Chemical Abundance Gradients in the Star‐forming Ring Galaxies

Корчагин, В. И.; Vorobyov, Eduard I.; Mayya, Y. D.

doi:10.1086/307695

Cited by 5 publications

(6 citation statements)

References 16 publications

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“…Density Wave or "Forest Fire"? Korchagin et al (1998Korchagin et al ( , 1999Korchagin et al ( , 2001) account for radial color gradients interior to the ring and slight offsets between the Hα and continuum rings by invoking a self-sustaining radially propagating starburst. This model dispenses with the orbit crowded ring altogether and is reminiscent of the explanation of flocculent spiral arms by Gerola & Seiden (1978).…”

Section: Follow-up Observationsmentioning

confidence: 99%

“…Ring galaxies are striking examples of the ability of collisions to transform both the morphology and star-forming activity of a spiral galaxy. Numerical studies since the mid-1970s argue persuasively that the optically prominent rings are in fact outwardly propagating zones of strong orbit crowding within the disk of a spiral induced by the near central passage of a companion galaxy (e.g., Lynds & Toomre 1976;Struck & Higdon 1993;Mapelli et al 2008, but see Korchagin et al 1999Korchagin et al , 2001 for a very different formation mechanism). The expanding rings are transient but maintain their coherence for roughly one outer-disk rotation period (∼300 Myr).…”

Section: Introductionmentioning

confidence: 99%

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Wheels of Fire. Iv. Star Formation and the Neutral Interstellar Medium in the Ring Galaxy Am0644-741

Higdon

Rand

2011

ApJ

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We combine data from the Australia Telescope National Facility and the Swedish ESO Submillimeter Telescope to investigate the neutral interstellar medium (ISM) in AM0644-741, a large and robustly star-forming ring galaxy. The galaxy's ISM is concentrated in the 42 kpc diameter starburst ring, but appears dominated by atomic gas, with a global molecular fraction (f mol ) of only 0.079 ± 0.005. Apart from the starburst peak, the gas ring appears stable against the growth of gravitational instabilities (Q gas = 2 − 7). Including the stellar component lowers Q overall, but not enough to make Q < 1 everywhere. The ring's global star formation efficiency (SFE) appears somewhat elevated relative to early spirals, but varies around the ring by more than an order of magnitude, peaking where star formation is most intense. AM0644-741's star formation law is peculiar: HI follows a Schmidt law while H 2 is uncorrelated with star formation rate density. Photodissociation models yield low volume densities in the ring, particularly in the starburst quadrant (n ≈ 2 cm −3 ), implying a warm neutral medium dominated ISM. At the same time, the ring's pressure and ambient far-ultraviolet radiation field lead to the expectation of a predominantly molecular ISM. We argue that the ring's peculiar star formation law, n, SFE, and f mol result from the ISM's 100 Myr confinement time in the starburst ring, which amplifies the destructive effects of embedded massive stars and supernovae. As a result, the ring's molecular ISM becomes dominated by small clouds where star formation is most intense, causing M H 2 to be underestimated by 12 CO line fluxes: in effect X CO ≫ X Gal despite the ring's solar metallicity. The observed large HI component is primarily a low density photodissociation product, i.e., a tracer rather than a precursor of massive star formation. Such an "over-cooked" ISM may be a general characteristic of evolved starburst ring galaxies.3 Visiting astronomer, European Southern Observatory. 4 Visiting astronomer, Cerro Tololo Inter-American Observatory.properties of the star-forming ISM in an evolved ring galaxy compare with other systems?This paper is organized as follows: The observations and data reduction are outlined in Section 2. The results derived using these observations are presented in Section 3, including the ring's metallicity, the distribution and kinematics of HI, the relative proportions of molecular and atomic gas, star formation efficiency, and their variations around the ring. We also consider the ring's gravitational stability, and whether or not star formation follows a Schmidt law. In Section 4 we consider the role played by pressure and ambient FUV radiation field in determining the ring's molecular fraction. We also discuss our results in the context of an alternate view of ring galaxies, in which the ring represents a self-sustaining propagating starburst. Our conclusions are given in Section 5. Throughout this paper we adopt a flat ΛCDM cosmology based on the 7 year WMAP results (Komatsu et al. 2011),...

