Centaurus A: Molecular gas shells or large-scale outflow?

Curran, Stephen J.

doi:10.1051/0004-6361:20011003

Cited by 2 publications

(3 citation statements)

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“…The consistent picture of an external origin of the outlying gas and dust also makes an collimated outflow of molecular gas from the central regions along the jets (Curran 2001) for the origin of the CO emission in the northern shell S1 less likely, although some outflow of ISM components from the central actively star forming region of NGC 5128 in form of a galactic wind is to be expected.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, locating the three HI emission regions (Schiminovich et al 1994) in the optical image showing the interleaved shell system (Peng et al 2002) reveals that only the northern S1 region lies outside the outermost shell whereas the other two are situated between shells. The CO detection in the northern shell region S1 was confirmed by Curran (2001), although a different interpretation in terms of an molecular outflow associated with the radio jet was suggested.…”

Section: Introductionmentioning

confidence: 92%

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First detection of cold dust in the northern shell of NGC 5128 (Centaurus A)

Stickel

Hulst²,

Gorkom

et al. 2004

A&A

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Abstract. Deep far-infrared (FIR) imaging data obtained with ISOPHOT at 90 µm, 150 µm, and 200 µm detected the thermal emission from cold dust in the northern shell region of NGC 5128 (Centaurus A), where previously neutral hydrogen and molecular gas has been found. A somewhat extended FIR emission region is present in both the 150 µm and 200 µm map, while only an upper flux limit could be derived from the 90 µm data. The FIR spectral energy distribution can be reconciled with a modified blackbody spectrum with very cold dust color temperatures and emissivity indices in the range 13 K < T Dust < 15.5 K and 2 > β > 1, respectively, where the data favor the low temperature end. A representative value for the associated dust mass is M Dust ≈ 7 × 10 4 M , which together with the HI gas mass gives a gas-to-dust ratio of ≈300, close the average values of normal inactive spiral galaxies. This value, in conjunction with the atomic to molecular gas mass ratio typical for a spiral galaxy, indicates that the interstellar medium (ISM) from the inner part of a captured disk galaxy is likely the origin of the outlying gas and dust. These observations are in agreement with recent theoretical considerations that in galaxy interactions leading to stellar shell structures the less dissipative clumpy component of the ISM from the captured galaxy can lead to gaseous shells. Alternatively, the outlying gas and dust could be a rotating ring structure resulting from an interaction or even late infall of tidal material of a merger in the distant past. With all three components (atomic gas, molecular gas, dust) of the ISM present in the northern shell region, local star formation may account for the chains of young blue stars surrounding the region to the east and north. The dust cloud may also be involved in the disruption of the large scale radio jet before entering the brighter region of the northern radio lobe.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

First detection of cold dust in the northern shell of NGC 5128 (Centaurus A)

Stickel

Hulst²,

Gorkom

et al. 2004

A&A

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“…Furthermore, a second population of masers are found to trace a wide‐angle outflow which coincides with the >100 pc‐scale ionization cone (Marconi et al 1994; Veilleux & Bland‐Hawthorn 1997) and molecular outflow (Curran et al 1999), as well as sharing the same position angle as the radio lobes (Harnett et al 1990; Elmouttie et al 1995). The lobes, cone and outflow are all directed along the minor axis of the galaxy, coincident with the rotation axis of the molecular ring (Curran et al 1999; Curran 2001).…”

Section: Introductionmentioning

confidence: 99%

The large-scale atomic and molecular gas in the Circinus galaxy

Curran¹,

Koribalski²,

Bains³

2008

Monthly Notices of the Royal Astronomical Society

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We have used the Australia Telescope Compact Array (ATCA) and the Swedish–ESO Submillimetre Telescope (SEST) to map the large‐scale atomic and molecular gas in the nearby (4 Mpc) Circinus galaxy. The ATCA H i mosaic of Circinus exhibits the warps in position angle and inclination revealed in the single‐pointing image of Jones et al., both of which appear to settle beyond the inner 30 kpc which was previously imaged. The molecular gas has been mapped in both the CO J= 1 → 0 and J= 2 → 1 transitions down to a column density of (3σ), where we derive a total molecular gas mass of . Within a radius of 3 kpc, i.e. where CO was clearly detected, the molecular fraction climbs steeply from ≈ 0.7 to unity (where , cf. NH i= 1021 cm−2) with proximity to the nucleus. Our H i mosaic gives an atomic gas mass of MH i≈ 6 × 109 M⊙, which is 70 per cent of the fully mapped single dish value. Combining the atomic and molecular gas masses gives a total gas mass of , cf. the total dynamical mass of ≈ 3 × 1011 M⊙ within the inner 50 kpc of our mosaiced image. The total neutral gas mass to dynamical mass ratio is therefore 3 per cent, consistent with the SAS3 (Third Small Astronomy Satellite) classification of Circinus. The high (molecular) gas mass fraction of per cent found by Curran et al., only occurs close to the central ≈ 0.5 kpc and falls to ≲10 per cent within and outwith this region, allaying previous concerns regarding the validity of applying the Galactic conversion ratio to Circinus. The rotation curve, as traced by both the H i and CO, exhibits a steep dip at ≈ 1 kpc, the edge of the atomic/molecular ring, within which the starburst is occurring. We find the atomic and molecular gases to trace different kinematical features and believe that the fastest part (≳130 km s−1) of the subkpc ring consists overwhelmingly of molecular gas. Beyond the inner kpc, the velocity climbs to settle into a solid body rotation of ≈ 150 km s−1 at ≳10 kpc. Most of the starlight emanates from within this radius and so much of the dynamical mass, which remains climbing to the limit of our data (≳50 kpc), must be due to the dark matter halo.

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Centaurus A: Molecular gas shells or large-scale outflow?

Cited by 2 publications

References 50 publications

First detection of cold dust in the northern shell of NGC 5128 (Centaurus A)

First detection of cold dust in the northern shell of NGC 5128 (Centaurus A)

The large-scale atomic and molecular gas in the Circinus galaxy

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