Neutral versus ionized gas kinematics at z ≃ 2.6: the AGN-host starburst galaxy PKS 0529-549

Abstract

We present a multiwavelength study of the AGN-host starburst galaxy PKS 0529-549 at z 2.6. We use (1) new ALMA observations of the dust continuum and of the [C I] 370 µm line, tracing molecular gas, (2) SINFONI spectroscopy of the [O III] 5007Å line, tracing ionized gas, and (3) ATCA radio continuum images, tracing synchrotron emission. Both [C I] and [O III] show regular velocity gradients, but their systemic velocities and position angles differ by ∼300 km s −1 and ∼30 • , respectively. The [C I]is consistent with a rotating disc, aligned with the dust and stellar continuum, while the [O III] likely traces an outflow, aligned with two AGN-driven radio lobes. We model the [C I] cube using 3D disc models, which give best-fit rotation velocities V rot 310 km s −1 and velocity dispersions σ V 30 km s −1 . Hence, the [C I] disc has V rot /σ V 10 and is not particularly turbulent, similar to local galaxy discs. The dynamical mass (∼10 11 M ) is comparable to the baryonic mass within the errors. This suggests that baryons dominate the inner galaxy dynamics, similar to massive galaxies at z 0. Remarkably, PKS 0529-549 lies on the local baryonic Tully-Fisher relation, indicating that at least some massive galaxies are already in place and kinematically relaxed at z 2.6. This work highlights the potential of the [C I] line to trace galaxy dynamics at high z, as well as the importance of multiwavelength data to interpret gas kinematics.

Quenching by gas compression and consumption

“…Its Lyα emission extent (∼40 kpc; Roettgering et al 1997) is well beyond its asymmetric double knot radio structure (two knots separated by ∼10 kpc; Broderick et al 2007). The radio lobes are embedded within and aligned with the more extended warm emission line gas traced by [O iii] and Hα, as expected for a bi-conical ionized gas outflow (Nesvadba et al 2017;Lelli et al 2018).…”

“…45 or ∼4 kpc in projection on the sky. We have already presented a detailed dynamical model of the [C i] (2-1) emission in Lelli et al (2018). The [C i] (2-1) emission is well-described by a dynamically cold rotating disk with rotation velocity of ∼310 km s −1 and intrinsic dispersion of σ [C i] 30 km s −1 (see Sect.…”

“…3.5.2), and similarly for the cold, star-forming gas from the [C i] spectrum (Sect. 4 and Lelli et al 2018). These narrow lines suggest strong and rapid dissipation of the mechanical energy in the gas.…”

“…3.5.1). On the other hand, ALMA [C i] observations of the cold star-forming gas of PKS 0529-549 has narrow velocity dispersion of σ [C i] 30 km s −1 , as we elaborated in Lelli et al (2018) and shall further discuss in Sect. 4.…”

“…We estimate Σ SFR and Σ gas for PKS 0529-549 using the SFR estimate from Table 5, gas mass inferred from the [C i] emission (Sect. 4), and use the deconvolved radius of the [C i] disk as the size of the star-forming region (R ∼ 4 kpc; Lelli et al 2018). As in Fig.…”