8264( 4) - 10/26/99 11:22 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8264 Version: 4 Check-in Date: 20-Jan-1999 09:31:08 1.Proposal Title: PDS 456: A radio-quiet analogue of 3C 273 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Paul O'Brien University of Leicester CoI: Dr Chris Simpson Subaru Telescope N CoI: Prof Martin Ward University of Leicester N CoI: Dr James Reeves University of Leicester N ------------------------------------------------------------------------------------ 5. Abstract To understand the nature of Active Galactic Nuclei (AGN), it is important to explore the full range of parameter space occupied by these powerful objects. For 35 years, the most luminous, nearby AGN known was the radio-loud quasar, 3C 273 --- the first quasar ever discovered. Now, we have a newly discovered quasar, PDS 456, which our IR/optical/X-ray data suggests may be the most luminous object in the local Universe. PDS 456 is radio-quiet, and therefore provides a view of the nucleus relatively unaffected by the relativistic jet, which either dominates or contaminates the observed emission from 3C 273. We propose to use one orbit of HST time to obtain a moderate-resolution STIS spectrum of PDS 456 in order to: (a) better elucidate its spectral energy distribution, and in particular its big-blue- bump, thereby constraining AGN accretion disc models; (b) see if the close similarity with 3C 273 in the optical/IR extends into the UV; (c) search for UV absorption lines possibly associated with the strong Fe edge seen in the ASCA data, or with a broad absorption line region; and (d) determine the UV emission-line spectrum, particularly LyAlpha for comparison with the very broad Balmer and Paschen lines. ------------------------------------------------------------------------------------ 8264( 4) - 10/26/99 11:22 - [ 2] Observations Description ------------------------ We propose a STIS observation of PDS 456 using the MAMA detectors and the G140L and G230L gratings. The spectral resolutions provided by these gratings are well suited to this program. For the declination of the target, we have about 54 minutes per orbit of visibility. Using the numbers in the Cycle 8 `Call for Proposals', allowing for the acquisition of guide stars (6 minutes), a STIS point-source target acquisition (6 minutes) and two MAMA exposures (6 minutes each), leaves about 30 minutes in the orbit to obtain science exposures. To detect the broad wings of the emission lines, simulations suggest we require S/N ~ 10 per resolution element in the adjacent continuum. We will use a fairly wide slit (52*0.5 arcseconds) to ensure good photometric accuracy. The AGN host -galaxy will not contaminate the UV spectrum significantly. Using the on-line STIS exposure simulator, and assuming a UV spectrum similar to that of 3C 273 normalized to the optical flux of PDS 456, allowing for the Galactic reddening, the required S/N can be achieved longward of ~ 1250 Angstrom\ by splitting the exposures into 19 minutes for G140L and 13 minutes for G230L. Thus our science goals can be achieved with only a single orbit of HST observing time. Real Time Justification ----------------------- None. Our desire to obtain near-simultaneous optical/infrared spectra (see Scientific Justification) does not affect the scheduling of the HST observations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: DAT Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8264( 4) - 10/26/99 11:22 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PDS456 GALAXY, QSO RA=17H 28M 19.8S +/- 0.01S, DEC= J2000 Z=0.1837 V = 14+/-0.2 -14D 15' 56.15" +/- 0.2", PLATE- 5 B-V = 0.7 ID=03YM F(1500)=5+/-4e-15 A(V) = 1.5+/-0.2 8264( 4) - 10/26/99 11:22 - [ 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 PDS456 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 PDS456 STIS/F ACCUM 52X0.5 G140L 1425 1 1140 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 PDS456 STIS/N ACCUM 52X0.5 G230L 2376 1 781 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8264( 4) - 10/26/99 11:22 - [ 5] Summary Form for Proposal 8264 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2, 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L G230L ------------------------------------------------------------------------------------------------------------------------------------ Target Names PDS456 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 2376 ------------------------------------------------------------------------------------------------------------------------------------