6539( 7) - 06/24/96 18:36 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6539 Version: 7 Check-in Date: 24-Jun-1996 18:32:34 1.Proposal Title: Ultraviolet Spectroscopy of Seyfert 2 Nuclei ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Timothy Heckman THE JOHNS HOPKINS UNIVERSITY CoI: Rosa Gonzalez-Delgado Space Telescope Science Institute N 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: Gerhardt Meurer Johns Hopkins University 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 in a circumnuclear starburst , or in some heretofore unknown way by the AGN. We propose a direct test of the starburst hypothesis: a starburst population 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 for three type 2 Seyfert nuclei selected on the basis of new 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 not, then the FC2 likely represents a truly new phenomenon in the AGN `bag of tricks'. In either case, this result will have significant implications for our understanding of AGNs. We stress that STIS will be much less sensitive than GHRS for these particular measurements. Thus, Cycle 6 represents the best chance in the foreseeable future to directly detect hot massive stars in these Seyfert galaxies. ------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 2] Observations Description ------------------------ sectionSample 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 has been to select type 2 Seyfert galaxies that are as representative as possible of the Seyfert 2 phenomenon, yet are bright enough in the UV so that adequate-quality spectra can be obtained in a reasonable amount of observing time. Thus, our initial selection criteria were unbiased with respect to 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 (Whittle 1992) are the flux of the OIIILambda5007 line (the brightest and best-studied line produced in Seyfert 2's) and the 1.4 GHz radio continuum flux. H95 defined and studied a sample of 20 such Seyfert 2's having IUE spectra. Archival FOC F210 images exist for two of these. We were awarded time in Cycle 5 to obtain images of seven additional targets. We have selected these so that the nine galaxies with F210M images comprise the five members of the H95 sample with the brightest OIIILambda5007 emission-line and the five members with the largest UV flux as measured with IUE (Mrk477 is a member of both samples). Based on these FOC images, there are four targets that are bright enough for us to obtain suitably high signal-to- noise UV spectra with the GHRS: Mrk477, IC3639 (=TOL1238-364), NGC5135, and NGC7130 (=IC5135). We have six unutilized orbits left in our Cycle 5 allocation. We will use these to obtain a GHRS spectrum of Mrk477, which is the most intrinsically luminous sample member. Here, we request time to obtain similar UV spectra of the other three targets. sectionFeasibility Our specific goal is to obtain spectra of sufficient quality to allow us to detect the stellar wind signatures of massive stars 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 an on-going starburst as the origin of the UV 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. It is important to stress that STIS will be significantly less sensitive than the GHRS for this type of measurement. The UV- bright regions we propose to observe typically cover an area of about 0.5 to 2 square arcsec and yield predicted GHRS count rates of 0.044 s^-1 diode^-1 (see below). This is significantly higher than the GHRS dark count rate. However, the dark count rate for STIS summed over all the pixels covering one square arcsec is expected to be about 0.1 s^-1. Since the throughput of STIS and GHRS are expected to be similar, the time to achieve the same signal-to-noise ratio with STIS will be about three times larger than with GHRS for our targets. Moreover, the resolving power of the G140L STIS grating will be only about half that of the GHRS G140L, a decided disadvantage for this application. Finally, the spatial multiplexing (long-slit capability) of STIS is not a major advantage in this program. The UV continuum is too faint for spectroscopy of regions lying outside the central arcsec-scale region, while even the central region itself is too faint to separately observe the individual UV knots at high signal-to-noise. Thus, Cycle 6 offers the best chance we will have in the foreseeable future to directly detect hot