up observations in Cycle 6, we ask at this time for an allocation of 3 orbits in Cycle 6. Real Time Justification ----------------------- N/A To support the proposed observations of four H II regions, we plan to obtain 2 cm VLA maps of the HST fields. These will be correlated with the HST HAlpha images to explore the relationship between compact radio continuum sources and the externally ionized circumstellar shells. Calibration Justification ------------------------- N/A Additional Comments ------------------- ------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2024-1 ISM, HII Region, Star RA=05H 41M 34.25S +/- 0.010S, J2000 Forming Region, STELLAR DEC= -01D 53' 21.8" +/- 0.10" CLUSTER, T Association Comments: Region of brightest Halpha emission on PC 2 NGC2024-2 ISM, HII Region, Star RA=05H 41M 31.55S +/- 0.010S, J2000 Forming Region, STELLAR DEC= -01D 52' 08.8" +/- 0.10" CLUSTER, T Association 3 NGC2024-3 ISM, HII Region, Star RA=05H 41M 31.55S +/- 0.010S, J2000 Forming Region, STELLAR DEC= -01D 54' 34.8" +/- 0.10" CLUSTER, T Association 4 S155-1 ISM, HII Region, Star RA=22H 57M 05.8S +/- 0.10S, DEC= J2000 Forming Region, STELLAR 62D 38' 19.0" +/- 0.10" CLUSTER, T Association Comments: Region of brightest Halpha emission on PC 5 S155-2 ISM, HII Region, Star RA=22H 56M 52.4S +/- 0.05S, DEC= J2000 Forming Region, STELLAR 62D 38' 53.2" +/- 0.50" CLUSTER, T Association 6 NGC2264-1 ISM, HII Region, Star RA=6H 41M 13.81S +/- 0.05S, DEC= J2000 Forming Region, STELLAR 9D 25' 26.2" +/- 0.50" CLUSTER, T Association Comments: HD 47887 (SAO 114264) near Nebula V= 7.0 RA= 06 41 09.56 Dec= +09 27 56.2 (J2000) 7 NGC2264-2 ISM, HII Region, Star RA=6H 41M 09.56S +/- 0.05S, DEC= J2000 Forming Region, STELLAR 9D 27' 56.2" +/- 0.5" CLUSTER, T Association Comments: HD 47887 (SAO 114264) on the PC V= 7.0 RA= 06 41 09.56 Dec= +09 27 56.2 (J2000) 8 NGC2264-3 ISM, HII Region, Star RA=6H 40M 58.62S +/- 0.05S, DEC= J2000 Forming Region, STELLAR 9D 53' 44.7" +/- 0.5" CLUSTER, T Association Comments: HD 47839 (SAO 114258) on PC V= 4.4 RA= 06 40 58.62 Dec= +09 53 44.7 9 NGC7023-1 ISM, Reflection Nebula, RA=21H 01M 31.9S +/- 0.05S, DEC= J2000 STELLAR CLUSTER 68D 09' 35.0" +/- 0.5" Comments: HD 200775 located at center of Nebula V= 7.7 RA= 21 01 36.76 Dec= +68 09 48.1 (J2000) Star not on chips, will see diffraction spikes. 10 NGC7023-2 ISM, Reflection Nebula, RA=21H 01M 44.3S +/- 0.05S, DEC= J2000 STELLAR CLUSTER 68D 08' 10.0" +/- 0.5" Comments: HD 200775 located at center of Nebula V= 7.7 RA= 21 01 36.76 Dec= +68 09 48.1 (J2000) Star not on chips, will see diffraction spikes. 11 NGC2264-4 ISM, HII Region, Star RA=06H 41M 19.42S +/- 0.010S, J2000 V = 0.0 Forming Region, STELLAR DEC= 09D 27' 13.8" +/- 0.10" CLUSTER, T Association 5983( 9) - 02/15/96 14:10 - [ 5] Visit: 01 Visit Requirements: ORIENT 312D TO 318D 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC2024-1 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 120S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC2024-1 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 6] Visit: 02 Visit Requirements: ORIENT 42D TO 48D 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 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC2024-2 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 120S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC2024-2 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 7] Visit: 03 Visit Requirements: SAME ORIENT AS 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC2024-3 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 120S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 32 NGC2024-3 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 8] Visit: 04 Visit Requirements: CVZ ORIENT 105D TO 115D 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 ------------------------------------------------------------------------------------------------------------------------------------ 41 S155-1 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 100S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 42 S155-1 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 43 S155-2 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 100S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 44 S155-2 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 9] Visit: 05 Visit