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

Abstract

During the last decades, rapid progress has been made in measurements of the rest-frame ultraviolet (UV) luminosity function (LF) for high-redshift galaxies (z ≥ 6). The faint-end of the galaxy LF at these redshifts provides powerful constraints on different dark matter models that suppress small-scale structure formation. In this work we perform full hydrodynamical cosmological simulations of galaxy formation using an alternative DM model composed of extremely light bosonic particles (m ∼ 10 −22 eV), also known as fuzzy dark matter (FDM), and examine the predictions for the galaxy stellar mass function and luminosity function at z ≥ 6 for a range of FDM masses. We find that for FDM models with bosonic mass m = 5 × 10 −22 eV, the number density of galaxies with stellar mass M * ∼ 10 7 M is suppressed by ∼ 40% at z = 9, ∼ 20% at z = 5, and the UV LFs within magnitude range of -16 < M UV < -14 is suppressed by ∼ 60% at z = 9, ∼ 20% at z = 5 comparing to the CDM counterpart simulation. Comparing our predictions with current measurements of the faint-end LFs (−18 M UV −14), we find that FDM models with m 22 < 5 × 10 −22 are ruled out at 3σ confidence level. We expect that future LF measurements by James Webb Space Telescope (JWST), which will extend down to M UV ∼ −13 for z 10, with a survey volume that is comparable to the Hubble Ultra Deep Field (HUDF) would have the capability to constrain FDM models to m 10 −21 eV.

The core-cusp problem revisited: ULDM vs. CDM

“…In this case, choosing parameters such that the theoretical profiles overlap with the data at small radii is easy (in this case m 22 = 0.1, M vir 5 × 10 11 M ); however, it is not clear whether this profile would fit data at larger radii were it available. Furthermore, while the choice m 22 = 0.1 provides a reasonable fit to the data in this case, a ULDM particle mass m 22 = 0.1 is in tension with constraints from the Lyman-α forest, as well as high-redshift UV luminosity function comparisons d (Amendola and Barbieri 2006;Bozek et al 2015;Armengaud et al 2017;Ni et al 2019;Nebrin, Ghara, & Mellema 2020). It must be acknowledged, however, that baryonic feedback is expected to have the greatest impact in the innermost regions of realistic halos.…”

“…Interestingly, however, a better fit to the lower velocity SPARC data is obtained from a ULDM profile where m 22 = 0.1 and M vir = 5 × 10 11 M . It must be noted, however, that a ULDM mass this small is in tension with other constraints [36][37][38][39][40]. Tightening these constraints on the plausible ULDM particle mass will inform future investigations of this type [41][42][43].…”

What is the Halo Mass Function in a Fuzzy Dark Matter Cosmology?

“…The Roman Space Telescope (WFIRST) High Latitude Survey is expected to observe many z ∼ 10 galaxies (Spergel et al 2013;Waters et al 2016) which can be studied in detail with the James Webb Space Telscope (JWST). The JWST is also expected to measure the faint-end of the UV luminosity function at high-redshift which can also be used to constrain the properties of the fuzzy dark matter (Corasaniti et al 2017;Ni et al 2019).…”

Ultra-light dark matter

“…In Bozek et al (2015), this was also analyzed but using the HMF (162) and shows that using the observed UV luminosity from HUDF, a mass of m = 10 −23 eV is excluded with at > 8σ , and therefore m 10 −22 eV is consistent with HUDF. Obtaining a luminosity function from a full hydrodynamical cosmological simulations of galaxy formation using the initial conditions from the FDM model was done in Ni et al (2019), they reach a similar conclusion, ruling out m < 5 × 10 −22 eV (3σ ). Combining the HUDF data with deep IRAC data from Spitzer Space Telescope over the Great Observatories Origins Deep Survey (GOODS) fields, in Song (2016) they can probe even higher redshifts z ∼ 8 and show that for m ∼ 10 − 5 × 10 −22 eV the FDM is consistent with their measurements, while m < 2 × 10 −22 eV is inconsistent.…”