7846( 2) - 11/17/97 16:09 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7846 Version: 2 Check-in Date: 17-Nov-1997 16:07:38 1.Proposal Title: IR Imaging of the AGN Accretion Disk In Centaurus A ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: ETHAN SCHREIER SPACE TELESCOPE SCIENCE INSTITUTE CoI: Duccio Macchetto Space Telescope Science Institute N CoI: Dave Axon Space Telescope Science Institute N CoI: Alessandro Marconi Space Telescope Science Institute N CoI: Nicola Caon Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract We propose to image the extended accretion disk around the nucleus of NGC 5128 which we recently detected with HST. NICMOS Camera 2 images in \PA\ (F187N) show the presence of not only the innermost knot (N1) of the Cen A jet, but also a disk of ionized gas at the nucleus, not aligned with either the jet or the dust lane. This disk radius is ~ 0.6", corresponding to ~ 11pc at 3.5 Mpc, and is significantly smaller than the hundred parsec scale stellar disks presumed to exist at the center of many galaxies. Our proposed followup observation will provide a deep image in Fe II\ with Camera 1. The shorter wavelenth of Fe II\ and smaller pixel size of NIC1 will combine to allow us to better resolve the disk with an oversampled FWHM ~ 2pc. Combining this image with the existing \PA\ image will provide a map of the N(ionpFe+)/N(\ionpH+), fundamental to determining the presence of shocks, and also establish whether knot N1 is photo- or shock-ionized. We also propose to study the interaction of the Cen A X-ray/radio jet with the interstellar medium of the galaxy, and to search for other emission features near the AGN, by obtaining \PA\ and Fe II\ images with Camera 3. The larger field of view will include Knot A, seen in X-ray and radio with significant substructure. The Fe/H ratio will allow us to localize the hypothesized particle acceleration sites. ------------------------------------------------------------------------------------ 7846( 2) - 11/17/97 16:09 - [ 2] Observations Description ------------------------ We will obtain high resolution images of the accretion disk with NICMOS Camera 1 in the F164N (Fe II) and F166N (adjacent continuum) filters. Since the photon noise of the continuum will dominate, the S/N of the continuum subtracted line image is given by: left(\\\\fracSN\\\\right)_Line = frac1(square)rt2 left(\\\\fracSN\\\\right)_Continuum fracW_LambdaDeltaLambda where W_Lambda is the equivalent width of the line and DeltaLambda is the width of the filter. According to the NIR spectra published by Meadows & Allen (1992, PASAu 10(2), 104), the observed ratio Fe II/\\\\BG is ~eq 6, which corresponds to Fe II/\\\\PA~eq 0.5 and the shape of the continuum is roughly F_Lambda\\\\proptoLambda. Hence assuming that Fe II\\\\ has a spatial distribution similar to \\\\PA we can predict from our observations that its equivalent width in the disk will be distributed within 5-20 Angstrom\\\\ and the continuum will have surface brightnesses of ~eq3 10^-15 erg cm^-2 s^-1 AA^- 1 arcsec^-2. Therefore 5000s (i.e. 2 orbits) of integration time in each of the narrow band filters (F164N, F166N) will achieve a S/N~eq150 on the continuum allowing us to image with S/N>3 all the structures with equivalent width larger than W_Lambda>5Angstrom. Therefore a total of 4 orbits is requested for the high resolution NIC1 imaging of the disk in Fe II\\\\Wide field images of the nucleus-to-jet (N + knots N1,A) region will be obtained with Camera 3 in the filters F164N, F166N and F187N, F190N (Fe II\\\\ and \\\\PA respectively). With an integration time of 2500s per filter (i.e. 1 orbit per filter), and for a continuum surface brightness of 2 10^- 16 erg cm^-2 s^-1 AA^-1 arcsec^-2, which is representative of the diffuse emission outside the nuclear region as derived from our images, we will be able to reach S/N~eq150 on the continuum and S/N>3 for equivalent widths greater than ~eq5 Angstrom. If the emission is concentrated at the edges of the radio jet, as is likely, we expect to have EW >15 Angstrom comparable with those of the bow-shock like structures detected in the nuclear region. Therefore a total of 4 orbits is needed for line imaging with camera 3. We note that since we are interested in line images, the background emission will be removed when subtracting one narrow band filter from the other. For each of our observations, we will also obtain parallel observations with the other NICMOS cameras (even if out of focus), in similarly matched filters as the primary ones, to check for line emission in the circumnuclear regions. In our GO programs 6578 and 7267 we were given time for both primary