News – Page 13 – UWC Astrophysics

Multi-wavelength spectroscopic probes: prospects for primordial non-Gaussianity and relativistic effects

30/07/2021 by codman

Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), combining the information via multi-tracer cross-correlations that suppress cosmic variance on ultra-large scales. In …

Magnification and evolution biases in large-scale structure surveys

29/07/2021 by codman

Measurements of the galaxy number density in upcoming surveys such as Euclid and the SKA will be sensitive to distortions from lensing magnification and Doppler effects, beyond the standard redshift-space distortions. The amplitude of these contributions depends sensitively on magnification bias and evolution bias in the galaxy number density. Magnification bias quantifies the change in …

Contributions from primordial non-Gaussianity and General Relativity to the galaxy power spectrum

23/07/2021 by codman

We compute the real space galaxy power spectrum, including the leading order effects of General Relativity and primordial non-Gaussianity from the fNL and gNL parameters. Such contributions come from the one-loop matter power spectrum terms dominant at large scales, and from the factors of the non-linear bias parameter bNL (akin to the Newtonian bϕ). We use our modelling to assess the ability …

SKAO HI Intensity Mapping: Blind Foreground Subtraction Challenge

23/07/2021 by codman

Neutral Hydrogen Intensity Mapping (HI IM) surveys will be a powerful new probe of cosmology. However, strong astrophysical foregrounds contaminate the signal and their coupling with instrumental systematics further increases the data cleaning complexity. In this work, we simulate a realistic single-dish HI IM survey of a 5000~deg2 patch in the 950−1400 MHz range, with both the MID telescope …

Anti-symmetric clustering signals in the observed power spectrum

23/07/2021 by codman

n this paper, we study how to directly measure the effect of peculiar velocities in the observed angular power spectra. We do this by constructing a new anti-symmetric estimator of Large Scale Structure using different dark matter tracers. We show that the Doppler term is the major component of our estimator and we show that …

Direction Dependent Corrections in Polarimetric Radio Imaging III: A-to-Z Solver — Modeling the full Jones antenna aperture illumination pattern

22/07/2021 by codman

In this third paper of a series describing direction dependent corrections for polarimetric radio imaging, we present the the A-to-Z solver methodology to model the full Jones antenna aperture illumination pattern (AIP) with Zernike polynomials. In order to achieve thermal noise limited imaging with modern radio interferometers, it is necessary to correct for the instrumental …

The radio loudness of SDSS quasars from the LOFAR Two-metre Sky Survey: ubiquitous jet activity and constraints on star formation

21/07/2021 by codman

We examine the distribution of radio emission from ~42,000 quasars from the Sloan Digital Sky Survey, as measured in the LOFAR Two-Metre Sky Survey (LoTSS). We present a model of the radio luminosity distribution of the quasars that assumes that every quasar displays a superposition of two sources of radio emission: active galactic nuclei (jets) …

Considerations for optimizing photometric classification of supernovae from the Rubin Observatory

19/07/2021 by codman

Survey telescopes such as the Vera C. Rubin Observatory will increase the number of observed supernovae (SNe) by an order of magnitude, discovering millions of events; however, it is impossible to spectroscopically confirm the class for all the SNe discovered. Thus, photometric classification is crucial but its accuracy depends on the not-yet-finalized observing strategy of …

New group of galaxies discovered by the MIGHTEE team

06/07/2021 by codman

When the science world decided to embark on the Square Kilometre Array (SKA) project, serendipitous discovery – essentially chance findings – was boldly cited as a scientific goal. The MeerKAT telescope is already proving this bet right, as new, previously unidentified galaxies were discovered by the MIGHTEE project team in a well-studied area in the sky. …

Redshift Evolution of Galaxy Group X-ray Properties in Simba

05/07/2021 by codman

We examine the evolution of intragroup gas X-ray scaling relations for group-sized halos (M500=1012.3−15M⊙) in the Simba galaxy formation simulation. X-ray luminosity LX vs M500 shows increasing deviation from self-similarity from z=3→0, with M500<1013.5M⊙ halos exhibiting a large reduction in LXand slight increase in X-ray luminosity-weighted temperature TX. These shifts are driven by a strong drop in fgas with time for these halos, and coincides with …