The clustering of z > 7 galaxies: predictions from the BLUETIDES simulation

Abstract

We study the clustering of the highest-z galaxies (from ∼ 0.1 to a few tens Mpc scales) using the BLUETIDES simulation and compare it to current observational constraints from Hubble legacy and Hyper Suprime Cam (HSC) fields (at z = 6 − 7.2). With a box length of 400 Mpc/h on each side and 0.7 trillion particles, BLUETIDES is the largest volume high resolution cosmological hydrodynamic simulation to date ideally suited for studies of high−z galaxies. We find that galaxies with magnitude m U V < 27.7 have a bias (b g ) of 8.1 ± 1.2 at z = 8, and typical halo masses M H 6 × 10 10 M . Given the redshift evolution between z = 8 to z = 10 (b g ∝ (1 + z)1.6 ), our inferred values of the bias and halo masses are consistent with measured angular clustering at z ∼ 6.8 from these brighter samples. The bias of fainter galaxies (in the Hubble legacy field at H 160 29.5) is 5.9 ± 0.9 at z = 8 corresponding to halo masses M H 10 10 M . We investigate directly the 1-halo term in the clustering and show that it dominates on scales r 0.1 Mpc/h (Θ 3 ) with non-linear effect at transition scales between the 1-halo and 2-halo term affecting scales 0.1 r 20 Mpc/h (3 Θ 90 ). Current clustering measurements probe down to the scales in the transition between 1-halo to 2-halo regime where non-linear effects are important. The amplitude of the 1-halo term implies that occupation numbers for satellites in BLUETIDES are somewhat higher than standard HODs adopted in these analyses (which predict amplitudes in the 1-halo regime suppressed by a factor 2-3). That possibly implies a higher number of galaxies detected by JWST (at small scales and even fainter magnitudes) observing these fields.

Galaxy Stellar Mass Functions from z ∼ 10 to z ∼ 6 using the Deepest Spitzer/Infrared Array Camera Data: No Significant Evolution in the Stellar-to-halo Mass Ratio of Galaxies in the First Gigayear of Cosmic Time

“…The above results are qualitatively consistent with the co-evolution between the star-formation rate density and the halo mass accretion rate recently found by Oesch et al (2018), indicating a scenario where the efficiency of star formation remained approximately con-stant through the first ∼ 1.5 Gyr of cosmic history, as also suggested by some of the recent models (e.g., Mason et al 2015, Mashian et al 2016, Wilkins et al 2017, Tacchella et al 2018, Bhowmick et al 2018, Ma et al 2018, Park et al 2019, Hutter et al 2021 and observations (e.g., Durkalec et al 2015, Harikane et al 2018. These results are also qualitatively consistent with the co-evolution between the specific SFR and the specific dark matter halo mass accretion rate found in recent studies (e.g., Stefanon et al 2021).…”

Halo occupation distribution (HOD) modelling of high redshift galaxies using the BlueTides simulation

“…We perform a power law fit to the large scale clustering from scales of 1 Mpc/h to 100 Mpc/h and look for deviations from power-law at smaller scales (r < 1 Mpc/h). We note that the powerlaw behavior prevails all the way to (r < 0.1 Mpc/h), which is a direct consequence of the non-linear halo bias in the two-halo regime (Jose et al 2017(Jose et al , 2016;BlueTides clustering confirms that non-linear bias is indeed required to model clustering at quasilinear scales (0.5 − 10Mpc/h) as seen in Figure 5 of our earlier paper (Bhowmick et al 2018). In the one-halo regime (r < 0.1 Mpc/h), simulations predict enhancement (by factors of upto ∼ 10) compared to power law.…”

Predictions for the abundance of high-redshift galaxies in a fuzzy dark matter universe

“…In this work we generate, for the first time, full hydrodynamical cosmological simulations of galaxy formation within the framework of FDM models to examine the predictions of the high-redshift galaxy abundance. Our fiducial galaxy formation model is built upon the successes of the B T simulation that has been validated against high-redshift galaxy population observations (Feng et al 2016;Wilkins et al 2017Wilkins et al , 2018Bhowmick et al 2018). We have run a suite of FDM simulations with FDM bosonic mass ranging from m 22 = 1.2 ∼ 10.…”