Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5501 Report Date: 18-Jul-95:17:32 Version: ********** Check-in Date: ********** 1.Proposal Title: THE STRUCTURE OF THE COMA CLUSTER: A SEARCH FOR COOL, ABSORBING GAS CYCLE 4 - MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO Sub Category CLUSTERS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Claudia M Urry STSCI USA 410-338-4593 ------------------------------------------------------------------------------------ 7. Abstract There is tantalizing new evidence that the intracluster medium of rich clusters of galaxies is not the simple, smooth, equilibrium fluid it may at first appear to be. Spatially resolved X-ray spectroscopy indicates the presence of cool, absorbing gas distributed across a number of clusters, including the Coma cluster of galaxies, even when extensive hot gas is clearly present and cooling flows are not. Ultraviolet resonance lines are the most sensitive probes of cool gas, down to quite low column densities. We propose to search for and characterize such gas in Coma, as well as gas associated with member galaxies, by observing two background UV light sources (QSOs) at different projected radii from the cluster center. Coma is uniquely suited for this study as it is rich, extremely well-studied at many wavelengths, and, most importantly, one of the very few clusters for which bright background QSOs are are known. Assuming we detect the cool intracluster gas seen in X-rays and/or gas associated with cluster galaxies, the HST data will probe its physical state. We can further investigate its spatial dependence by observing additional background sources. The presence of cool absorbing gas has implications for the physical state of the intracluster medium, for the evolution of galactic halos in diverse environments, and for the formation of QSO absorption lines. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 6.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5501 PI: Claudia M Urry Proposal Title: THE STRUCTURE OF THE COMA CLUSTER: A SEARCH FOR COOL, ABSORBING GAS CYCLE 4 - MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Claudia M Urry 3470 USA Richard F Mushotzky 2856 USA Laura Danly 3470 USA Graziella Branduardi-Raymont 8054 UNITED KING X Michael J Fitchett 8018 UNITED KING X David S Davis 2620 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose to obtain a single FOS G130H blue spectrum of the brightest QSO from a sample of six bright QSOs known to lie behind the Coma cluster. We will acquire the target with a binary acquisition, which should work well with the COSTAR- improved PSF. Our goal is to observe Ly-alpha absorption from cool gas condensations in the intergalactic medium and/or in the halo of a nearby galaxy. The mean velocity of the Coma cluster is 6932 km/s, with a dispersion of ~1000 km/s, so that Ly-alpha from the IGM would appear at ~1244 A. The requested exposure time is that necessary to achieve a signal to noise ratio of 10 (per diode) at 1300 A, estimated using the FOS simulator with the post-COSTAR efficiencies. We assumed a V magnitude of 17.4 a power-law spectrum with index alpha=0.5, comparable to the average UV spectral index for a sample of quasars (O'Brien et al., 1988, MNRAS, 233, 801). We made no correction for interstellar extinction since the Coma cluster lies near the North Galactic Pole (bII=87 deg) and contributions from Galactic extinction should be very small. The observed column density toward the NGP from 21-cm maps is less than 1E20 cm-2 (e.g., Stark et al. 1992, ApJS, 79, 77), indicating E(B-V)<0.02, or less than 0.2 magnitudes of extinction at 1250 A (from Seaton's curves for UV extinction). The spectral region covered with the FOS G130H blue grating, 1150-1606 A, includes many species from abundant ions including HI, OI, SiII, FeII, CII, SiIV, CIV, and NV. Many of these species have several observable lines with a range of f-values. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. As in studies of the interstellar medium of our own galaxy, information about the structure, distribution, temperature, and density of weakly and moderately ionized gas is accessible primarily through ultraviolet spectroscopy. The targets of this proposal are too faint to have been observed previously, even at low resolution with IUE. Substantial information is available on the optical properties of the Coma cluster galaxies and on the X-ray properties of the hot gas. For the latter in particular there is new information available from long Rosat observations showing evidence of cool absorbing gas covering ~1/2 of the cluster. More sensitive X-ray observations will be made with ASCA (Astro-D), a cooperative Japanese-US moderate-to-high resolution X-ray spectroscopy experiment launched in February 1993; R. Mushotzky has access to those data as part of the ASCA science working group. In addition, the same QSOs discussed here will make excellent targets for X-ray absorption line studies with ASCA. The availability of vast amounts of complementary data from other wavelengths makes the Coma cluster a particularly desirable subject for complete study. