Jet-Driven Motions in the Narrow-Line Region of NGC 1068

Axon, D. J.; Marconi, A.; Capetti, A.; Macchetto, F.; Schreier, E.; Robinson, Andrew

doi:10.1086/311249

Cited by 103 publications

(150 citation statements)

References 30 publications

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“…Because only one H 2 emission line is detected, we cannot conclude on the excitation mechanism of molecular hydrogen. However, the jet of NGC 1068 with a velocity greater than 700 km s −1 (Axon et al 1998) is dissociative for H 2 . The excitation may be caused by UV pumping from stars or by radiative UV shocks caused by the jet, or both.…”

Section: Ro-vibrationnal H 2 1-0 S(1) Linementioning

confidence: 98%

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Star formation and jet-induced coronal lines near the core of NGC 1068

Exposito

Gratadour

Clénet

et al. 2011

A&A

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Context. Active galactic nuclei (AGNs) are very luminous galaxies from the ultraviolet (UV) to the far infrared (FIR). To study regions near the core, which are dominated by dust, IR is the perfect spectral range because of the lower optical depth of the dust. However, these galaxies are usually distant, and the structures near the core are faint compared to the central source. High resolution and high contrast are mandatory to study the inner structures of AGNs and better understand the interaction between the central core and its surroundings. Aims. Our goal is to propose an explanation for the coronal lines in our spectra of NGC 1068 at a far distance (few tens of parsec) from the central source inside wave-like structures that we call nodules. Methods. NGC 1068 was observed with NaCo at ESO/VLT, using long-slit spectroscopy at 2.2 μm and 3.5 μm. Reduced spectra were compared to the output of Cloudy, using various ionizing continua: the continuum of the central source, young stars, and radiative shocks caused by the jet. Results. For the first time, thanks to the resolution provided by NaCo, near-IR coronal emission can be precisely associated to structures observable in the IR broad-band images. We found that coronal lines observed in the nodules cannot be caused by photoionization by the central source but are instead caused by a local jet-induced ionizing continuum. In addition, studying the Brackett-γ line (Brγ) and CO 2-0 band head, we deduced a star density within the four nodules (∼800 000 stars) compatible with super star cluster (hereafter SSC) models.

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Section: Ro-vibrationnal H 2 1-0 S(1) Linementioning

confidence: 98%

“…Their ionization potentials (>100 eV) imply an excitation by hard photons from the AGN or an excitation by shocks from the NGC 1068's radio jet (Gallimore et al 1996b,a;Axon et al 1998). At a lower spatial resolution than NaCo, both mechanisms have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Star formation and jet-induced coronal lines near the core of NGC 1068

Exposito

Gratadour

Clénet

et al. 2011

A&A

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“…b "" r ÏÏ denotes redshifted and "" b ÏÏ denotes blueshifted (with respect to systemic). Axon et al (1998) found evidence for an increase in emission-line Ñux and ionization state at a region º150 pc northeast of the nucleus, which may be due to the interaction of the radio jet which traverses the NLR of NGC 1068 (Wilson & Ulvestad 1983) with interstellar gas clouds. In fact, several authors have argued that the ionizing radiation emitted by fast (D500 km s~1) shocks, arising either from cloud/cloud interactions (cf.…”

Section: Introductionmentioning

confidence: 94%

Resolved Spectroscopy of the Narrow‐Line Region in NGC 1068. III. Physical Conditions in the Emission‐Line Gas

