NGC 4945: The Brightest Seyfert 2 Galaxy at 100 keV

Done, Chris; Madejski, G. M.; Smith, David A.

doi:10.1086/310056

Cited by 90 publications

(83 citation statements)

References 28 publications

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“…The comparison sample of normal and starburst galaxies is limited to sources with ISO 6.2 lm spectroscopy, where the beam includes the whole galaxy or the same region as the LWS beam. Among the comparison sample of galaxies, four galaxies-NGC 6240, NGC 4945, NGC 1068, and Circinus-with optical, X-ray, or gamma ray signatures of active galactic nuclei (AGNs) are included (e.g., Done, Madejski, & Smith 1996;Vignati et al 1999).…”

Section: Sourcementioning

confidence: 99%

The [Cii] 158 Micron Line Deficit in Ultraluminous Infrared Galaxies Revisited

Luhman

Satyapal

Fischer

et al. 2003

ApJ

215

350

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We present a study of the [C ii] 157.74 lm fine-structure line in a sample of 15 ultraluminous infrared (IR) galaxies (IR luminosity L IR k10 12 L ; ULIRGs) using the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We confirm the observed order of magnitude deficit (compared to normal and starburst galaxies) in the strength of the [C ii] line relative to the far-infrared (FIR) dust continuum emission found in our initial report, but here with a sample that is twice as large. This result suggests that the deficit is a general phenomenon affecting 4 out of 5 ULIRGs. We present an analysis using observations of generally acknowledged photodissociation region (PDR) tracers ([C ii], [O i] 63 and 145 lm, and FIR continuum emission), which suggests that a high ultraviolet flux G 0 incident on a moderate density n PDR could explain the deficit. However, comparisons with other ULIRG observations, including CO (1-0), [C i] (1-0), and 6.2 lm polycyclic aromatic hydrocarbon (PAH) emission, suggest that high G 0 =n PDRs alone cannot produce a self-consistent solution that is compatible with all of the observations. We propose that non-PDR contributions to the FIR continuum can explain the apparent [C ii] deficiency. Here, unusually high G 0 and/ or n physical conditions in ULIRGs as compared to those in normal and starburst galaxies are not required to explain the [C ii] deficit. Dust-bounded photoionization regions, which generate much of the FIR emission but do not contribute significant [C ii] emission, offer one possible physical origin for this additional non-PDR component. Such environments may also contribute to the observed suppression of FIR fine-structure emission from ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The implications for observations at higher redshifts are also revisited.

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Section: Sourcementioning

confidence: 99%

The [Cii] 158 Micron Line Deficit in Ultraluminous Infrared Galaxies Revisited

Luhman

Satyapal

Fischer

et al. 2003

ApJ

215

350

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“…NGC 4945 is a nearby (3.9 Mpc [23]) edge-on spiral galaxy containing an obscured nuclear starburst and is the second-brightest Seyfert 2 galaxy in the X-ray sky at 100 keV [24]. Its nucleus hosts water masers with up to 10 Jy [25].…”

Section: Detection Of Ngc 4945mentioning

confidence: 99%

Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy

Roy¹,

Goss²,

Mohan³

et al. 2005

AIP Conference Proceedings

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Abstract.A renewed attempt to detect radio recombination lines from external galaxies has resulted in the measurement of lines from several bright starburst galaxies. The lines are produced by hydrogen ionized by young, high-mass stars and are diagnostic of the conditions and gas dynamics in the starburst regions without problems of dust obscuration. We present here detections of the lines H91α and H92α near 8.6 GHz from the starburst nuclei in NGC 3256, NGC 4945, and the Circinus galaxy using the ATCA and VLA. Modelling the line emitting region as a collection of H II regions, we derive the required number of H II regions, their temperature, density, and distribution.

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“…Evidence for a heavily obscured AGN comes from hard X-ray observations (Done, Madejski, & Smith 1996 ;Guainazzi et al 2000). However, NGC 4945 is peculiar in that the AGN has not yet been successfully traced, neither in the NIR FIG.…”

Section: Ngc 4945mentioning

confidence: 99%

N‐Band Imaging of Seyfert Nuclei and the Mid‐Infrared–X‐Ray Correlation

Krabbe¹,

Maiolino²

2001

ApJ

111

118

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We present new mid-infrared (N-band) images of a sample of eight nearby Seyfert galaxies. In all of our targets, we detect a central unresolved source, which in some cases has been identiÐed for the Ðrst time. In particular, we have detected the mid-infrared emission from the active nucleus of NGC 4945, which previously remained undetected at any wavelength but hard X-rays. We also detect circumnuclear extended emission in the Circinus galaxy along its major axis and Ðnd marginal evidence for extended circumnuclear emission in NGC 3281. The high spatial resolution of our data allows us to separate (1A .7) the Ñux of the nuclear point sources from the extended circumnuclear starburst (if present). We complement our sample with literature data for a number of nonactive starburst galaxies and relate the nuclear N-band Ñux to published hard (2È10 keV) X-ray Ñuxes. We Ðnd tight and well-separated correlations between the nuclear N-band Ñux and X-ray Ñux for both Seyfert and starburst nuclei that span over 3 orders of magnitude in luminosity. We demonstrate that these correlations can be used as a powerful classiÐcation tool for galactic nuclei. For example, we Ðnd strong evidence against NGC 1808 currently harboring an active Seyfert nucleus based on its position in the mid-infraredÈX-ray diagram. On the other hand, we conÐrm that NGC 4945 is in fact a Seyfert 2 galaxy.

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NGC 4945: The Brightest Seyfert 2 Galaxy at 100 keV

Cited by 90 publications

References 28 publications

The [Cii] 158 Micron Line Deficit in Ultraluminous Infrared Galaxies Revisited

The [Cii] 158 Micron Line Deficit in Ultraluminous Infrared Galaxies Revisited

Radio Recombination Lines from Starbursts: NGC 3256, NGC 4945 and the Circinus Galaxy

N‐Band Imaging of Seyfert Nuclei and the Mid‐Infrared–X‐Ray Correlation

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