Spiral Density Wave Triggering of Star Formation in Sa and Sab Galaxies

Martínez-García, Eric E.; González-Lópezlira, Rosa A.; Bruzual-A., Gustavo

doi:10.1088/0004-637x/694/1/512

Cited by 72 publications

(79 citation statements)

References 102 publications

(119 reference statements)

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“…It was found that the surface star formation rate densities are higher in arms than that in the interarm regions by approximately 0.6 dex, and that the star formation rate changes along the spiral arm, being higher in the leading part than in the trailing part of the arm (Martínez-García et al 2009;Silva-Villa & Larsen 2012). As was shown in our simulations (models 75, 76 in Figs.…”

Section: Figsupporting

confidence: 84%

The relation between magnetic and material arms in models for spiral galaxies

Moss

Beck

Sokoloff

et al. 2013

A&A

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Context.Observations of polarized radio emission show that large-scale (regular) magnetic fields in spiral galaxies are not fully axisymmetric, but generally stronger in interarm regions. In some nearby galaxies such as NGC 6946 they are organized in narrow magnetic arms situated between the material spiral arms. Aims. The phenomenon of magnetic arms and their relation to the optical spiral arms (the material arms) calls for an explanation in the framework of galactic dynamo theory. Several possibilities have been suggested but are not completely satisfactory; here we attempt a consistent investigation. Methods. We use a 2D mean-field dynamo model in the no-z approximation and add injections of small-scale magnetic field, taken to result from supernova explosions, to represent the effects of dynamo action on smaller scales. This injection of small scale field is situated along the spiral arms, where star-formation mostly occurs. Results. A straightforward explanation of magnetic arms as a result of modulation of the dynamo mechanism by material arms struggles to produce pronounced magnetic arms, at least with realistic parameters, without introducing new effects such as a time lag between Coriolis force and α-effect. In contrast, by taking into account explicitly the small-scale magnetic field that is injected into the arms by the action of the star forming regions that are concentrated there, we can obtain dynamo models with magnetic structures of various forms that can be compared with magnetic arms. These are rather variable entities and their shape changes significantly on timescales of a few 100 Myr. Properties of magnetic arms can be controlled by changing the model parameters. In particular, a lower injection rate of small-scale field makes the magnetic configuration smoother and eliminates distinct magnetic arms. Conclusions. We conclude that magnetic arms can be considered as coherent magnetic structures generated by large-scale dynamo action, and associated with spatially modulated small-scale magnetic fluctuations, caused by enhanced star formation rates within the material arms.

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Section: Figsupporting

confidence: 84%

The relation between magnetic and material arms in models for spiral galaxies

Moss

Beck

Sokoloff

et al. 2013

A&A

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“…This estimate is of course affected by inclination, the photometric bands used, metallicity, etc. Martínez-García et al (2009) studied the color gradient variation over different spiral galaxies. The authors used a sample of 13 spiral galaxies, and showed how a fraction of the arms analyzed clearly showed the expected color gradient suggested by the density wave theory.…”

Section: Discussionmentioning

confidence: 99%

The relation between surface star formation rate density and spiral arms in NGC 5236 (M 83)

Silva-Villa

Larsen

2012

A&A

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Context. For a long time the consensus has been that star formation rates are higher in the interior of spiral arms in galaxies, compared to inter-arm regions. However, recent studies have found that the star formation inside the arms is not more efficient than elsewhere in the galaxy. Previous studies have based their conclusion mainly on integrated light. We use resolved stellar populations to investigate the star formation rates throughout the nearby spiral galaxy NGC 5236. Aims. We aim to investigate how the star formation rate varies in the spiral arms compared to the inter-arm regions, using optical space-based observations of NGC 5236. Methods. Using ground-based Hα images we traced regions of recent star formation, and reconstructed the arms of the galaxy. Using HST/ACS images we estimate star formation histories by means of the synthetic CMD method. Results. Arms based on Hα images showed to follow the regions where stellar crowding is higher. Star formation rates for individual arms over the fields covered were estimated between 10 to 100 Myr, where the stellar photometry is less affected by incompleteness.Comparison between arms and inter-arm surface star formation rate densities (Σ SFR ) suggested higher values in the arms (∼0.6 dex). Over a small fraction of one arm we checked how the Σ SFR changes for the trailing and leading part. The leading part of the arm showed to have a higher Σ SFR in the age range 10-100 Myr. Conclusions. Predictions from the density wave theory of a rapid increase in the star formation at the edge where the stars and the gas enter the density wave are confirmed. The Σ SFR presents a steep decrease with distance from the center of the arms through the inter-arm regions.

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“…Star formation occurs mainly in the midplane of the thin disks, in particular along spiral arms, where recent events are impressively traced by giant H ii regions. Spiral density waves may induce star formation (see Martínez-García et al 2009; and references therein), although it has been suggested that this mechanism may contribute less than 50 % to the overall star formation rate (Elmegreen & Elmegreen 1986). …”

Section: Disks and Long-term Evolutionary Trends For Disk Galaxiesmentioning

confidence: 99%

Observational Comparison of Star Formation in Different Galaxy Types

Grebel

2010

Proc. IAU

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Abstract. Galaxies cover a wide range of masses and star formation histories. In this review, I summarize some of the evolutionary key features of common galaxy types. At the high-mass end, very rapid, efficient early star formation is observed, accompanied by strong enrichment and later quiescence, well-described by downsizing scenarios. In the intermediate-mass regime, early-type galaxies may still show activity in low-mass environments or when being rejuvenated by wet mergers. In late-type galaxies, we find continuous, though variable star formation over a Hubble time. In the dwarf regime, a wide range of properties from bursty activity to quiescence is observed. Generally, stochasticity dominates here, and star formation rates and efficiencies tend to be low. Morphological types and their star formation properties correlate with environment.

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Spiral Density Wave Triggering of Star Formation in Sa and Sab Galaxies

Cited by 72 publications

References 102 publications

The relation between magnetic and material arms in models for spiral galaxies

The relation between magnetic and material arms in models for spiral galaxies

The relation between surface star formation rate density and spiral arms in NGC 5236 (M 83)

Observational Comparison of Star Formation in Different Galaxy Types

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