Journal Article

The impact of the warm outflow in the young (GPS) radio source and ULIRG PKS 1345+12 (4C 12.50)

J. Holt, C. N. Tadhunter, R. Morganti and B. H. C. Emonts

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 410, issue 3, pages 1527-1536
Published in print January 2011 | ISSN: 0035-8711
Published online January 2011 | e-ISSN: 1365-2966 | DOI:
The impact of the warm outflow in the young (GPS) radio source and ULIRG PKS 1345+12 (4C 12.50)

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We present new deep Very Large Telescope (VLT)/FORS optical spectra with intermediate resolution and large wavelength coverage of the compact radio source and ultra-luminous IR galaxy (ULIRG) PKS 1345+12 (4C 12.50; z= 0.122), taken with the aim of investigating the impact of the nuclear activity on the circumnuclear interstellar medium (ISM). PKS 1345+12 is a powerful quasar [L(Hβ)NLR∼ 1042 erg s−1] and is also the best studied case of an emission line outflow in a ULIRG. Using the density-sensitive transauroral emission lines [S ii]4068,4076 and [O ii]7318,7319,7330,7331, we pilot a new technique to accurately model the electron density for cases in which it is not possible to use the traditional diagnostic [S ii]6716/6731, namely sources with highly broadened complex emission line profiles and/or high (Ne≳ 104 cm−3) electron densities. We measure electron densities of Ne= (2.94+0.71−1.03) × 103 cm−3, Ne= (1.47+0.60−0.47) × 104 cm−3 and Ne= (3.16+1.66−1.01) × 105 cm−3 for the regions emitting the narrow, broad and very broad components, respectively. We therefore calculate a total mass outflow rate of M yr−1, similar to the range estimated for another compact radio source, PKS 1549−79. We estimate the total mass in the warm gas outflow is Mtotal= (8+3−3) × 105 M with filling factors of ε= (4.4+1.8−1.5) × 10−4 and ε= (1.6+0.7−0.5) × 10−7 for the regions emitting the broad and very broad components, respectively. The total kinetic power in the warm outflow is erg s−1. Taking the black hole properties published by Dasyra et al., we find that only a small fraction [] of the available accretion power is driving the warm outflow in PKS 1345+12, which is significantly less than that currently required by the majority of quasar feedback models (∼5–10 per cent of Lbol), but similar to the recent suggestion of Hopkins & Elvis if a two-stage feedback model is implemented (∼0.5 per cent of Lbol). The models also predict that active galactic nuclei (AGN)-driven outflows will eventually remove the gas from the bulge of the host galaxy. Our observations show that the visible warm outflow in PKS 1345+12 is not currently capable of doing so. However, it is entirely possible that much of the outflow is either obscured by a dense and dusty natal cocoon and/or in cooler or hotter phases of the ISM. This result is important not just for studies of young Gigahertz-Peaked Spectrum/Compact Steep Spectrum radio sources, but for AGN in general.

Keywords: ISM: jets and outflows; ISM: kinematics and dynamics; galaxies: active; galaxies: individual: PKS 1345+12 (4C12.50); galaxies: ISM; galaxies: kinematics and dynamics

Journal Article.  7452 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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