Prof. David Alonso

Abstract:

<jats:title>Abstract</jats:title> <jats:p> We analyse the large-scale angular clustering of quasars in the <jats:italic>Gaia</jats:italic> - <jats:italic>unWISE</jats:italic> quasar catalog, <jats:italic>Quaia</jats:italic> , and their cross-correlation with maps of the lensing convergence of the Cosmic Microwave Background (CMB), to constrain the level of primordial non-Gaussianity (PNG). Specifically, we target the scale-dependent bias that would be induced by PNG on biased tracers of the matter inhomogeneities on large scales. The <jats:italic>Quaia</jats:italic> sample is particularly well suited for this analysis, given the large effective volume covered, and our ability to map out the main potential sources of systematic contamination and mitigate their impact. Using the universality relation to characterise the response of the quasar overdensity to PNG ( <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1), we report constraints on the local-type PNG parameter   <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> of <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> = -20.5 <jats:sup>+19.0</jats:sup> <jats:sub>-18.1</jats:sub> (68% C.L.) by combining the quasar auto-correlation and its cross-correlation with CMB lensing in two tomographic redshift bins (or <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> = -28.7 <jats:sup>+26.1</jats:sup> <jats:sub>-24.6</jats:sub> if assuming a lower response for quasars, <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1.6). The error on <jats:italic>f</jats:italic> <jats:sub>NL</jats:sub> can be further improved if the cross-correlation between the tomographic redshift bins is included. Using the CMB lensing cross-correlations alone, we find <jats:italic> f <jats:sub>NL</jats:sub> </jats:italic> = -13.8 <jats:sup>+26.7</jats:sup> <jats:sub>-25.0</jats:sub> and <jats:italic> f <jats:sub>NL</jats:sub> </jats:italic> = -15.6 <jats:sup>+42.3</jats:sup> <jats:sub>-34.8</jats:sub> for <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1 and <jats:italic> p <jats:sub>ϕ</jats:sub> </jats:italic> = 1.6 respectively. These are the tightest constraints on <jats:italic> f <jats:sub>NL</jats:sub> </jats:italic> to date from angular clustering statistics and cross-correlations with CMB lensing. </jats:p>

Abstract:

We measure the angular power spectrum and bispectrum of the projected overdensity of photometric DESI luminous red galaxies, and its cross-correlation with maps of the Cosmic Microwave Background lensing convergence from Planck. This analysis is enabled by the use of the “filtered-squared bispectrum” approach, introduced in previous work, which we generalise here to the case of cross-correlations between multiple fields. The projected galaxy bispectrum is detected at very high significance (above <math display="inline"> <mrow> <mn>30</mn> <mi>σ</mi> </mrow> </math> in all redshift bins), and the galaxy-galaxy-convergence bispectrum is detected above <math display="inline"> <mrow> <mn>5</mn> <mi>σ</mi> </mrow> </math> in the three highest-redshift bins. We find that the bispectrum is reasonably well described over a broad range of scales by a tree-level prediction using the linear galaxy bias measured from the power spectrum. We carry out the first cosmological analysis combining projected power spectra and bispectra under a relatively simple model, and show that the galaxy bispectrum can be used in combination with the power spectrum to place a constraint on the amplitude of matter fluctuations, <math display="inline"> <msub> <mi>σ</mi> <mn>8</mn> </msub> </math> , an on the non-relativistic matter fraction <math display="inline"> <msub> <mi>Ω</mi> <mi>m</mi> </msub> </math> . We find that data combinations involving the galaxy bispectrum recover constraints on these parameters that are in good agreement with those found from the traditional “2 <math display="inline"> <mo>×</mo> </math> 2-point” combination of galaxy-galaxy and galaxy-convergence power spectra, across all redshift bins.