5944( 14) - 01/05/96 13:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5944 Version: 14 Check-in Date: 05-Jan-1996 13:12:35 1.Proposal Title: The Featureless Continuum & the Starburst -AGN Connection in Seyfert 2 Nuclei ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Timothy Heckman Dept. of Phys&Astr, Johns Hopkins University CoI: Anne Kinney Space Telescope Science Institute N CoI: Anuradha Koratkar Space Telescope Science Institute N CoI: Julian Krolik Johns Hopkins University N CoI: Claus Leitherer Space Telescope Science Institute N CoI: Andrew Wilson University of Maryland N ------------------------------------------------------------------------------------ 6. Abstract One of the most striking properties of type 2 Seyfert nuclei is a 'featureless' continuum (FC) in the optical and UV that is considerably bluer than the light from an old stellar population. Recent optical spectropolarimetry and our analysis of archival IUE UV spectra show that only a minority of the FC can be produced by scattered light from a hidden type 1 Seyfert nucleus. The majority of the FC (the 'FC2') may be produced by hot massive stars, or in some heretofore unknown way by the AGN (e.g. free-free emission from fast shocks and/or from the 'mirror' of warm electrons seen in some Seyfert 2's). We propose a decisive test of the hypothesis that hot stars produce the FC2: such stars should produce a clear spectroscopic signature in the form of broad, blue- shifted NVLambda1240 and SiIVLambda1396 stellar wind absorption features. We show that these should be detectable in high quality GHRS G140L spectra, and we propose to obtain such data (plus a short FOS G160L spectrum to measure the UV spectral-energy distribution) for one or more type 2 Seyfert nuclei selected on the basis of FOC UV images of nine of the brightest- known Seyfert 2 nuclei. If we see the stellar features, it will establish the existence of a close link between the Seyfert and starburst phenomena. If we do not, then the FC2 must represent a truly new phenomenon in the AGN 'bag of tricks'. In either case, this result will have significant implications for our understanding of AGNs. ------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 2] Observations Description ------------------------ Sample Selection Since it is not feasible to obtain the requisite HST data for a large sample of type 2 Seyferts, the galaxies to be examined must be selected with care. Our goal is to select type 2 Seyfert galaxies that are as representative as possible of the Seyfert 2 phenomenon, yet have FC2's in the far-UV that are bright enough so that adequate-quality spectra can be obtained in a reasonable amount of observing time. Selecting strictly on the basis of far- UV flux in the IUE aperture might bias the sample towards cases like NGC7496 in which a rather feeble Seyfert nucleus is surrounded by a very bright circumnuclear starburst (Veron et al 1981) which clearly dominates the IUE spectrum (Kinney et al 1993). Rather, we want our initial selection criterion to be unbiased with respect the presence or absence of a starburst. Selecting on the brightness of the Seyfert nucleus itself seems the most sensible choice. The most widely available such measures are the flux of the OIIILambda5007 line, (which is the brightest and best-studied line produced in Seyfert 2's), and the nuclear far-UV continuum flux. We have therefore defined a sample of the brightest known type 2 Seyfert nuclei (apart from the 'oddball' NGC1068), using the compilation of the OIII fluxes in Whittle (1992) and the UV spectra compiled by (Kinney et al 1991;1993). We propose to use FOC UV images of the nine brightest nuclei to select three objects for UV spectroscopy with the GHRS+G140L+LSA. These galaxies are as follows (with the IUE flux at 1480 Angstrom\\ given in units of 10^-15 erg cm^-2 s^-1 ang^-1): Mrk573 (3.0), Mrk3 (1.4), NGC3081 (2.9), NGC3393 (1.9), Mrk463 (5.2), NGC5135 (9.4), IC5135 (7.9), Mrk477 (6.5), and IC3639 (9.2). sectionGeneral Remarks on Feasibility Our specific goal is to obtain spectra of sufficient quality to allow us to detect the stellar wind signatures of massive stars in via the NVLambda1240 and SiIVLambda1396 features - if they are present at the strength predicted for a starburst population that dominates the UV continuum. Thus a null result will also be significant since it will rule out hot stars as the origin of the FC2. The instrument of choice is the GHRS and the G140L grating with the LSA. As noted above, the NV and SiIV lines are our prime targets because they will be significantly less contaminated by the Seyfert emission-lines than CIV. In this wavelength region, the GHRS is a factor of about 2 to 7 more efficient than the FOS with the G130H grating. A fringe benefit is that it can also provide significantly better spectral resolution (0.7Angstrom\\ vs. 1.0Angstrom\\ for a point source). The IUE aperture is large (10x20 arcsec), so that there may be some concern about the fraction of the IUE flux that will be contained within the 1.74 arcsec square GHRS LSA. We believe it is likely that most of the IUE flux will be encompassed by the GHRS LSA. To show this, we have estimated the flux of the optical FC in a small (few arcsec) aperture using the data in Kay (1994), Koski (1978), Yee (1980), Whittle (1992), and Dahari & DeRobertis (1988). If the UV FC source were much larger than a few arcsec, we would expect that an extrapolation of the IUE-measured continuum into the optical would significantly over-predict the flux of the FC in the optical small-aperture spectra. This is not the case (if anything an extrapolation of the IUE spectrum tends to underpredict the optical FC). While it is therfore highly likely that UV continuum source is compact (less than a few arcsec in size), we believe that the most efficient use of the GHRS can be made if the targets for spectroscopy are selected on the basis of images of the UV-continuum source. These images will allow us to select the targets with the maximum UV flux contained within the 1.74x1.74 arcsec LSA. The images will also allow us to exclude cases in which the UV morphology on scales of a few arcsec is so complex that the target acquisition software for the GHRS is likely to fail. Finally, these UV images will have significant scientific worth in their own right as a morphological diagnostic of the nature of the UV continuum. sectionFOC Images Of the nine members of our flux-limited sample, two (Mrk3 and Mrk573) aleady have post-costar UV images with the FOC (PI - Macchetto). These images will be in the HST Archives in Spring 1995. We propose to obtain FOC images with the F210M filter in the f/96 512x512 unzoomed mode (7 x 7 arcsec field) of the remaining seven nuclei. In five of these seven cases, we will also obtain images in the zoomed mode (14 x 14 arcsec field). These five targets are relatively nearby galaxies in which the UV source MAY be quite large in angular size. Combining the 7x7 and the 14x14 arcsec images will give us the best combination of dynamic range and field-of-view. We have selected the FOC because it is superior to the WFPC in terms of throughput and red-leak in the far-UV, and because we are interested in only a small field-of view. We have selected the F210M filter because it has a reasonable throughput, has a minimal red-leak, avoids the LyAlpha and OI airglow lines, and avoids any bright Seyfert emission-lines. If we use a typical IUE flux of 3 x 10^-15 erg cm^-2 s^-1 ang^-1, the FOC Instrument Handbook then implies a total count rate of 13 s^-1 In a 2100s exposure, 27000 source photons will be detected. For a diffuse UV source with a size of 3 arcsec^2 (the size of the LSA), this corresponds to 1.8 photons per (unzoomed) pixel or about 36 photons per resolution element. The corresponding background (detector) counts will be 1.5 per unzoomed pixel and 30 per resolution element. The signal- to-noise will then be 4.4:1 per resolution element. The situation improves dramatically if the source is more compact (e.g. a point source would be detected with a signal -to-noise of about 100:1). Even in the case that the entire IUE flux is produced by a point source, the count rate in the central unzoomed pixel is only 1.2 s^-1, so we do not need to worry about saturation. We will use one orbit per target (7 orbits for the imaging portion of this program). section Spectra To simulate our GHRS observations, we have used our HST UV spectra of actual starburst galaxies to make a 'starburst template'. We have then added NV and SiIV emission-lines from the NLR whose fluxes are the maximum allowed by the IUE spectra of Seyfert 2's, and whose widths are matched to the average width of the optical NLR emission- lines in our Seyferts as given in Whittle (1992). We have also added a scattered Seyfert 1 component that contributes the maximum allowable 25\\ the broad blue-shifted SiIV stellar wind line can be clearly seen in the simulated spectrum, provided that the signal-to-noise in the continuum is at least 20:1 per diode. The NV line is also detectable, but its detectability is more sensitive to the strength of any LyAlpha and NV emission-lines contributed by a 'hidden' Seyfert 1 BLR. Using the IUE fluxes given above, and the GHRS+G140L+LSA sensitivities given in the GHRS Instrument Handbook, the predicted count rates at 1400 Angstrom\\ range from 0.03 to 0.09 s^-1 diode^-1. The background (sky plus dark) will be unimportant. We therefore calculate that to get an SNR of 20:1 per diode in the continuum near the NV and SiIV lines requires total integration times ranging from 1.3 hours for the brightest cases to 4 hours for the faintest. These translate into a range of 3 to 7 orbits per target. These estimates assume that all the IUE flux passes through the LSA. We will use the 6 total remaining orbits to get spectra of one (or possibly two, pending the outcome of the imaging) targets. In addition to the long GHRS exposures, we will also obtain a short (5M) FOS exposure with the G160L grating. This will allow us to measure the overall UV spectral energy distribution and combine this with ground-based measurements of the optical SED. This will provide important information about reddening. Real Time Justification ----------------------- We require that the FOC images be obtained well in advance of the spectra, since we will use the former to select the specific targets for the latter. Flux-calibrated optical spectra are available for these targets, and will be used to further constrain models of the FC2 and the stellar population in the nuclei. