This resubmission fixes errors in calculating the COS BUFFER-TIME of the targets. The PI affiliation was changed to the updated entry in the STScI database. ----- Attempting Submission 1 (Tue Jun 24 14:11:41 GMT 2008) ----- Phase II Proposal 11742 (he2cos.apt) successfully submitted. ----- Attempting Submission 2 (Wed Jun 17 01:41:15 GMT 2009) ----- Assigned ID: 316 ----- Attempting Submission 1 (Fri Mar 07 11:40:25 GMT 2008) ----- Phase I Proposal 316 (he2cos.apt) successfully submitted. ----- Attempting Submission 2 (Fri Mar 07 23:27:35 GMT 2008) ----- Phase I Proposal 316 (he2cos.apt) successfully submitted. Probing HeII Reionization with GALEX-selected Quasar Sightlines and HST/COS We propose spectroscopic observations with COS of eight z~3 QSOs that we found to be bright in the far ultraviolet. Our aim is to study intergalactic absorption caused by the onset of the He II Lyman forest. Several lines of evidence suggest that helium reionization occurred at z~3. Understanding this process is critical for a complete picture of the intergalactic medium and its evolution; it also gives clues to hydrogen reionization at z>6. The only direct means of assessing He II reionization is through far-UV observations of the He II Lyman alpha forest. Only 6 sightlines are known to date where this is feasible, despite extensive surveys. Our programme is designed to double the number of available sightlines. To this effect, we cross-correlated all known z>2.73 quasars with UV source lists from the GALEX satellite. The selected quasars were all significantly detected in the far UV by GALEX, and their UV colors are similar to those of already known quasars with transparent sightlines. Spectra obtained with COS will allow us to compile the first comprehensive sample of He II absorption spectra probing similar redshifts, enabling a systematic investigation of the He II reionization epoch and the spectral shape of the UV background.
We will take FUV spectra of 8 high-redshift quasars with COS in order to search for intergalactic HeII absorption. For each target we plan a single visit with 2-3 orbits. All spectroscopic observations use the low-resolution grating G140L in the 1105A setup to record the flux at the shortest wavelengths accessible to HST. With GALEX photometry available for every target, we used the COS ETC to estimate the exposure times with the grating G140L in the 1105A setup. We adopted a flat FUV spectral energy distribution in f_lambda normalized to the GALEX FUV magnitude and chose average background conditions. We aim at a S/N=6-7 per resolution element which results in a request of 2 orbits each for the three targets at m_FUV<21 and 3 orbits each for the 5 targets at m_FUV>21. Thus, we arrive at a total of 21 orbits for the 8 targets. Since all targets are faint, direct acquisition in the NUV is the only option. In the updated COS Instrument Handbook it was strongly suggested to perform an ACQ/SEARCH before object acquisition, even if the object coordinates are accurate. Thus, the acquisition times have been substantially revised compared to Phase I, where we had assumed acquisition only via ACQ/IMAGE. The targets will be acquired using a 2x2 ACQ/SEARCH, followed by an ACQ/IMAGE. The COS ETC was used to estimate the exposure time to reach S/N=40 in a direct NUV exposure. Target fluxes were calibrated to the GALEX NUV magnitudes. Two of our targets are very faint, so that almost the complete first orbit has to be spent on target acquisition. According to the COS Instrument Science Team, a lower S/N in the acquisition exposures is not recommended. We adjusted the spectroscopic exposure times to use the full visibility period in each orbit. The expected S/N is well below the maximum S/N achievable without dithering around the central wavelength. Nevertheless, we use two FP-POS positions to correct for possible fixed pattern detector features. All spectra will be recorded in TIME-TAG mode with concurrent wavelength calibration (TAGFLASH). All proposed targets have reliable GALEX FUV fluxes well below the bright object limits of COS. We ran the COS BOT in APT, finding all objects near the targets to be safe except two, which are actually targets. Thus, all targets are safe to acquire. QUASAR ABSORPTION LINES AND IGM 12 false 0.0 0.0 false false false false false SUPPORTED EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=5.3+/-1.0E-16, F(2316)=3.8+/-0.3E-16 CTSB20.11 GSC2S03301001519 J2000 02 16 23.1000 -39 07 55.00 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=2.6+/-0.1E-16, F(2316)=1.26+/-0.04E-16 CSO806 GSC2N122211116333 J2000 13 04 12.0000 +29 53 49.00 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=1.3+/-0.4E-16, F(2316)=2.3+/-1.7E-17 Q0058+0215 GSC2N32013123134 J2000 01 00 58.4000 +02 31 32.00 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=2.1+/-0.6E-16, F(2316)=1.3+/-0.3E-16 GSC2N23303326088 J2000 09 36 43.5100 +29 27 13.60 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=1.3+/-0.1E-16, F(2316)=5.7+/-0.3E-17 SDSSJ08188+4908 GSC2N23023113004 J2000 08 18 50.0200 +49 08 17.20 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=1.2+/-0.3E-16, F(2316)=6.8+/-1.7E-17 SDSSJ09247+4852 GSC2N23210107803 J2000 09 24 47.3600 +48 52 42.80 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=1.5+/-0.4E-16, F(2316)=5.4+/-1.6E-17 SDSSJ11019+1053 GSC2N20311011627 J2000 11 01 55.7400 +10 53 2.30 J2000 EXT-MEDIUM ABSORPTION LINE SYSTEM - EXTRAGALACTIC IGM UV fluxes from GALEX data F(1539)=1.3+/-0.4E-16, F(2316)=3.2+/-1.7E-17 SDSSJ12378+0126 GSC2N12001016551 J2000 12 37 48.9900 +01 26 7.00 J2000 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 COS/FUV Spectroscopic No No G140L 1105 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit13645.xml (Tic-Visit :proposal-id 11742 :visit-id "01" :proposal-version -1 :trans-version "20080807" :date "16-Jun-2009 18:28:24.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174032 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11742 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11742 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2977 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3310 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11742 :visit-id "01" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3115 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3310 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit13646.xml (Tic-Visit :proposal-id 11742 :visit-id "02" :proposal-version -1 :trans-version "20080807" :date "16-Jun-2009 18:28:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 174032 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11742 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11742 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2934 :al-overhead-at-end 0 :internal-dur-at-end 116 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11742 :visit-id "02" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3072 :al-overhead-at-end 0 :internal-dur-at-end 428 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3267 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 17.2. 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