Observations of Feedback from Radio-Quiet Quasars - II. Kinematics of Ionized Gas Nebulae (1305.6922v2)

Abstract: The prevalence and energetics of quasar feedback is a major unresolved problem in galaxy formation theory. In this paper, we present Gemini Integral Field Unit observations of ionized gas around eleven luminous, obscured, radio-quiet quasars at z~0.5 out to ~15 kpc from the quasar; specifically, we measure the kinematics and morphology of [O III]5007 emission. The round morphologies of the nebulae and the large line-of-sight velocity widths (with velocities containing 80% of the emission as high as 1000 km/s combined with relatively small velocity difference across them (from 90 to 520 km/s) point toward wide-angle quasi-spherical outflows. We use the observed velocity widths to estimate a median outflow velocity of 760 km/s, similar to or above the escape velocities from the host galaxies. The line-of-sight velocity dispersion declines slightly toward outer parts of the nebulae (by 3% per kpc on average). The majority of nebulae show blueshifted excesses in their line profiles across most of their extents, signifying gas outflows. For the median outflow velocity, we find a kinetic energy flow between 4x10^{44} and 3x10^{45} erg/s and mass outflow rate between 2000 and 20000 Msun/yr. These values are large enough for the observed quasar winds to have a significant impact on their host galaxies. The median rate of converting bolometric luminosity to kinetic energy of ionized gas clouds is ~2%. We report four new candidates for "super-bubbles" -- outflows that may have broken out of the denser regions of the host galaxy.

• The paper reveals quasi-spherical, high-velocity outflows in radio-quiet quasars, with [O III] emission widths often exceeding 1000 km/s.
• The paper employs Gemini IFU spectroscopy to spatially resolve ionized gas nebulae extending up to 15 kpc from the quasar centers.
• The paper demonstrates that converting about 2% of bolometric luminosity into kinetic energy can significantly impact host galaxies by potentially quenching star formation.

Observations of Feedback from Radio-Quiet Quasars: Kinematics of Ionized Gas Nebulae

The paper of quasar feedback is integral to the understanding of galaxy formation and evolution. In this paper, the authors investigate the kinematics of ionized gas around a sample of eleven radio-quiet quasars at a median redshift of $z \sim 0.5$. The primary aim is to understand how such quasars influence the interstellar medium of their host galaxies. By utilizing the Gemini Integral Field Unit, the spatially resolved kinematic data of ionized gas, specifically the [O III]λ5007Å emission, was analyzed to shed light on the nature of these interactions.

Key Findings

1. Kinematic Structure: The paper reveals that such quasars exhibit wide-angle, quasi-spherical gas outflows extending up to $\sim$15 kpc. The velocity dispersion of these ionized gas regions is exceedingly high, with $W_{80}$ values (velocity width enclosing 80% of the emission) often surpassing 1000 km s$^{-1}$. This indicates that the gas is not gravitationally bound to the galaxy, reinforcing the scenario of a dynamic, non-equilibrium state induced by quasar activity.
2. Morphological and Velocity Considerations: The nebulae exhibit relatively round morphologies and significant blueshifts, suggesting wide-angle outflows rather than narrowly collimated jets. The variations in line-of-sight velocities are rather modest compared to the line widths, supporting the hypothesis of nearly spherical outflows with collimation and extinction effects being minimal. This simplicity contrasts with the complex morphologies seen in radio-loud quasars, where radio jets may dominate.
3. Outflow Velocity and Energy: A median outflow velocity of approximately 760 km s$^{-1}$ was estimated, which is comparable to or greater than the escape velocities from many of the host galaxies. Derived kinetic energy fluxes of the outflows are substantial, ranging from $4 \times 10^{44}$ to $3 \times 10^{45}$ erg s$^{-1}$, signifying a significant energy impact upon the host systems.
4. Super-bubble Candidates: The paper identifies candidates for "super-bubbles," representing gas outflows that break through dense regions of the host galaxy. These phenomena imply that quasars can create pathways for gas to escape from the central dense regions of galaxies.
5. Feedback Implications: The conversion rate of bolometric luminosity to the kinetic energy of ionized gas is around 2%. This conversion efficiency is sufficient to suggest that over typical quasar lifetimes, these feedback effects could substantially inhibit star formation by ejecting or heating the gas needed for star formation.

Implications and Future Directions

The paper supports the role of quasars in galaxy evolution through energetic outflows that can potentially quench star formation. The findings invite further exploration into the spatially resolved kinematics of other quasar types, including those at different evolutionary stages or in different environmental contexts. The notable presence of quasi-spherical outflows induces a reconsideration of quasar feedback models, emphasizing wide-angle wind mechanisms over jet-dominated influences, especially in radio-quiet systems.

In future research, integrating multi-wavelength observations (e.g., radio, infrared) and more advanced simulations could lead to a more comprehensive understanding of the multidimensional feedback processes and their long-term effects on galaxy properties. This exploration is vital to elucidating the complex dance between black holes and galaxies that governs the cosmic landscape.