9095( 2) - 11/05/02 11:51 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9095 Version: 2 Check-in Date: 16-Jan-2001 10:50:02 1.Proposal Title: Simultaneous HST, Chandra and FUSE Observations of Intrinsic Absorbers in AGN ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Gerard Kriss Space Telescope Science Institute CoI: Dr. Tal Alexander Space Telescope Science Institute N CoI: Dr. Michael Brotherton National Optical Astronomy Observatories N CoI: Dr. Richard Green National Optical Astronomy Observatories N CoI: Dr. John Hutchings Dominion Astrophysical Observatory N CoI: Dr. Mary Beth Kaiser The Johns Hopkins University N CoI: Dr. Julia Lee MIT Center for Space Research N CoI: Dr. Herman Marshall MIT Center for Space Research N CoI: Dr. William Oegerle The Johns Hopkins University N CoI: Dr. Patrick Ogle MIT Center for Space Research N CoI: Dr. Wei Zheng The Johns Hopkins University N ------------------------------------------------------------------------------------ 5. Abstract Photoionized, warm absorbing gas is an important component of the nuclear structure of AGN. Approximately half of all low-z AGN show high-ionization UV absorption lines and X-ray warm absorbers, but the relationship of the UV-absorbing gas to the even higher ionization X-ray absorbing material is not yet understood. Only a handful of high-spectral-resolution observations with HST, Chandra or FUSE currently exist (NGC 4151, NGC 3516, NGC 3783, NGC 5548, Mrk 509). These show a diversity of kinematic structure and ionization states in the absorbers. We propose to increase significantly the sample of low-redshift AGN studied at high spectral resolution in the UV and the X-ray by obtaining simultaneous HST, Chandra, and FUSE spectra of NGC 7469 and Mrk 279. Both are bright AGN with O vi absorption resolved in recent FUSE observations. The new simultaneous observations will resolve the kinematics and ionization state of both the UV and X-ray absorbers. This will permit a definitive assessment of their relationship and give clues to their location in the nuclear region. Using the variety of ionization states and the multiple absorbing components, we will also reconstruct the ionizing spectrum. Understanding the absorbing gas and its influence on the radiation escaping from AGN has important implications for the radiative input to the IGM and the origins of the X-ray background. ------------------------------------------------------------------------------------ 9095( 2) - 11/05/02 11:51 - [ 2] Observations Description ------------------------ We propose to obtain medium-resolution far-UV echelle spectra of NGC 7469 using the STIS FUV-MAMA, grating E140M, and the 0.2X0.2 aperture. NGC 7469 has a mean continuum flux at 1450 Angstrom\ of ~4 * 10^-14 erg cm^-2 s^-1 AA^-1, and it is variable at the level of tens of percent (Wanders et al. 1997, ApJS, 113, 69). The cycle 10 call for proposals gives a nominal visibility for NGC 7469 of 52 m. For a 5-orbit visit, the time available is Orbit 1: GS Acq (6m) + Target Acq (6m) + MAMA Ovhd (8m) leaves 32m. Orbits 2--5: GS Re-acq (5m) + MAMA Ovhd (1m) leaves 46m. Thus a 5-orbit visit allows 12, 960 s for science exposures. Using the STIS on-line ETC, a 13, 000s observation would yield a S/N per resolution element of 7--8 in the Lyalpha+Nv region, and similar results in the Civ region. The absorption features of interest have FWHM of 30--60 km s^-1 (e.g., Kriss et al. 2000b, ApJ, 538, L17), so we can bin the echelle data up to this level (a factor of 4.5--7.5 for a resolving power of 45, 000), still resolve the features of interest, and achieve a S/N per bin of ~15 in the continuum. Such results would be comparable to the STIS/E140M observation of NGC 5548 reported by Crenshaw & Kraemer (1999, ApJ, 521, 572), which had an integration time of 4750 s on a continuum flux level of ~ 1 * 10^-13 erg cm^-2 s^-1 AA^-1, about twice as bright as our proposed targets. Our planned S/N per bin is also similar to the FUSE spectra shown in Figures 1 and 2, and that obtained by Kriss et al. (2000, ApJ, 538, L17) for the FUSE spectrum of Mrk 509. This quality is adequate to resolve features and measure their column densities. Real Time Justification ----------------------- We propose to coordinate our HST observations with FUSE and with Chandra. If this