Probing inflationary features with galaxy ultraviolet luminosity function observables

Abstract

We use the galaxy ultraviolet luminosity function measurements at $z=6-9$ to constrain modification to standard inflationary power spectrum. These observables are sensitive to the matter power spectrum which itself depends on inflationary initial conditions. We consider specific models where a bump or oscillatory features are introduced to the standard power law inflation spectrum. We find that the galaxy luminosity observables can probe such modifications at wavenumbers $0.5\lesssim k \lesssim 20$ Mpc$^{-1}$. We obtain upper limits on the amplitude of bump-like features at the mentioned wavenumbers. We obtain constraints which are similar to previous constraints on these models using measurements of optical depth of reionization. However, the galaxy luminosity functions are a more direct probe for these type of models and, therefore, can complement indirect constraints coming from measurements of IGM properties.

Figures (6)

• Figure 1: Modified inflationary power spectrum with a single bump like feature, $k_{\rm peak}=0.5$ Mpc$^{-1}$ and amplitude as denoted in the plot. We plot the standard power law spectrum in black with parameters as denoted in the text.
• Figure 2: $\sigma(M_h)$ as a function of halo mass at $z=0$ for different $k_{\rm peak}$ and $A_I=10^{-9}$. We have chosen the normalization $\sigma_8=0.8111$Planck2020 for all the curves. We note that $\sigma_8$ is a derived parameter and a choice of $A_s$ or $\sigma_8$ fixes the other one.
• Figure 3: (a) Left panel: UVLF measurements as a function of luminosity or magnitude for a few different redshifts. For $z=6-8$, we use the result of Bouwens2015 while for $z=9$, we use the data from Donnan2023. (b) Right panel: Theoretical prediction for UVLF at $z=6$ for different $k_{\rm peak}$ and $A_I=10^{-9}$. We have used $f_{*,10}=0.1$ and $\alpha_*=0.4$ which are the best fit parameters to the data in the standard case with $A_I=0$ (drawn in solid black).
• Figure 4: Constraints on $A_I$ (at 95 percent confidence interval) as a function of scale from different probes as denoted in the plot. Our new constraints cover range between $k\in [0.3-20]$ Mpc$^{-1}$. Our constraints are competitive with constraints derived from CMB optical depth $\tau_{\rm Planck}$NCSMF2025. In deriving the optical depth constraint, a fiducial astrophysical model with fixed parameter values was assumed.
• Figure 5: (a) Left panel: Modified inflationary power spectrum with linear and log-damped oscillatory features. For linear- damped case, the parameters are $\alpha=0.5$, ${\rm log_{10}}\omega=1$ while for log-damped case we use $\alpha=0.5$, ${\rm log_{10}}\omega=0.5$. We use $k'=50$ Mpc$^{-1}$, $\beta=5$, $\mu=0.01$ for both cases. (b) Right panel: variance $\sigma(M_h)$ with the normalization $\sigma_8=0.8111$.