Kavli Affiliate: Anthony Challinor
| First 5 Authors: Carmen Embil Villagra, Carmen Embil Villagra, , ,
| Summary:
We measure the amplitude of matter fluctuations over a wide range of
redshifts by combining CMB lensing observations from ACT DR6 and
$textitPlanck$ PR4 with the overdensity of quasars from Quaia, a
$textitGaia$ and $textitunWISE$ quasar catalog. Our analysis includes the
CMB lensing power spectrum from ACT DR6, the auto-correlation of two Quaia
quasar samples centered at $z simeq 1.0$ and $z simeq 2.1$, and their
cross-correlations with CMB lensing from both ACT DR6 and $textitPlanck$
PR4. By performing a series of contamination and systematic null tests, we find
no evidence for contamination in the lensing maps, contrary to what was
suggested in previous Quaia cross-correlation analyses using $textitPlanck$
PR4 CMB lensing data. From the joint analysis of the quasar auto- and
cross-correlations with CMB lensing, and including BOSS BAO data to break the
degeneracy between $Omega_m$ and $sigma_8$, we obtain $sigma_8 =
0.802^+0.045_-0.057$, consistent with $Lambda$CDM predictions from
$textitPlanck$ primary CMB measurements. Combining the CMB lensing
auto-spectrum with the cross-correlation measurement improves the constraint on
$sigma_8$ by $12%$ relative to the lensing auto-spectrum alone, yielding
$sigma_8 = 0.804 pm 0.013$. This dataset combination also enables a
reconstruction of structure growth across redshifts. We infer a $12%$
constraint on the amplitude of matter fluctuations at $z > 3$, with a
measurement at the median redshift of the signal of $sigma_8(tildez=5.1) =
0.146^+0.021_-0.014$, consistent with $textitPlanck$ at the $1.4sigma$
level. These results provide one of the highest redshift constraints on the
growth of structure to date.
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