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Section: Follow-up Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Wheels of Fire. Iv. Star Formation and the Neutral Interstellar Medium in the Ring Galaxy Am0644-741

Higdon

Rand

2011

ApJ

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“…The star-formation rate found in the outer ring of the Cartwheel galaxy is about 6.7 × 10 7 M Myr −1 (Higdon 1995). After the passage of such star-forming rings, colour gradients are expected in the disc and have been observed in several ring galaxies (Korchagin et al 1999). In particular, such radial age gradients have been found in the optical and the NIR in the Cartwheel galaxy (Marcum, Appleton & Hidgon 1992).…”

Section: Rings and Spokesmentioning

confidence: 96%

Numerical simulations of interacting gas-rich barred galaxies: vertical impact of small companions

Berentzen¹,

Athanassoula

Heller

et al. 2003

Monthly Notices of the Royal Astronomical Society

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We investigate the dynamical effects of an interaction between an initially barred galaxy and a small spherical companion using an N‐body/smoothed‐particle‐hydrodynamics algorithm. In the models described here the small companion passes through the disc of the larger galaxy nearly perpendicular to its plane. The impact positions and times are varied with respect to the phase of the bar and the dynamical evolution of the disc. The interactions produce expanding ring structures, offset bars, spokes and other asymmetries in the stars and gas. These characteristic signatures of the interaction are present in the disc for about 1 Gyr. We find that in some cases it is possible to destroy the bar while keeping the disc structure. In general, the central impacts cause larger damage to the bar and the disc than the peripheral ones. The interaction tends to accelerate the transition from a strongly‐barred galaxy to a weakly‐ or non‐barred galaxy. The final disc morphology is determined more by the impact position relative to the bar rather than the impact time.

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“…An intruder has only a role of triggering the first event of star formation close to the point of impact; phenomena related to massive stars control the star formation at all other radii. As a particular case of the latter scenario we use the "fire in the forest" (hereafter FIF) model earlier applied for the interpretation of the surface brightness and the chemical abundance gradients in ring galaxies (Korchagin et al 1998;Korchagin et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Optical Color Gradients in Star‐forming Ring Galaxies

Корчагин

Mayya

Vorobyov

2001

ApJ

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We compute radial color gradients produced by an outwardly propagating circular wave of star formation and compare our results with color gradients observed in the classical ring galaxy, the "Cartwheel". We invoke two independent models of star formation in the ring galaxies. The first one is the conventional density wave scenario, in which an intruder galaxy creates a radially propagating density wave accompanied by an enhanced star formation following the Schmidt's law. The second scenario is a pure self-propagating star formation model, in which the intruder only sets off the first burst of stars at the point of impact. Both models give essentially the same results. Systematic reddening of B − V , V − K colors towards the center, such as that observed in the Cartwheel, can be obtained only if the abundance of heavy elements in the starforming gas is a few times below solar. The B − V and V − K color gradients observed in the Cartwheel can be explained as a result of mixing of stellar populations born in a star-forming wave propagating through a low-metallicity gaseous disk, and a pre-existing stellar disk of the size of the gaseous disk with color properties typical to those observed in nearby disk galaxies.

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Chemical Abundance Gradients in the Star‐forming Ring Galaxies

Cited by 5 publications

References 16 publications

Wheels of Fire. Iv. Star Formation and the Neutral Interstellar Medium in the Ring Galaxy Am0644-741

Wheels of Fire. Iv. Star Formation and the Neutral Interstellar Medium in the Ring Galaxy Am0644-741

Numerical simulations of interacting gas-rich barred galaxies: vertical impact of small companions

Optical Color Gradients in Star‐forming Ring Galaxies

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