The impact of AGN-driven winds on physical and observable galaxy sizes

Creators: Cochrane, R. K.; Anglés-Alcázar, D.; Mercedes-Feliz, J.; Hayward, C. C.; Faucher-Giguère, C.-A.; Wellons, S.; Terrazas, B. A.; Wetzel, A.; Hopkins, P. F.¹; Moreno, J; Su, K.-Y.; Somerville, R. S.

1. California Institute of Technology

Abstract

Without active galactic nucleus (AGN) feedback, simulated massive, star-forming galaxies become too compact relative to observed galaxies at z ≲ 2. In this paper, we perform high-resolution re-simulations of a massive (⁠𝑀⋆ ∼ 10¹¹ M_⊙⁠) galaxy at z ∼ 2.3, drawn from the Feedback in Realistic Environments (FIRE) project. In the simulation without AGN feedback, the galaxy experiences a rapid starburst and shrinking of its half-mass radius. We experiment with driving mechanical AGN winds, using a state-of-the-art hyper-Lagrangian refinement technique to increase particle resolution. These winds reduce the gas surface density in the inner regions of the galaxy, suppressing the compact starburst and maintaining an approximately constant half-mass radius. Using radiative transfer, we study the impact of AGN feedback on the magnitude and extent of the multiwavelength continuum emission. When AGN winds are included, the suppression of the compact, dusty starburst results in lowered flux at FIR wavelengths (due to decreased star formation) but increased flux at optical-to-near-IR wavelengths (due to decreased dust attenuation, in spite of the lowered star formation rate), relative to the case without AGN winds. The FIR half-light radius decreases from ∼1 to ∼0.1kpc in ≲40Myr when AGN winds are not included, but increases to ∼2kpc when they are. Interestingly, the half-light radius at optical-NIR wavelengths remains approximately constant over 35Myr⁠, for simulations with and without AGN winds. In the case without winds, this occurs despite the rapid compaction, and is due to heavy dust obscuration in the inner regions of the galaxy. This work highlights the importance of forward-modelling when comparing simulated and observed galaxy populations.

Copyright and License

© 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Acknowledgement

We thank the anonymous referee for helpful suggestions. RKC, DAA, and CCH are grateful for funding from the Flatiron Institute. The Flatiron Institute is supported by the Simons Foundation. DAA acknowledges support by NSF grants AST-2009687 and AST-2108944, CXO grant TM2-23006X, Simons Foundation Award CCA-1018464, and Cottrell Scholar Award CS-CSA-2023-028 by the Research Corporation for Science Advancement. CAFG was supported by NSF through grants AST-1715216, AST-2108230, and CAREER award AST-1652522; by NASA through grants 17-ATP17-0067 and 21-ATP21-0036; by STScI through grants HST-AR-16124.001-A and HST-GO-16730.016-A; by CXO through grant TM2-23005X; and by the Research Corporation for Science Advancement through a Cottrell Scholar Award. Support for PFH was provided by NSF Research Grants 1911233, 20009234, 2108318, NSF CAREER grant 1455342, NASA grants 80NSSC18K0562, HST-AR-15800. Numerical calculations were run on the Caltech compute cluster ‘Wheeler’, allocations AST21010 and AST20016 supported by the NSF and TACC, and NASA HEC SMD-16-7592. JM is funded by the Hirsch Foundation.

Some of the simulations presented in this work were run on the Flatiron Institute’s research computing facilities (Gordon-Simons, Popeye, and Iron compute clusters), supported by the Simons Foundation. Other simulations were run using Northwestern University’s compute cluster ‘Quest’ and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by NSF grant ACI-1053575.

This research has used the SVO Filter Profile Service, supported from the Spanish MINECO through grant AyA2014-55216.

Data Availability

The data underlying this article will be shared on reasonable request to the corresponding author. FIRE-2 simulations are publicly available (Wetzel et al. 2023) at http://flathub.flatironinstitute.org/fire. Additional FIRE simulation data are available at https://fire.northwestern.edu/data.

Code Availability

A public version of the GIZMO code is available at http://www.tapir.caltech.edu/~phopkins/Site/GIZMO.html.

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