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Register a new userMeasuring AGN Feedback with the Sunyaev-Zeldovich Effect
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One of the most important and poorly-understood issues in structure formation is the role of outflows driven by active galactic nuclei (AGN). Using large-scale cosmological simulations, we compute the impact of such outflows on the small-scale distribution of the cosmic microwave background (CMB). Like gravitationally-heated structures, AGN outflows induce CMB distortions both through thermal motions and peculiar velocities, by processes known as the thermal and kinetic Sunyaev-Zeldovich (SZ) effects, respectively. For AGN outflows the thermal SZ effect is dominant, doubling the angular power spectrum on arcminute scales. But the most distinct imprint of AGN feedback is a substantial increase in the thermal SZ distortions around elliptical galaxies, post-starburst ellipticals, and quasars, which is linearly proportional to the outflow energy. While point source subtraction is difficult for quasars, we show that by appropriately stacking microwave measurements around early-type galaxies, the new generation of small-scale microwave telescopes will be able to directly measure AGN feedback at the level important for current theoretical models.
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Combined with X-ray imaging and spectral data, observations of the Sunyaev-Zeldovich effect (SZE) can be used to determine direct distances to galaxy clusters. These distances are independent of the extragalactic distance ladder and do not rely on clusters being standard candles or rulers. Observations of the SZE have progressed from upper limits to high signal-to-noise ratio detections and imaging of the SZE. SZE/X-ray determined distances to galaxy clusters are beginning to trace out the theoretical angular-diameter distance relation. The current ensemble of 41 SZE/X-ray distances to galaxy clusters imply a Hubble constant of H_0~ 61 +/- 3 +/- 18 km s-1 Mpc-1, where the uncertainties are statistical followed by systematic at 68% confidence. With a sample of high-redshift galaxy clusters, SZE/X-ray distances can be used to measure the geometry of the Universe.
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalogue, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We constrain the form of the far-infrared emission and find 3$sigma$-4$sigma$ evidence for the thermal Sunyaev-Zeldovich (SZ) effect, characteristic of a hot ionized gas component with thermal energy $(6.2 pm 1.7)times 10^{60}$ erg. This amount of thermal energy is greater than expected assuming only hot gas in virial equilibrium with the dark matter haloes of $(1-5)times 10^{12}h^{-1}$M$_odot$ that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. Our measurements are consistent with quasars depositing up to $(14.5 pm 3.3)~tau_8^{-1}$ per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is $tau_8times~10^8$ yr. For high quasar host masses, $sim10^{13}h^{-1}$M$_odot$, this percentage will be reduced. Furthermore, the uncertainty on this percentage is only statistical and additional systematic uncertainties enter at the 40 per cent level. The SEDs are dust dominated in all bands and we consider various models for dust emission. While sufficiently complex dust models can obviate the SZ effect, the SZ interpretation remains favoured at the 3$sigma$-4$sigma$ level for most models.
The nature and energetics of feedback from thermal winds in quasars can be constrained via observations of the Sunyaev-Zeldovich Effect (SZE) induced by the bubble of thermal plasma blown into the intergalactic medium by the quasar wind. In this letter, we present evidence that we have made the first detection of such a bubble, associated with the hyperluminous quasar HE0515-4414. The SZE detection is corroborated by the presence of extended emission line gas at the same position angle as the wind. Our detection appears on only one side of the quasar, consistent with the SZE signal arising from a combination of thermal and kinetic contributions. Estimates of the energy in the wind allow us to constrain the wind luminosity to the lower end of theoretical predictions, ~0.01% of the bolometric luminosity of the quasar. However, the age we estimate for the bubble, ~0.1 Gyr, and the long cooling time, ~0.6 Gyr, means that such bubbles may be effective at providing feedback between bursts of quasar activity.
Energetic feedback from active galactic nuclei (AGNs) is often used in simulations to resolve several outstanding issues in galaxy formation, but its impact is still not fully understood. Here we derive new constraints on AGN feedback by comparing observations and simulations of the thermal Sunyaev-Zeldovich (tSZ) effect. We draw on observational results presented in Spacek et al. (2016, 2017) who used data from the South Pole Telescope (SPT) and Atacama Cosmology Telescope (ACT) to measure the tSZ signal from >= 10^11 M_Sun and >= 1 Gyr galaxies at z=0.5-1.0 (low-z) and z=1.0-1.5 (high-z). Using the large-scale cosmological hydrodynamical simulations Horizon-AGN and Horizon-NoAGN, which include and omit AGN feedback, we extract simulated tSZ measurements around galaxies equivalent to the observational work. We find that the Horizon-AGN results only differ from the SPT measurements at levels of 0.4 sigma (low-z) and 0.6 sigma (high-z), but differ from the ACT measurements by 3.4 sigma (low-z) and 2.3 sigma (high-z). The Horizon-NoAGN results provide a slightly better fit to the SPT measurements by differing by 0.2 sigma (low-z) and 0.4 sigma (high-z), but a significantly better match to the ACT measurements by differing by only 0.5 sigma (low-z) and 1.4 sigma (high-z). We conclude that, while the lower-mass (<~ 5 x 10^11 M_Sun) SPT results allow for the presence AGN feedback energy, the higher-mass (>~ 5 x 10^11 M_Sun) ACT results show significantly less energy than predicted in the simulation including AGN feedback, while more closely matching the simulation without AGN feedback, indicating that AGN feedback may be milder than often predicted in simulations.
An understanding of astrophysical feedback is important for constraining models of galaxy formation and for extracting cosmological information from current and future weak lensing surveys. The thermal Sunyaev-Zeldovich effect, quantified via the Compton-$y$ parameter, is a powerful tool for studying feedback, because it directly probes the pressure of the hot, ionized gas residing in dark matter halos. Cross-correlations between galaxies and maps of Compton-$y$ obtained from cosmic microwave background surveys are sensitive to the redshift evolution of the gas pressure, and its dependence on halo mass. In this work, we use galaxies identified in year one data from the Dark Energy Survey and Compton-$y$ maps constructed from Planck observations. We find highly significant (roughly $12sigma$) detections of galaxy-$y$ cross-correlation in multiple redshift bins. By jointly fitting these measurements as well as measurements of galaxy clustering, we constrain the halo bias-weighted, gas pressure of the Universe as a function of redshift between $0.15 lesssim z lesssim 0.75$. We compare these measurements to predictions from hydrodynamical simulations, allowing us to constrain the amount of thermal energy in the halo gas relative to that resulting from gravitational collapse.
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