6830( 8) - 11/25/96 12:14 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6830 Version: 8 Check-in Date: 25-Nov-1996 12:11:11 1.Proposal Title: FOS Spectroscopy of NGC 1316 (Fornax A) ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle GALAXIES & CLUSTERS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: DOUGLAS G. CURRIE University of Maryland CoI: Edward Shaya University of Maryland N ------------------------------------------------------------------------------------ 6. Abstract The elliptical galaxy NGC 1316, also known as Fornax A, is the third brightest radio source in the sky. It has twin jets on opposite sides of the nucleus, but no opaque radio core. Ground based spectra of the core hint at a rising mass-to- light ratio with increasing resolution and allow the possibility of a 3 * 10^9 M_SUN dark object. Stellar absorption lines are quite strong and easily measured for the purpose of velocity dispersion measurements, but only the HST has the spatial resolution required to focus in on scales where stars would no longer dominate the mass. FOC measurements reveal a central bright bright point source at Lambda1750Angstrom\ which indicates that the center is free of gas and dust. There is also no observable HAlpha observed in the central 1". A spectrum of the inner 0arcs13 (10 pc) in radius, would allow a decisive measurement of the mass of the central engine to be made. The spectra will be analyzed using the Fourier quotient method, a cross-correlation method, and a deconvolution method. Each method will determine a line width and evaluate deviations from a Gaussian line profile. A complete dynamical description of the core of this galaxy will then be possible. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to use the smallest circular apertures on the FOS (0.26" diameter) to obtain a deep optical spectrum of the central peak of NGC 1316. We are expecting the velocity dispersion to be in excess of Sigma = 190 km s^-1 (no massive dark object) and perhaps as high as 800 km s^-1 (dark object of 3 * 10^9 M_SUN). Experience from similar observations of elliptical galaxies has established that velocity dispersion can be determined to an accuracy of ~ 10\\% with signal-to-noise ratio of about 20 per Angstrom (Faber; personal communication). This seems to hold for FOS spectra as well as typical ground based spectra. Each diode covers 4.37 angstroms. So the signal-to-noise ratio per diode should be 87. This signal-to-noise ratio is comparible to the flat field determination errors. The central surface brightness is V=13.6 mag arcsec^-2 which translates into 16.79 mag within the aperture. If a V=15 magnitude G2 star gets 5.1 counts per second per diode at 4600Angstrom (Table 1 -9 of Handbook) and the throughput is 0.86 (Table 1-8), then we expect 5.1*0.86*dex(15-16.8 / 2.5) = 0.85 counts/s. The exposure time is 87^2/0.85 = 8900s = 148 minutes. Although we want high signal-to-noise, positioning is made slightly less critical by the fact that the core of the galaxy fills the selected apertures. I have discussed acquisition of this object in detail with an FOS Instrument Team member. The acquisition will be A+B1+C1+F1+D3. The overhead for this is 7+12+10+10+17 minutes. At the declination of this object, the visibility is typically 54 minutes. Guide star acquisition takes 8 minutes and reacquisition takes 6 minutes. The target acquisition is completed 23 (6+17) minutes into the second orbit. Using the remaining time in the second orbit 31 min plus 3 additional orbits, each with 48 min on target time, totals to 175 minutes on target for a signal-to-noise ratio of 21.6 per angstrom. We will not require the observation of red stars for templates since these have been made by several FOS observations in previous cycles. NOTE: The above Target Acquisition scenario has been modified to that currently in the program as per further work by the Contact Scientist, the PC, and the observers ( co-I Ed Shaya ). The 5th step especially had to be revised further downward in order to keep the program within its newly increased ( from 5 to 6 ) allocation of orbits. Real Time Justification ----------------------- None. Calibration Justification ------------------------- None. Additional Comments ------------------- None. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6830( 8) - 11/25/96 12:14 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1316-GC EXT-CLUSTER,Globular RA=03H 22M 42.5381S +/- 0.1S, 2000 V=+1635 V = 18.5+/-0.2 Cluster,CALIBRATION,Ape DEC=-37D 12' 41.214" +/- 0.5", rture Location PLATE-ID=02IW Comments: GC RV is value for galaxy. GC color is V-I=1.7. Assume K2III continuum for GC. GC position is from Westphal's GTO WFPC-I image of NGC 1316. GC is being used as an offset "star" for target acquisition. Guide stars used for Westphal's observations were from GS Plate- ID=02IW. 2 NGC1316- GALAXY, RADIO GALAXY, RA=03H 22M 41.7915S +/- 0.1S, 2000 V=+1635 SURF(V) = 13.5+/-0.2 NUCLEUS ELLIPTICAL DEC=-37D 12' 29.745" +/- 0.5", PLATE-ID=02IW Comments: Position of nucleus is from Westphal's GTO WFPC-I image of NGC 1316. Guide stars used for Westphal's observations were from GS Plate-ID=02IW. 6830( 8) - 11/25/96 12:14 - [ 2] Visit: 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1316-GC FOS/RD ACQ/PEA 4.3 MIRROR SCAN-STEP-X=3.33,SCAN-STEP-Y=1.23 1 8 S ONBOARD ACQ FOR 20 K ,SEARCH-SIZE-X=2,SEARCH-SIZE-Y=6 ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1316-GC FOS/RD ACQ/PEA 1.0 MIRROR SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 8 S ONBOARD ACQ FOR 30 K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 Comments: STAGE 2 OF 5 STAGE PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC1316-GC FOS/RD ACQ/PEA 0.5 MIRROR SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 8 S ONBOARD ACQ FOR 40 K ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 Comments: STAGE 3 OF 5 STAGE PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC1316-GC FOS/RD ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.11,SCAN-STEP-Y=0.11 1 8 S ONBOARD ACQ FOR 50 K ,SEARCH-SIZE-X=4,SEARCH-SIZE-Y=4 Comments: STAGE 4 OF 5 STAGE PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC1316-GC FOS/RD ACQ/PEA 0.3 MIRROR SCAN-STEP-X=0.052, 1 24 S ONBOARD ACQ FOR 60 K SCAN-STEP-Y=0.052,SEARCH-SIZE-X=5 ,SEARCH-SIZE-Y=5 Comments: STAGE 5 OF 5 STAGE PEAKUP ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC1316-NUC FOS/RD ACCUM 0.3 G570H 1 920 S LEUS Comments: Do blind offset from GC ( offset "star" ) to galaxy nucleus for this and subsequent science exposures. ------------------------------------------------------------------------------------------------------------------------------------ 70 NGC1316-NUC FOS/RD ACCUM 0.3 G570H 3 2460 S LEUS ------------------------------------------------------------------------------------------------------------------------------------ 6830( 8) - 11/25/96 12:14 - [ 3] Summary Form for Proposal 6830 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-X=3.33 SCAN-STEP-Y=1.23 SEARCH-SIZE-X=2 SEARCH-SIZE-Y=6 SEARCH-SIZE-Y=2 SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=4 SEARCH-SIZE-Y=5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20 ONBOARD ACQ FOR 30 ONBOARD ACQ FOR 40 ONBOARD ACQ FOR 50 ONBOARD ACQ FOR 60 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G570H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1316-GC NGC1316-NUCLEUS ------------------------------------------------------------------------------------------------------------------------------------