The SDSS-DR12 large-scale cross-correlation of damped Lyman alpha systems with the Lyman alpha forest

Abstract

We present a measurement of the DLA mean bias from the cross-correlation of DLA and the Lyα forest, updating earlier results of Font-Ribera et al. (2012) with the final BOSS Data Release and an improved method to address continuum fitting corrections. Our cross-correlation is well fitted by linear theory with the standard ΛCDM model, with a DLA bias of b DLA = 1.99 ± 0.11; a more conservative analysis, which removes DLA in the Lyβ forest and uses only the cross-correlation at r > 10 h −1 Mpc, yields b DLA = 2.00 ± 0.19. This assumes the cosmological model from Planck Collaboration (2016) and the Lyα forest bias factors of Bautista et al. (2017), and includes only statistical errors obtained from bootstrap analysis. The main systematic errors arise from possible impurities and selection effects in the DLA catalogue, and from uncertainties in the determination of the Lyα forest bias factors and a correction for effects of high column density absorbers. We find no dependence of the DLA bias on column density or redshift. The measured bias value corresponds to a host halo mass ∼ 4 · 10 11 h −1 M if all DLA were hosted in halos of a similar mass. In a realistic model where host halos over a broad mass range have a DLA cross section Σ(M h ) ∝ M α h down to M h > M min = 10 8.5 h −1 M , we find that α > 1 is required to have b DLA > 1.7, implying a steeper relation or higher value of M min than is generally predicted in numerical simulations of galaxy formation.

Intensity mapping with neutral hydrogen and the Hidden Valley simulations

“…The horizontal grey band is the redshift-average value from ref. [19]. The inset shows the same bias prediction from our models up to z = 6.…”

“…Squares with error bars are the measurements from ref. [19] while the circles and line show the predictions from our models. The horizontal grey band is the redshift-average value from ref.…”

Linking gas and galaxies at high redshift: MUSE surveys the environments of six damped Lyα systems at z ≈ 3

“…Furthermore, Font-Ribera et al (2012), using the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), found an unexpected large linear bias of DLAs (b DL A = 2.17 ± 0.20, with an assumption on the bias of the Lyα forest) by cross-correlating these absorbers with the Lyα forest. This measurement was more recently updated by Pérez-Ràfols et al (2018b), who found a linear bias of b DL A = 2.00 ± 0.19, which is only slightly lower than the clustering amplitude of Lyman Break Galaxies (LBGs; see also Cooke et al 2006). This value of the bias, which implies masses of 10 11 M , appears uncomfortably high for some galaxy formation simulations and models (see e.g Pontzen et al 2008; Barnes & Haehnelt 2014;Padmanabhan et al 2017) if DLAs sample a very wide range in galaxy sizes (e.g.…”

LyaCoLoRe: synthetic datasets for current and future Lyman-α forest BAO surveys

“…We first determine potential HCD locations by computing a threshold value of the Gaussian field, set by an input bias b HCD (z). In our realisations, we choose b HCD (z) = 2.0 to be constant with redshift, and in line with [62]. This picks out peaks in the field that are sufficiently dense to host an HCD.…”

“…Making such an extreme cut in rest-frame wavelength greatly reduces the number of HCDs in our catalogue. In this work we use approximately 30 times the number of skewers 10 It should be noted that [62] includes only HCDs at least 5000 km/s away from their host quasar, equivalent to a rest-frame wavelength cut of approximately 1195Å. We choose to use λr,HCD < λLyα in the right panel of Figure 6 in order to explain the relationship between the geometry of the problem and the observed effect more clearly.…”