7357( 13) - 01/25/99 07:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7357 Version: 13 Check-in Date: 25-Jan-1999 07:17:26 1.Proposal Title: Testing the Nature of ''Type 2'' LINERs Using UV Spectroscopy ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Luis Ho Observatoaries of the Carnegie Institution of Washington CoI: Aaron Barth University of California, Berkeley N CoI: Alex Filippenko University of California, Berkeley N CoI: Joseph Shields Ohio University N ------------------------------------------------------------------------------------ 5. Abstract LINERs, like Seyferts, come in two varieties: ``type 1'' have broad permitted lines and ``type 2'' only have narrow lines. While LINER 1s undoubtedly are genuine AGNs, the true nature of LINER 2s remains unknown. Since LINER 2s make up most of the LINER population, determining their ionization mechanism has become the key problem in understanding the origin of LINERs and their place in the AGN paradigm. The leading candidates for the energy source are photoionization (by an AGN-like continuum or by hot stars) and fast shocks. We propose to discriminate between these two mechanisms by means of UV and optical spectroscopy, since ionization by fast shocks predicts much stronger high-excitation UV lines such as C IV 1549, C III] 1909, and [Ne IV] 3426. In the cases where the UV continuum is strong enough, photoionization by hot stars can be further discerned through characteristic stellar absorption and/or P Cygni emission lines. We have selected two LINER 2 nuclei from our ground-based spectroscopic survey (NGC 3507 and NGC 4486 [M87]) for which we wish to acquire low-resolution (~500 km/s) STIS spectra covering the region ~1150 to 10270 Angstrom. ------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 2] Observations Description ------------------------ To determine the feasibility of the experiment, we performed a number of simulations using the STIS exposure time calculator. We generated an artificial spectrum containing the main UV and optical lines, which were assumed to have a fixed FWHM of 400 km/s. The fluxes of the UV lines were scaled relative to that of H-beta according to the shock calculations shown in Table 1. The flux of H- beta was allowed to vary, and a constant continuum level of 5e-17 erg/s/cm2/Ang consistent with the upper limits from the UV imaging studies of Maoz et al. (1995) and Barth et al. (1996a) was added. The simulations show that, for F(H- beta) = 1e-15 erg/s/cm2, a 40- min exposure in G140L yields a S/N (integrated over the line) of ~6 for C IV, while an exposure of the same length in G230L gives S/N ~ 6 and 10 for C III] and C II], respectively. Similarly, H-beta (G430L) and H-alpha (G750L) will have S/N ~ 40 and 100, respectively, in 15 min. Thus, fairly confident detections of the key emission lines can be achieved in ~3 orbits for a fiducial H-beta flux of 1e-15 erg/s/cm2. Our two chosen targets are estimated to have an H-beta flux of 5 to 7 times this value within the STIS 52X0.5 aperture. The targets will be observed with STIS in ACCUM mode and with the following detector/gratings combinations: FUV- MAMA/G140L, NUV-MAMA/G230L, CCD/G430L, and CCD/G750L (one tilt position only, for the latter). This will provide complete wavelength coverage from ~1150- 10270 Angstrom. Ideally, all observations would be done through either the 52X0.1 or 52X0.2 aperture to best isolate the point source in the nucleus. However, these small apertures require rather long peak-up times for our relatively faint sources, and the transmitted flux in the UV lines is expected to be very small. We have consequently adopted the compromise of using the 52X0.5 aperture, which increases the expected signal for a distributed source and also decreases expected errors in photometry resulting from aperture centering uncertainties. With the 52X0.5 aperture, additional peakup acquisition is unnecessary. The expected pointing accuracy (0.1") of the basic STIS target acquisition (ACQ) will center the nuclei of the galaxies reasonably well in our chosen aperture. We will use 3 orbits per galaxy. Guide star acquisition followed by target acquisition will require about half of the initial orbit on each target, the remainder of which will be spent on one 15- min (CR-split) exposure in G430L and another in G750L. This will be followed by one orbit each devoted to the G140L and G230L exposures. Real Time Justification ----------------------- None. None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 3] Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3507 GALAXY, LINER, NUCLEUS RA=11H 3M 25.398S +/- 0.5", J2000 V = +978 V = 17.0 DEC=18D 8' 7.25" +/- 0.5", PLATE F(2200)=5e-17 -ID=01AJ F(6000)=5e-16 2 NGC4486 GALAXY, LINER, NUCLEUS RA=12H 30M 49.39S +/- 0.1", J2000 V = V = 17.0 DEC=12D 23' 27.97" +/- 0.1", +1282 F(1400)=7.3e-16 PLATE-ID=00IY F(2200)=7.4e-16 F(5550)=7.1e-16 7357( 13) - 01/25/99 07:18 - [ 5] 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 NGC3507 STIS/C ACQ F28X50L MIRROR 1 5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3507 STIS/C ACCUM 52X0.5 G430L 4300 1 900 S MAX DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3507 STIS/C ACCUM 52X0.5 G750L 7751 1 1000 S MAX DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 4 CCDFLAT STIS/C ACCUM 52X0.5 G750L 7751 CR-SPLIT=NO ,GAIN=4 ,BINAXIS1=1 , 2 DEF CD BINAXIS2=1 Comments: G750L Flat-Field Calibration: Lambda=7751 Angstroms **Do not move MSM between the science exposure (exposure # 3) and this calibration exposure** ------------------------------------------------------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 6] Visit: 02 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 NGC3507 STIS/C ACQ F28X50L MIRROR 1 5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3507 STIS/N ACCUM 52X0.5 G230L 2376 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3507 STIS/F ACCUM 52X0.5 G140L 1425 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 231D TO 261D On Hold Comments: Additional Comments: The slit should be oriented to a position angle (on the sky) of 21D+-15D (i.e. 6D to 36D). Since the offset angle is 45D, the final angle for ORIENT is 51D to 81D. This range of angles is unschedulable according to RPS2, so we chose the nominal angle + 180 degrees, namely 231D to 261D. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4486 STIS/C ACQ F28X50L MIRROR 1 5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4486 STIS/C ACCUM 52X0.5 G430L 4300 1 900 S MAX DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4486 STIS/C ACCUM 52X0.5 G750L 7751 1 1000 S MAX DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 4 CCDFLAT STIS/C ACCUM 52X0.5 G750L 7751 CR-SPLIT=NO ,GAIN=4 ,BINAXIS1=1 , 2 DEF CD BINAXIS2=1 Comments: G750L Flat-Field Calibration: Lambda=7751 Angstroms **Do not move MSM between the science exposure (exposure # 3) and this calibration exposure** ------------------------------------------------------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 8] Visit: 04 Visit Priority: Visit Requirements: AFTER 03 BY 90 M TO 24 H On Hold Comments: Additional Comments: The orientation of the slit for this visit should remain as close as possible to that for visit 3. Therefore, this visit should follow as soon as possible after visit 3, and should not be separated by more than 24 hours. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4486 STIS/C ACQ F28X50L MIRROR 1 5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4486 STIS/N ACCUM 52X0.5 G230L 2376 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4486 STIS/F ACCUM 52X0.5 G140L 1425 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 9] Visit: 51 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 NGC3507 STIS/C ACQ F28X50L MIRROR 1 5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3507 STIS/C ACCUM 52X0.5 G430L 4300 1 900 S MAX DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3507 STIS/C ACCUM 52X0.5 G750L 7751 1 1000 S MAX DUR CD ------------------------------------------------------------------------------------------------------------------------------------ 4 CCDFLAT STIS/C ACCUM 52X0.5 G750L 7751 CR-SPLIT=NO ,GAIN=4 ,BINAXIS1=1 , 2 DEF CD BINAXIS2=1 Comments: G750L Flat-Field Calibration: Lambda=7751 Angstroms **Do not move MSM between the science exposure (exposure # 3) and this calibration exposure** ------------------------------------------------------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 10] Visit: 52 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 NGC3507 STIS/C ACQ F28X50L MIRROR 1 5 S ONBOARD ACQ FOR 2, 3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3507 STIS/N ACCUM 52X0.5 G230L 2376 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3507 STIS/F ACCUM 52X0.5 G140L 1425 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7357( 13) - 01/25/99 07:18 - [ 11] Summary Form for Proposal 7357 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO GAIN=4 BINAXIS1=1 BINAXIS2=1 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2, 3 MAX DUR ORIENT 231D TO 261D AFTER 03 BY 90 M TO 24 H ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G750L G230L G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC3507 CCDFLAT NGC4486 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 7751 2376 1425 ------------------------------------------------------------------------------------------------------------------------------------