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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 421361.0, MPI für Astronomie / Publikationen_mpia
Molecular gas and dust in Arp 94: the formation of a recycled galaxy in an interacting system
Authors:Lisenfeld, U.; Mundell, C. G.; Schinnerer, E.; Appleton, P. N.; Allsopp, J.
Date of Publication (YYYY-MM-DD):2008
Title of Journal:The Astrophysical Journal
Journal Abbrev.:ApJ
Start Page:181
End Page:193
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We present new results for the molecular gas, dust emission, and the ionized gas in J1023+1952, an H I-rich intergalactic star-forming tidal dwarf galaxy candidate. It is located at the projected intersection of two faint stellar tidal streams wrapped around the interacting pair of galaxies NGC 3227/6 (Arp 94). Using the IRAM 30 m telescope, emission from 12CO(1-0) and 12CO(2-1) was detected across the entire extent of the neutral hydrogen cloud associated with J1023+1952, a region of the size of 8.9×5.9 kpc. The molecular gas is found to be abundant over the entire H I cloud, with H2-to-H I gas mass ratios between 0.5 and 1.7. New Spitzer mid-infrared observations at 3.6, 4.5, 5.8, 8.0, 15, and 24 mum show that young SF is restricted to the southern part of the cloud. Despite the relatively uniform H2 and H I column density across the cloud, young SF occurs only in those regions where the velocity dispersion in the CO and H I is a factor of ~2 lower (FWHM of 30-70 km s-1) than elsewhere in the cloud (FWHM of 80-120 km s-1). Thus, the kinematics of the gas, in addition to its column density, seems to be a crucial factor in triggering SF. Optical/infrared spectral energy distributions (SEDs) and Halpha photometry confirm that all the knots are young. Optical spectroscopy of the brightest SF region allowed us to determine the metallicity [12+log(O/H)=8.6+/-0.2] and the extinction (AB=2.4). This shows that J1023+1952 is made from metal-enriched gas which is inconsistent with the hypothesis that it represents a preexisting dwarf galaxy. Instead, it must be formed from recycled, metal-enriched gas, expelled from NGC 3227 or NGC 3226 in a previous phase of the interaction.
Free Keywords:Galaxies: Active; galaxies: individual (Arp 94); galaxies: individual (J1023+1952); Galaxies: Individual: NGC Number: NGC 3227; Galaxies: Interactions; Galaxies: ISM- Molecular Data
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2008ApJ...685..181L [ID No:1]
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