Meier, David S. and Turner, Jean L. and Beck, Sara C. and Gorjian, Varoujan and Tsai, Chao-Wei and Van Dyk, Schuyler D. (2010) First Views of a Nearby LIRG: Star Formation and Molecular Gas in IRAS 04296+2923. Astronomical Journal, 140 (5). pp. 1294-1305. ISSN 0004-6256 http://resolver.caltech.edu/CaltechAUTHORS:20101111-100138404
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We present a first look at the local luminous infrared galaxy (LIRG) IRAS 04296+2923. This barred spiral galaxy, overlooked because of its location behind the Taurus molecular cloud, is among the half dozen closest (D = 29 Mpc) LIRGs. More IR-luminous than either M82 or the Antennae, it may be the best local example of a nuclear starburst caused by bar-mediated secular evolution. We present Palomar J and Pa β images, Very Large Array continuum maps from λ= 20-1.3 cm, a subarcsecond Keck Long Wavelength Spectrometer image at 11.7 μm and Owens Valley Millimeter Array CO(1-0), ^(13)CO(1-0), and 2.7 mm continuum images. The J-band image reveals a symmetric barred spiral galaxy. Two bright, compact mid-infrared and radio sources in the nucleus mark a starburst that is energetically equivalent to ~10^5 O7 stars, separated by ≲50 pc. This is probably a pair of young super star clusters, with estimated stellar masses of ~10^7 M_☉ each. The nuclear starburst is forming stars at the rate of ~12 ± 6 M_☉ yr^(–1), or about half of the total star formation rate for the galaxy of ~25 ± 10 M_☉ yr^(–1). IRAS 04296+2923 is very bright in CO, and among the most gas-rich galaxies in the local universe. The ^(12)CO luminosity of the inner half kpc is equivalent to that of the entire Milky Way. While the most intense CO emission is extended over a 15" (2 kpc) diameter region, the nuclear starburst is confined to within 1"-2" (150-250 pc) of the dynamical center. Based on masses obtained with ^(13)CO, we find that the CO conversion factor in the nucleus is lower than the Galactic value, X^(Gal)_(CO) by a factor of three to four, typical of gas-rich spiral nuclei. The nuclear star formation efficiency (SFE) is ^(nuc)M_(gas)/SFR^(nuc) = 2.7 × 10^(–8)yr^(–1), corresponding to a gas consumption timescale, τ^(nuc)_(SF) ~ 4 × 10^7 yr. The SFE is 10 times lower in the disk, with τ^(disk)_(SF) ~ 3.3 × 10^8 yr. The low absolute SFE in the disk implies that the molecular gas is not completely consumed before it drifts into the nucleus, and is capable of fueling a sustained nuclear starburst. IRAS 04296+2923 appears to be beginning a 100 Myr period as an LIRG, during which it will turn much of its 6 × 10^9 M_☉ of molecular gas into a nuclear cluster of stars.
|Additional Information:||© 2010 American Astronomical Society. Received 2008 December 18; accepted 2010 August 26; published 2010 October 13. D.S.M. acknowledges support from the National Radio Astronomy Observatory which is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation. The anonymous referee is thanked for a helpful report. The Owens Valley Millimeter Interferometer is operated by Caltech with support from the NSF under grant AST-9981546. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Facilities: CMA, Hale (Wide-field Infrared Camera), Keck:I (Long Wavelength Spectrometer), VLA|
|Subject Keywords:||galaxies: individual (IRAS 04296+2923, 2MASX J04324860+2929578); galaxies: ISM; galaxies: starburst; radio continuum: galaxies|
|Classification Code:||PACS: 98.35.Ac; 98.38.Dq; 95.85.Hp; 98.20.Gm; 98.20.Di; 98.35.Hj|
|Official Citation:||David S. Meier et al 2010 The Astronomical Journal 140 1294 doi: 10.1088/0004-6256/140/5/1294|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||11 Nov 2010 21:17|
|Last Modified:||26 Dec 2012 12:37|
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