6674( 4) - 07/24/96 16:23 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6674 Version: 4 Check-in Date: 24-Jul-1996 16:17:34 1.Proposal Title: Fine Structure in the Nuclear Superbubble of NGC 3079 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle GALAXIES & CLUSTERS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: GERALD CECIL UNIVERSITY OF NORTH CAROLINA CoI: Sylvain Veilleux University of Maryland, College Park N CoI: Alex Filippenko University of California, Berkeley N CoI: Joss Bland-Hawthorn Anglo-Australian Observatory N ------------------------------------------------------------------------------------ 6. Abstract The nearby (17 Mpc), nearly edge-on spiral galaxy NGC 3079 contains the most energetic known example of a windblown superbubble. The bubble has ionized mass 10^7/n_e Msun and kinetic energy 2x^56/n_e ergs (for average electron density n_e), a compact apex at the nucleus, and protrudes 1 kpc (12") above the disk plane. It is the visually emitting part of a larger superwind-driven complex that comprises radio loops and spatially extended thermal x-ray emission. Our Fabry -Perot spectrophotometry has mapped Doppler velocity gradients of >1150kms across the superbubble, and we infer that space velocities increase radially from the nucleus. The boundary just resolves in 1" seeing. However, the emission-line profiles here range over 350 kms, indicating unresolved (turbulent?) kinematic substructure. An HST WFPC2 image is required to resolve fluctuations in surface brightness across the superbubble. These will improve constraints on the gaseous volume filling factor, and establish if the input kinetic energy comes solely from the starburst (small filling factor) or if the AGN must also contribute. If the AGN dominates, the superbubble will join the NLR of NGC 1068 as the most spatially extended structures thought to have been blown by an accretion-disk wind. The proposed image of this superbubble will provide insight into the simultaneity of AGN/starbursts, jet formation and collimation, winds in broad- absorption line quasars, and the extended x-ray halos of galaxies. ------------------------------------------------------------------------------------ 6674( 4) - 07/24/96 16:23 - [ 2] Observations Description ------------------------ Our FP spectrophotometry shows that F658N will pass all H Alpha except for the most blueshifted gas at the very top of the bubble, and all N II blueward of the galaxy's systemic velocity. The fluxes passed in each line are similar, and total 10^-13 erg s^-1 cm^-2. The flux ratio [N II]/H Alpha doesn't vary much across the bubble (e.g. Fig. 4 of Veilleux Etal 1994), so we can separate the two lines and more tightly constrain variations in filling factors Epsilon. We have used our data to locate regions (by their kinematics) where background emission from H II regions farther out in the disk of NGC 3079 is faint compared to the bubble shell. For planning, we estimate exposures near the bubble center because we wish to minimize the column length of the emitting gas, to get the tightest possible constraint. We approximate the superbubble as a circular shell of diameter 12", and assume that half of its total flux comes from the edge-brightened ring (Veilleux Etal 1994) of 1/3 the total area. We begin with 2 x 400s ( e.g. 800s ) F814W images to accurately subtract off the galaxy starlight. In the worst but unlikely case, where the gas is uniformly distributed across the boundary of the superbubble in the WF2 image, the average flux on each pixel near the center will be 0.12 photons s^-1 for an unobstructed telescope area of 45239 cm^2. The conversion efficiency from unobstructed photons to detected electrons is 0.12 for F658N. Because we are already taking multiple exposures, to minimize total readout noise we will not CR-SPLIT exposures through F658N. Assuming a dark rate of 0.003 e^- s^-1 (- 88degrees C on WF2), we reach S/N = 8 in each WF2 pixel after 4 orbits (exposures of 1500 s + 3*3000 s). (The sky contributes ~110 electrons.) This S/N ratio suffices to establish an accurate mean surface bightness, and will be increased substantially in the clumped gas that we expect to map. Dark current is minimized by imaging the superbubble on WF2. The individual exposures will be dithered to improve sampling. NOTE: F814W was changed from F791W in consultation between CS and PI. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6674( 4) - 07/24/96 16:23 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3079 GALAXY, Spiral, Radio RA=10H 01M 58.46S +/- 0.2S, 2000 V=+1128 V = 9.7 Galaxy, Starburst DEC=+55D 41' 02.3" +/- 1", PLATE -ID=01RP 6674( 4) - 07/24/96 16:23 - [ 4] Visit: 01 Visit Requirements: ORIENT 297D TO 318D On Hold Comments: Additional Comments: There is a bright star in PC1 quadrant which may cause scattered light to fall onto the PC, but this is OK. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC3079 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO 1 400 S POS TARG 0,0 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC3079 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO 1 400 S POS TARG 0.25,0.25 ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC3079 WFPC2 IMAGE WF2 F658N CR-SPLIT=NO 1 1700 S POS TARG 0,0 EXPAND ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC3079 WFPC2 IMAGE WF2 F658N CR-SPLIT=NO 1 1400 S POS TARG 0.25,0.25 ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC3079 WFPC2 IMAGE WF2 F658N CR-SPLIT=NO 1 1500 S POS TARG 0,0 EXPAND ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC3079 WFPC2 IMAGE WF2 F658N CR-SPLIT=NO 1 2900 S POS TARG 0.25,0.25 EXPAND ------------------------------------------------------------------------------------------------------------------------------------ 6674( 4) - 07/24/96 16:23 - [ 5] Summary Form for Proposal 6674 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 297D TO 318D POS TARG 0,0 POS TARG 0.25,0.25 POS TARG 0,0 EXPAND POS TARG 0.25,0.25 EXPAND ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F658N ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC3079 ------------------------------------------------------------------------------------------------------------------------------------