The unusual radio galaxy NGC 6240

Fosbury, R. A. E.; Wall, J. V.

doi:10.1093/mnras/189.1.79

Cited by 49 publications

(35 citation statements)

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“…The optical emission-line spectrum (Fosbury & Wall 1979;Zasov & Karachentsev 1979;Fried & Schulz 1983;Morris & Ward 1988;Keel 1990;Heckman et al 1987;Veilleux et al 1995;Schmitt et al 1996;Rafanelli et al 1997) is dominated by LINER-like line ratios over the central ∼10 kpc. This spectrum is preferentially associated with shocks produced by cloud-cloud collisions in the merging system and not with a central photoionizing AGN continuum (see, e.g., Fosbury & Wall 1979;Fried & Schulz 1983).…”

Section: Introductionmentioning

confidence: 99%

“…This spectrum is preferentially associated with shocks produced by cloud-cloud collisions in the merging system and not with a central photoionizing AGN continuum (see, e.g., Fosbury & Wall 1979;Fried & Schulz 1983). Nevertheless, a few high-excitation features in IR spectra and in optical HST narrowband images indicate possible weak AGN signatures in the southern region of the galaxy (Rafanelli et al 1997).…”

Section: Introductionmentioning

confidence: 99%

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Hard X-ray emission of the luminous infrared galaxy NGC 6240 as observed by NuSTAR

Puccetti

Comastri

Bauer

et al. 2016

A&A

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We present a broadband (∼0.3−70 keV) spectral and temporal analysis of NuSTAR observations of the luminous infrared galaxy NGC 6240 combined with archival Chandra, XMM-Newton, and BeppoSAX data. NGC 6240 is a galaxy in a relatively early merger state with two distinct nuclei separated by ∼1. 5. Previous Chandra observations resolved the two nuclei and showed that they are both active and obscured by Compton-thick material. Although they cannot be resolved by NuSTAR, we were able to clearly detect, for the first time, both the primary and the reflection continuum components thanks to the unprecedented quality of the NuSTAR data at energies >10 keV. The NuSTAR hard X-ray spectrum is dominated by the primary continuum piercing through an absorbing column density which is mildly optically thick to Compton scattering (τ 1.2, N H ∼ 1.5 × 10 24 cm −2 ). We detect moderately hard X-ray (>10 keV) flux variability up to 20% on short (15−20 ks) timescales. The amplitude of the variability is largest at ∼30 keV and is likely to originate from the primary continuum of the southern nucleus. Nevertheless, the mean hard X-ray flux on longer timescales (years) is relatively constant. Moreover, the two nuclei remain Compton-thick, although we find evidence of variability in the material along the line of sight with column densities N H ≤ 2 × 10 23 cm −2 over long (∼3−15 yr) timescales. The observed X-ray emission in the NuSTAR energy range is fully consistent with the sum of the best-fit models of the spatially resolved Chandra spectra of the two nuclei.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hard X-ray emission of the luminous infrared galaxy NGC 6240 as observed by NuSTAR

Puccetti

Comastri

Bauer

et al. 2016

A&A

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“…Although it is slightly less luminous (L FIR 6 × 10 11 L for H 0 = 75 km s −1 Mpc −1 ; Genzel et al 1998) than the typical IR luminosity used to define a ULIRG, it exhibits all of the ULIRG characteristics, and it is thus studied as a prototype of this class of sources. Optical/IR observations show a complex system with a disturbed morphology consisting of two gravitationally interacting nuclei (Fosbury & Wall 1979;Fried & Schulz 1983). An IS O observation of NGC 6240 (Genzel et al 1998) favors a starburst-dominated power source, in which the high infrared emission arises from warm, absorbing dust, surrounding the inner parts of the galaxy.…”

Section: Introductionmentioning

confidence: 99%

XMM-Newtonobservation of the ULIRG NGC 6240

Boller

Keil

Hasinger

et al. 2003

A&A

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Abstract.We report on an XMM-Newton observation of the ultraluminous infrared galaxy NGC 6240. The 0.3-10 keV spectrum can be successfully modelled with: (i) three collisionally ionized plasma components with temperatures of about 0.7, 1.4, and 5.5 keV; (ii) a highly absorbed direct power-law component; and (iii) a neutral Fe Kα and Kβ line. We detect a significant neutral column density gradient which is correlated with the temperature of the three plasma components. Combining the XMM-Newton spectral model with the high spatial resolution Chandra image we find that the temperatures and the column densities increase towards the center. With high significance, the Fe K line complex is resolved into three distinct narrow lines: (i) the neutral Fe Kα line at 6.4 keV; (ii) an ionized line at about 6.7 keV; and (iii) a higher ionized line at 7.0 keV (a blend of the Fe XXVI and the Fe Kβ line). While the neutral Fe K line is most probably due to reflection from optically thick material, the Fe XXV and Fe XXVI emission arises from the highest temperature ionized plasma component. We have compared the plasma parameters of the ultraluminous infrared galaxy NGC 6240 with those found in the local starburst galaxy NGC 253. We find a striking similarity in the plasma temperatures and column density gradients, suggesting a similar underlying physical process at work in both galaxies.

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“…: photoionization by very hot Wolf-Rayet stars (Warmers), hot O stars, or old post-AGB stars (Terlevich & Melnick 1985;Filippenko & Terlevich 1992;Binette et al 1994), cooling accretion flows (Heckman 1981;Voit & Donahue 1997), shock heating through cloud collisions induced by accretion, galaxy interactions, mergers or starburst-driven winds (Fosbury et al 1978;Fosbury & Wall 1979;Dopita & Sutherland 1995, 1996Alonso-Herrero et al 2000), etc.…”

Section: The Emission-line Spectramentioning

confidence: 99%

The nuclear region of low luminosity flat radio spectrum sources

Gonçalves

Roos²

2003

A&A

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Abstract.We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marchã's et al. (1996) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources.

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The unusual radio galaxy NGC 6240

Cited by 49 publications

References 0 publications

Hard X-ray emission of the luminous infrared galaxy NGC 6240 as observed by NuSTAR

Hard X-ray emission of the luminous infrared galaxy NGC 6240 as observed by NuSTAR

XMM-Newtonobservation of the ULIRG NGC 6240

The nuclear region of low luminosity flat radio spectrum sources

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