Abstract
AbstractWe use the LLAMA survey to study the density and outflow rate of ionized gas in a complete volume limited sample of local (<40 Mpc) luminous (43.0 < log LAGN(erg/s) < 44.5) AGN selected by very hard 14-195 keV X-rays. The detailed data available for this survey enable us to measure the density of the outflowing ionized gas in the central 300 pc of these AGN using three different and independent methods (the standard [SII] doublet ratio; a method comparing [OII] and [SII] ratios that include auroral and transauroral lines; and a recently proposed method based on the ionization parameter). For each method there is, as expected, a modest spread of densities among the AGN in the sample. But remarkably, the median densities for each method differ hugely, by an order of magnitude from below 400 cm-3 to almost 5000 cm-3. We discuss how the derived densities can be reconciled, and what the impact is on the implied outflow rate.
Highlights
That outflows driven by star formation and AGN play a fundamental role in the evolution of galaxies is undisputed
Our conclusion here is that, in contrast to some observations where a ‘core+wing’ decomposition may make sense, this is neither possible nor meaningful here. These nuclear measurements of local luminous AGN are fully dominated by AGN photoionized outflow, and any systemic component related to the host galaxy disk is negligible
We have measured the density of the ionized gas in three independent ways. In this data the [SII] doublet underestimates the density by a factor 5–10. It has been known for a long time that in AGN photoionized gas, the low excitation lines
Summary
That outflows driven by star formation and AGN play a fundamental role in the evolution of galaxies is undisputed. The density is estimated using the [SII] doublet ratio This is applicable up to ∼104 cm−3 for stellar HII regions; but may be biased in AGN photoionized gas because the high energy photons penetrate deep into the clouds and create a partially ionized zone, which is responsible for the enhanced emisson from low excitation lines around AGN. A set of inactive galaxies were selected to match them in terms of host galaxy type, mass (using H-band luminosity as a proxy), inclination, presence of a bar, and distance Small, this volume limited sample is sufficient for detailed studies of emission line ratios, the molecular and ionized gas kinematics and distributions, as well as the stellar kinematics and populations, in the nuclear and circumnuclear regions. We focus on the optical spectroscopy from Xshooter (Vernet et al 2011) of a subset comprising Seyfert 2 and inactive galaxies, using spectra extracted from a 1.8 × 1.8 aperture that corresponds to sizes of 200–350 pc at the distances of the targets
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