massive stars in these Seyfert 2 galaxies. To simulate our GHRS observations, we have used 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 emission-lines in our Seyferts as given in Whittle (1992). We have also added a scattered Seyfert 1 component that contributes the maximum allowable 20\\% of the UV continuum. As shown in Fig. 2, 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 BLR seen in reflection. We emphasize that the redshifts of our targets (z ~ 0.011 to 0.016) are sufficient to shift the NV line safely away from the geocoronal LyAlpha emission-line. We have used the FOC F210M images to measure the fluxes at 2100 Angstrom\\ in the brightest region matched to the 1.74 by 1.74 arcsec GHRS LSA. We have then extrapolated to 1400 Angstrom\\ using the IUE spectra, and find that all three targets have fluxes of about 3 x 10^-15 erg cm^-2 s^-1 ang^-1. The GHRS+G140L+LSA sensitivities given in the GHRS Instrument Handbook then yield a predicted count rate at 1400 Angstrom\\ of about 0.044 s^-1 diode^-1. The background (dark) will be about 0.008 s^-1 diode^-1. We therefore calculate that to get an SNR of 20:1 per diode in the continuum near the NV and SiIV lines requires a total integration time of about 3.0 hours per target. Including one orbit for acquisition and set-up, this translates into five orbits per target. We therefore request 15 total orbits for this program. We believe that it is important to obtain spectra for at least four galaxies (one in Cycle 5 and three more in Cycle 6). This is because we want to make a general statement about the nature of the UV continuum in Seyfert 2's. The case of NGC1068 (which is often referred to a the `prototypical' Seyfert 2, but whose FC has striking spectropolarimetric differences from the other well- studied Seyfert 2's) is a warning in this regard. section*References defMNRAS Mon. Not. R. astr. Soc. defAngstrom Astr. Astrophys. defAngstroms Astr. Astrophys. Suppl. defAp.J. Astrophys. J. def\\pasp P.A.S.P. defA.J. Astron. J. defAp.J. Supp. Astrophys. J. Suppl. Antonucci, R., & Miller, J. 1985, apj, 297, 621 Cid Fernandes, R., & Terlevich, R. 1995, mnras, 272, 423 Filippenko, A. 1993, in Physics of Active Galactic Nuclei, ed. S. Wagner & W. Duschl, Springer-Verlag, 345 Heckman, T. 1991, in Massive Stars in Starburst Galaxies, ed. C. Leitherer, N. Wal- born, T. Heckman, & C. Norman, Cambridge University Press, p. 289 Heckman, T., Krolik, J., Meurer, G., Calzetti, D., Kinney, A., Koratkar, A., Leitherer, C., Robert, C., & Wilson, A. 1995, Ap.J., 20 October issue Kinney, A., Antonucci, R., Ward, M., Wilson, A., & Whittle, M. 1991, apj, 377, 100 Koski, A. 1978, apj, 223, 56 Leitherer, C., Robert, C., & Heckman, T. 1995, apjs, 99, 173 Miller, J. 1994, in The Physics of Active Galaxies, ed. G. Bicknell, M. Dopita, & P. Quinn, ASP Conf. Series, 54, 149 Miller, J. & Goodrich, R. 1990, apj, 355, 456 Shuder, J. 1981, apj, 244, 12 Tran, H. 1995, apj, 440, 597 Whittle, M. 1992, apjs, 79, 49 Real Time Justification ----------------------- Flux-calibrated optical spectra and images of these targets will be used to further constrain models of the UV continuum and the stellar population. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5135 GALAXY, SEYFERT, RA=13H 25M 44.03S +/- 0.02S, J2000 V = 12.0 STARBURST DEC= -29D 50' 01.1" +/- 0.3", F-CONT(1400)=3.3e-15 PLATE-ID=02EF F-CONT(2100)=3.1e-15 2 IC3639 GALAXY, SEYFERT, RA=12H 40M 52.88S +/- 0.02S, J2000 V = 12.2 STARBURST DEC= -36D 45' 21.8" +/- 0.3", F-CONT(1400)=1.7e-15 PLATE-ID=04HH F-CONT(2100)=1.2e-15 3 NGC7130 GALAXY, SEYFERT, RA=21H 48M 19.48S +/- 0.5S, DEC= J2000 V = 12.2 STARBURST -34D 57' 05.4" +/- 5", PLATE- F-CONT(1400)=3.6e-15 ID=0483 F-CONT(2100)=2.1e-15 6539( 7) - 06/24/96 18:36 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5135 FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP-Y=1.23,SEARCH-SIZE-X=1, 1 1 S ONBOARD ACQ FOR 2 K SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC5135 FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 1.25 S ONBOARD ACQ FOR 3 K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC5135 FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 1.5 S ONBOARD ACQ FOR 5 K ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC5135 FOS/BL ACQ 4.3 MIRROR 1 5 M SAVE OFFSET OFF ------------------------------------------------------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 