Galaxy Collisions: Modeling Star Formation in Different Environments

AbstractIn this contribution, we will overview the NANTEN observations of molecular clouds faced to HIIregions, supershells, and interacting galaxies, which demonstrate that star/molecular cloud formation is being triggered by young OB associations, supershells, and collisions between galaxies. The large volume filling factor of explosive events like supernovae, ultraviolet radiation fields and stellar winds of massive stars suggest that most of the interstellar medium has been agitated by such strong impacts and triggered star formation is a common event at all scales from small molecular clouds to large galaxy-galaxy mergers. The consequence is the increase of star formation efficiency in many cases, and that more massive stars or clusters of more member stars tend to be formed by triggering than in spontaneous star formation.

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Virgo and other Late-Type Dwarfs

Highlights of Astronomy ◽

10.1017/s1539299600020098 ◽

1998 ◽

Vol 11 (1) ◽

pp. 105-106

Author(s):

N. Brosch ◽

A. Heller ◽

E. Almoznino

Keyword(s):

Star Formation ◽

Virgo Cluster ◽

Disk Galaxies ◽

Late Type ◽

Morphological Classification ◽

External Effects ◽

Low Mass ◽

Galaxy Collisions ◽

Intracluster Matter

We attempt to solve the question of star formation triggers and star formation laws by studying samples of simple objects and defining carefully the possible external effects. Among the star formation (SF) triggers there are some that can operate only in large disk galaxies. These are shear instabilities and density waves, and we can eliminate them if we restrict the sample to diskless objects of low mass. Such galaxies, which do show star formation, are late-type dwarf galaxies (DGs). Other SF triggers are related to the neighborhood a galaxy finds itself in. Such triggers are galaxy-galaxy collisions and galaxy-intracluster matter interactions (stripping, shocks, etc.). These also can be eliminated by properly choosing the sample to study; one selects galaxies from neigh-borhoods of widely different densities (of galaxies) and compares their SF parameters. We selected our first samples in a region of relatively high galaxy density, where a complete morphological classification of objects was available, and suitable depth in brightness sampling could readily be achieved. This is the Virgo cluster, where Binggeli, Sandage and Tammann (1985, BST) provide a sample of more than 2000 DGs. Among those, some 25% are of late type and are classified by BST as blue compact dwarfs (BCDs), as Magellanic irregulars (Im) of five possible sub-classes, or as combinations of those two classifications.

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Case Studies of Mass Transfer and Star Formation in Galaxy Collisions

Symposium - International Astronomical Union ◽

10.1017/s0074180900198031 ◽

2004 ◽

Vol 217 ◽

pp. 400-405

Author(s):

Curtis Struck

Keyword(s):

Mass Transfer ◽

Star Formation ◽

Case Studies ◽

Structural Parameters ◽

Dynamical Models ◽

Star Forming ◽

Star Forming Regions ◽

Individual Star ◽

Galaxy Collisions

The amount, timing and ultimate location of mass transfer and induced star formation in galaxy collisions are sensitive functions of orbital and galaxy structural parameters. I discuss the role of detailed case studies and describe the results for two systems, Arp 284 and NGC 2207/IC 2163, that have been studied with both multiwaveband observations, and detailed dynamical models. The models yield the mass transfer and compressional histories of the encounters and the “probable causes” or triggers of individual star-forming regions.

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A Multiwavelength Survey of Interacting Galaxies

International Astronomical Union Colloquium ◽

10.1017/s0252921100005236 ◽

1990 ◽

Vol 124 ◽

pp. 285-290 ◽

Cited By ~ 1

Author(s):

H. Bushouse ◽

S. Lamb ◽

K.-Y. Lo ◽

S. Lord ◽

M. Werner

Keyword(s):

Star Formation ◽

Emission Line ◽

Near Infrared ◽

Sample Selection ◽

Far Infrared ◽

Infrared Photometry ◽

Star Formation Activity ◽

Comparison Of The Results ◽

Galaxy Collisions ◽

Tidal Tails

Galaxy-galaxy collisions are known to produce drastic changes in morphology and, in many cases, enhance the level of star formation activity in galaxies. In order to better quantify the effects that interactions have on the star formation characteristics of galaxies we have undertaken a multiwavelength survey of a large sample of interacting disk-type galaxies. The sample is optically-selected, the inclusion of systems having been based upon the presence of unusual morphological features—such as tidal tails, plumes, rings, warped disks—suggestive of tidal interaction. The sample is composed of about 115 systems, most of which are spiral-spiral pairs, with a few spiral-elliptical pairs and a few merging systems (see Bushouse 1986 for more details of the sample selection). This sample has now been studied in the optical, infrared, and radio regimes, including optical spectra and Ha images, near-infrared photometry and imaging, far-infrared photometry, HI 21cm emission-line measurements, VLA 20cm maps, and CO emission-line measurements. This paper presents an overview and comparison of the results of the optical, infrared and CO surveys. With these data we can compare the far-infrared and CO properties of the galaxies with the classic optical and radio indicators of star formation activity and thereby determine what, if any, relationships exist between star formation activity and the far-infrared and CO properties of the galaxies.

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