8347( 4) - 05/12/99 11:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8347 Version: 4 Check-in Date: 18-Feb-1999 09:24:05 1.Proposal Title: The Gravitational Lens Candidate \PKS ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Arsen Hajian United States Naval Observatory CoI: Dr. Alan Fey United States Naval Observatory N CoI: Dr. Ralph Gaume United States Naval Observatory N CoI: Dr. Kenneth Johnston United States Naval Observatory N ------------------------------------------------------------------------------------ 5. Abstract High resolution radio interferometric observations of the radio target \PKS show a bright, compact central source surrounded by several weaker discrete clumps of emission. These data are difficult to reconcile with the standard `core- jet' paradigm for active galaxies. Instead, modeling the radio image as a gravitational lens appears to provide a much better interpretation of the data. If true, \PKS represents the smallest gravitational lens yet discovered. Furthermore, since it seems likely that the lensing object is a single galaxy, the mass distribution of \PKS is simpler than many known lenses, and can be more accurately modeled, thus potentially providing a valuable determination of H_ o. The goal of this proposal is to confirm (or refute) the gravitational lens model for \PKS through determination of the optical continuum morphology and redshift(s). Since the total spatial extent of the radio emission associated with \PKS is < 200 milliarcseconds, we propose to use t he high spatial resolution imaging capability of STIS imaging mode to determine the optical emission structure of \PKSns, and then will followup with spectroscopic observations using STIS in low dispersion spectroscopy mode to measure the redshifts of the individual components of the putatively lensed background source. ------------------------------------------------------------------------------------ 8347( 4) - 05/12/99 11:18 - [ 2] Observations Description ------------------------ We propose to obtain images and spectra of the components of \PKS using STIS. The imaging observations involve integrating for one orbit using the clear CCD. For the spectroscopy, the slit (52^''*0arcs1) must be placed along the line defined by A2--B1 in Figure 1. The coordinates we have provided are accurate to +/-50 mas, and so positioning the slit should not be problematic. Due to the faintness of the targets (R<21), obtaining quality spectra requires five orbits using the G430L grating, and six using the G750 grating. Real Time Justification ----------------------- None. See Scientific Justification Section. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8347( 4) - 05/12/99 11:18 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PKS1445-161 GALAXY, GRAVITATIONAL RA=14H 48M 15.0575S +/- 0.035", J2000 Z = 2.4 V = 22+/-0.5 LENS, QUASAR, DEC=-16D 20' 24.573" +/- 0.035" UNIDENTIFIED, RADIO EMITTER Comments: We are hoping to detect faint lensed components in close proximity to the V=22 galaxy. 8347( 4) - 05/12/99 11:18 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BEFORE 20-Aug-1999 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PKS1445-161 STIS/C ACCUM 50CCD MIRROR PATTERN=BOX,NUM-POS=4 1 500 S CD ------------------------------------------------------------------------------------------------------------------------------------ 8347( 4) - 05/12/99 11:18 - [ 5] Summary Form for Proposal 8347 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PATTERN=BOX NUM-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 20-Aug-1999 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names PKS1445-161 ------------------------------------------------------------------------------------------------------------------------------------