The Quasar Outflow Contribution to AGN Feedback: VLT Measurements of SDSS J0318-0600 (0911.3896v1)

Abstract: We present high spectral resolution VLT observations of the BAL quasar SDSS J0318-0600. This high quality data set allows us to extract accurate ionic column densities and determine an electron number density of n_e=10^3.3 +/- 0.2 cm^-3 for the main outflow absorption component. The heavily reddened spectrum of SDSS J0318-0600 requires purely silicate dust with a reddening curve characteristic of predominately large grains, from which we estimate the bolometric luminosity. We carry out photoionization modeling to determine the total column density, ionization parameter and distance of the gas and find that the photionization models suggest abundances greater than solar. Due to the uncertainty in the location of the dust extinction, we arrive at two viable distances for the main ouflow component from the central source, 6 and 18 kpc, where we consider the 6 kpc location as somewhat more physically plausable. Assuming the canonical global covering of 20% for the outflow and a distance of 6 kpc, our analysis yields a mass flux of 120 M_sun yr^-1 and a kinetic luminosity that is ~0.1% of the bolometric luminosity of the object. Should the dust be part of the outflow, then these values are ~4x larger. The large mass flux and kinetic luminosity make this outflow a significant contributor to AGN feedback processes.

Analysis of Quasar Outflows in SDSS J0318-0600

In the paper of active galactic nuclei (AGN) feedback mechanisms, understanding quasar outflows is crucial due to their role in influencing the evolution of supermassive black holes (SMBH) and their host galaxies. The paper at hand presents a detailed investigation of the broad absorption line (BAL) quasar SDSS J0318-0600 using high-resolution spectral data obtained from the Very Large Telescope (VLT). The authors focus on characterizing the physical properties of the quasar's outflow, thereby contributing to the broader understanding of AGN feedback.

Spectral Analysis and Ionization Dynamics

The central component of the analysis is the identification and measurement of ionic column densities from several ions, including $\mathrm{Si\,II}$, $\mathrm{Al\,III}$, $\mathrm{C\,IV}$, and $\mathrm{Fe\,II}$. By meticulously measuring these densities across different absorption features, the authors establish a comprehensive characterization of the outflow's electron density and ionization states. The paper reports an electron number density of $\log \, n_e = 3.3 \pm 0.2 \, \mathrm{cm}^{-3}$, determined through the analysis of silicon absorption lines and supported by other ionic transitions wherever possible.

Influence of Dust and Reddening

A notable feature of the SDSS J0318-0600 is its heavy reddening, which the authors attribute to silicate dust with a specific grain size distribution. The paper robustly models this intrinsic extinction and evaluates different scenarios for the location of dust relative to the quasar outflow, emphasizing challenges correlating dust with the outflow dynamics. Such modeling is vital given the effect of dust on the observed spectral energy distribution (SED) and its implications for photoionization modeling.

Photoionization Models and Abundance Patterns

Through detailed photoionization modeling, the authors explore the implications of different assumed SEDs and chemical abundances. Their findings suggest supersolar abundances, notably requiring enhancements in elements like Si, Fe, and Ni to match observed column densities accurately. The paper compares several metallicity models, concluding that a high metallicity scenario (up to 7 times solar) offers the best agreement with the observed spectral features.

Outflow Characteristics and AGN Feedback

The calculated mass flux and kinetic luminosity of the outflow present the outflow in SDSS J0318-0600 as a significant contributor to AGN feedback mechanisms. The authors provide estimates of kinetic luminosity relative to the bolometric luminosity of the quasar, highlighting the outflow's potential in influencing the intergalactic medium (IGM) and intracluster medium (ICM) within which these quasars reside. The kinetic luminosity determined—potentially driven by the large-scale dynamics of mass ejection over the quasar's active cycle—implicates this outflow in galaxy evolution models that require feedback processes to regulate star formation and SMBH growth.

Implications and Future Directions

The paper presents an intriguing insight into how sophisticated observations and modeling can bolster our understanding of quasar outflows. The findings regarding silicate dust and enriched abundances open pathways for further observational and theoretical research into similar BAL quasars, emphasizing the necessary role of outflow dynamics in AGN feedback theories. The continuation of such research promises to refine our comprehension of the delicate balance between quasar activity, galaxy dynamics, and interstellar medium evolution.

Future investigations may further explore outflows exhibiting high-ionization states and their relation to the putative dusty torus and potential relativistic effects beyond the capabilities of current models. Such advancements will contribute significantly to the precise quantification of outflow parameters and the establishment of more comprehensive AGN models.