arXiv subjects

J. Clancy

Publications and source records attributed to J. Clancy.

4 recordsLinked to original sources

arXiv2025

The Simons Observatory: forecasted constraints on primordial gravitational waves with the expanded array of Small Aperture Telescopes

We present updated forecasts for the scientific performance of the degree-scale (0.5 deg FWHM at 93 GHz), deep-field survey to be conducted by the Simons Observatory (SO). By 2027, the SO Small Aperture Telescope (SAT) complement will be doubled from three to six telescopes, including a doubling of the detector count in the 93 GHz and 145 GHz channels to 48,160 detectors. Combined with a planned extension of the survey duration to 2035, this expansion will significantly enhance SO's search for a $B$-mode signal in the polarisation of the cosmic microwave background, a potential signature of gravitational waves produced in the very early Universe. Assuming a $1/f$ noise model with knee multipole $\ell_{\rm knee} = 50$ and a moderately complex model for Galactic foregrounds, we forecast a $1\sigma$ (or 68% confidence level) constraint on the tensor-to-scalar ratio $r$ of $\sigma_r = 1.2\times10^{-3}$, assuming no primordial $B$-modes are present. This forecast assumes that 70% of the $B$-mode lensing signal can ultimately be removed using high resolution observations from the SO Large Aperture Telescope (LAT) and overlapping large-scale structure surveys. For more optimistic assumptions regarding foregrounds and noise, and assuming the same level of delensing, this forecast constraint improves to $\sigma_r = 7\times10^{-4}$. These forecasts represent a major improvement in SO's constraining power, being a factor of around 2.5 times better than what could be achieved with the originally planned campaign, which assumed the existing three SATs would conduct a five-year survey.

astro-ph.CO↗

arXiv2025

The Simons Observatory: Science Goals and Forecasts for the Enhanced Large Aperture Telescope

We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of Planck. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at $z < 3$; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from Rubin of overlapping sky.

astro-ph.IM↗

arXiv2023

Polarization fraction of Planck Galactic cold clumps and forecasts for the Simons Observatory

We measure the polarization fraction of a sample of $6282$ Galactic cold clumps at $353 \, \mathrm{GHz} $, consisting of $Planck$ Galactic cold clump (PGCC) catalogue category 1 objects (flux densities measured with signal-to-noise ratio $(\mathrm{S/N}) > 4$). We find the mean-squared polarization fraction at $353 \, \mathrm{GHz} $ to be $ \langle \Pi ^ 2 \rangle = [ 4.79 \pm 0.44 ] \times 10 ^ {-4} $ equating to an $ 11 \, \sigma $ detection of polarization. We test if the polarization fraction depends on the clumps' physical properties, including flux density, luminosity, Galactic latitude and physical distance. We see a trend towards increasing polarization fraction with increasing Galactic latitude, but find no evidence that polarization depends on the other tested properties. The Simons Observatory, with an angular resolution of order $1 \, \mathrm{arcmin } $ and noise levels between $22$ and $54$ $ \mu \mathrm{ K-arcmin } $ at high frequencies, will substantially enhance our ability to determine the magnetic field structure in Galactic cold clumps. At $\ge5\,\sigma$ significance, we predict the Simons Observatory will detect at least $\sim12,000$ cold clumps in intensity and $\sim430$ cold clumps in polarization. This number of polarization detections would represent a two orders of magnitude increase over the current $Planck$ results. We also release software that can be used to mask these Galactic cold clumps in other analyses.

astro-ph.GA↗

arXiv2021

Clash of Titans: a MUSE dynamical study of the extreme cluster merger SPT-CL J0307-6225

We present VLT/MUSE spectroscopy, along with archival Gemini/GMOS spectroscopy, Magellan/Megacam imaging, and Chandra X-ray emission for SPT-CL J0305-6225, a z=0.58 major merging galaxy cluster with a large BCG-SZ centroid separation and a highly disturbed X-ray morphology. The galaxy density distribution shows two main overdensities with separations of 0.144 and 0.017 arcmin to their respective BCGs. We characterize the central regions of the two colliding structures, namely 0307-6225N and 0307-6225S, finding velocity derived masses of $M_{200,N}=$ 2.44 $\pm$ 1.41 $\times10^{14}$ M$_\odot$ and $M_{200,S}=$ 3.16 $\pm$ 1.88 $\times10^{14}$ M$_\odot$, with a line-of-sight velocity difference of $|\Delta v| = 342$ km s$^{-1}$. The total dynamically derived mass is consistent with the SZ derived mass of 7.63 h$_{70}^{-1}$ $\pm$ 1.36 $\times10^{14}$ M$_\odot$. We model the merger using the Monte Carlo Merger Analysis Code, estimating a merging angle of 36$^{+14}_{-12}$ degrees with respect to the plane of the sky. Comparing with simulations of a merging system with a mass ratio of 1:3, we find that the best scenario is that of an ongoing merger that began 0.96$^{+0.31}_{-0.18}$ Gyr ago. We also characterize the galaxy population using H$\delta$ and [OII] $\lambda 3727$ \AA \ lines. We find that most of the emission-line galaxies belong to 0307-6225S, close to the X-ray peak position, with a third of them corresponding to red-cluster sequence galaxies, and the rest to blue galaxies with velocities consistent with recent periods of accretion. Moreover, we suggest that 0307-6225S suffered a previous merger, evidenced through the two equally bright BCGs at the center with a velocity difference of $\sim$674 km s$^{-1}$.

astro-ph.GA↗