Browsing by Author "Lacey, Cedric G."

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    The clustering of Lyα emitters in a ΛCDM Universe
    (2008) Orsi, Alvaro; Lacey, Cedric G.; Baugh, Carlton M.; Infante, Leopoldo
    We combine a semi-analytical model of galaxy formation with a very large simulation which follows the growth of a large-scale structure in a Lambda cold dark matter (Lambda CDM) universe to predict the clustering of Ly alpha emitters. We find that the clustering strength of Ly alpha emitters has only a weak dependence on Ly alpha luminosity but a strong dependence on redshift. With increasing redshift, Ly alpha emitters trace progressively rarer, higher density regions of the universe. Due to the large volume of the simulation, over 100 times bigger than any previously used for this application, we can construct mock catalogues of Ly alpha emitters and study the sample variance of current and forthcoming surveys. We find that the number and clustering of Ly alpha emitters in our mock catalogues are in agreement with measurements from current surveys, but there is a considerable scatter in these quantities. We argue that a proposed survey of emitters at z = 8.8 should be extended significantly in solid angle to allow a robust measurement of Ly alpha emitter clustering.
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    The environments of high-redshift radio galaxies and quasars : probes of protoclusters
    (2016) Orsi Moyano, Alvaro; Fanidakis, Nikos; Lacey, Cedric G.; Baugh, Carlton M.
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    The environments of Ly α blobs - I. Wide-field Ly α imaging of TN J1338-1942, a powerful radio galaxy at z ≃ 4.1 associated with a giant Ly α nebula
    (2015) Saito, Tomoki; Matsuda, Yuichi; Lacey, Cedric G.; Smail, Ian; Orsi, Alvaro; Baugh, Carlton M.; Inoue, Akio K.; Tanaka, Ichi; Yamada, Toru; Ohta, Kouji; De Breuck, Carlos; Kodama, Tadayuki; Taniguchi, Yoshiaki
    We exploit wide-field Ly alpha imaging with Subaru to probe the environment around TN J1338-1942, a powerful radio galaxy with a > 100 kpc Ly alpha halo at z = 4.11. We used a sample of Ly alpha emitters (LAEs) down to log (L-Ly alpha [erg s(-1)]) similar to 42.8 to measure the galaxy density around TN J1338-1942, compared to a control sample from a blank field taken with the same instrument. We found that TN J1338-1942 resides in a region with a peak over-density of delta(LAE) = 2.8 +/- 0.5 on scales of 8 h(-1) Mpc (on the sky) and 112 h(-1) Mpc (line of sight) in comoving coordinates. Adjacent to this overdensity, we found a strong underdensity where virtually no LAEs are detected. We used a semi-analytical model of LAEs derived from the Millennium Simulation to compare our results with theoretical predictions. While the theoretical density distribution is consistent with the blank field, overdense regions such as that around TN J1338-1942 are very rare, with a number density of 6.4 x 10(-8) Mpc(-3) (comoving), corresponding to the densest < 0.4 percentile at z similar or equal to 4.1. We also found that the Ly alpha luminosity function in the TN J1338-1942 field differs from that in the blank field: the number of bright LAEs (log(L-Ly alpha [ergs(-1)]) greater than or similar to 43.3) is enhanced, while the number of fainter LAEs is relatively suppressed. These results suggest that some powerful radio galaxies associated with Ly a nebulae reside in extreme overdensities on similar to 3-6 Mpc scales, where star formation and AGN activity may be enhanced via frequent galaxy mergers or high rates of gas accretion from the surroundings.
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    The origin of the atomic and molecular gas contents of early-type galaxies - I. A new test of galaxy formation physics
    (2014) Lagos, Claudia del P.; Davis, Timothy A.; Lacey, Cedric G.; Zwaan, Martin A.; Baugh, Carlton M.; González Pérez, Violeta; Padilla, Nelson