Abstract
ABSTRACT We present a comparative analysis of the $\rm CH^+$(1–0) and Lyα lines, observed with the Atacama Large Millimeter Array and Keck telescope, respectively, in the field of the submillimetre-selected galaxy SMM J02399−0136 at z ∼ 2.8, which comprises a heavily obscured starburst galaxy and a broad absorption line quasar, immersed in a large Lyα nebula. This comparison highlights the critical role played by turbulence in channelling the energy across gas phases and scales, splitting the energy trail between hot/thermal and cool/turbulent phases in the circumgalactic medium (CGM). The unique chemical and spectroscopic properties of $\rm CH^+$ are used to infer the existence of a massive (∼3.5 × 1010 M⊙), highly turbulent reservoir of diffuse molecular gas of radius ∼20 kpc coinciding with the core of the Lyα nebula. The whole cool and cold CGM is shown to be inflowing towards the galaxies at a velocity ∼ 400 km s−1. Several kpc-scale shocks are detected tentatively in $\rm CH^+$ emission. Their linewidth and specific location in space and velocity with respect to the high-velocity Lyα emission suggest that they lie at the interface of the inflowing CGM and the high-velocity outflowing gas. They signpost the feeding of CGM turbulence by active galactic nuclei- and stellar-driven outflows. The mass and energy budgets of the CGM require net mass accretion at a rate commensurate with the star formation rate. From this similarity, we infer that the merger-driven burst of star formation and black-hole growth are ultimately fuelled by large-scale gas accretion.
Highlights
In cosmological simulations, the growth of galaxies in the early universe results from the accretion of pristine gas in virialized dark matter haloes, modulo ejection of matter by stars and active galactic nuclei (AGNs; e.g. Madau & Dickinson 2014; Schaye et al 2015; Somerville & Dave 2015; Hopkins et al 2018; Tacconi, Genzel & Sternberg 2020)
We show the unique power of combining CH+ and Lyα spectroscopy to get some insight into the circumgalactic medium (CGM) gas dynamics on a 50 kpc scale
Thanks to the unique kinematic information carried out jointly by the CH+ and Lyα lines, augmented by the ancillary CO data, we are able to draw a coherent picture in which a large-scale inflow interacts with powerful AGN- and stellar-driven outflows, and where the mass and energy injection rates from both the galactic winds and gravitational accretion sustain the co-existence over the starburst phase of the massive turbulent CGM and the high star formation rate
Summary
The growth of galaxies in the early universe results from the accretion of pristine gas in virialized dark matter haloes, modulo ejection of matter by stars and active galactic nuclei (AGNs; e.g. Madau & Dickinson 2014; Schaye et al 2015; Somerville & Dave 2015; Hopkins et al 2018; Tacconi, Genzel & Sternberg 2020). Madau & Dickinson 2014; Schaye et al 2015; Somerville & Dave 2015; Hopkins et al 2018; Tacconi, Genzel & Sternberg 2020). The growth of galaxies in the early universe results from the accretion of pristine gas in virialized dark matter haloes, modulo ejection of matter by stars and active galactic nuclei This gas regulation involves complex exchanges of mass and energy that take place in the circumgalactic medium (CGM) around growing galaxies. While ejection is observed via ubiquitous ionized and neutral galactic winds (e.g. Rupke 2018; Faisst et al 2020; Veilleux et al 2020) and contributes to the self-regulation of cosmic star formation, evidence of accretion is slowly building up (Boucheet al. 2013; Schroetter et al 2019; Zabl et al 2019; Bielby et al 2020; Walter et al 2020; Fu et al 2021)
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