Kraemer¹,

Crenshaw²

2000

ApJ

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The physical conditions in the inner narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068 are examined using ultraviolet and optical spectra and photoionization models. The spectra were taken with the Hubble Space T elescope Space Telescope Imaging Spectrograph (STIS), through the slit, 0A .1 ] 52A .0 covering the full STIS 1200È10000waveband. The slit was centered on a position north of the A 0A .14 optical continuum peak (or "" hot spot ÏÏ) at a position angle of 202¡, bisecting the brighter part of the biconical emission-line region. We have measured the emission-line Ñuxes for a region extending 3A .8 northeast (D270 pc) to southwest (D130 pc) of this point. The emission lines on each side show 1A .8 evidence of two principal kinematic components, one blueshifted with respect to the systemic velocity and the other redshifted (the kinematics were discussed in a separate paper). Based on the photoionization modeling results, we Ðnd that the physical conditions vary among these four quadrants. (1) The emission-line gas in the blueshifted northeast quadrant is photoionized by the hidden central source out to D100 pc, at which point we Ðnd evidence of another source of ionizing radiation, which may be due to fast (D1000 km s~1) shocks resulting from the interaction of the emission-line knots and the interstellar medium. Interestingly, this occurs at approximately the location where the knots begin to show signs of deceleration. (2) The gas in the redshifted northeast quadrant is photoionized by continuum radiation that has been heavily absorbed by gas within D30 pc of the central source. We Ðnd no strong evidence of the e †ects of shocks in this component. (3) The redshifted emission-line gas in the southwest quadrant is photoionized by unabsorbed continuum from the central source, similar to that in the inner D100 pc of the blueshifted northeast quadrant. Finally, (4) the emission-line spectrum of the blueshifted southwest quadrant appears to be the superposition of highly ionized, tenuous component within the ionization cone and gas outside the cone, the latter photoionized by scattered continuum radiation. There are several implications of this complicated physical scenario. First, the hidden active nucleus is the dominant source of ionizing radiation in the inner NLR. The absorption of continuum radiation along the line of sight to the redshifted northeast quadrant may result from the intersection of the ionization cone and the plane of the host galaxy. Finally, the evidence for shock-induced continuum radiation at the point where the emission-line knots begin to decelerate indicates that the deceleration is due to the interaction of emission-line knots with slower moving gas, such as the interstellar medium of NGC 1068.

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“…A major obstacle in identifying binary AGNs using the NEL splitting signature, however, is that such profiles can also arise from NLR gas kinematics around single AGNs, such as rotating disks or bi-conical outflows (Axon et al 1998;Veilleux et al 2001;Crenshaw et al 2010;Shen et al 2011a;Rosario et al 2010;Fischer et al 2011;Smith et al 2011Smith et al , 2012. Nevertheless, our followup observations (Liu et al 2010a;Shen et al 2011a) of a subset of a systematically selected sample of 167 AGNs with double-peaked NELs (Liu et al 2010b; see also Smith et al 2010;Wang et al 2009), as well as studies by other groups Fu et al 2012), have demonstrated the feasibility and importance of combining higher resolution NIR imaging (Fu et al 2011a;Rosario et al 2011) and spatially resolved optical spectroscopy (Comerford et al 2012) to discriminate kpcscale binary AGNs from single-AGN-NLR gas kinematics.…”

Section: Systematic Searches For Kpc-scale Binary Agnsmentioning

confidence: 99%

CHANDRAX-RAY ANDHUBBLE SPACE TELESCOPEIMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. I. NATURE OF THE NUCLEAR IONIZING SOURCES

Liu

Civano

Shen

et al. 2012

ApJ

111

165

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Kiloparsec-scale binary active galactic nuclei (AGNs) signal active supermassive black hole (SMBH) pairs in merging galaxies. Despite their significance, unambiguously confirmed cases remain scarce and most have been discovered serendipitously. In a previous systematic search, we optically identified four kpc-scale binary AGNs from candidates selected with double-peaked narrow emission lines at z = 0.1-0.2. Here we present Chandra and Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging of these four systems. We critically examine and confirm the binary-AGN scenario for two of the four targets, by combining high angular resolution X-ray imaging spectroscopy with Chandra ACIS-S, better nuclear position constraints from WFC3 F105W imaging, and direct starburst estimates from WFC3 F336W imaging; for the other two targets, the existing data are still consistent with the binary-AGN scenario, but we cannot rule out the possibility of only one AGN ionizing gas in both merging galaxies. We find tentative evidence for a systematically smaller X-rayto-[O III] luminosity ratio and/or higher Compton-thick fraction in optically selected kpc-scale binary AGNs than in single AGNs, possibly caused by a higher nuclear gas column due to mergers and/or a viewing angle bias related to the double-peak narrow line selection. While our result lends some further support to the general approach of optically identifying kpc-scale binary AGNs, it also highlights the challenge and ambiguity of Xray confirmation.

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Jet-Driven Motions in the Narrow-Line Region of NGC 1068

Cited by 103 publications

References 30 publications

Star formation and jet-induced coronal lines near the core of NGC 1068

Star formation and jet-induced coronal lines near the core of NGC 1068

Resolved Spectroscopy of the Narrow‐Line Region in NGC 1068. III. Physical Conditions in the Emission‐Line Gas

CHANDRAX-RAY ANDHUBBLE SPACE TELESCOPEIMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. I. NATURE OF THE NUCLEAR IONIZING SOURCES

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