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. None Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None ------------------------------------------------------------------------------------ 9. Description of previous HST work. None by PI ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). STScI will provide sufficient hardware and software for the data reduction and subsequent analysis. A number of science Data Analysts specifically trained in STSDAS/IRAF and the analysis of HST data are available at STScI, greatly facilitating the prompt and proper reduction of the data. ------------------------------------------------------------------------------------ 11. Address Information Name: Claudia M Urry Category: PI Institution: 3470 Address: 3700 San Martin Drive City: Baltimore State: MD Zip Code: 21218 Country: USA Telephone: 410-338-4593 Telex (or e-mail): cmu@stsci.edu ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5501 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO-1258+285 H, 519 RA = 13H 01M 00.897S +/- J2000 Z = 1 V = 17.2 US136 0.01S, 1.355 2 B-V = 0.3 DEC = +28D 19' 44.21" +/- 0.1", PLATE-ID=002K ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5501 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO- FOS/RD ACQ/ 4.3 MIRROR SCAN-STEP- 1 10S 1 1 CYCLE 4 / 1-16 1258+285 PEAK Y=1.204 ONBOARD ACQ FOR SEARCH-SIZE-X=1 1.1 SEARCH-SIZE-Y=3 Comments: EXPOSURE TIME DETERMINED FROM FOS SIMULATOR. ORDER OF RED SIDE VERSUS BLUE SIDE NOT IMPORTANT ------------------------------------------------------------------------------------------------------------------------------------ 1.1 QSO- FOS/RD ACQ/ 1.0 MIRROR SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR 1258+285 PEAK X=0.602 1.2 SCAN-STEP- Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 1.2 QSO- FOS/RD ACQ/ 0.3 MIRROR SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR 1258+285 PEAK X=.172 1.3 SCAN-STEP- Y=.172 SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 ------------------------------------------------------------------------------------------------------------------------------------ 1.3 QSO- FOS/RD ACCUM 1.0 G270H 2223- 1 35M 1 1 1258+285 3278 ------------------------------------------------------------------------------------------------------------------------------------ 2 QSO- FOS/BL ACQ/ 4.3 MIRROR SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR 1258+285 PEAK Y=1.204 2.1 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 Comments: EXPOSURE TIME DETERMINED FROM FOS SIMULATOR. ORDER OF RED SIDE VERSUS BLUE SIDE NOT IMPORTANT ------------------------------------------------------------------------------------------------------------------------------------ 2.1 QSO- FOS/BL ACQ/ 1.0 MIRROR SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR 1258+285 PEAK X=0.602 2.2 SCAN-STEP- Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 2.2 QSO- FOS/BL ACQ/ 0.5 MIRROR SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR 3- 1258+285 PEAK X=0.30 16 SCAN-STEP- Y=0.30 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 3 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5501 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 4 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 5 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 6 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 7 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 8 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 9 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 10 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 11 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 12 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 13 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 14 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 15 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=FOUR 1 20M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ 16 QSO- HRS ACCUM 2.0 G140L 1150- FP-SPLIT=TWO 1 10M 1 1 1258+285 1606 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5501 [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD FOS/BL HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.204 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-X=0.602 SCAN-STEP-Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 SCAN-STEP-X=.172 SCAN-STEP-Y=.172 SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 SCAN-STEP-X=0.30 SCAN-STEP-Y=0.30 SEARCH-SIZE-X=3 FP-SPLIT=FOUR FP-SPLIT=TWO ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 6.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 / 1-16; ONBOARD ACQ FOR 1.1 ONBOARD ACQ FOR 1.2 ONBOARD ACQ FOR 1.3 ONBOARD ACQ FOR 2.1 ONBOARD ACQ FOR 2.2 ONBOARD ACQ FOR 3-16 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G270H G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names QSO-1258+285 US136 ------------------------------------------------------------------------------------------------------------------------------------