Requirements: ORIENT 110D TO 116D 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 ------------------------------------------------------------------------------------------------------------------------------------ 51 NGC2264-1 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 120S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 52 NGC2264-1 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 10] Visit: 06 Visit Requirements: ORIENT 99D TO 106D 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 ------------------------------------------------------------------------------------------------------------------------------------ 61 NGC2264-2 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 120S POS TARG -12.0,2.0 -GAIN=15 Comments: Bright star on PC will saturate ------------------------------------------------------------------------------------------------------------------------------------ 62 NGC2264-2 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S POS TARG -12.0,2.0 - TOLERANCE=0.0,A TD-GAIN=7 Comments: Bright star on PC will saturate ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 11] Visit: 07 Visit Requirements: ORIENT 260D TO 270D 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 ------------------------------------------------------------------------------------------------------------------------------------ 71 NGC2264-3 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD 1 120S -GAIN=15 Comments: Bright star on PC will saturate ------------------------------------------------------------------------------------------------------------------------------------ 72 NGC2264-3 WFPC2 IMAGE PC1 F656N CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,A TD-GAIN=7 Comments: Bright star on PC will saturate ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 12] Visit: 08 Visit Requirements: CVZ ORIENT 130D TO 140D 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 ------------------------------------------------------------------------------------------------------------------------------------ 81 NGC7023-1 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO,ATD 1 5S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 82 NGC7023-1 WFPC2 IMAGE PC1 F606W CR- 1 100S SPLIT=NO,CLOCKS =YES,ATD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 83 NGC7023-1 WFPC2 IMAGE PC1 F606W CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,C LOCKS=YES,ATD- GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 84 NGC7023-2 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO,ATD 1 5S -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 85 NGC7023-2 WFPC2 IMAGE PC1 F606W CR- 1 100S SPLIT=NO,CLOCKS =YES,ATD-GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 86 NGC7023-2 WFPC2 IMAGE PC1 F606W CR-SPLIT=0.5,CR 1 1800S - TOLERANCE=0.0,C LOCKS=YES,ATD- GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 13] Visit: 09 Visit Requirements: ORIENT 82D TO 86D 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 ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC2264-4 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO,ATD 1 120S POS TARG 24.0,-6.0 -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC2264-4 WFPC2 IMAGE WF2 F656N CR-SPLIT=NO,ATD 1 1000S POS TARG 24.0,-6.0 -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC2264-4 WFPC2 IMAGE WF2 F656N CR-SPLIT=NO,ATD 1 1100S POS TARG 24.0,-6.0 -GAIN=7 ------------------------------------------------------------------------------------------------------------------------------------ 5983( 9) - 02/15/96 14:10 - [ 14] Summary Form for Proposal 5983 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ATD-GAIN=7 CR-TOLERANCE=0.0 CR-SPLIT=0.5 ATD-GAIN=15 CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 312D TO 318D ORIENT 42D TO 48D SAME ORIENT AS 02 CVZ ORIENT 105D TO 115D ORIENT 110D TO 116D ORIENT 99D TO 106D POS TARG -12.0,2.0 ORIENT 260D TO 270D CVZ ORIENT 130D TO 140D ORIENT 82D TO 86D POS TARG 24.0,-6.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F656N F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2024-1 NGC2024-2 NGC2024-3 S155-1 S155-2 NGC2264-1 NGC2264-2 NGC2264-3 NGC7023-1 NGC7023-2 NGC2264-4 ------------------------------------------------------------------------------------------------------------------------------------