Molecular Gas and Dust in Arp 94 : the Formation of a Recycled Galaxy in an Interacting System

Content Provider	Semantic Scholar
Author	Mundell, Carole G. Schinnerer, Eva
Copyright Year	2008
Abstract	We present new results for the molecular gas, dust emission and the ionized gas in J1023+1952, an Hi 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 30m telescope, emission from CO(1-0) and CO(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, as well as in the nuclear region and outer disk of NGC 3227. The molecular gas is found to be abundant over the entire Hi cloud, with H2-to-Hi 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 μm show that young SF is restricted to the southern part of the cloud. Despite the relatively uniform H2 and Hi column density across the cloud, young SF occurs only in those regions where the velocity dispersion in the CO and Hi is a factor of ∼two 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 Hα photometry confirm that all the knots are young, with a tentative age sequence from the south-west (oldest knots) to the north-east (youngest). 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 pre-existing dwarf galaxy. Instead, it must be formed from recycled, metal-enrichd gas, expelled from NGC 3227 or NGC 3226 in a previous phase of the interaction. Subject headings: molecular data – galaxies: active – galaxies: interactions – galaxies : ISM – galaxies: individual (Arp 94, J1023+1952, NGC 3227)
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://arxiv.org/pdf/0807.0176v1.pdf
Alternate Webpage(s)	http://authors.library.caltech.edu/12601/1/LISapj08b.pdf
Language	English
Access Restriction	Open
Subject Keyword	ARP spoofing Active galactic nucleus Cloud computing Computer recycling DWARF Eighty Extinction, Psychological Full Width at Half Maximum GUCY2C protein, human Galaxy Hardware-based full disk encryption Hydrogen Implicit Shape Model Indolent Systemic Mastocytosis Interaction Intersection of set of elements Knot (unit) Mandibular right first molar mesial hemisection Medical Subject Headings New General Catalogue Photometry Projections and Predictions Stellar (payment network) Velocity (software development)
Content Type	Text
Resource Type	Article