Primordial Non-Gaussianity from LAMOST Surveys

TL;DR

This paper evaluates the potential of LAMOST galaxy and quasar surveys to constrain primordial non-Gaussianity, finding that quasar surveys could significantly improve current limits on the PNG parameter f_NL.

Contribution

It provides an analysis of LAMOST survey capabilities for detecting primordial non-Gaussianity, including new constraints and the potential for improved limits using the relative bias method.

Findings

Main galaxy survey provides weak PNG constraints.

Quasar survey can constrain |f_NL| between 50 and 103.

Quasar survey with Planck priors can tighten constraints to |f_NL|<43.

Abstract

The primordial non-Gaussianity (PNG) in matter density perturbation is a very powerful probe of the physics of the very early Universe. The local PNG can induce a distinct scale-dependent bias on the large scale structure distribution of galaxies and quasars, which could be used for constraining it. We study the detection limits on PNG from the surveys of the LAMOST telescope. The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and the quasar survey of different magnitude limits are considered. We find that the MAIN1 sample (i.e. the main galaxy survey with one magnitude deeper than the SDSS main galaxy survey, or r<18.8) could only provide very weak constraint on PNG. For the MAIN2 sample (r<19.8) and the LRG survey, the 2\sigma (95.5%) limit on the PNG parameter f_{NL} are |f_{NL}|<145 and |f_{NL}|<114 respectively, comparable to the current limit from cosmic microwave background (CMB) data. The quasar survey could provide much more stringent constraint, and we find that the 2\sigma limit for |f_{NL}| is between 50 and 103, depending on the magnitude limit of the survey. With Planck-like priors on cosmological parameters, the quasar survey with g<21.65 would improve the constraints to |f_{NL}|<43 (2\sigma). We also discuss the possibility of further tightening the constraint by using the relative bias method proposed by Seljak(2008).