9754( 3) - 05/13/03 13:28 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9754 Version: 3 Check-in Date: 13-May-2003 13:26:23 1.Proposal Title: Intergalactic O VI absorption at redshift <0.004 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 12 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Dr. Bart P. Wakker University of Wisconsin - Madison CoI: Dr. Blair D. Savage University of Wisconsin - Madison N CoI: Dr. Kenneth R. Sembach Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract Simulations of the formation of large-scale structure in the universe predict that at the present time a large fraction of the baryons in the intergalactic medium (IGM) is in a warm/hot phase, with T=10^5-10^7 K. The warm phase has been detected with HST in absorption through the OVI 1031.926, 1037.671 doublet at redshifts ~0.15-0.3. In a sample of 100 extra-galactic objects observed with FUSE, we find 12 detections of OVI at redshifts z=0.0008-0.004 (v=250 to 1200 km/s). Many of these occur within 400 kpc and 50 km/s of a nearby galaxy, making it much easier to understand the relation between the OVI absorbers and galaxies. Our sample allows a comparison of the properties of nearby vs more distant OVI absorbers. However, modeling the physical conditions in the gas requires measurements of HI, OVI, CIV, NV and CIII. High velocity resolution is required to resolve the HI, CIV and NV lines in order to discriminate between collisional and photoionization. We propose to obtain improved HI data, as well as the CIV and NV measurements for two absorbers at z<0.004. One appears to represent collisional ionization (Mrk 876), while the other probably represents a case of a photoionized system (Ton S180). Understanding the ionization of the warm IGM is essential for determining elemental abundance and the baryonic content of the gas. ------------------------------------------------------------------------------------ 9754( 3) - 05/13/03 13:28 - [ 2] Observations Description ------------------------ We propose to observe Mrk876 and Ton S180 with the STIS E140M echelle, placing the objects in the 0.2x0.06 slit in order to obtain the simplest line spreak function. For the Ly-alpha line at 950 km/s toward Mrk876 the 7 km/s resolution is an essential improvement over the existing data, which have only 30 km/s resolution. The requested resolution is also essential to measure the line widths of any detected CIV and NV, in order to determine whether these ions could originate by collisional ionization rather than photoionization: at T=2E5 K the FWHM of the CIV line is ~20 km/s, whereas in cooler photoionized gas it should be 15 km/s. The E140M spectrum covers the wavelength range 1150 to 1700 A. We require this coverage in order to simultaneously observe the Ly-alpha, NV and CIV lines. The wavelength range also contains the strong absorption lines of OI-1302 and SiII-1193, 1260, 1526, which will show absorption by HVC complex C, providing additional abundance information for this cloud. During the FUSE observations of both objects in late 1999, the FUV flux was measured as 9E-14 erg/cm2/s/A at lambda<1200 A. The FUV spectrum of both objects is rather flat, decreasing only slightly between 1200 and 1600 A. At this flux level achieving an S/N of 15 per 7 km/s resolution element at 1550 A requires 24000 sec for each AGN. At declinations of +65 (Mrk876) and -22 (Ton S180), the visibility is 57 and 53 minutes, respectively. In the first orbit six minutes goes to guide star acquisition, six to target acquisition and seven to target peakup. A peak up is required because we use the 0.2x0.06 arcsec slit. The peak up time is done using STIS/CCD with the mirror. According to the acquisition calculator plenty of counts should be obtained in 3 seconds for a 15th magnitude object. Since both objects are Seyferts, almost all of the light should be concentrated within the aperture. The 10 orbits for each object have been split into 2 5- orbit visits. In subsequent orbits a reqacquisition will be needed. Five exposures have been specified, such that only the reacquisition will be done, no separate peakups are assumed to be needed, something which has worked in the past for similar kinds of observations. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9754( 3) - 05/13/03 13:28 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MRK876 GALAXY, SEYFERT RA=16H13M57.16S +/- 0.1", J2000 V = 15.49 DEC=+65D43'9.7" +/- 0.1", PLATE- ID=034O Coordinate Source: GSC_SURVEY_PLATE 2 TONS180 GALAXY, SEYFERT RA=00H57M20.03S +/- 0.1", DEC=- J2000 V = 14.14 22D22'56.6" +/- 0.1", PLATE- ID=024J Coordinate Source: GSC_SURVEY_PLATE 9754( 3) - 05/13/03 13:28 - [ 4] 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 MRK876 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 3 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 MRK876 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 3 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2200 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 4 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 5 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 6 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 7 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 9754( 3) - 05/13/03 13:28 - [ 5] 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 MRK876 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 3 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 MRK876 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 3 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2200 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 4 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 5 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 6 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 7 MRK876 STIS/F ACCUM 0.2X0.0 E140M 1425 1 3100 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 9754( 3) - 05/13/03 13:28 - [ 6] Visit: 03 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 TONS180 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 3 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 TONS180 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 3 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1920 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 4 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 5 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 6 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 7 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 9754( 3) - 05/13/03 13:28 - [ 7] Visit: 04 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 TONS180 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 3 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 TONS180 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3 S CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 3 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1920 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 4 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 5 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 6 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 7 TONS180 STIS/F ACCUM 0.2X0.0 E140M 1425 1 2850 S UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 9754( 3) - 05/13/03 13:28 - [ 8] Summary Form for Proposal 9754 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 0.2X0.06 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names MRK876 TONS180 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------