CMC2 - Speakers
Dr Sebastian Von Hausegger
Invited opening talk: Title available soon
Abstract: Available soon.
Dr. Indranil Banik
Invited talk: The observed local supervoid could solve the Hubble and bulk flow tensions
Abstract: Galaxy number counts reveal that we are in a significant underdensity out to at least 300 Mpc (Keenan+ 2013; Wong+ 2022). This KBC void is incompatible with $\Lambda$CDM, but it can plausibly induce outflows sufficient to inflate the locally measured expansion rate by about 10% and thereby solve the Hubble tension (Haslbauer+ 2020). This detailed study used a semi-analytic MOND cosmological model as a guide to what might happen if structure formation is faster than expected in $\Lambda$CDM, as would be needed to form the KBC void. A generic consequence is that peculiar velocities would also be faster than in $\Lambda$CDM. We tested this using the bulk flow, the average velocity of matter in a sphere of fixed radius centred on our location (Watkins+ 2023). The observed bulk flow curve disagrees significantly with ΛCDM expectations independently of the local expansion rate. I found the predicted bulk flow curve in my previously published model using techniques similar to those used by observers, with Watkins acting as referee. Out of six combinations of void density profile and our location within the void, two gave a good match to the observed bulk flow curve. In addition, it has recently been reported that the apparent H_0 declines with redshift (Arxiv:2406.02019). This suggests a local resolution to the Hubble tension, which is in any case required for consistency with the ages of the oldest stars (Cimatti & Moresco 2023). Those interested in the local void can join a mailing list to discuss the idea further.
Dr Nikolaus Sulzenauer
Invited talk: Correlated galaxy formation at the scale of the sound horizon: What can proto superclusters tell us about the distant Cosmic Web?
Abstract: On scales much larger than 100 cMpc the Universe is assumed to be homogeneous and isotropic. Smaller-scale fluctuations grow into sheets, filaments, clusters, and voids over billions of years--resembling a large-scale cosmic web. Cosmological simulations trace the early evolution of these fluctuations in the first few Gys, but still struggle to capture the baryonic complexity (particularly that of cold gas and star-formation) that arises from non-linear structure growth at the galaxy level. Informed by observations of rare hyperluminous submillimeter galaxies (HyLIRG SMGs), with star-formation rates exceeding one thousand solar masses per year, the puzzling phenomenon of spatially correlated star-formation among massive galaxies is found. On comoving distances much larger than what is expected for the formation of individual galaxy clusters, several objects are now known to trace enhanced and correlated structure formation at the scale of the sound horizon in the early Universe. In this talk, I will present the case of HS1549+19 at z=2.85, a potential proto supercluster hosting a surprisingly large number of massive, bright SMGs--of which 15 are rare HyLIRGs--spread over a flattened "pancake"-like sheet of 20 x 30 pMpc (80 x 120 cMpc). The velocity distribution of this enormous collapsing sheet predicts a size that is larger than 99.99% of simulated protoclusters at z=3. Moreover, only a fraction of all galaxies will end up in a central massive cluster, instead, the SMGs will likely be pushed by the Hubble flow and assemble a rich supercluster by z=0. At this point, it is unclear whether HS1549+19 presents a real challenge to concordance cosmology as no adequate benchmark cosmological simulation exists to date that unites a large volume with appropriate star-formation physics to sample such extreme outliers.
For more details, please see this link (available soon)