A multi-wavelength study of a massive, active galaxy at $z\sim 2$: coupling the kinematics of the ionized and molecular gas

Abstract

We report a multi-wavelength study of the massive ($M_{\star} \gtrsim 10^{11} \rm{M}_{\odot}$), $z\sim 2$ star-forming galaxy GMASS 0953, which hosts an obscured AGN. We combined near-infrared observations of the GNIRS, SINFONI and KMOS spectrographs to study the kinematics of the [O III]$\lambda 5007$ and H$\alpha$ emission lines. Our analysis shows that GMASS 0953 may host an ionized disc extending up to 13 kpc, which rotates at a velocity of $V_{\rm{ion}} = 203^{+17}_{-20} {\ \rm kms}^{-1}$ at the outermost radius. Evidence of rotation on a smaller scale ($R \sim 1$ kpc) arises from the CO(J=6-5) line. The central velocity $V_{\rm{CO}} = 320^{+ 92}_{-53} {\ \rm kms}^{-1}$ traced by the molecular gas is higher than $V_{\rm{ion}}$, suggesting that the galaxy harbors a multi-phase disc with a rotation curve that peaks in the very central regions. The galaxy appears well located on the $z = 0$ baryonic Tully-Fisher relation. We also discuss the possibility that the [O III]$\lambda 5007$ and H$\alpha$ velocity gradients are due to a galactic-scale wind. Besides, we found evidence of an AGN-driven outflow traced by a broad blueshifted wing affecting the [O III]$\lambda 5007$ line, which presents a velocity offset $\Delta v = -535 \pm 152 {\ \rm kms}^{-1}$ from the systemic velocity. Because of the short depletion timescale ($\tau_{\rm{dep}}\sim 10^8$ yr) due to gas ejection and gas consumption by star formation activity, GMASS 0953 may likely evolve into a passive galaxy. However, the role of the AGN in depleting the gas reservoir of the galaxy is quite unclear because of the uncertainties affecting the outflow rate.