Testing cosmic anisotropy with Pantheon sample and quasars at high redshifts

Abstract

In this paper, we investigate the cosmic anisotropy from the SN-Q sample, consisting of the Pantheon sample and quasars, by employing the hemisphere comparison (HC) method and the dipole fitting (DF) method. Compared to the Pantheon sample, the new sample has a larger redshift range, a more homogeneous distribution, and a larger sample size. For the HC method, we find that the maximum anisotropy level is ALmax = 0.142 ± 0.026 in the direction (l, b) = (316.08°−129.48+27.41, 4.53°−64.06+26.29). The magnitude of anisotropy is A = (−8.46−5.51+4.34) × 10−4 and the corresponding preferred direction points toward (l, b) = (29.31°−30.54+30.59, 71.40°−9.72+9.79) for the quasar sample from the DF method. The combined SN and quasar sample is consistent with the isotropy hypothesis. The distribution of the dataset might impact the preferred direction from the dipole results. The result is weakly dependent on the redshift from the redshift tomography analysis. There is no evidence of cosmic anisotropy in the SN-Q sample. Though some results obtained from the quasar sample are not consistent with the standard cosmological model, we still do not find any distinct evidence of cosmic anisotropy in the SN-Q sample.

A tomographic test of cosmic anisotropy with the recently-released quasar sample

“…Cosmological models are rarely tested in the intermediate redshift range 2.3 ≤ z ≤ 1100. An incomplete list of the datasets and related works to test cosmological models in the intermediate redshift range include the gamma-ray burst [55][56][57][58][59][60][61][62][63][64][65][66], the HIIG starburst galaxy [59,[67][68][69][70][71][72][73], the quasar angular size [59,69,[74][75][76], and the X-ray and UV flux of quasars [77][78][79][80][81][82][83][84][85][86][87].…”

“…Besides the SNe Ia sample, galaxy [18][19][20]54], galaxy cluster [51][52][53], number counts of radio and mid-IR sources [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50], gamma-ray burst [13,66,108], gravitational wave [109], fast radio burst [109,110], and quasar [83,87] are also used to investigate the cosmic anisotropy. The UV and X-ray luminosity of quasars are used to test the cosmic anisotropy by Hu etc.…”

“…The UV and X-ray luminosity of quasars are used to test the cosmic anisotropy by Hu etc. [87]. They combined the 2019 compilation of quasars [78] with the Pantheon sample [91] to test the dipole-modulated CDM model.…”

Constraining the anisotropy of the Universe with the X-ray and UV fluxes of quasars

“…In recent years, quasars are tentatively used to investigate the cosmological parameters. An incomplete list includes the relation between the UV emission lines and the continuum luminosity [31], the relation between the radius of quasars and its luminosity [32][33][34], the relation between luminosity and mass of super Eddington accreting quasars [35], the correlation between X-ray variability and luminosity of quasars [36], the non-linear relation between UV and X-ray luminosity [37][38][39][40][41][42][43]. The non-linear relation between UV and X-ray luminosity was firstly discovered by the X-ray surveys [44][45][46].…”

“…Hu etc. tested the cosmic anisotropy with Pantheon sample and quasars by employing the hemisphere comparison method and the dipole fitting method in the CDM model, and they didn't find any distinct evidence of cosmic anisotropy [43].…”