proposal is successful, the FUSE observations will be proposed for NRA 3, which covers observations starting in December 2001 and overlaps the HST Cycle 10 observing windows for NGC 7469. The FUSE spectra would cover the 912--1187 Angstrom\ range, including the O vi and LyBeta absorption lines shown in Figures 1 and 2. The Chandra observations are proposed here; these Chandra Cycle 3 observations also overlap the FUSE NRA 3 and HST Cycle 10 observing windows for NGC 7469 We will use ACIS-S with the HETG in place to observe NGC 7469 with Chandra for 80 ks. We will use the standard modes for HETG observations: ``Timed Event" for the exposure mode, ``Faint" format, and chips 0--5 of ACIS-S. Each observation should be scheduled to occur within 1 day of the corresponding HST observation. Chandra has the unique capability to resolve the many narrow emission and absorption lines present in Seyfert spectra, and accurately measure their velocities with its high spectral resolution (E/Delta E ~ 1000). Such high resolution is not available with XMM- Newton, even though it has greater effective area, and the ability to kinematically associate X-ray and UV absorbing components would not be possible with XMM observations. Our team has extensive experience in observing with Chandra and in analyzing HETG data. NGC 7469 is a strong X-ray source with a 0.5--2.0 keV mean flux of ~ 2.2 * 10^-11 erg cm^-2 s^-1. Chandra HETG/ACIS-S observations will yield ~ 1.2 cts s^-1 in the first order dispersed spectra. This is well below the telemetry saturation level of 170 cts s^-1 for Timed-Event exposures in Faint mode. The 0-order images will be significantly piled up (80%); 1st order spectra will not. An exposure of 80 ks gives a total of 1.6 * 10^5 counts integrated over the dispersed spectrum. Fig. 3 shows a simulated HETG spectrum of NGC 7469 based on the warm absorber model in Kriss et al. (2000a, ApJ, 535, 58). Absorption lines of O vii, O viii, and N vii are visible in this section of the simulated spectrum. All lines are detected at high levels of confidence (4.5-- 7.5 Sigma). The exposure time was calculated to give high enough S/N to measure the velocities of these individual spectral features to a precision of 100 km 9095( 2) - 11/05/02 11:51 - [ 3] s^-1. (These are the strongest lines seen in other Seyfert spectra.) Given the minimum spacings of the kinematic components seen in the UV spectrum of NGC 7469 (400 km s^-1), this level of precision is necessary to match unambiguously the X- ray and UV absorbing components. For comparison, NGC 3783 has a 1 keV flux which is 1.3 times less than NGC 7469. Kaspi et al. (2000, ApJ, 535, L17) measured absorption line velocities in this object to an accuracy of ~150 km s^-1 at these energies with a 56 ks HETG observation. Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- ------------------------------------------------------------------------------------ 9095( 2) - 11/05/02 11:51 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7469 GALAXY, SEYFERT RA=23H 03M 15.62S +/- 0.1S, J2000 Z=0.016 V = 13.1 DEC=+08D 52' 25.6" +/- 1.0", B-V = 0.5 PLATE-ID=028Z F-CONT(1450)=4.0+/-2.0e-14 Coordinate Source: GUIDE_STAR_CATALOG Comments: UV flux is variable by factors of tens of percent. 9095( 2) - 11/05/02 11:51 - [ 5] Visit: 01 Visit Priority: Visit Requirements: SCHED 100% On Hold Comments: Additional Comments: To be coordinated to within 1 day with FUSE and Chandra Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC7469 STIS/C ACQ F28X50L MIRROR 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC7469 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2200 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC7469 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2800 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC7469 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2800 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC7469 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2800 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC7469 STIS/F ACCUM 0.2X0.2 E140M 1425 1 2800 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9095( 2) - 11/05/02 11:51 - [ 6] Summary Form for Proposal 9095 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC7469 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------