Probing the Reionization Epoch of IGM Helium: A Detailed Follow-up Study of Three High-Quality He II Quasars

Assigned ID: 105 ----- Attempting Submission 1 (Wed Feb 22 18:21:28 GMT 2012) ----- ----- Attempting Submission 1 (Wed Jul 11 01:02:02 GMT 2012) ----- The first warning is silly - the errors on the positions (0.1" rms, SDSS) are GIVEN in the phase II. 0.1 < 0.4. We do use all four FP-POS for the G130M observations. The G140L is only for continuum calibration, and we don't care about loss of sensitivity in small regions (wire shadows, etc.) Probing the Reionization Epoch of IGM Helium: A Detailed Follow-up Study of Three High-Quality He II Quasars The full reionization of intergalactic helium likely occurred at redshifts between z=2.7 and 4, dramatically affecting the state of the IGM, including strong heating of the gas. Detailed UV spectral studies of He II Ly-alpha absorption toward a handful of quasars at 2.7<z<3.3 confirm the potential of such IGM probes, but the very small sample (3 sightlines) with detailed, high-S/N information limits the confidence in cosmological inferences. In recent cycles we have been very successful in identifying many new He II quasars at a wide range of redshifts. Here we follow up on the best of these, three uniquely bright He II quasars, including one at higher redshift. SDSSJ0915+4756, at z=3.34, is the brightest confirmed in the FUV at z>2.9, while HS1024+1849 and 4C57.27 are the brightest He II quasars without existing high-resolution and high-S/N observations. We propose a 25-orbit program that will study: (1) the currently ill-constrained evolution of He II reionization, from its end to well before completion; (2) the He II Ly-alpha forest; (3) the interaction of quasars and the IGM with the line-of-sight and transverse proximity effects; (4) high-redshift, high-opacity IGM He II using both Ly-alpha and Ly-beta Gunn-Peterson troughs. We will conduct a detailed study of three of the brightest and most interesting He II quasars, filling 25 orbits. Most of the data will be taken in G130M/1222 to exploit the ability to obtain moderate resolution in He II Ly-alpha down to redshift 2.5. Some G140L data will be taken for continuum calibration. Accurate SDSS coordinates and prior HST observation allow us to use ACQ/IMAGE only to acquire targets (to S/N=40 for the given times). None of the targets comes close to violating overlight safety, and GALEX imaging directly verifies no nearby UV-bright objects. All FP-POS are used for the G130M observations to maximize usable spectral coverage and S/N. We use defaults for SEGMENT and FLASH. QUASAR ABSORPTION LINES AND IGM 12 false 0.0 0.0 false false false false SUPPORTED GALAXY QUASAR J2000 J2000 GALEX NUV: 5.3e-16; COS FUV: 9.0e-16; SDSS: u=18.29, g=17.42, r=17.34, i=17.26, z=17.12 GALAXY QUASAR J2000 J2000 GALEX NUV: 2.4e-16; COS FUV: 4.7e-16; SDSS: u=18.90, g=18.01, r=17.83, i=17.70, z=17.70 GALAXY QUASAR J2000 J2000 GALEX NUV: 2.0e-16; COS FUV: 3.8e-16; SDSS: u=19.57, g=18.16, r=17.85, i=17.81, z=17.73 COS/NUV Imaging No No MIRRORA COS/FUV Spectroscopic No No G130M 1222 COS/FUV Spectroscopic No No G140L 1105 COS/NUV Imaging No No MIRRORA COS/FUV Spectroscopic No No G130M 1222 COS/FUV Spectroscopic No No G140L 1105 COS/NUV Imaging No No MIRRORA COS/FUV Spectroscopic No No G130M 1222 COS/FUV Spectroscopic No No G140L 1105 1341967439031 /Users/dsyphers/proposals/hst/cyc20/phaseII/OP-cache/12816_phaseII-v01.xml The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 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ETC buffer time is ~13ks, so we use the exposure time instead. 1341967440543 /Users/dsyphers/proposals/hst/cyc20/phaseII/OP-cache/12816_phaseII-v02.xml The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 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ETC buffer time is ~14ks, so we use the exposure time instead. ETC buffer time is ~14ks, so we use the exposure time instead.