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| Main Authors: | , |
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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2604.02470 |
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| _version_ | 1866911660442124288 |
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| author | Dressler, Alan Monson, Andrew |
| author_facet | Dressler, Alan Monson, Andrew |
| contents | We used the FourStar near-IR camera on Magellan-Baade to obtain high S/N H-Band imaging of 66 galaxies with radial velocities of 2000 < V < 5000 km/s. Our goal was to use the superior distance measurements of surface-brightness-fluctuations (SBF) to derive ``peculiar velocities'' to test claims that the CMB dipole anisotropy, equivalent to $\approx$600 km/s with respect to the Local Group, arises from a 'local' overdensity in the galaxy/dark-matter distribution -- the Great Attractor. SBF's ability to measure distances with 5% accuracy confirms a strong flow over a steradian of the sky peaking at Vpec $\sim$ 1000 km/s and converging to zero at D $\approx$70 Mpc from the Local Group. The modest spatial extent of this flow $R_V$ $\sim$ 5000 km/s is consistent with the original Great Attractor model (a diameter D $\sim$ 140 Mpc), as well as the magnitude and direction of the CMB dipole anisotropy, and the power spectrum of CMB fluctuations -- the latter two arguably the most secure measurements in astrophysics. In contrast, our results are at-odds with reports of comparable amplitude 'bulk flows' on scales of hundreds of Mpc that themselves may be inconsistent with the expected fluctuations in the CMB for a $Λ$CDM universe. We contend that only distance-estimators as accurate as SBF are able settle the question of whether the CMB dipole arises from the gravitational influence of large-scale structure within, or without $\sim$100 Mpc of the Local Group. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_02470 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Return to the Great Attractor: Strong Evidence for a Steradian-sized Flow Converging at $\sim$70 Mpc within the GA Supercluster and Aligned with the CMB Dipole Dressler, Alan Monson, Andrew Cosmology and Nongalactic Astrophysics We used the FourStar near-IR camera on Magellan-Baade to obtain high S/N H-Band imaging of 66 galaxies with radial velocities of 2000 < V < 5000 km/s. Our goal was to use the superior distance measurements of surface-brightness-fluctuations (SBF) to derive ``peculiar velocities'' to test claims that the CMB dipole anisotropy, equivalent to $\approx$600 km/s with respect to the Local Group, arises from a 'local' overdensity in the galaxy/dark-matter distribution -- the Great Attractor. SBF's ability to measure distances with 5% accuracy confirms a strong flow over a steradian of the sky peaking at Vpec $\sim$ 1000 km/s and converging to zero at D $\approx$70 Mpc from the Local Group. The modest spatial extent of this flow $R_V$ $\sim$ 5000 km/s is consistent with the original Great Attractor model (a diameter D $\sim$ 140 Mpc), as well as the magnitude and direction of the CMB dipole anisotropy, and the power spectrum of CMB fluctuations -- the latter two arguably the most secure measurements in astrophysics. In contrast, our results are at-odds with reports of comparable amplitude 'bulk flows' on scales of hundreds of Mpc that themselves may be inconsistent with the expected fluctuations in the CMB for a $Λ$CDM universe. We contend that only distance-estimators as accurate as SBF are able settle the question of whether the CMB dipole arises from the gravitational influence of large-scale structure within, or without $\sim$100 Mpc of the Local Group. |
| title | Return to the Great Attractor: Strong Evidence for a Steradian-sized Flow Converging at $\sim$70 Mpc within the GA Supercluster and Aligned with the CMB Dipole |
| topic | Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2604.02470 |