[Paper Review] Bubbles and outflows: the novel JWST/NIRSpec view of the z=1.59 obscured quasar XID2028

G. Cresci, G. Tozzi+21 more|arXiv (Cornell University)|Jan 26, 2023

Galaxies: Formation, Evolution, Phenomena6 citations

TL;DR

Using JWST/NIRSpec IFU observations, this study reveals a complex, jet-driven expanding bubble in the z=1.59 obscured quasar XID2028, where a low-luminosity radio jet inflates a hot, low-surface-brightness bubble that drives a fast, extended ionized outflow. The data confirm a multi-phase outflow with a total mass outflow rate of ~110 M☉/yr, demonstrating the critical role of radio jets in AGN feedback at high redshift.

ABSTRACT

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, although direct observational evidence is still scarce and debated. Here we present Early Release Science JWST NIRSpec IFU observations of the z=1.59 prototypical obscured Active Galactic Nucleus (AGN) XID2028: This target represents a unique test case for studying quasar feedback at the peak epoch of AGN-galaxy co-evolution because extensive multi-wavelength coverage is available and a massive and extended outflow is detected in the ionised and molecular components. With the unprecedented sensitivity and spatial resolution of the JWST, the NIRSpec dataset reveals a wealth of structures in the ionised gas kinematics and morphology that were previously hidden in the seeing-limited ground-based data. In particular, we find evidence of an interaction between the interstellar medium of the galaxy and the quasar-driven outflow and radio jet that produces an expanding bubble from which the fast and extended wind detected in previous observations emerges. The new observations confirm the complex interplay between the AGN jet, wind and the interstellar medium of the host galaxy, highlighting the role of low-luminosity radio jets in AGN feedback. They also clearly show the new window that NIRSpec opens for detailed studies of feedback at high redshift.

Motivation & Objective

• To investigate the physical mechanism driving quasar feedback in a prototypical obscured AGN at z=1.59 during the peak epoch of galaxy evolution.
• To resolve the kinematic and morphological structure of ionized, neutral, and molecular outflows with unprecedented spatial and spectral resolution.
• To determine the role of low-luminosity radio jets in driving and shaping outflows in the host galaxy's interstellar medium.
• To quantify the energetics and mass outflow rates across ionized, neutral, and molecular gas phases.
• To test the hypothesis that expanding bubbles from jet-ISM interaction can simultaneously drive negative and positive feedback.

Proposed method

• Acquisition of deep, spatially resolved IFU spectroscopy using JWST/NIRSpec in the near-infrared (1–5 μm) to map ionized gas kinematics and morphology.
• Use of 3D radiative transfer modeling (MOKA^3D) to simulate the expanding bubble and collimated outflow geometry and match observed kinematics.
• Direct measurement of extinction and electron density in the outflow using diagnostic line ratios (e.g., [SII]/Hα, [OII]/Hβ) from spatially resolved spectra.
• Cross-identification of radio structures from archival VLA 3 GHz data to correlate jet emission with ionized outflow morphology.
• Estimation of mass outflow rates using kinematic decomposition of emission lines and assumptions on covering factors and ionization fractions.
• Comparison of observed outflow energetics with theoretical feedback thresholds to assess quenching potential.

Figure 1: H $\beta$ (left panel) and H $\alpha$ (right panel) spectral region fit in $5\times 5$ NIRSpec spaxels centred on the QSO position. In the upper panels, the data are shown in black, and the best-fitting broad line region components (e.g. H $\beta$ , H $\alpha$ , and FeII) are shown in blue

Experimental results

Research questions

• RQ1 What is the origin and morphology of the extended ionized outflow in XID2028, and how is it related to the radio jet?
• RQ2 How do the kinematics of ionized, neutral, and molecular gas phases interrelate in the feedback process?
• RQ3 To what extent do low-luminosity radio jets contribute to driving large-scale outflows in high-redshift obscured quasars?
• RQ4 What is the total mass outflow rate across all gas phases, and does it exceed the star formation rate?
• RQ5 Can the observed expanding bubble structure explain both the observed kinematics and the feedback efficiency?

Key findings

• The NIRSpec data reveal a filamentary, expanding bubble structure in the ionized gas, with enhanced emission at the edges, driven by a low-luminosity radio jet interacting with the host galaxy's interstellar medium.
• The bubble's kinematics are best reproduced by a 3D model combining a spherical expanding shell and a collimated outflow, confirming the jet-inflated origin of the outflow.
• The ionized gas mass outflow rate is measured as 6 ± 3 M☉/yr with a kinetic power of ~2 × 10^42 erg s⁻¹, indicating significant feedback energy input.
• A neutral gas outflow rate of ~30 M☉/yr is inferred from blueshifted NaID absorption, consistent with previous MgII-based estimates.
• The total mass outflow rate across ionized, neutral, and molecular phases reaches ~110 M☉/yr, implying a gas depletion timescale of only ~30 Myr.
• The observed feedback geometry supports both negative feedback (gas removal) and potential positive feedback (compression-induced star formation), though no residual Hα emission from star formation is detected.

Figure 2: Representative examples of our multi-component fitting of H $\beta$ and [OIII] emission lines in single spaxels from three different regions of the galaxy, as marked with coloured crosses in Fig. 3 . From the top, the panels refer to a nuclear region spaxel, to a filament spaxel (see text)