Star formation efficiency along the radio jet in Centaurus A

Salomé, Quentin; Salomé, P.; Combes, F.; Hamer, Stephen; Heywood, Ian

doi:10.1051/0004-6361/201526409

Cited by 38 publications

(56 citation statements)

References 66 publications

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“…We find a similar situation in many blue compact dwarfs, which show recent clustered star formation even in very isolated locations after a long period of quiescence (Fuse et al 2012). We also mention the possibility of "jet-induced star formation" that has been discussed, for example to explain the existence of a young stellar population near Centaurus A at a galactocentric distance of 15 kpc (Mould et al 2000;Santoro et al 2016;Salomé et al 2016). In that case the age of SH2 would indicate the epoch of the last nuclear activity in NGC1316.…”

Section: Possible Formation and Evolution Of Sh2supporting

confidence: 76%

The globular cluster system of NGC 1316

Richtler

Hilker

Puzia

et al. 2017

A&A

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Context. The light of the merger remnant NGC 1316 (Fornax A) is dominated by old and intermediate-age stars. The only sign of current star formation in this big galaxy is the HII region SH2, an isolated star cluster complex with a ring-like morphology and an estimated age of 0.1 Gyr at a galactocentric distance of about 35 kpc. A nearby intermediate-age globular cluster, surrounded by weak line emission and a few more young star clusters, is kinematically associated. The origin of this complex is enigmatic. Aims. We want to investigate the nature of this star cluster complex. The nebular emission lines permit a metallicity determination which can discriminate between a dwarf galaxy or other possible precursors. Methods. We used the Integrated Field Unit (IFU) of the VIMOS instrument at the Very Large Telescope of the European Southern Observatory in high dispersion mode to study the morphology, kinematics, and metallicity employing line maps, velocity maps, and line diagnostics of a few characteristic spectra. Results. The line ratios of different spectra vary, indicating highly structured HII regions, but define a locus of uniform metallicity. The strong-line diagnostic diagrams and empirical calibrations point to a nearly solar or even super-solar oxygen abundance. The velocity dispersion of the gas is highest in the region offset from the bright clusters. Star formation may be active on a low level. There is evidence for a large-scale disk-like structure in the region of SH2, which would make the similar radial velocity of the nearby globular cluster easier to understand. Conclusions. The high metallicity does not fit to a dwarf galaxy as progenitor. We favour the scenario of a free-floating gaseous complex having its origin in the merger 2 Gyr ago. Over a long period the densities increased secularly until finally the threshold for star formation was reached. SH2 illustrates how massive star clusters can form outside starbursts and without a considerable field population.

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Section: Possible Formation and Evolution Of Sh2supporting

confidence: 76%

The globular cluster system of NGC 1316

Richtler

Hilker

Puzia

et al. 2017

A&A

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“…Given the upper limit from the [S ii]λ6717/λ6731 line ratio, we chose an intermediate value of 40 cm −3 for the gas electron density. The metallicity is assumed to be solar, close to the value found by Salomé et al (2016) across the entire outer filament (∼0.8 Z ).…”

Section: Photoionization Modelsmentioning

confidence: 99%

“…Further study by Salomé et al (2016) has suggested that, in other locations the interaction with the jet is quenching the star formation instead. Coincident with the H i cloud, they detected three unresolved CO clouds that, probably due to the kinetic energy of the AGN jet, are not gravitationally bound and thus do not form stars efficiently.…”

Section: Introductionmentioning

confidence: 99%

“…Coincident with the H i cloud, they detected three unresolved CO clouds that, probably due to the kinetic energy of the AGN jet, are not gravitationally bound and thus do not form stars efficiently. The overall star formation rate along the ionized gas filaments is estimated to be low and has a negligible effect on galaxy scales (see Mould et al 2000;Oosterloo & Morganti 2005;Salomé et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Embedded star formation in the extended narrow line region of Centaurus A: Extreme mixing observed by MUSE

Santoro

Oonk

Morganti

et al. 2016

A&A

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We present a detailed study of the complex ionization structure in a small (∼250 pc) extended narrow line region (ENLR) cloud near Centaurus A using the Multi Unit Spectroscopic Explorer. This cloud is located in the so-called outer filament of ionized gas (about 15 kpc from the nucleus) where jet-induced star formation has been suggested to occur by different studies. We find that, despite the small size, a mixture of ionization mechanisms is operating, resulting in considerable complexity in the spatial ionization structure.The area includes two H ii regions where star formation is occurring and another location where star formation must have ceased very recently. Interestingly, the extreme Balmer decrement of one of the star forming regions (Hα/Hβ obs ∼ 6) indicates that it is still heavily embedded in its natal cocoon of gas and dust. At all three locations a continuum counterpart is found with spectra matching those of O/B stars local to Centaurus A. The H ii regions are embedded in a larger gas complex which is photoionized by the radiation of the central active galactic nucleus (AGN), but the O/B stars affect the spatial ionization pattern in the ENLR cloud very locally. In particular, in the surroundings of the youngest star forming region, we can isolate a tight mixing sequence in the diagnostic diagram going from gas with ionization due to a pure stellar continuum to gas only photoionized by the AGN. These results emphasize the complexity and the mixture of processes occurring in star forming regions under the influence of an AGN radiation. This is relevant for our understanding of AGN-induced star formation suggested to occur in a number of objects, including this region of Centaurus A. They also illustrate that these young stars influence the gas over only a limited region.

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“…The dashed lines approximately delineate the path of the radio jet (Morganti et al 1999); the arrow shows the flow direction of the jet. of kinetic energy by the jet (Salomé et al 2016a). The Balmer decrement (Hα/Hβ) across the MUSE fields confirms that the ionised gas is dusty.…”

Section: Special Region: the Outer Filamentmentioning

confidence: 99%

The missing link: Tracing molecular gas in the outer filament of Centaurus A

Morganti

Oosterloo

Oonk

et al. 2016

A&A

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We report the detection, using observations of the CO(2−1) line performed with the Atacama Pathfinder EXperiment (APEX), of molecular gas in the region of the outer filament of Centaurus A, a complex region known to show various signatures of an interaction between the radio jet, an H i cloud, and ionised gas filaments. We detect CO(2−1) at all observed locations, which were selected to represent regions with very different physical conditions. The H 2 masses of the detections range between 0.2 × 10 6 and 1.1 × 10 6 M , for conservative choices of the CO to H 2 conversion factor. Surprisingly, the stronger detections are not coincident with the H i cloud, but instead are in the region of the ionised filaments. We also find variations in the widths of the CO(2−1) lines throughout the region, with broader lines in the region of the ionised gas, i.e. where the jet-cloud interaction is strongest, and with narrow profiles in the H i cloud. This may indicate that the molecular gas in the region of the ionised gas has the momentum of the jet-cloud interaction encoded in it, in the same way as the ionised gas does. These molecular clouds may therefore be the result of very efficient cooling of the down-stream gas photo-or shock-ionised by the interaction. On the other hand, the molecular clouds with narrower profiles, which are closer to or inside the H i cloud, could be pre-existing cold H 2 cores which manage to survive the effects of the passing jet.

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Star formation efficiency along the radio jet in Centaurus A

Cited by 38 publications

References 66 publications

The globular cluster system of NGC 1316

The globular cluster system of NGC 1316

Embedded star formation in the extended narrow line region of Centaurus A: Extreme mixing observed by MUSE

The missing link: Tracing molecular gas in the outer filament of Centaurus A

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