Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

We present a detailed kinematic study of a sample of 32 massive (9.5 ⩽ log( M * /M ⊙ ) ⩽ 10.9) main sequence star-forming galaxies (MS SFGs) at 4 < z < 6 from the ALMA-CRISTAL programme. The data consist of deep (up to 15 hr observing time per target), high-resolution (∼1 kpc) ALMA observations of [C  II ]158 μm line emission. This dataset allowed us to carry out the first systematic, kiloparsec-scale (kpc-scale) characterisation of the kinematics nature of typical massive SFGs at these epochs. We find that ∼50% of the sample are disk-like, with a number of galaxies located in systems of multiple components. Kinematic modelling reveals these main sequence disks exhibit high-velocity dispersions ( σ 0 ), with a median disk velocity dispersion of ∼70 km s −1 and V rot / σ 0 ∼ 2, which is consistent with dominant gravity driving. The elevated disk dispersions are in line with the predicted evolution based on Toomre theory and the extrapolated trends from z ∼ 0–2.5 MS star-forming disks. The inferred dark matter (DM) mass fraction within the effective radius f DM (< R e ) for the disk systems decreases with the central baryonic mass surface density. This is consistent with the trend reported by kinematic studies at z ≲ 3; roughly half the disks display f DM (< R e )≲ 30%. The CRISTAL sample of massive MS SFGs provides a reference of the kinematics of a representative population and extends the view onto typical galaxies beyond previous kpc-scale studies at z ≲ 3.

Abstract:

The recent observational evidence of deviations from the Lambda cold dark matter model points toward the presence of evolving dark energy. The simplest possibility consists of a cosmological scalar field <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"> <mi>φ</mi> </math> , dubbed “quintessence,” driving the accelerated expansion. We assess the evidence for the existence of such a scalar field. We find that, if the accelerated expansion is driven by quintessence, the data favor a potential energy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"> <mi>V</mi> <mo stretchy="false">(</mo> <mi>φ</mi> <mo stretchy="false">)</mo> </math> that is concave, i.e., <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"> <mrow> <msup> <mrow> <mi>m</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msup> <mo>=</mo> <msup> <mrow> <mi>d</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msup> <mi>V</mi> <mo>/</mo> <mi>d</mi> <msup> <mrow> <mi>φ</mi> </mrow> <mrow> <mn>2</mn> </mrow> </msup> <mo>&lt;</mo> <mn>0</mn> </mrow> </math> . Furthermore, and more significantly, the data strongly favor a scalar field that is nonminimally coupled to gravity [Bayes factor <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"> <mrow> <mi>log</mi> <mo stretchy="false">(</mo> <mi>B</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mn>7.34</mn> <mo>±</mo> <mn>0.6</mn> </mrow> </math> ], leading to time variations in the gravitational constant on cosmological scales, and the existence of fifth forces on smaller scales. The fact that we do not observe such fifth forces implies that new physics must come into play on noncosmological scales that quintessence is an unlikely explanation for the observed cosmic acceleration.

Abstract:

We measure the cross-correlation between cosmic shear from the third-year release of the Dark Energy Survey, thermal Sunyaev-Zel’dovich (tSZ) maps from , and x-ray maps from ROSAT. We investigate the possibility of developing a physical model able to jointly describe both measurements, simultaneously constraining the spatial distribution and thermodynamic properties of hot gas. We find that a relatively simple model is able to describe both sets of measurements and to make reasonably accurate predictions for other observables (the tSZ autocorrelation, its cross-correlation with x-rays, and tomographic measurements of the bias-weighted mean gas pressure). We show, however, that contamination from x-ray active galactic nuclei (AGN), as well as the impact of nonthermal pressure support, must be incorporated in order to fully resolve tensions in parameter space between different data combinations. Combining the tSZ and x-ray cross-correlations with cosmic shear we obtain simultaneous constraints on the mass scale at which half of the gas content has been expelled from the halo, ${\log }_{10}{M}_c=14.83_{-0.23}^{+0.16}$ , on the polytropic index of the gas, $\mathrm{\Gamma }=1.144_{-0.013}^{+0.016}$ , and on the ratio of the central gas temperature to the virial temperature ${\alpha }_T=1.30_{-0.28}^{+0.15}$ , marginalizing over AGN contributions to the signal.

Abstract:

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 the Planck satellite. 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 redshifts 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 the Vera C. Rubin Observatory of overlapping sky.