Browsing by Author "Prochaska, J. Xavier"

Now showing 1 - 5 of 5
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    A VLT/MUSE galaxy survey towards QSO Q1410: looking for awhim traced by blas in inter-cluster filaments
    (2018) Pessa, Ismael; Tejos, Nicolas; Felipe Barrientos, L.; Werk, Jessica; Bielby, Richard; Padilla, Nelson; Morris, Simon L.; Prochaska, J. Xavier; Lopez, Sebastian; Hummels, Cameron
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    Mapping the Most Massive Overdensities through Hydrogen (MAMMOTH). II. Discovery of the Extremely Massive Overdensity BOSS1441 at z=2.32
    (IOP PUBLISHING LTD, 2017) Cai, Zheng; Fan, Xiaohui; Bian, Fuyan; Zabludoff, Ann; Yang, Yujin; Prochaska, J. Xavier; McGreer, Ian; Zheng, Zhen Ya; Kashikawa, Nobunari; Wang, Ran; Frye, Brenda; Green, Richard; Jiang, Linhua
    Cosmological simulations suggest a strong correlation between high optical-depth Lya absorbers, which arise from the intergalactic medium, and 3D mass overdensities on scales of 10-30 h(-1) comoving Mpc. By examining the absorption spectra of similar to 80,000 QSO sight lines over a volume of 0.1 Gpc(3) in the Sloan Digital Sky Survey III (SDSS-III), we have identified an extreme overdensity, BOSS1441, which contains a rare group of strong Lya absorbers at z = 2.32 +/- 0.02. This absorber group is associated with six QSOs at the same redshift on a 30 comoving Mpc scale. Using Mayall/MOSAIC narrowband and broadband imaging, we detect Lya emitters (LAEs) down to 0.7 x L-Ly alpha ' * a and reveal a large-scale structure of LAEs in this field. Our follow-up LBT observations have spectroscopically confirmed 20 galaxies in the density peak. We show that BOSS1441 has an LAE overdensity of 10.8 +/- 2.6 on a 15 comoving Mpc scale, which could collapse to a massive cluster with M greater than or similar to 10(15) M-circle dot at z similar to 0. This overdensity is among the most massive large-scale structures at z similar to 2 discovered to date.
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    Project AMIGA: A Minimal Covering Factor for Optically Thick Circumgalactic Gas around the Andromeda Galaxy
    (2017) Howk, Jay Christopher; Wotta, Christopher B.; Berg, Michelle A.; Lehner, Nicolas; Lockman, Felix J.; Hafen, Zachary; Pisano, D. J.; Faucher-Guiguere, Claude André; Wakker, Bart P.; Prochaska, J. Xavier
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    The COS-Halos Survey: Metallicities in the Low-redshift Circumgalactic Medium
    (IOP PUBLISHING LTD, 2017) Prochaska, J. Xavier; Werk, Jessica K.; Worseck, Gabor; Tripp, Todd M.; Tumlinson, Jason; Burchett, Joseph N.; Fox, Andrew J.; Fumagalli, Michele; Lehner, Nicolas; Peeples, Molly S.; Tejos, Nicolas
    We analyze new far-ultraviolet spectra of 13 quasars from the z similar to 0.2 COS-Halos survey that cover the H I Lyman limit of 14 circumgalactic medium (CGM) systems. These data yield precise estimates or more constraining limits than previous COS-Halos measurements on the H I column densities N-H (I). We then apply a Monte-Carlo Markov chain approach on 32 systems from COS-Halos to estimate the metallicity of the cool (T similar to 10(4) K) CGM gas that gives rise to low-ionization state metal lines, under the assumption of photoionization equilibrium with the extragalactic UV background. The principle results are: (1) the CGM of field L* galaxies exhibits a declining H I surface density with impact parameter R-perpendicular to (at >99.5% confidence), (2) the transmission of ionizing radiation through CGM gas alone is 70 +/- 7%; (3) the metallicity distribution function of the cool CGM is unimodal with a median of 10(-0.51) Z(circle dot) and a 95% interval approximate to 1/50 Z(circle dot) to > 3 Z(circle dot); the incidence of metal=poor(< 1/100 Z) gas is low, implying any such gas discovered along quasar sightlines is typically unrelated to L* galaxies; (4) we find an unexpected increase in gas metallicity with declining N-H (I) (at >99.9% confidence) and, therefore, also with increasing R-perpendicular to; the high metallicity at large radii implies early enrichment; and (5) a non-parametric estimate of the cool CGM gas mass is M-CGM (cool) = (9.2 +/- 4.3) x 10(10) M-circle dot, cool 10, which together with new mass estimates for the hot CGM may resolve the galactic missing baryons problem. Future analyses of halo gas should focus on the underlying astrophysics governing the CGM, rather than processes that simply expel the medium from the halo.
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    Towards the statistical detection of the warm–hot intergalactic medium in intercluster filaments of the cosmic web
    (2016) Tejos, Nicolás; Prochaska, J. Xavier; Crighton, Neil H.M.; Morris, Simon L.; Werk, Jessica K.; Theuns, Tom; Padilla, Nelson; Bielby, Rich M.; Finn, Charles W.