11344( 5) - 10/17/07 06:42 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11344 Version: 5 Check-in Time: 17-Oct-2007 10:42:35 STScI Edit Number: 0 Title Velocity Gradients in the Jets of BL Lac Objects ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Alan P. Marscher Boston University CoI: Dr. Svetlana G. Jorstad Boston University N ------------------------------------------------------------------------------------ Abstract We propose to observe the arcsec-scale jets of 2 BL Lac objects with highly relativistic jets (bulk Lorentz factor of 16) on parsec scales in order to determine whether a velocity gradient exists between the axis and edge of the jet and along the length of the jet. Models both for the morphology of jets in BL Lac objects and for the launching of the jet predict such gradients. If radio-selected BL Lac objects are end-on FR 1 sources, there should be strong X-ray emission from inverse Compton scattering of CMB photons along the highly beamed fast spine of the jet. The imaging observations with Chandra, HST, SST, and the VLA will therefore verify whether such a spine exists and on what length scale it decelerates to nonrelativistic speeds. ------------------------------------------------------------------------------------ 11344( 5) - 10/17/07 06:42 - [ 2] Observations Description ------------------------ We will use WFPC2/WFC with filter F606W to observe the BL Lac object OJ287 (the target accepted in Phase I) during two orbits in order to detect and measure the flux of knots in the extended jet. On VLA radio images, the jet extends 10 arcsec to the west of the nucleus, with knots at about 5 and 9 arcsec and possibly some closer. The nucleus has a magnitude of about 14 (highly variable, range of 13-15 mag.) in R-band. We expect the jet knots to have a magnitude of roughly 25, so we will need to use drizzle and Tiny Tim PSF subtraction in order to detect the knots with certainty and to either measure or place interesting upper limits on their angular sizes. Our observations will be long exposures in a boxed dither pattern. We require an orientation of the telescope so that the diffraction spikes are not along the jet, which lies at a position angle of 270D relative to the nucleus. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11344( 5) - 10/17/07 06:42 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 OJ287 GALAXY, BL LAC, JET, RA=08H54M48.9000S +/- 0.1", J2000 Z = V = 14.5+/-1.0 KNOT DEC=+20D06'30.60" +/- 0.1" 0.306 R-band: 14.0+/-1 Reference Frame: Other: NED Comments: This object was generated by the targetselector and retrieved from the NED database. The dec given by NED was adjusted slightly to be accurate to within 0.1 arcsec. The main object is highly variable in flux. 11344( 5) - 10/17/07 06:42 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.559017 Line_Spacing 0.559017 Coordinate_Frame POS-TARG Pattern_Orient 26.56505 Angle_Between_Sides 143.130102 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 11344( 5) - 10/17/07 06:42 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 120.0D TO 150.0 D; ORIENT 300.0D TO 330.0 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 OJ287 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 3 230 S PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ OJ287 1 WFPC2 IMAGE PC1 F606W 1 none 1 none 1 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 1 none 2 none 1 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 1 none 3 none 1 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 2 none 1 none 1 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 2 none 2 none 1 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 2 none 3 none 1 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 3 none 1 none 2 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 3 none 2 none 2 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 3 none 3 none 2 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 4 none 1 none 2 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 4 none 2 none 2 N/A OJ287 1 WFPC2 IMAGE PC1 F606W 4 none 3 none 2 N/A 11344( 5) - 10/17/07 06:42 - [ 6] Summary Form for Proposal 11344 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 120.0D TO 150.0 D; ORIENT 300.0D TO 330.0 D; PATTERN 1 1; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names OJ287 ------------------------------------------------------------------------------------------------------------------------------------