9076( 3) - 05/06/01 14:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9076 Version: 3 Check-in Date: 06-May-2001 14:11:58 1.Proposal Title: The z = 0.93 DLA in the Gravitationally Lensed QSO HE 0512-3329: a Test of Dust Bias in DLA Samples ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Max Pettini University of Cambridge CoI: Dr. David V. Bowen Princeton Observatory N CoI: Dr. Sara Ellison European Southern Observatory N ------------------------------------------------------------------------------------ 5. Abstract Gregg et al have recently discovered that the bright QSO HE 0512-3329 is gravitationally lensed into two closely separated images and that the lensing galaxy is in all probability a damped LyAlpha system at z_ abs = 0.9313. Here we request two HST orbits to use STIS to record the profile of the LyAlpha absorption line with sufficient S/N to deduce the column density of H I. This observation will make it possible to measure, for the first time, the abundances of several elements--- including Zn, Cr, Fe, Si, and Mn---close (2-3 kpc) to the nucleus of a galaxy at z ~eq 1. There is a suspicion that DLAs at such close impact parameters may be missing from current samples due to dust obscuration, but this obstacle is overcome in this case by the boost provided by gravitational lensing. Establishing whether the metallicity of the galaxy is close to solar, as expected, will provide the first indication of the importance of dust in biasing absorption studies of the universe at z <=q 1. In addition the resolved STIS spectra along the two sight-lines will probe the spatial structure of a DLA on small scales; no such measurement has been performed before. ------------------------------------------------------------------------------------ 9076( 3) - 05/06/01 14:12 - [ 2] Observations Description ------------------------ We wish to use the G230L grating and 52x0.1 slit to observe the damped LyAlpha profile from the lensing object at 2349 Angstrom . Both components of the lens have identical B magnitudes of B=18.4. We assume standard overheads of 18 mins in the first orbit for GS ACQ, target ACQ and ACQ/PEAK, and 13 mins in subsequent orbits for GS RE-ACQ and exposure overhead. Assuming the conservative value of -1 for the power law index of the QSO flux, and using a predicted reddening of E(B-V)=0.03, the ETC shows that a S/N of 19 can be obtained in the two orbits we request. This will be sufficient to reliably calculate N(H I) from profile fitting to the observed damped Ly-alpha\ line. Further, we will align the STIS slit so as to enable observations of both components of the lens simultaneously. The orientation can be calculated accurately from the STIS images available in the Archive. With a pixel scale of 0.051 arcsec pix^-1 for the MAMA detectors, spatially resolved spectra of the two components 0.6 arcsec apart should be easily obtained. Real Time Justification ----------------------- As noted above, we will use the UVES echelle spectrograph at the VLT to obtain high resolution, high S/N optical data to measure absorption lines from several key elements, including Zn, Cr, Fe, Si, and Mn. All the lines of interest are expected to occur in the wavelength range 1800--2600 Angstrom\ at z_rmabs=0.9313 where the UVES is highly efficient. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9076( 3) - 05/06/01 14:12 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PKS1243-072 GALAXY, QUASAR RA=12H 46M 4.24S +/- 0.05", DEC= J2000 Z = B = 18.2+/-0.1 -07D 30' 46.74" +/- 0.05", PLATE 1.286 V = 18.4+/-0.1 -ID=024P Coordinate Source: GSC_SURVEY_PLATE 9076( 3) - 05/06/01 14:12 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE 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 PKS1243-072 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 6 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 PKS1243-072 STIS/C ACQ/PEA 52X0.1 MIRROR 1 12 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 PKS1243-072 STIS/N ACCUM 52X0.1 G230L 2376 1 30 M EXPAND UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 PKS1243-072 STIS/N ACCUM 52X0.1 G230L 2376 1 44 M EXPAND UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9076( 3) - 05/06/01 14:12 - [ 5] Summary Form for Proposal 9076 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE EXPAND ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230L ------------------------------------------------------------------------------------------------------------------------------------ Target Names PKS1243-072 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2376 ------------------------------------------------------------------------------------------------------------------------------------