Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

We analyse the large-scale angular clustering of quasars in the Gaia-unWISE quasar catalog, Quaia, and their cross-correlation with maps of the lensing convergence of the Cosmic Microwave Background (CMB), to constrain the level of primordial non-Gaussianity (PNG). Specifically, we target the scale-dependent bias that would be induced by PNG on biased tracers of the matter inhomogeneities on large scales. The Quaia sample is particularly well suited for this analysis, given the large effective volume covered, and our ability to map out the main potential sources of systematic contamination and mitigate their impact. Using the universality relation to characterise the response of the quasar overdensity to PNG (pϕ = 1), we report constraints on the local-type PNG parameter f NL of f NL = -20.5+19.0 -18.1 (68% C.L.) by combining the quasar auto-correlation and its cross-correlation with CMB lensing in two tomographic redshift bins (or f NL = -28.7+26.1 -24.6 if assuming a lower response for quasars, pϕ = 1.6). The error on f NL can be further improved if the cross-correlation between the tomographic redshift bins is included. Using the CMB lensing cross-correlations alone, we find fNL = -13.8+26.7 -25.0 and fNL = -15.6+42.3 -34.8 for pϕ = 1 and pϕ = 1.6 respectively. These are the tightest constraints on fNL to date from angular clustering statistics and cross-correlations with CMB lensing.

Abstract:

One of the most pressing problems in current cosmology is the cause of the Hubble tension. We revisit a two-rung distance ladder, composed only of Cepheid periods and magnitudes, anchor distances in the Milky Way, Large Magellanic Cloud, NGC4258, and host galaxy redshifts. We adopt the SH0ES (Supernovae and H0 for the Equation of State of dark energy) data for the most up-to-date and carefully vetted measurements, where the Cepheid hosts were selected to harbour also Type Ia supernovae. We introduce two important improvements: a rigorous selection modelling and a state-of-the-art density and peculiar velocity model using Manticore-Local, based on the Bayesian Origin Reconstruction from Galaxies (borg) algorithm. We infer H0 = 71.7 ± 1.3 km s^-1 Mpc^-1, assuming the Cepheid host sample was selected by supernova magnitudes. However, the actual selection criteria are not clear, and other assumptions can increase H0 by up to one statistical standard deviation. The posterior has a lower central value and a 45 percent smaller uncertainty than a previous study using the same distance-ladder data. The result is also slightly lower than the supernova-based SH0ES inferred value of H0 = 73.2 ± 0.9 km s^-1 Mpc^-1, and is in 3.3σ tension with the latest cosmic microwave background results in the standard cosmological model. These results demonstrate that a measurement of H0 of sufficient precision to weigh in on the Hubble tension is achievable using second-rung data alone, underscoring the importance of robust and accurate statistical and velocity-field modelling.

Abstract:

Star clusters are valuable indicators of galaxy evolution, offering insights into the buildup of stellar populations across cosmic time. Understanding the intrinsic star cluster populations of dwarf galaxies is particularly important given these systemsa role in the hierarchical growth of larger systems. We use data from Euclida s Early Release Observation programme to study star clusters in two star-forming dwarf irregular galaxies in the Local Group, NGC 6822 and IC 10 [Ma ~ (1 4) A-108 Ma ]. With Euclid, star clusters are resolved into individual stars across the main bodies and haloes of both galaxies. Through visual inspection of the IE images, we uncover 30 new star cluster candidates in NGC 6822 and 16 in IC 10, ranging from compact to diffuse extended clusters. We compile and re-evaluate previously identified literature candidates, resulting in final combined catalogues of 52 (NGC 6822) and 71 (IC 10) cluster candidates with confidence-based classifications. We present homogeneous photometry in IE, YE, JE, and HE, and in archival UBVRI data, alongside size measurements and properties derived from the spectral energy distribution fitting code BAGPIPES. Through synthetic cluster injection, we conclude our sample is ~50% complete to M a ² 103 Ma for ages a ²100 Myr, and to M a ² 2 A-104 Ma for ages of ~10 Gyr. We find that IC 10 has more young clusters than NGC 6822, and its young clusters extend to higher masses, consistent with its starburst nature. We find several old massive (a ³105 Ma ) clusters in both dwarfs, including an exceptional cluster in NGC 6822a s outskirts with a mass of 1.3 A-106 Ma , nearly twice as massive as any other old cluster in either galaxy. In NGC 6822, we also identify a previously undetected, old, and extended cluster (Rh = 12.4 ± 0.11 pc). Using well-defined criteria, we identify 11 candidate GCs in NGC 6822 and nine in IC 10. Both galaxies have high specific frequencies (SN) for their luminosities but remain consistent with the known GC scaling relationships in the low-luminosity regime.