codman

Cosmological constraints on Newton’s gravitational constant

We study the variation of the gravitational Newton’s constant on cosmological scales in scalar-tensor theories of gravity. We focus on the simplest models of scalar-tensor theories with a coupling to the Ricci scalar of the form F(σ)=N2pl+ξσ2, such as extended Jordan-Brans-Dicke (Npl=0), or a non-minimally coupled scalar field with Npl=Mpl, which permits the gravitational constant to vary …

Read more

Measurements of the diffuse Galactic synchrotron spectral index and curvature from MeerKLASS pilot data

21cm intensity mapping experiments are bringing an influx of high spectral resolution observational data in the ∼100 MHz −1 GHz regime. We use pilot 971−1075 MHz data from MeerKAT in single-dish mode, recently used to test the calibration and data reduction scheme of the upcoming MeerKLASS survey, to probe the spectral index of diffuse synchrotron emission below 1 GHz within 145∘<α<180∘, −1∘<δ<8∘. Through …

Read more

Inferring halo masses with Graph Neural Networks

Understanding the halo-galaxy connection is fundamental in order to improve our knowledge on the nature and properties of dark matter. In this work we build a model that infers the mass of a halo given the positions, velocities, stellar masses, and radii of the galaxies it hosts. In order to capture information from correlations among …

Read more

High Molecular-Gas to Dust Mass Ratios Predicted in Most Quiescent Galaxies

Observations of cold molecular gas reservoirs are critical for understanding the shutdown of star formation in massive galaxies. While dust continuum is an efficient and affordable tracer, this method relies upon the assumption of a “normal” molecular-gas to dust mass ratio, δGDR, typically of order one hundred. Recent null detections of quiescent galaxies in deep dust …

Read more

Large MeerKAT data release reveals beautiful new cosmic puzzles

An international team led by a young South African researcher has just announced a comprehensive overview paper for the MeerKAT Galaxy Cluster Legacy Survey (MGCLS). The paper to be published in the Astronomy & Astrophysicsjournal presents some exciting, novel results, and is accompanied by the public release of a huge trove of curated data now available …

Read more

Superhorizon perturbations: A possible explanation of the Hubble–Lemaître Tension and the Large Scale Anisotropy of the Universe

Current cosmological observations point to a serious discrepancy between the observed Hubble parameter obtained using direct and cosmic microwave background radiation (CMBR) measurements. Besides this, the so called Hubble–Lemaître tension, we also find considerable evidence in diverse cosmological observables that indicate violation of the cosmological principle. In this paper, we suggest that both these discrepancies …

Read more

Real-time detection of anomalies in large-scale transient surveys

New time-domain surveys, such as the Rubin Observatory Legacy Survey of Space and Time (LSST), will observe millions of transient alerts each night, making standard approaches of visually identifying new and interesting transients infeasible. We present two novel methods of automatically detecting anomalous transient light curves in real-time. Both methods are based on the simple …

Read more

COSMOS2020: A panchromatic view of the Universe to z∼10 from two complementary catalogs

The Cosmic Evolution Survey (COSMOS) has become a cornerstone of extragalactic astronomy. Since the last public catalog in 2015, a wealth of new imaging and spectroscopic data has been collected in the COSMOS field. This paper describes the collection, processing, and analysis of this new imaging data to produce a new reference photometric redshift catalog. …

Read more

KiDS-1000 Cosmology: machine learning -accelerated constraints on Interacting Dark Energy with CosmoPower

We derive constraints on a coupled quintessence model with pure momentum exchange from the public ∼1000 deg2 cosmic shear measurements from the Kilo-Degree Survey and the Planck 2018 Cosmic Microwave Background data. We compare this model with ΛCDM and find similar χ2 and log-evidence values. We accelerate parameter estimation by sourcing cosmological power spectra from the neural network emulator CosmoPower. We highlight the …

Read more