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3081 GALAXY, SEYFERT, RA=9H 59M 29.52S +/- 0.02S, DEC= J2000 V = 12.2 STARBURST -22D 49' 34.9" +/- 0.3", PLATE- ID=04A1 2 NGC3393 GALAXY, SEYFERT, RA= 10H 48M 23.40S +/- 0.02S, J2000 V = 12.4 STARBURST DEC= -25D 09' 43.6" +/- 0.3", PLATE-ID=00GU 3 MRK463 GALAXY, SEYFERT, RA=13H 56M 02.85S +/- 0.02S, J2000 V = 13.8 STARBURST DEC= 18D 22' 18.9" +/- 0.3", PLATE-ID=019M 4 MRK477 GALAXY, SEYFERT, RA=14H 40M 38.03S +/- 0.02S, J2000 V = 14.7 STARBURST DEC= 53D 30' 15.67" +/- 0.3", PLATE-ID=01AL 5 NGC5135 GALAXY, SEYFERT, RA=13H 25M 43.9S +/- 0.02S, DEC= J2000 V = 12.0 STARBURST -29D 50' 02.7" +/- 0.3", PLATE- ID=02EF 6 IC3639 GALAXY, SEYFERT, RA=12H 40M 52.82S +/- 0.02S, J2000 V = 12.2 STARBURST DEC= -36D 45' 21.0" +/- 0.3", PLATE-ID=04HH 7 IC5135 GALAXY, SEYFERT, RA=21H 48M 19.49S +/- 0.5S, DEC= J2000 V = 12.2 STARBURST -34D 57' 05.1" +/- 5", PLATE- ID=0483 5944( 14) - 01/05/96 13:18 - [ 5] Visit: 01 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3081 FOC/96 IMAGE 512X102 F210M PIXEL=50X25 1 30M MAX DUR 200% 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3081 FOC/96 IMAGE 512X512 F210M PIXEL=25X25 1 3M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 6] Visit: 02 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3393 FOC/96 IMAGE 512X102 F210M PIXEL=50X25 1 30M MAX DUR 200% 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3393 FOC/96 IMAGE 512X512 F210M PIXEL=25X25 1 3M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 7] Visit: 03 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MRK463 FOC/96 IMAGE 512X512 F210M 1 30M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 8] Visit: 04 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MRK477 FOC/96 IMAGE 512X512 F210M 1 30M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 9] Visit: 05 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5135 FOC/96 IMAGE 512X102 F210M PIXEL=50X25 1 30M MAX DUR 200% 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5135 FOC/96 IMAGE 512X512 F210M PIXEL=25X25 1 3M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 10] Visit: 06 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC3639 FOC/96 IMAGE 512X102 F210M PIXEL=50X25 1 30M MAX DUR 200% 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 IC3639 FOC/96 IMAGE 512X512 F210M PIXEL=25X25 1 3M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 11] Visit: 07 Visit Requirements: BEFORE 31-JAN-1996 On Hold Comments: Additional Comments: EARLY ACQ IMAGES FOR SPECTROSCOPY Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 IC5135 FOC/96 IMAGE 512X102 F210M PIXEL=50X25 1 30M MAX DUR 200% 4 ------------------------------------------------------------------------------------------------------------------------------------ 2 IC5135 FOC/96 IMAGE 512X512 F210M PIXEL=25X25 1 3M MAX DUR 200% ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 12] Visit: 10 Visit Requirements: On Hold Comments: Additional Comments: Visit has now been updated and taken off hold. P. Stanley 10/24/95 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MRK477 FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP- 1 3S ONBOARD ACQ FOR 2 K Y=1.23,SEARCH- SIZE-X=1,SEARCH -SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 MRK477 FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP- 1 3.4S ONBOARD ACQ FOR 3 K X=0.61,SCAN- STEP- Y=0.61,SEARCH- SIZE-X=6,SEARCH Comments: -SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 MRK477 FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP- 1 4S ONBOARD ACQ FOR 4-10 K X=0.29,SCAN- STEP- Y=0.29,SEARCH- SIZE-X=3,SEARCH Comments: -SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 4 WAVE HRS ACCUM SC2 G140L 1343 1 60S ------------------------------------------------------------------------------------------------------------------------------------ 5 MRK477 HRS ACCUM 2.0 G140L 1343 1 50M ------------------------------------------------------------------------------------------------------------------------------------ 6 MRK477 HRS ACCUM 2.0 G140L 1343 1 50M ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE HRS ACCUM SC2 G140L 1487 1 60S ------------------------------------------------------------------------------------------------------------------------------------ 8 MRK477 HRS ACCUM 2.0 G140L 1487 1 50M ------------------------------------------------------------------------------------------------------------------------------------ 9 MRK477 HRS ACCUM 2.0 G140L 1487 1 50M ------------------------------------------------------------------------------------------------------------------------------------ 10 MRK477 HRS ACCUM 2.0 G140L 1487 1 50M ------------------------------------------------------------------------------------------------------------------------------------ 5944( 14) - 01/05/96 13:18 - [ 13] Summary Form for Proposal 5944 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PIXEL=50X25 PIXEL=25X25 SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=2 SEARCH-SIZE-X=3 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 31-JAN-1996 MAX DUR 200% ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 4-10 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F210M MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC3081 NGC3393 MRK463 MRK477 NGC5135 IC3639 IC5135 WAVE ------------------------------------------------------------------------------------------------------------------------------------