10552( 3) - 05/13/05 15:57 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10552 Version: 3 Check-in Date: 13-May-2005 19:56:37 1.Proposal Title: The distance of the Orion Nebula Cluster ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 14 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Massimo Robberto Space Telescope Science Institute - ESA CoI: Dr. Vera Kozhurina-Platais Space Telescope Science Institute N CoI: Dr. Kailash Sahu Space Telescope Science Institute N CoI: Dr. Kester Smith Space Telescope Science Institute N CoI: Dr. Richard Hook Space Telescope - European Coordinating N Facility CoI: Dr. David R. Soderblom Space Telescope Science Institute N CoI: Mr. Louis Bergeron Space Telescope Science Institute N CoI: Dr. Jay Anderson Rice University N CoI: Dr. George Fritz Benedict University of Texas at Austin N CoI: Dr. Barbara McArthur University of Texas at Austin N CoI: Dr. Peter McCullough Space Telescope Science Institute N CoI: Dr. Nino Panagia Space Telescope Science Institute - ESA N CoI: Mr. Russell Makidon Space Telescope Science Institute N CoI: Dr. John Stauffer Jet Propulsion Laboratory N CoI: Dr. I. Neill Reid Space Telescope Science Institute N ------------------------------------------------------------------------------------ 6. Abstract The HST Treasury program on the Orion Nebula, currently in execution, has surprisingly found that background sources are easily detected by HST at long wavelengths through selected fields within the nebula. We propose to use these background sources as a reference system to measure the trigonometric parallax of the Orion Nebula cluster. Using ACS in the F850LP filter and with a modest investment of HST time, we will reduce the error on the ~500pc distance of the Orion Nebula to ~15pc, or less, improving by a factor ~6 over current estimates. Our new value will have a major impact on star formation studies, allowing to determine with high accuracy the absolute luminosity of the cluster members and all derived stellar parameters (ages, masses, mass accretion rates...). Our current understanding of a great range of phenomena associated to the star formation activity in Orion will also benefit from an improved distance estimate. ------------------------------------------------------------------------------------ 10552( 3) - 05/13/05 15:57 - [ 2] Observations Description ------------------------ We observe a field withing the Orion Nebula at two epochs ~6 months apart to measure the parallax of the Orion Nebula Cluster against the background stars. Each epoch corresponds to a visit of 2 consecutive orbits, where we take long and short exposures. We opted for the F814W filter, which has better PSF and field distorsion calibration than the similar F850LP. The two visits are identical and at the same target point, with aperture at the center of the ACS/WFC. The orient angles of the telescope are 40 and 248 degrees for the two visits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- For our scientific goal it is important to maximize the time difference between the two visits, which should be as close as possible to 6 months. The current planning assumes 2 gyro mode. This forces us to schedule the observations around Aug 15, 2005 (ORIENT=248) and around Jan 20, 2006 (ORIENT=40deg), approximately 5 months apart. At these dates the ORIENT angles are strongly constrained and turn out to be different by more than 180deg. Thus, the corners of the ACS field are not imaged both times, reducing the number of sourcers useful to estimate the parallax. If three gyro mode becomes available either in one of both visits, we would like to replan this program to increase the time/parallactic baseline and equalize the telescope ORIENT angles. ------------------------------------------------------------------------------------ 10552( 3) - 05/13/05 15:57 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ORI- STELLAR CLUSTER, STAR RA=05H35M24.1000S +/- 0.1", J2000 V = 18.0+/-5.0 PARALLAX1 FORMING REGION DEC=-05D30'53.00" +/- 0.1" Coordinate Source: HST_IMAGE 2 ORI- STELLAR CLUSTER, STAR RA=05H35M26.1000S +/- 0.1", J2000 V = 18.0+/-5.0 PARALLAX2 FORMING REGION DEC=-05D30'57.00" +/- 0.1" Coordinate Source: HST_IMAGE 10552( 3) - 05/13/05 15:57 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 3.2 Line_Spacing 3.2 Coordinate_Frame POS-TARG Pattern_Orient 19.91 Angle_Between_Sides 97.36 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 10552( 3) - 05/13/05 15:57 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 248.0D TO 248.0 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 20 S X1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 360 S X1 ------------------------------------------------------------------------------------------------------------------------------------ 3 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 170 S PATTERN 1 3 X1 see below ------------------------------------------------------------------------------------------------------------------------------------ 4 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 20 S X2 ------------------------------------------------------------------------------------------------------------------------------------ 5 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 170 S PATTERN 1 5 X2 see below ------------------------------------------------------------------------------------------------------------------------------------ 6 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 20 S SAME POS AS 5 X2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ ORI-PARALLAX1 1 ACS/WFC ACCUM WFCENTER F814W none none none none 1 N/A ORI-PARALLAX1 2 ACS/WFC ACCUM WFCENTER F814W none none none none 1 N/A ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 1 none none none 1 360.0 S ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 2 none none none 1 360.0 S ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 3 none none none 1 360.0 S ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 4 none none none 1 360.0 S ORI-PARALLAX2 4 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 1 none none none 2 360.0 S ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 2 none none none 2 360.0 S ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 3 none none none 2 360.0 S ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 4 none none none 2 360.0 S ORI-PARALLAX2 6 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A 10552( 3) - 05/13/05 15:57 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 40.0D TO 40.0 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 20 S X1 ------------------------------------------------------------------------------------------------------------------------------------ 2 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 360 S X1 ------------------------------------------------------------------------------------------------------------------------------------ 3 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 170 S PATTERN 1 3 X1 see below ------------------------------------------------------------------------------------------------------------------------------------ 4 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 20 S X2 ------------------------------------------------------------------------------------------------------------------------------------ 5 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 170 S PATTERN 1 5 X2 see below ------------------------------------------------------------------------------------------------------------------------------------ 6 ORI-PARALLA ACS/WFC ACCUM WFCENTER F814W CR-SPLIT=NO,GAIN=2 1 20 S SAME POS AS 5 X2 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ ORI-PARALLAX1 1 ACS/WFC ACCUM WFCENTER F814W none none none none 1 N/A ORI-PARALLAX1 2 ACS/WFC ACCUM WFCENTER F814W none none none none 1 N/A ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 1 none none none 1 360.0 S ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 2 none none none 1 360.0 S ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 3 none none none 1 360.0 S ORI-PARALLAX1 3 ACS/WFC ACCUM WFCENTER F814W 4 none none none 1 360.0 S ORI-PARALLAX2 4 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 1 none none none 2 360.0 S ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 2 none none none 2 360.0 S ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 3 none none none 2 360.0 S ORI-PARALLAX2 5 ACS/WFC ACCUM WFCENTER F814W 4 none none none 2 360.0 S ORI-PARALLAX2 6 ACS/WFC ACCUM WFCENTER F814W none none none none 2 N/A 10552( 3) - 05/13/05 15:57 - [ 7] Summary Form for Proposal 10552 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFCENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO GAIN=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 248.0D TO 248.0 D PATTERN 1 3 PATTERN 1 5 SAME POS AS 5 ORIENT 40.0D TO 40.0 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ORI-PARALLAX1 ORI-PARALLAX2 ------------------------------------------------------------------------------------------------------------------------------------