Ultraviolet and infrared diagnostics of star formation and dust in NGC 7331



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Gil de Paz, Armando and otros, ... (2007) Ultraviolet and infrared diagnostics of star formation and dust in NGC 7331. Astrophysical journal supplement series, 173 (2). pp. 572-596. ISSN 0067-0049

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Official URL: http://dx.doi.org/10.1086/516646


We present images of NGC 7331 obtained with GALEX and Spitzer, tracing UV and IR signatures of star formation. NGC 7331's morphology at 8-850 μm is dominated by a central dust ring. This structure is a vigorous site of star formation (hosting one-third of the present activity) but remains inconspicuous in our GALEX UV imagery. Radial profile analysis and photometry for discrete UV- and UV+IR-selected substructures indicate a decline in UV extinction with increasing galactocentric distance, although highly attenuated star-forming regions can be found throughout the disk. UV-optical surface brightness profiles suggest a recent birthrate parameter (b_8) that is highest in the outer part of the disk, even though the local star formation intensity peaks in the ring. Bolometric luminosity and UV attenuation are correlated in substructures on 0.4 kpc scales, with a relationship similar to that established for starburst galaxies. The distribution of substructures in L(IR)/L(FUV), L_λ(FUV)/L_λ(NUV) space suggests that the majority of the disk is best characterized by Milky Way-type dust, with the exception of sources in the star-forming ring. As found by Calzetti et al. in M51, the observed 8 and 24 μm luminosity for substructures in NGC 7331 are correlated, showing a decline in L_ν(8 μm)/L_ν(24 μm) with increasing luminosity. We demonstrate the dependence of L_ν(8 μm)/L_ν(24 μm) on the local extinction-corrected Hα surface brightness (hence current Σ_SFR). A power law of slope 1.64 (1.87) accurately describes the Schmidt-law relation versus Σ_H_2 (Σ_gas) for molecular-dominated environments. The same locations show no correlation between Σ_SFR and Σ_HI . For atomic-dominated regions above an apparent local star formation threshold, we found a trend for increasing Σ_SFR at higher Σ_HI , although the Schmidt-law correlation with molecular-only surface density persists in areas dominated by atomic gas.

Item Type:Article
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© 2007. The American Astronomical Society. All rights reserved. Artículo firmado por 31 autores. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. Support for this work, part of the Spitzer Space Telescope Legacy Science Program, was provided by NASA through contract 1224769 issued by the Jet Propulsion Laboratory (JPL), California Institute of Technology, under NASA contract 1407. This research has made use of the NASA/ IPAC Extragalactic Database (NED) which is operated by JPL, California Institute of Technology, under contract with NASA. This research has made use of NASA’s Astrophysics Data System.

Uncontrolled Keywords:Nearby galaxies survey; Multiband imaging photometer; Radial extinction profiles; Spitzer-space-telescope; Virgo cluster galaxies; Large-magellanic-cloud; Global Schmidt law; Spiral galaxies; Forming galaxies; HII-regions
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:35800
Deposited On:18 Feb 2016 15:06
Last Modified:10 Dec 2018 15:05

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