(An)isotropy of the Hubble diagram: comparing hemispheres

By D. Schwarz, B. Weinhorst. 2007

147 citations recorded by the source corpus.

Aims. We test the isotropy of the Hubble diagram. At small redshifts, this is possible without assumptions on the cosmic inventory and provides a fundamental test of the cosmological principle. At higher redshift we check for the self-consistency of the ΛCDM model. Methods. At small redshifts, we use public supernovae (SNe) Ia data to determine the deceleration parameter q0 and the SN calibration on opposite hemispheres. For the complete data sets we fit ΩM and the SN calibration on opposite hemispheres. Results. A statistically significant anisotropy of the Hubble diagram at redshifts z 95%C.L.). While data from the North Galactic hemisphere favour the accelerated expansion of the Universe, data from the South Galactic hemisphere are not conclusive. The hemispheric asymmetry is maximal toward a direction close to the equatorial poles. The discrepancy between the equatorial North and South hemispheres shows up in the SN calibration. For the ΛCDM model fitted to all available SNe, we find the same asymmetry. Conclusions. The alignment of discrepancies between hemispheric Hubble diagrams with the equatorial frame seems to point toward a systematic error in the SN search, observation, analysis or data reduction. We also find that our model independent test cannot exclude the case of the deceleration of the expansion at a statistically significant level.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/43d25590bcdbbe0f1d58aaa3f3a252ac129df288

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Tomi Koivisto
2. D. Mota
3. L. Lovisari
4. G. Schellenberger
5. S. Tsujikawa
6. Roya Mohayaee
7. T. Reiprich
8. D. Scolnic

In Nuclear and High Energy Physics

1. Tomi Koivisto
2. D. Mota
3. G. Schellenberger
4. T. Reiprich
5. D. Scolnic
6. F. Schmidt
7. S. Sarkar
8. L. Lovisari

Citations in the corpus

• Probing the anisotropic local Universe and beyond with SNe Ia data (2010, background): “…have been examined previously to test the isotropy of the Universe (Kolatt & Lahav 2001; Bonvin, Durrer & Kunz 2006; Gordon, Land & Slosar 2007; Schwarz & Weinhorst 2007; Gupta, Saini & Laskar 2008; Koivisto & Mota 2008a,b; Blomqvist, Enander & Mortsell 2008; Cooray, Holz & Caldwell 2010;…”
• Testing ΛCDM at the lowest redshifts with SN Ia and galaxy velocities (2016, background): “[20, 24, 29, 30, 32, 39]), it contains only SNe which have been placed on a consistent, and newly improved, calibration footing.”
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the LX–T scaling relation (2020, background): “…claim to detect mild-significance anisotropies in the SNIa samples that more often than not approximately match the direction of the CMB dipole (Schwarz & Weinhorst 2007; Antoniou & Perivolaropoulos 2010; Colin et al. 2011, 2017; Mariano & Perivolaropoulos 2012; Kalus et al. 2013; Appleby et…”
• Accelerating Cosmologies with an Anisotropic Equation of State (2007, background): “The luminosity distance as a probe of anisotropies has been considered in [88, 89].”