8165( 3) - 02/05/99 15:38 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8165 Version: 3 Check-in Date: 05-Feb-1999 15:37:37 1.Proposal Title: Pervasive Hot Gas Hidden in Galaxy Groups: A Substantial Baryon Reservoir? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Edward Jenkins Princeton University Observatory CoI: Dr. Todd Tripp Princeton University Observatory Y CoI: Dr. Blair Savage University of Wisconsin-Madison N ------------------------------------------------------------------------------------ 5. Abstract We propose to use STIS to search for hidden and pervasive hot gas in the intracluster media of groups of galaxies. Cosmological simulations predict that at z ~ 0, most groups of galaxies should be embedded in large filaments and sheets of shock heated gas at 10^5 -- 10^6 ^degreesK. This hot gas may contain a substantial fraction of the baryons in the universe at the present epoch, but its quantity and existence is not firmly established because gas in this temperature range is difficult to detect in x-ray emission. However, it can easily be detected via absorption lines of highly ionized species such as O VI. We propose to observe H1821+643 and PG1116+215 to search for O VI and broad H I LyAlpha absorption due to the intracluster media of thirteen known galaxy groups pierced by the sight lines. Toward H1821+643, we have already discovered O VI absorption associated with a galaxy group at z = 0.225 using low resolution HST GHRS spectra, but we could not determine if the O VI absorber is collisionally ionized or photoionized. With the vastly improved resolution and sensitivity provided by STIS, we will be able to identify the ionization mechanism in this absorber by (1) searching for broad H I absorption in collisionally ionized gas or narrow H I indicative of photionized gas, (2) measuring C II/C III/C IV and Si II/Si III/Si IV, and (3) examining the velocity widths of low and high ionization stages. ------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 2] Observations Description ------------------------ We have proposed STIS observations to search for hot gas in galaxy groups and to constrain the ionization mechanism in the O VI absorber at z_ abs = 0.2250 toward H1821+643. To achieve the goals of the program, we will obtain E140M echelle observations with the FUV-MAMA detector of H1821+643 (z_ em = 0.297) and PG1116+215 (z_ em = 0.177). These integrations will include all of the H I LyAlpha lines at the redshifts of the galaxy groups identified in Figure 2 and will cover the O VI 1031.9, 1037.6 Angstrom\ doublet for all galaxy groups at z > 0.114. The E140M observation of H1821+643 will also cover the Si II, Si III, C II, C III, H I LyBeta and H I LyGamma lines at z_ abs = 0.2250. In addition, we will obtain two shorter integrations on H1821+643 with the NUV-MAMA and the first order G230M grating to measure (or place useful limits on) the Si IV and C IV column densities associated with the O VI absorber at z_ abs = 0.2250 (we have opted to use the first order grating for Si IV and C IV because these lines fall in a region where both E140M and E230M have poor sensitivity and consequently require unacceptably long integration times). A summary of the proposed observations is provided in Table 1 along with signal-to-noise estimates calculated with the WWW STIS Spectroscopic Exposure Time Calculator. We will use the supported narrow slits (e.g., 0.2*0.06'' for E140M) to maintain the full spectroscopic resolution of the data. However, for most purposes of this project we have the option to bin the echelle data to increase the S/N by sqrt2, and we will still have quite adequate resolution. The S/N requirements in Table 1 are based on predicted equivalent widths of the H I and O VI lines in various models (see, e.g., \S 3.2 in Savage et al. 1998) with the additional consideration that the H I lines could be quite broad and therefore require additional S/N so that they can be distinguished from undulations in the QSO continuum. Orbit estimates in Table 1 include times required for overhead due to guide star acquisitions, target acquisitions and peakups, exposure setups and wavelength calibrations. Real Time Justification ----------------------- None. H1821+643 and PG1116+215 are high priority FUSE Science Team targets that will probably be observed in the first year of FUSE operations. These FUSE observations will be highly complementary to our program by providing coverage of the O VI doublet associated with several of the lowest redshift galaxy groups (see Figure 2) and by providing an opportunity to search for ultra- highly ionized species such as Ne VIII associated with the higher z groups. We will have rapid access to these data and will analyze them simultaneously with the STIS data if possible. However, as emphasized in the Scientific Justification, the proposed STIS observations are crucial for constraining the ionization mechanisms in the highly ionized metal absorbers, especially in the case of the known O VI system at z = 0.2250 in the spectrum of H1821+643. We have been collaborating with R. Cen and J. Ostriker to model and predict the high ion absorption profiles and properties expected from hot gas in the vicinity of galaxy groups based on their state-of-the-art cosmological simulations. This modeling effort will be very useful for intrepreting the proposed STIS observations. For example, comparison of the STIS observations to these models will help constrain the amount of baryons in the 10^5 -- 10^6 K hot phase. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PG1116+215 GALAXY, QSO, EXT- RA=11H 19M 8.7S +/- 0.3", J2000 Z = V = 14.8 MEDIUM, ABSORPTION LINE DEC=21D 19' 18.2" +/- 0.3", 0.177 F(1400)=5.0+/-0.5e-14 SYSTEM PLATE-ID=01TL E(B-V) = 0.027 2 H1821+643 GALAXY, QSO, EXT- RA=18H 21M 57.1S +/- 0.3", J2000 Z = V = 14.1 MEDIUM, ABSORPTION LINE DEC=64D 20' 36.7" +/- 0.3", 0.297 E(B-V) = 0.073 SYSTEM PLATE-ID=00T0 F(1400)=4.0+/-0.5e-14 8165( 3) - 02/05/99 15:38 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PG1116+215 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 3.0 S ONBOARD ACQ FOR 20, 30, CD P 40, 50, 60, 70, 80, 90 ------------------------------------------------------------------------------------------------------------------------------------ 20 PG1116+215 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3.0 S ONBOARD ACQ FOR 30, 40, CD K 6 50, 60, 70, 80, 90 ------------------------------------------------------------------------------------------------------------------------------------ 30 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1980.