5934( 5) - 09/09/96 16:19 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 5934 Version: 5 Check-in Date: 09-Sep-1996 16:15:41 1.Proposal Title: A SEARCH FOR UV ABSORPTION LINES IN THE INTRACLUSTER MEDIUM OF ABELL 1030 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Galaxies & Clusters GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Christopher P. O'Dea SPACE TELESCOPE SCIENCE INSTITUTE CoI: Dr. Stefi A. Baum Space Telescope Science Institute N CoI: Dr. Craig Sarazin University of Virginia N CoI: Dr. Frazer Owen National Radio Astronomy Observatory N ------------------------------------------------------------------------------------ 6. Abstract The existence of a cold component of the ICM is suggested by the recent observations of low-energy x-ray absorption (e.g., White Etal 1991). However, the physical state of this cold gas is completely unknown. Abell 1030 (z=0.177) contains the brightest uv source currently known in an Abell cluster -- the quasar B2 1028+313. We propose to seize this unique opportunity to use the bright uv continuum of the quasar to probe the ICM. We will conduct a very sensitive search (with only modest amounts of observing time) for absorption lines from a cold component of the ICM. If the material cannot be detected, very restrictive limits will be placed on the amounts of any such material in the form of molecular gas, atomic gas, or ionized gas up to temperatures of ~ 5 * 10^5 K, i.e., N_H lae 10^14 cm^-2 in atomic hydrogen or N_H_2 lae 10^15 cm^-2 in molecular hydrogen. If strong UV absorption lines are detected, (1) the physical state of this material will be assessed from the species responsible for the absorption (molecules, atoms, or ions); (2) we will determine its kinematics from the velocity structure of the absorption lines; and (3) we will use the set of absorptions to determine better estimates of the column densities, velocity widths, and abundances of the clouds. The detection of a colder component of the ICM would have profound implications for our understanding of (1) cooling flows, (2) Lyman-Alpha forest systems, (3) galaxy formation, and (4) the magnetic field in the ICM. ------------------------------------------------------------------------------------ Observations Description ------------------------ Observable absorption lines exist covering the full range of temperatures and ionizations from cold molecular or neutral gas up to very highly ionized gas (O VI). The higher ionization lines would be detected if the X-ray absorption is due to ``warm'' gas at ~10^5 K, as has been suggested in A2256 (Miyaji Etal 1993). At the reshift of the source, the hydrogen Lyman-Alpha line and the H_2 and HD Lyman and Werner bands are within the spectral range covered by the G130H grating. In our integrations, columns smaller than N_H lae 10^14 cm^-2 in atomic hydrogen or N_H_2 lae 10^15 cm^-2 in molecular hydrogen will be detectable. In this proposal, we are taking the point of view that our object is to place the broadest possible observational limits on the cold component of the ICM, without resort to theory. centerline TABLE 1 We are proposing observations with the FOS using the G130H (blue detector), G190H (red detector), and G270H (red detector) gratings through the 1.0 arcsec aperture. The spectral resolution (1300) implies a velocity resolution of 230 km sec. The measured IUE flux F_2000 ~eq 10^-14 ergs s^-1 cm^-2 AA^-1 (Lanzetta Etal 1993) gives the following count rates in the three gratings, (these are wavelength dependent and represent conservative choices). N_Lambda(G130H) = 0.06 countssdiode N_Lambda(G190H) = 0.75 countssdiode N_Lambda(G270H) = 4 countssdiode Since the source is bright enough for a binary acquisition, the overall overheads are low and the proposal is relatively efficient. With 3 orbits at G130H and one orbit each at G190H and G270H, the signal to noise ratio per pixel will be 20 in G130H, 43 in G190H, and 100 in G270H. This implies that the errors in determining the equivalent widths will be less than 0.05 Angstrom in all three gratings. Appendix: Details of the Equivalent Width Calculations The measured excess X-ray absorptions in clusters of galaxies are typically 1--3 * 10^21 cm^-2. For the purposes of estimating the strengths of absorption lines, we will assume N_H = 1.5 * 10^21 cm^-2. As noted above, the bulk of the absorption is actually due to oxygen. Real Time Justification ----------------------- There are no special requirements. We are conducting VLA and ground based optical imaging and spectroscopic observations. We also plan to conduct searches for HI and CO in the ICM. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 5934( 5) - 09/09/96 16:19 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 B21028+313 Cluster of Galaxies, RA=10H 30M 59.09S +/- 0.01S, J2000 z=0.177 V = 16.75 BCM, Rich Cluster, DEC=31D 02' 55.6" +/- 0.1", U = 16.40 Galaxy, Quasar PLATE-ID=01AK F-CONT(3000)=1.0e-14 Comments: COORDS ARE FROM GASP. 5934( 5) - 09/09/96 16:19 - [ 2] Visit: 01 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 B21028+313 FOS/RD ACQ/BIN 4.3 MIRROR 1 5.0 S ONBOARD ACQ FOR 2 ARY Comments: ACQ/BIN exposure time of 5.0s is the value recommended by the FOS Instrument Scientist based on simulations using the flux from IUE. It is a compromise value given the spectral shape of the object. ------------------------------------------------------------------------------------------------------------------------------------ 2 B21028+313 FOS/RD ACCUM 1.0 G400H 1 5 M ------------------------------------------------------------------------------------------------------------------------------------ 3 B21028+313 FOS/RD ACCUM 1.0 G270H 1 30 M EXPAND MAX DUR 40M MIN DUR 15M END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 4 B21028+313 FOS/RD ACCUM 1.0 G190H 1 40 M EXPAND MAX DUR 90M MIN DUR 20M END ORBIT Comments: Do blind offset to GHRS. ------------------------------------------------------------------------------------------------------------------------------------ 5 WAVE HRS ACCUM SC2 G140L 1293 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 6 B21028+313 HRS ACCUM 2.0 G140L 1293 FP-SPLIT=NO 1 40 M Comments: Pad to fill orbit. ------------------------------------------------------------------------------------------------------------------------------------ 7 B21028+313 HRS ACCUM 2.0 G140L 1293 FP-SPLIT=NO 1 40 M Comments: Pad to fill orbit. ------------------------------------------------------------------------------------------------------------------------------------ 8 WAVE HRS ACCUM SC2 G140L 1559 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 9 B21028+313 HRS ACCUM 2.0 G140L 1559 FP-SPLIT=NO 1 40 M Comments: Pad to fill orbit. ------------------------------------------------------------------------------------------------------------------------------------ 5934( 5) - 09/09/96 16:19 - [ 3] Visit: 51 Visit Requirements: On Hold Comments: Additional Comments: HOPR Repeat for lost G190H observations which failed previously due to a loss of GS lock. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 B21028+313 FOS/RD ACQ/BIN 4.3 MIRROR 1 5.0 S ONBOARD ACQ FOR 2 ARY Comments: ACQ/BIN exposure time of 5.0s is the value recommended by the FOS Instrument Scientist based on simulations using the flux from IUE. It is a compromise value given the spectral shape of the object. ------------------------------------------------------------------------------------------------------------------------------------ 2 B21028+313 FOS/RD ACCUM 1.0 G190H 1 40 M EXPAND MAX DUR 90M MIN DUR 20M END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 5934( 5) - 09/09/96 16:19 - [ 4] Summary Form for Proposal 5934 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FP-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Galaxies & Clusters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 EXPAND MAX DUR 40M MIN DUR 15M END ORBIT EXPAND MAX DUR 90M MIN DUR 20M END ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G400H G270H G190H G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names B21028+313 WAVE ------------------------------------------------------------------------------------------------------------------------------------