7290( 7) - 12/03/98 11:19 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7290 Version: 7 Check-in Date: 03-Dec-1998 11:18:44 1.Proposal Title: CIV in extensive gaseous halos of QSO Lyman alpha absorbing galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Xavier Barcons Instituto De Fisica De Cantabria CoI: Kenneth M. Lanzetta State University of New York at Stony N Brook CoI: John K. Webb University of New South Wales N ------------------------------------------------------------------------------------ 5. Abstract The distinction between Lyman alpha and heavy element absorbers towards QSOs has become fuzzy after the discovery by Cowie et al. (1995, AJ, 109, 1522) that about one half of Lyman-alpha absorbers with HI column density larger than 3* 10^14, cm^-2 show CIV absorption as well. On the other hand, on-going imaging and spectroscopic surveys in the fields of HST/FOS target QSOs demonstrate that a large fraction of Lyman-alpha absorbers at low redshifts arise in gaseous envelopes of galaxies at galactocentric radii of up to 160 kpc (H_0=100 km/s/Mpc is used throughout). In contrast, only some of the galaxies being crossed by the QSO light at an impact parameter of less than 65 kpc show CIV absorption in the HST/FOS spectra. Here we propose to use STIS to search for CIV absorption associated with the Lyman-alpha absorbing galaxies at galactocentric distances in the range 100-500 kpc. Detection of such absorption features would imply that the halo gas of these galaxies has been enriched by either some sort of galactic fountain or in-situ halo star formation and would also determine up to which radius this process has operated. ------------------------------------------------------------------------------------ 7290( 7) - 12/03/98 11:19 - [ 2] Observations Description ------------------------ Here is a table with the QSOs to be observed, the redshift and equivalent width of the Lyman alpha absorption and the wavelength where CIV is expected to occur. Target QSO | Absorption | Impact param | W(LyAlpha) | Lambda (CIV) | ...........| redshift | (h^-1 kpc) |(Angstrom ) | (Angstrom ) |---------------- ---------------------------------------------------- PKS0405-12 | 0.4065 | 478.7 | 0.62 | 2179 | ...........| 0.3520 | 105.4 | 0.70 | 2094 | ...........| 0.2973 | 157.4 | 0.30 | 2009 | TON28 | 0.2127 | 163.7 | 0.57 | 1878 |---------- ---------------------------------------------------------- The number of orbits has been estimated with the aid of the STIS handbook and some specific simulations that we carried out trying to mimic the conditions of the proposed observations with model input spectra. The source flux (as measured with the Faint Object Spectrograph archival observations) = 2* 10^-14 erg/cm2/s/AA produces count rates from 0.02 to 0.05 cts/s/pix which makes the sky background irrelevant and the dark current only important in the worst cases. A signal to noise of 15 has been used to compute exposure times to which the necessary overheads have been added: Guide Star Acquisition, Target-acquision (no peakup acquisition needed with the 0.5 arcsec slit), and instrument overheads. Standard wavelength calibrations are enough for our purposes. The simulations show that the CIV Lambda1548 line is detected for a column density as low as 2* 10^13 cm^-2 for the requested S/N=15. At 3* 10^13 cm^-2 both lines of the CIV doublet are detected. We must stress that we know the redshift of the features and therefore we know where we have to look for the absorption lines. Real Time Justification ----------------------- None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: DAT Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7290( 7) - 12/03/98 11:19 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PKS0405-12 GALAXY, QSO, LYMAN RA=4H 7M 48.42S +/- 1", DEC=-12D J2000 F-CONT(2100)=2+/-0.5e-14 ALPHA CLOUD, EXT- 11' 36.0" +/- 1", PLATE-ID=0238 V = 14.8+/-0.5 MEDIUM, ABSORPTION LINE SYSTEM - EXTRAGALACTIC Comments: Coords are from GSC and Plate-ID=0238. 2 TON28 GALAXY, QSO, LYMAN RA=10H 4M 2.63S +/- 1", DEC=28D J2000 F-CONT(1900)=2+/-0.5e-14 ALPHA CLOUD, EXT- 55' 35.15" +/- 1", PLATE-ID=021H V = 16.0+/-0.5 MEDIUM, ABSORPTION LINE SYSTEM - EXTRAGALACTIC 7290( 7) - 12/03/98 11:19 - [ 4] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 PKS0405-12 STIS/C ACQ F28X50L MIRROR 1 10 S ONBOARD ACQ FOR 10, 11, CD P 20, 21, 30, 31 ------------------------------------------------------------------------------------------------------------------------------------ 10 PKS0405-12 STIS/N ACCUM 52X0.5 G230M 2176 1 38 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 11 PKS0405-12 STIS/N ACCUM 52X0.5 G230M 2176 1 20 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 20 PKS0405-12 STIS/N ACCUM 52X0.5 G230M 2095 1 20 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 21 PKS0405-12 STIS/N ACCUM 52X0.5 G230M 2095 1 50 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 PKS0405-12 STIS/N ACCUM 52X0.5 G230M 2014 1 40 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 31 PKS0405-12 STIS/N ACCUM 52X0.5 G230M 2014 1 50 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7290( 7) - 12/03/98 11:19 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 TON28 STIS/C ACQ F28X50L MIRROR 1 10 S ONBOARD ACQ FOR 10, 11 CD P ------------------------------------------------------------------------------------------------------------------------------------ 10 TON28 STIS/N ACCUM 52X0.5 G230M 1884 1 35 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 11 TON28 STIS/N ACCUM 52X0.5 G230M 1884 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7290( 7) - 12/03/98 11:19 - [ 6] Summary Form for Proposal 7290 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 10, 11, 20, 21, 30, 31 ONBOARD ACQ FOR 10, 11 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names PKS0405-12 TON28 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2176 2095 2014 1884 ------------------------------------------------------------------------------------------------------------------------------------