Atomic-to-molecular gas phase transition triggered by the radio jet in Centaurus A

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

doi:10.1051/0004-6361/201628970

Cited by 20 publications

(34 citation statements)

References 40 publications

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“…In the other part of the filaments, star formation appears to be inefficient compared to the Kennicutt-Schmidt law (Salomé et al 2016b). However, the jet-gas interaction seems to trigger the atomic-to-molecular gas phase transition (Salomé et al 2016a), suggesting that positive feedback is occuring in the filaments.…”

Section: Introductionmentioning

confidence: 97%

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Inefficient jet-induced star formation in Centaurus A

Salomé

Miville-Deschênes

et al. 2017

A&A

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NGC 5128 (Centaurus A) is one of the best targets to study AGN feedback in the local Universe. At 13.5 kpc from the galaxy, optical filaments with recent star formation lie along the radio jet direction. This region is a testbed for positive feedback, here through jet-induced star formation. Atacama Pathfinder EXperiment (APEX) observations have revealed strong CO emission in star-forming regions and in regions with no detected tracers of star formation activity. In cases where star formation is observed, this activity appears to be inefficient compared to the Kennicutt-Schmidt relation. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to map the 12 CO(1-0) emission all along the filaments of NGC 5128 at a resolution of 1.3 ∼ 23.8 pc. We find that the CO emission is clumpy and is distributed in two main structures: (i) the Horseshoe complex, located outside the HI cloud, where gas is mostly excited by shocks and where no star formation is observed, and (ii) the Vertical filament, located at the edge of the HI shell, which is a region of moderate star formation. We identified 140 molecular clouds using a clustering method applied to the CO data cube. A statistical study reveals that these clouds have very similar physical properties, such as size, velocity dispersion, and mass, as in the inner Milky Way. However, the range of radius available with the present ALMA observations does not enable us to investigate whether or not the clouds follow the Larson relation. The large virial parameter α vir of the clouds suggests that gravity is not dominant and clouds are not gravitationally unstable. Finally, the total energy injection in the northern filaments of Centaurus A is of the same order as in the inner part of the Milky Way. The strong CO emission detected in the northern filaments is an indication that the energy injected by the jet acts positively in the formation of dense molecular gas. The relatively high virial parameter of the molecular clouds suggests that the injected kinetic energy is too strong for star formation to be efficient. This is particularly the case in the horseshoe complex, where the virial parameter is the largest and where strong CO is detected with no associated star formation. This is the first evidence of AGN positive feedback in the sense of forming molecular gas through shocks, associated with low star formation efficiency due to turbulence injection by the interaction with the radio jet.

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Section: Introductionmentioning

confidence: 97%

“…In Salomé et al (2016a), we mapped the outer filaments (hereafter the northern filaments) in 12 CO(2-1) with APEX. The molecular gas was found to be very extended with a surprisingly CO bright region outside the HI cloud.…”

Section: Introductionmentioning

confidence: 99%

Inefficient jet-induced star formation in Centaurus A

Salomé

Miville-Deschênes

et al. 2017

A&A

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“…These jets are observed in positive feedback cases, wherein the effect of the jet serves to enhance star formation, including Centaurus A (Salomé et al 2016, and references therein), 4C 41.17 (Bicknell et al 2000), and Minkowski's Object (hereafter M.O.) (Croft et al 2006, hereafter C06).…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulations of a Jet–Cloud Collision and Starburst: Application to Minkowski’s Object

Fragile

Anninos

Croft

et al. 2017

ApJ

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We present results of three-dimensional, multi-physics simulations of an AGN jet colliding with an intergalactic cloud. The purpose of these simulations is to assess the degree of "positive feedback," i.e. jet-induced star formation, that results. We have specifically tailored our simulation parameters to facilitate comparison with recent observations of Minkowski's Object (M.O.), a stellar nursery located at the termination point of a radio jet coming from galaxy NGC 541. As shown in our simulations, such a collision triggers shocks which propagate around and through the cloud. These shocks condense the gas and under the right circumstances may trigger cooling instabilities, creating runaway increases in density, to the point that individual clumps can become Jeans unstable. Our simulations provide information about the expected star formation rate, total mass converted to H I, H 2 , and stars, and the relative velocity of the stars and gas. Our results confirm the possibility of jet-induced star formation, and agree well with the observations of M.O.

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“…This suggests that some processes may prevent the star formation to proceed in the cold gas. These processes can be due to high kinetic energy injection from the AGN that suppress the star formation processes [44].…”

Section: Discussionmentioning

confidence: 99%

“…In each box the molecular gas mass surface density was calculated using conversion factor CO = 2 × 10 20 cm −2 (K km s −1 ) −1 [42,43]. The molecular gas mass and surface density of each region are listed in Table 2, which shows that some regions have huge amount of molecular gas mass (1-14 × 10 6 ⊙ ) this indicates that several GMC associations are located there [44].…”

Section: Molecular Gas Mass and Surfacementioning

confidence: 99%

Star Formation Law at Sub-kpc Scale in the Elliptical Galaxy Centaurus A as Seen by ALMA

Azeez

Abidin

Hwang

et al. 2017

Advances in Astronomy

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We present an extensive analysis of the relationship between star formation rate surface density (∑ SFR) and molecular gas surface density (∑ H 2 ) at sub-kpc scale in the elliptical galaxy Centaurus A (also known as NGC 5128) at the distance 3.8 Mpc.12 CO ( = 2-1) data from Atacama Large Millimetre/Sub-Millimetre Array SV data with very high resolution (2.9 , 0.84 ), as well as 24 m data from the Spitzer Space Telescope, were used. This is one of the first studies of the SF law on Centaurus A at this very high spatial resolution. The results showed a breakdown in star formation law with a 0.49 ± 0.05 index relating ∑ SFR and ∑ H 2 at 185 pc. A significant correlation exists between surface densities of molecular gas and SFR with very long depletion time (68 Gy). In addition we examined the spatially resolved relationship between velocity dispersion and star formation rate surface density for the outer disk of this galaxy and we found that the average velocity dispersion is equal to 11.78 km/s. The velocity dispersion of the molecular ISM for the outer disk is found to follow a power relation with the star formation rate surface density ∝ (∑ SFR) , where is the slope from the ordinary least square fitting. The value of is about 1/ ≈ 2.16 ± 0.40 and is the power law index of the star formation law.

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Atomic-to-molecular gas phase transition triggered by the radio jet in Centaurus A

Cited by 20 publications

References 40 publications

Inefficient jet-induced star formation in Centaurus A

Inefficient jet-induced star formation in Centaurus A

Numerical Simulations of a Jet–Cloud Collision and Starburst: Application to Minkowski’s Object

Star Formation Law at Sub-kpc Scale in the Elliptical Galaxy Centaurus A as Seen by ALMA

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