and coordinated parallel observations with WFPC2 and STIS in order to explore the young stellar associations and globular cluster system in the inner regions of NGC5128, measuring their sizes and shapes and determining their luminosity function. We request similar coordinated parallel observations with WFPC2 and STIS, if possible, in order to enlarge our sample of clusters from different fields in Centaurus A. Real Time Justification ----------------------- None. None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7846( 2) - 11/17/97 16:09 - [ 3] Data Distribution Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7846( 2) - 11/17/97 16:09 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CENTAURUS-A- GALAXY,RADIO RA=13H 25M 27.5S +/- 1",DEC=-43D J2000 V = 7.8+/-0.5 NUC GALAXY,SEYFERT,ACCRETIO 1' 10.0" +/- 1",PLATE-ID=02EI N DISK,NUCLEUS 7846( 2) - 11/17/97 16:09 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: In case the parallel observations with NIC3 require a dump of the buffer which takes away observing time from the primary observations, please take away the parallel NIC3 observations but contact the PI first. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 CENTAURUS-A NIC1 MULTIAC NIC1-FI F164N PATTERN=SPIRAL-DITH,NUM-POS=4, 1 DEF PAR 11-15 WITH 10 -NUC CUM X DITH-SIZE=0.5,PATTERN-ORIENT=0, SAMP-SEQ=STEP128,NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ 11 ANY NIC2 MULTIAC NIC2 F187N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 12 ANY NIC3 MULTIAC NIC3 F187N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY WFPC2 IMAGE WFALL F336W 1 300 S ------------------------------------------------------------------------------------------------------------------------------------ 15 ANY STIS/C ACCUM F28X50L MIRROR 1 500 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 CENTAURUS-A NIC1 MULTIAC NIC1-FI F166N PATTERN=SPIRAL-DITH,NUM-POS=4, 1 DEF PAR 21-25 WITH 20 -NUC CUM X DITH-SIZE=0.5,PATTERN-ORIENT=0, SAMP-SEQ=STEP128,NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ 21 ANY NIC2 MULTIAC NIC2 F190N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 22 ANY NIC3 MULTIAC NIC3 F190N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 24 ANY WFPC2 IMAGE WFALL F336W 1 300 S ------------------------------------------------------------------------------------------------------------------------------------ 25 ANY STIS/C ACCUM F28X50L MIRROR 1 500 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 30 CENTAURUS-A NIC1 MULTIAC NIC1-FI F164N PATTERN=SPIRAL-DITH,NUM-POS=4, 1 DEF PAR 31-35 WITH 30 -NUC CUM X DITH-SIZE=0.5,PATTERN-ORIENT=0, SAMP-SEQ=STEP128,NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ 31 ANY NIC2 MULTIAC NIC2 F187N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 32 ANY NIC3 MULTIAC NIC3 F187N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 34 ANY WFPC2 IMAGE WFALL F555W 1 300 S ------------------------------------------------------------------------------------------------------------------------------------ 7846( 2) - 11/17/97 16:09 - [ 6] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 35 ANY STIS/C ACCUM F28X50L MIRROR 1 500 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 40 CENTAURUS-A NIC1 MULTIAC NIC1-FI F166N PATTERN=SPIRAL-DITH,NUM-POS=4, 1 DEF PAR 41-45 WITH 40 -NUC CUM X DITH-SIZE=0.5,PATTERN-ORIENT=0, SAMP-SEQ=STEP128,NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ 41 ANY NIC2 MULTIAC NIC2 F190N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 42 ANY NIC3 MULTIAC NIC3 F190N SAMP-SEQ=STEP128,NSAMP=14 1 DEF CUM ------------------------------------------------------------------------------------------------------------------------------------ 44 ANY WFPC2 IMAGE WFALL F814W 1 300 S ------------------------------------------------------------------------------------------------------------------------------------ 45 ANY STIS/C ACCUM F28X50L MIRROR 1 500 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 7846( 2) - 11/17/97 16:09 - [ 7] Summary Form for Proposal 7846 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations NIC1 NIC2 NIC3 WFPC2 STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PATTERN=SPIRAL-DITH NUM-POS=4 DITH-SIZE=0.5 PATTERN-ORIENT=0 SAMP-SEQ=STEP128 NSAMP=14 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PAR 11-15 WITH 10 PAR 21-25 WITH 20 PAR 31-35 WITH 30 PAR 41-45 WITH 40 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F164N F187N F336W MIRROR F166N F190N F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names CENTAURUS-A-NUC ANY ------------------------------------------------------------------------------------------------------------------------------------