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 40 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 50 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 60 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 70 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 80 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 90 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 PG1116+215 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 3.0 S ONBOARD ACQ FOR 20, 30, CD P 40, 50, 60, 70, 80, 90 ------------------------------------------------------------------------------------------------------------------------------------ 20 PG1116+215 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 3.0 S ONBOARD ACQ FOR 30, 40, CD K 6 50, 60, 70, 80, 90 ------------------------------------------------------------------------------------------------------------------------------------ 30 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1980.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 40 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 50 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 60 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 70 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 80 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 90 PG1116+215 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1330.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 7] Visit: 03 Visit Priority: Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 H1821+643 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.3 S ONBOARD ACQ FOR 20, 30, CD P 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ------------------------------------------------------------------------------------------------------------------------------------ 20 H1821+643 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 1.3 S ONBOARD ACQ FOR 30, 40, CD K 6 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ------------------------------------------------------------------------------------------------------------------------------------ 30 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 40 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 50 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 60 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 70 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 80 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 90 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 100 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 110 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 8] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 120 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 130 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 140 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 150 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 160 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 9] Visit: 04 Visit Priority: Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 H1821+643 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.3 S ONBOARD ACQ FOR 20, 30, CD P 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ------------------------------------------------------------------------------------------------------------------------------------ 20 H1821+643 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 1.3 S ONBOARD ACQ FOR 30, 40, CD K 6 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ------------------------------------------------------------------------------------------------------------------------------------ 30 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 40 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 50 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 60 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 70 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 80 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 90 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 100 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 110 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 10] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 120 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 130 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 140 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 150 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 160 H1821+643 STIS/F ACCUM 0.2X0.0 E140M 1425 1 1819.0 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 11] Visit: 05 Visit Priority: Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 H1821+643 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.3 S ONBOARD ACQ FOR 20, 30, CD P 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 ------------------------------------------------------------------------------------------------------------------------------------ 20 H1821+643 STIS/C ACQ/PEA 52X0.05 MIRROR 1 1.3 S ONBOARD ACQ FOR 30, 40, CD K 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 ------------------------------------------------------------------------------------------------------------------------------------ 30 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 60 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 70 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 80 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 90 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 100 H1821+643 STIS/N ACCUM 52X0.05 G230M 1687 1 1962 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 110 H1821+643 STIS/N ACCUM 52X0.05 G230M 1933 1 1908 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 12] Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 120 H1821+643 STIS/N ACCUM 52X0.05 G230M 1933 1 1908 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 130 H1821+643 STIS/N ACCUM 52X0.05 G230M 1933 1 1908 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 140 H1821+643 STIS/N ACCUM 52X0.05 G230M 1933 1 1908 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 150 H1821+643 STIS/N ACCUM 52X0.05 G230M 1933 1 1908 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8165( 3) - 02/05/99 15:38 - [ 13] Summary Form for Proposal 8165 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 0.2X0.06 52X0.05 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20, 30, 40, 50, 60, 70, 80, 90 ONBOARD ACQ FOR 30, 40, 50, 60, 70, 80, 90 CVZ ONBOARD ACQ FOR 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ONBOARD ACQ FOR 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 ONBOARD ACQ FOR 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 ONBOARD ACQ FOR 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M G230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names PG1116+215 H1821+643 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 1687 1933 ------------------------------------------------------------------------------------------------------------------------------------