6] Visit: 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 4 WAVE HRS ACCUM SC2 G140L 1311 1 54.4 S USE OFFSET OFF SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC5135 HRS ACCUM 2.0 G140L 1311 1 2992 S USE OFFSET OFF ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE HRS ACCUM SC2 G140L 1452 1 54.4 S USE OFFSET OFF ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC5135 HRS ACCUM 2.0 G140L 1452 1 2203.2 USE OFFSET OFF ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC5135 HRS ACCUM 2.0 G140L 1452 1 2203.2 USE OFFSET OFF ------------------------------------------------------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 7] Visit: 03 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 NGC7130 FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP-Y=1.23,SEARCH-SIZE-X=1, 1 1.5 S ONBOARD ACQ FOR 2 K SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7130 FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 1.75 S ONBOARD ACQ FOR 3 K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7130 FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 2 S ONBOARD ACQ FOR 5-9 K ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE HRS ACCUM SC2 G140L 1314 1 54.4 S SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7130 HRS ACCUM 2.0 G140L 1314 1 3155.2 ------------------------------------------------------------------------------------------------------------------------------------ 7 WAVE HRS ACCUM SC2 G140L 1455 1 54.4 S ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC7130 HRS ACCUM 2.0 G140L 1455 1 2556.8 ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC7130 HRS ACCUM 2.0 G140L 1455 1 2638.4 ------------------------------------------------------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 8] Visit: 04 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 IC3639 FOS/BL ACQ/PEA 4.3 MIRROR SCAN-STEP-Y=1.23,SEARCH-SIZE-X=1, 1 3.5 S ONBOARD ACQ FOR 2 K SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 IC3639 FOS/BL ACQ/PEA 1.0 MIRROR SCAN-STEP-X=0.61,SCAN-STEP-Y=0.61 1 4 S ONBOARD ACQ FOR 3 K ,SEARCH-SIZE-X=6,SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 3 IC3639 FOS/BL ACQ/PEA 0.5 MIRROR SCAN-STEP-X=0.29,SCAN-STEP-Y=0.29 1 4.5 S ONBOARD ACQ FOR 5-12 K ,SEARCH-SIZE-X=3,SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE HRS ACCUM SC2 G140L 1308 1 54.4 S SAME POS AS 6 ------------------------------------------------------------------------------------------------------------------------------------ 6 IC3639 HRS ACCUM 2.0 G140L 1308 1 3046.4 ------------------------------------------------------------------------------------------------------------------------------------ 7 IC3639 HRS ACCUM 2.0 G140L 1308 1 3046.4 ------------------------------------------------------------------------------------------------------------------------------------ 8 WAVE HRS ACCUM SC2 G140L 1448 1 54.4 S ------------------------------------------------------------------------------------------------------------------------------------ 9 IC3639 HRS ACCUM 2.0 G140L 1448 1 2692.8 ------------------------------------------------------------------------------------------------------------------------------------ 10 IC3639 HRS ACCUM 2.0 G140L 1448 1 2692.8 ------------------------------------------------------------------------------------------------------------------------------------ 11 IC3639 HRS ACCUM 2.0 G140L 1448 1 2692.8 ------------------------------------------------------------------------------------------------------------------------------------ 12 IC3639 HRS ACCUM 2.0 G140L 1448 1 2638.4 ------------------------------------------------------------------------------------------------------------------------------------ 6539( 7) - 06/24/96 18:36 - [ 9] Summary Form for Proposal 6539 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.23 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SEARCH-SIZE-Y=2 SEARCH-SIZE-X=3 SEARCH-SIZE-X=6 SCAN-STEP-Y=0.29 SCAN-STEP-Y=0.61 SCAN-STEP-X=0.29 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ONBOARD ACQ FOR 5 SAVE OFFSET OFF USE OFFSET OFF SAME POS AS 6 USE OFFSET OFF ONBOARD ACQ FOR 5-9 ONBOARD ACQ FOR 5-12 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5135 WAVE NGC7130 IC3639 ------------------------------------------------------------------------------------------------------------------------------------