Gastrophysics

Uncovering the Evolution of Galaxies and Gas

Key CMB-HD Science Objectives

1. Separately measure the density, pressure, temperature, and velocity profiles of intrahalo gas, as a function of halo mass and redshift, by combining CMB-HD’s tSZ and kSZ measurements.

1. Separately measure the density, pressure, temperature, and velocity profiles of intrahalo gas, as a function of halo mass and redshift, by combining CMB-HD’s tSZ and kSZ measurements. This would probe thermal, non-thermal, and non-equilibrium processes associated with cosmic accretion, merger dynamics, and energy feedback from stars and supermassive black holes and their impact on the gas.

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2. Probe the gas physics in and around halos out to z ∼ 2 and with masses below 1012 M⊙, by stacking low-mass and high-redshift halos detected via the tSZ effect in the CMB-HD survey.

2. Probe the gas physics in and around halos out to z ∼ 2 and with masses below 1012 M⊙, by stacking low-mass and high-redshift halos detected via the tSZ effect in the CMB-HD survey. The circumgalactic reservoirs of 1012 M⊙ (Milky-Way-mass) halos are predicted by multiple simulations, such as EAGLE and Illustris-TNG, to be intimately linked to the appearance of, and activity within, the galaxy. These and other simulations find that galactic star-formation rates, colors, and morphologies are inextricably linked not only to the mass in the circumgalactic medium but also to the location of baryons ejected beyond R200,c, which can be uniquely constrained by CMB-HD. Thus, the science gain of such measurements is a more complete understanding of galaxy cluster astrophysics, the physics of the intergalactic and circumgalactic medium, and galaxy evolution.

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GASTRO

Figure 1:

SZ signals of a merging galaxy cluster extracted from the Omega500 cosmological hydrodynamical simulation; for comparison, some X-ray quantities are shown. Here is the thermal Sunyaev-Zel’dovich (tSZ) signal (top-left), kinetic Sunyaev-Zel’dovich (kSZ) signal (top-middle), projected mass-weighted temperature (top-right), X-ray surface brightness (bottom-left), electron opacity (bottom-middle), and projected X-ray temperature (bottom-right). The combination of tSZ and kSZ measurements from CMB-HD allows one to separate the pressure, density, temperature, and velocity profiles of the gas.

References (see these works and references therein)

K. Nelson, E. T. Lau, D. Nagai, D. H. Rudd, and L. Yu. Weighing Galaxy Clusters with Gas. II.
On the Origin of Hydrostatic Mass Bias in ΛCDM Galaxy Clusters. ApJ, 782:107, February 2014.
(Reference for Figure 1.)

Sehgal, N et al, CMB-HD:
Astro2020 RFI Response, Feb 2020, https://arxiv.org/abs/2002.12714

Sehgal, N et al, CMB-HD:
An Ultra-Deep, High-Resolution Millimeter-Wave Survey Over Half the Sky, September 2019,
https://arxiv.org/pdf/1906.10134.pdf