7737( 3) - 01/21/98 12:00 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7737 Version: 3 Check-in Date: 17-Jun-1997 09:59:53 1.Proposal Title: Low Redshift Lyman Alpha Forest Clouds: Their Kinematics and Their Relation to Galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/CAR 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: MICHAEL RAUCH CALTECH CoI: Ray Weymann Carnegie Observatories N CoI: Simon Morris Dominion Astrophysical Observatory N CoI: Guenther Hasinger Astrophys. Institut Potsdam N CoI: Lance Miller Royal Observatory Edinburgh N CoI: Mike Read Royal Observatory Edinburgh N ------------------------------------------------------------------------------------ 5. Abstract We wish to study the physical nature of low redshift Lyman Alpha absorption systems and their relation to galaxies. The recent ROSAT discovery of the optically-bright x -ray selected QSO RX J1230.8+0115 (z_em = 0.117, m_v = 14.7) has fortuitiously provided us with a bright quasar only 0.9 degrees away from 3C273 (the brightest QSO in the sky). We propose to obtain high dispersion spectroscopy of RX J1230.8+0115 with the STIS E140M grating in order to investigate the presence and the kinematics of common absorption features in both QSO spectra, on scales between 211 h_75^-1 kpc and 4.9 h_75^-1 Mpc, probing down to column densities of 10^12 cm^-2. Recent Cy4 results suggest Ly Alpha length scales of ~ 1 h_75^-1 Mpc for the higher column density systems. Measurements of velocity and column density in both lines-of-sight, along with redshifts of nearby galaxies will help to discriminate between models of galactic absorption and to map the distribution of Hydrogen gas in the local universe. This project is unique in two aspects: we are observing two of the brightest QSOs on the sky, along lines-of-sight running through the outskirts of the Virgo cluster, and, the line-of- sight to and the galaxy field around 3C273 has been studied in great detail during the past few years. Information available on the low redshift absorbers towards 3C273 includes unique echelle UV spectroscopy, a deep 21 cm map, a redshift survey of nearby galaxies, and a 54'*54' deep mosaic of the field. Combining this information with a new line-of-sight which can also be probed to very low column density, we will be able to shed light on the question of whether the low redshift Lyman Alpha forest is related to galaxies or represents a truly intergalactic phenomenon. ------------------------------------------------------------------------------------ 7737( 3) - 01/21/98 12:00 - [ 2] Observations Description ------------------------ THIS PHASE II PROPOSAL IS A REPLACEMENT FOR PROP. 6410, MOST ORBITS OF WHICH WERE LOST DUE TO TWO SAFING EVENTS. WE ARE NOW USING STIS INSTEAD OF GHRS. OUR ORIGINAL SCIENTIFIC PURPOSE, A HIGH RESOLUTION STUDY OF INDIVIDUAL LYMAN ALPHA LINES, IS BEST SERVED BY USING THE E140M ECHELLE GRATING, CENTERED ON 1425 A. ACCORDING TO THE STIS EXPOSURE TIME CALCULATOR, WE SHOULD BE ABLE TO REACH A S/N RATIO ~8 PER RESOLUTION ELEMENT AT 1287 A, APPROXIMATELY IN THE MIDDLE OF THE LYMAN ALPHA FOREST OF THIS QSO. THIS WOULD ALLOW US TO ADDRESS BOTH ISSUES CENTRAL TO THE ORIGINAL PROPOSAL, LARGE SCALE STRUCTURE, AND PROFILES OF INDIVIDUAL ABSORPTION LINES WITH A SINGLE SPECTROSCOPIC SETUP. BELOW IS PART OF THE ORIGINAL GHRS "DESCRIPTION OF OBSERVATIONS". We propose to observe the x- ray selected QSO RX J1230.8+0115 (z_em = 0.117, m_v = 14.7), a companion to 3C273 only 0.9degreespoint away, to study absorption features common to both lines-of-sight, and their relation to galaxies. Our proposal has two objectives: o (A) study the three lowest redshift clouds (for which we have obtained detailed information along the 3C273 line-of-sight) towards QSO RX J1230.8+0115 at high resolution with the GHRS and the G160M grating. As a result we will obtain very accurate (a few km/s) velocities, column densities, and line profiles. The grating will be set such as to cover about 1217-1253 A. medskip o (B) study the whole line of sight towards QSO RX J1230.8+0115 at intermediate resolution