A molecular gas bridge between the Taffy galaxies

Braine, J.; Davoust, E.; Zhu, Meiping; Lisenfeld, U.; Motch, C.; Seaquist, E. R.

doi:10.1051/0004-6361:20031148

Cited by 54 publications

(115 citation statements)

References 11 publications

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“…We thus conclude that the bridge region delimited by Braine et al (2003, Fig. A.1) is somewhat too small.…”

Section: Isolating the Bridge Regionmentioning

confidence: 76%

“…In the Taffy system, this conversion factor varies significantly between the disk and bridge regions (Braine et al 2003;Zhu et al 2007). Because of the uncertainty of the local conversion factor, we apply a constant Galactic CO-H 2 conversion factor N(H 2 )/I CO = 10 20 cm −2 (K km s −1 ) −1 to the whole Taffy system (Zhu et al 2007).…”

Section: Gas Distributionmentioning

confidence: 99%

“…A.1 30 m CO(1−0) spectra together with VLA Hi spectra of the Taffy system (Fig. 1 of Braine et al 2003) for the comparison with our simulations.…”

Section: Hi and Co Spectramentioning

confidence: 99%

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A dynamical model for the Taffy galaxies UGC 12914/5

Vollmer¹,

Braine²,

Soida³

2012

A&A

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The spectacular head-on collision of the two gas-rich galaxies of the Taffy system, UGC 12914/15, gives us a unique opportunity to study the consequences of a direct ISM-ISM collision. To interpret existing multi-wavelength observations, we made dynamical simulations of the Taffy system including a sticky particle component. To compare simulation snapshots to Hi and CO observations, we assume that the molecular fraction of the gas depends on the square root of the gas volume density. For the comparison of our simulations with observations of polarized radio continuum emission, we calculated the evolution of the 3D large-scale magnetic field for our simulations. The induction equations including the time-dependent gas-velocity fields from the dynamical model were solved for this purpose. Our simulations reproduce the stellar distribution of the primary galaxy, UGC 12914, the prominent Hi and CO gas bridge, the offset between the CO and Hi emission in the bridge, the bridge isovelocity vectors parallel to the bridge, the Hi double-line profiles in the bridge region, the large line-widths (∼200 km s −1 ) in the bridge region, the high field strength of the bridge large-scale regular magnetic field, the projected magnetic field vectors parallel to the bridge and the strong total power radio continuum emission from the bridge. The stellar distribution of the secondary model galaxy is more perturbed than observed. The observed distortion of the Hi envelope of the Taffy system is not reproduced by our simulations which use initially symmetric gas disks. The model allows us to define the bridge region in three dimensions. We estimate the total bridge gas mass (Hi, warm and cold H 2 ) to be 5 to 6× 10 9 M , with a molecular fraction M H 2 /M HI of about unity. Despite the enormous mass of molecular gas in the bridge, very little star formation is present, similar to other systems with extraplanar gas and broad CO lines. The structure of the model gas bridge is bimodal: on kpc-scales there is a dense ( 0.01 M pc −3 ) component with a high velocity dispersion >100 km s −1 and a less dense (∼10 −3 M pc −3 ) component with a smaller, but still high, velocity dispersion ∼50 km s −1 . The synchrotron lifetime of relativistic electrons is only long enough to be consistent with the existence of the radio continuum bridge for the less dense component. On the other hand, only the high-density gas undergoes a high enough mechanical energy input to produce the observed strong emission of warm H 2 . We propose that, despite the high local gas densities, this high input of mechanical energy drives strong turbulence and quenches star formation in the bridge gas except for the giant Hii region near UGC 12915. Our model suggests that we observe this galaxy head-on collision near the time of maximum CO and H 2 emission.

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“…We thus conclude that the bridge region delimited by Braine et al (2003, Fig. A.1) is somewhat too small.…”

Section: Isolating the Bridge Regionmentioning

confidence: 76%

Section: Gas Distributionmentioning

confidence: 99%

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A dynamical model for the Taffy galaxies UGC 12914/5

Vollmer¹,

Braine²,

Soida³

2012

A&A

Self Cite

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“…low impact parameter), in which the ISM of the progenitors collides. The best example of this is UGC 12914/5 (the Taffy Galaxies; Braine et al 2003), in which about 25% of the CO emission originates between the nuclei. In this system, the progenitors collided at about 600 km s −1 .…”

Section: Merger Geometry and Stage And Cold Gas Concentrationmentioning

confidence: 99%

“…In this system, the progenitors collided at about 600 km s −1 . Braine et al (2003) argued that while this would have ionised the gas, the cooling time is short enough that H 2 could reform while the discs are still passing through each other. From the ratio of 12 CO to 13 CO these authors found that the optical depth of CO in the bridge was far less than on the nuclei.…”

Section: Merger Geometry and Stage And Cold Gas Concentrationmentioning

confidence: 99%

NGC 6240: merger-induced star formation and gas dynamics

Engel

Davies

Genzel

et al. 2010

A&A

111

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We present spatially resolved integral field spectroscopic K-band data at a resolution of 0.13 (60 pc) and interferometric CO(2-1) line observations of the prototypical merging system NGC 6240. Despite the clear rotational signature, the stellar kinematics in the two nuclei are dominated by dispersion. We use Jeans modelling to derive the masses and the mass-to-light ratios of the nuclei. Combining the luminosities with the spatially resolved Brγ equivalent width shows that only 1/3 of the K-band continuum from the nuclei is associated with the most recent star forming episode; and that less than 30% of the system's bolometric luminosity and only 9% of its stellar mass is due to this starburst. The star formation properties, calculated from typical merger star formation histories, demonstrate the impact of different assumptions about the star formation history. The properties of the nuclei, and the existence of a prominent old stellar population, indicate that the nuclei are remnants of the progenitor galaxies' bulges.

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Shock Acceleration of Relativistic Particles in Galaxy Collisions

Lisenfeld

Völk

2013

Cosmic Rays in Star-Forming Environments

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A molecular gas bridge between the Taffy galaxies

Cited by 54 publications

References 11 publications

A dynamical model for the Taffy galaxies UGC 12914/5

A dynamical model for the Taffy galaxies UGC 12914/5

NGC 6240: merger-induced star formation and gas dynamics

Shock Acceleration of Relativistic Particles in Galaxy Collisions

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