1998/04/23 by Patrick Petitjean, Petitjean, Patrick, Jean Surdej +13
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9804242
4 pages, 2 figures, A&A Letter acccepted
arxiv created 1998/04/23 · openalex publication_date 1998/04/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The spatial distribution of the Lyα forest is studied using new HST data for the quasar pair Q~1026--0045 A and B at zem = 1.438 and 1.520 respectively. The angular separation is 36 arcsec and corresponds to transverse linear separations between lines of sight of ∼300h-150 kpc (qo = 0.5) over the redshift range 0.833 < z < 1.438. From the observed numbers of coincident and anti-coincident Lyα absorption lines, we conclude that, at this redshift, the Lyα structures have typical dimensions of ∼500h-150 kpc, larger than the mean separation of the two lines of sight. The velocity difference, ΔV, between coincident lines is surprisingly small (4 and 8 pairs with ΔV < 50 and 200 km/s respectively). Metal line systems are present at zabs = 1.2651 and 1.2969 in A, zabs = 0.6320, 0.7090, 1.2651 and 1.4844 in B. In addition we tentatively identify a weak Mg II system at zabs = 0.11 in B. It is remarkable that the zabs = 1.2651 system is common to both lines of sight. The system at zabs = 1.4844 %is probably associated and has strong O~VI absorption. There is a metal-poor associated system at zabs = 1.4420 along the line of sight to A with complex velocity profile. We detect a strong Lyα absorption along the line of sight to B redshifted by only 300 km/s relatively to the associated system. It is tempting to interpret this as the presence of a disk of radius larger than 300h-150 kpc surrounding quasar A.