with GHRS and the G140L grating. This will provide us with statistical estimates of the coherence length/spatial correlation function of the low redshift LyAlpha clouds on scales up to several Mpc. medskip RX J1230.8+0115 has optical colors which are very similar to 3C273 and a V magnitude two magnitudes fainter than 3C273. The flux at 1220 Angstrom in 3C273 is 2.1 * 10^-13, from which we estimate the corresponding flux in its companion to be ~ 3.3* 10^-14. From the GHRS handbook we estimate, taking into account the dark count rate, that 9.8 hours or 15 orbits will be required to obtain the same S/N as for the 3C273 observations. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- DURING THOSE ORBITS OF THE CYCLE 6 OBSERVATIONS THAT WERE EXECUTED WE LOST A GUIDE STAR DUE TO UNKNOWN REASONS. IT MAY BE WORTH USING DIFFERENT STARS THIS TIME. BELOW IS PART OF THE MESSAGE WE GOT ABOUT THIS: Your observations of QSO- 123050+011522 on July 11, 1996 for proposal 06410 were taken in a backup guiding mode because one of the Fine Guidance Sensors was unable to achieve fine lock on its guide star. In this situation, the telescope is controlled in roll by gyros, which may allow a slow drift around the axis defined by the direction toward the single guide star. Dorothy Fraquelli, of the ST ScI's OPUS team examined the data and provided the following assessment. "These observations were obtained under single star guidance rather than the planned two FGS guidance. Otherwise they appear to have executed as planned. A comparison of the mean counts per group, as produced by the iraf command groupstat, suggests that the spacecraft did not roll significantly during the obset." The guide star acquisition failure is documented as HST anomaly report #5654. ------------------------------------------------------------------------------------ 7737( 3) - 01/21/98 12:00 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7737( 3) - 01/21/98 12:00 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO- GALAXY,QSO,LYMAN ALPHA RA=12H 30M 50.04S +/- J2000 Z = V = 14.7+/-0.4 123050+01152 CLOUD 0.3",DEC=01D 15' 21.7" +/- 0.117 F(1220)=3.3e-14 2 0.3",PLATE-ID=00BB Comments: Could not retrieve the GSC plate to check with finding chart (not available at STScI ?). Assume, however, that our object is identical to GSC 289-430, which is within 2.4 arcsecs of our nominal position. 7737( 3) - 01/21/98 12:00 - [ 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 QSO-123050+ STIS/C ACQ F28X50L MIRROR 1 1.5 S ONBOARD ACQ FOR 20 011522 CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 QSO-123050+ STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 1. S ONBOARD ACQ FOR 30-40 011522 CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 30 QSO-123050+ STIS/F ACCUM 0.2X0.0 E140M 1425 1 1800 S 011522 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 40 QSO-123050+ STIS/F ACCUM 0.2X0.0 E140M 1425 4 2500 S 011522 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 7737( 3) - 01/21/98 12:00 - [ 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 QSO-123050+ STIS/C ACQ F28X50L MIRROR 1 1.5 S ONBOARD ACQ FOR 20 011522 CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 QSO-123050+ STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 1.0 S ONBOARD ACQ FOR 30-40 011522 CD K 6 ------------------------------------------------------------------------------------------------------------------------------------ 30 QSO-123050+ STIS/F ACCUM 0.2X0.0 E140M 1425 1 1800 S 011522 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 40 QSO-123050+ STIS/F ACCUM 0.2X0.0 E140M 1425 4 2500 S 011522 UV-MAM 6 A ------------------------------------------------------------------------------------------------------------------------------------ 7737( 3) - 01/21/98 12:00 - [ 7] Summary Form for Proposal 7737 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20 ONBOARD ACQ FOR 30-40 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names QSO-123050+011522 ------------------------------------------------------------------------------------------------------------------------------------