Day 1740

Monday.

2007.15657

Constraining the gravitational lensing of $z\gtrsim6$ quasars from their proximity zones

Davies, et al

Since their discovery twenty years ago, the observed luminosity function of $z\gtrsim6$ quasars has been suspected to be biased by gravitational lensing. Apart from the recent discovery of UHS J0439+1634 at $z\approx6.52$, no other strongly lensed $z\gtrsim6$ quasar has been conclusively identified. The hyperluminous $z\approx6.33$ quasar SDSS J0100+2802, believed to host a supermassive black hole of $\sim10^{10} M_\odot$, has recently been claimed to be lensed by a factor of $\sim450$, which would negate both its extreme luminosity and black hole mass. However, its Ly$\alpha$-transparent proximity zone is the largest known at $z>6$, suggesting an intrinsically extreme ionizing luminosity. Here we show that the lensing hypothesis of $z\gtrsim6$ quasars can be quantitatively constrained by their proximity zones. We first show that our proximity zone analysis can recover the strongly lensed nature of UHS J0439+1634, with an estimated magnification $\mu=28.0^{+18.4}_{-11.7}(^{+44.9}_{-18.3})$ at 68% (95%) credibility that is consistent with previously published lensing models. We then show that the large proximity zone of SDSS J0100+2802 rules out lensing magnifications of $\mu>4.9$ at 95% probability, and conclusively rule out the proposed $\mu>100$ scenario. Future proximity zone analyses of existing $z\gtrsim6$ quasar samples have the potential to identify promising strongly lensed candidates, constrain the distribution of $z\gtrsim6$ quasar lensing, and improve our knowledge of the shape of the intrinsic quasar luminosity function.

2007.16153

Euclid: forecast constraints on the cosmic distance duality relation with complementary external probes

Martinelli, et al

In metric theories of gravity with photon number conservation, the luminosity and angular diameter distances are related via the Etherington relation, also known as the distance-duality relation (DDR). A violation of this relation would rule out the standard cosmological paradigm and point at the presence of new physics. We quantify the ability of Euclid, in combination with contemporary surveys, to improve the current constraints on deviations from the DDR in the redshift range $0<z<1.6$. We start by an analysis of the latest available data, improving previously reported constraints by a factor of 2.5. We then present a detailed analysis of simulated Euclid and external data products, using both standard parametric methods (relying on phenomenological descriptions of possible DDR violations) and a machine learning reconstruction using Genetic Algorithms. We find that for parametric methods Euclid can (in combination with external probes) improve current constraints by approximately a factor of six, while for non-parametric methods Euclid can improve current constraints by a factor of three. Our results highlight the importance of surveys like Euclid in accurately testing the pillars of the current cosmological paradigm and constraining physics beyond the standard cosmological model.

2007.16166

Baryonic feedback measurement fro mKV450 cosmic shear analysis

Yoon, Jee

While baryonic feedback is one of the most important astrophysical systematics that we need to address in order to achieve precision cosmology, few weak lensing studies have directly measured its impact on the matter power spectrum. In this letter, with cosmic shear alone we report the first measurement of the baryonic feedback parameter with the full constraints on its lower and upper limits. We use the public data from the Kilo-Degree Survey and the VISTA Kilo-Degree Infrared Galaxy Survey spanning 450 deg$^2$. Estimating both cosmological and feedback parameters simultaneously, we obtain $A_{\rm b}=1.01_{-0.85}^{+0.80}$, which shows a consistency with the dark matter-only (DMO) case at the ~1.2$\sigma$ level and a tendency toward positive feedback; the $A_{\rm b}=0$ ($0.81$) value corresponds to the DMO (OWLS AGN) case. Despite this full constraint of the feedback parameter, our $S_8~(\equiv \sigma_8 \sqrt{\Omega_m / 0.3})$ measurement ($0.739^{+0.036}_{- 0.035}$) shifts by only ~$6$% of the statistical error, compared to the previous measurement. When we assume the flat $\Lambda$CDM cosmology favored by the Nine-Year Wilkinson Microwave Anisotropy Probe (Planck) result, the feedback parameter is constrained to be $A_{\rm b}=1.21_{-0.54}^{+0.61}$ ($1.60_{-0.52}^{+0.53}$), which excludes the DMO case at the ~$2.2~\sigma$ (~$3.1~\sigma$) level.