A High Yield of New Sightlines for the Study of Intergalactic Helium: Far-UV-Bright Quasars from SDSS, GALEX, and HST - AstrophysicsReport as inadecuate




A High Yield of New Sightlines for the Study of Intergalactic Helium: Far-UV-Bright Quasars from SDSS, GALEX, and HST - Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Investigations of He II Ly-alpha 304 A rest absorption toward a half-dozenquasars at z~3-4 have demonstrated the great potential of helium studies of theIGM, but the current critically small sample size of clean sightlines for theHe II Gunn-Peterson test limits confidence in cosmological inferences, and alarger sample is required. Although the unobscured quasar sightlines to highredshift are extremely rare, SDSS DR6 provides thousands of z>2.8 quasars. Wehave cross-correlated these SDSS quasars with GALEX GR2-GR3 to establish acatalog of 200 higher-confidence ~70% secure cases of quasars at z=2.8-5.1potentially having surviving far-UV restframe flux. We also catalog another112 likely far-UV-bright quasars from GALEX cross-correlation with othernon-SDSS quasar compilations. Reconnaissance UV prism observations with HSTof 24 of our SDSS-GALEX candidates confirm 12 as detected in the far-UV, withat least 9 having flux extending to very near the He II break; with refinementsour success rate is even higher. Our SDSS-GALEX selection approach is therebyconfirmed to be an order of magnitude more efficient than previous He II quasarsearches, more than doubles the number of spectroscopically confirmed cleansightlines to high redshift, and provides a resource list of hundreds ofhigh-confidence sightlines for upcoming He II and other far-UV studies fromHST. Our reconnaissance HST prism spectra suggest some far-UV diversity,confirming the need to obtain a large sample of independent quasar sightlinesacross a broad redshift range to assess such issues as the epochs of heliumreionization, while averaging over individual-object pathology and-or cosmicvariance.



Author: David Syphers 1, Scott F. Anderson 1, Wei Zheng 2, Daryl Haggard 1, Avery Meiksin 3, Kuenley Chiu 4, Craig Hogan 1, Donald P. Sch

Source: https://arxiv.org/







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