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Ultraviolet and Infrared Diagnostics of Star Formation and Dust in NGC 7331

Thilker, David A. and Boissier, Samuel and Bianchi, Luciana and Calzetti, Daniela and Boselli, Alessandro and Dale, Daniel A. and Seibert, Mark and Braun, Robert and Burgarella, Denis and Gil de Paz, Armando and Helou, George and Walter, Fabian and Kennicutt, R. C., Jr. and Madore, Barry F. and Martin, D. Christopher and Barlow, Tom A. and Forster, Karl and Friedman, Peter G. and Morrissey, Patrick and Neff, Susan G. and Schiminovich, David and Small, Todd and Wyder, Ted K. and Donas, José and Heckman, Timothy M. and Lee, Young-Wook and Milliard, Bruno and Rich, R. Michael and Szalay, Alex S. and Welsh, Barry Y. and Yi, Sukyoung K. (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. doi:10.1086/516646.

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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
Related URLs:
URLURL TypeDescription
Thilker, David A.0000-0002-8528-7340
Boissier, Samuel0000-0002-9091-2366
Calzetti, Daniela0000-0002-5189-8004
Dale, Daniel A.0000-0002-5782-9093
Seibert, Mark0000-0002-1143-5515
Gil de Paz, Armando0000-0001-6150-2854
Helou, George0000-0003-3367-3415
Walter, Fabian0000-0003-4793-7880
Kennicutt, R. C., Jr.0000-0001-5448-1821
Madore, Barry F.0000-0002-1576-1676
Martin, D. Christopher0000-0002-8650-1644
Forster, Karl0000-0001-5800-5531
Morrissey, Patrick0000-0001-8177-1023
Rich, R. Michael0000-0003-0427-8387
Additional Information:© 2009 American Astronomical Society. Print publication: Issue 2 (2007 December); received 2006 July 17; accepted for publication 2006 September 26. 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 withNASA. This research has made use of NASA’s Astrophysics Data System.
Group:Space Radiation Laboratory, Space Astrophysics Laboratory, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:galaxies: evolution; galaxies: individual (NGC 7331); infrared: galaxies; ultraviolet: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20091203-140413022
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Official Citation:Ultraviolet and Infrared Diagnostics of Star Formation and Dust in NGC 7331 David A. Thilker, Samuel Boissier, Luciana Bianchi, Daniela Calzetti, Alessandro Boselli, Daniel A. Dale, Mark Seibert, Robert Braun, Denis Burgarella, Armando Gil de Paz, George Helou, Fabian Walter, R. C. Kennicutt, Jr., Barry F. Madore, D. Christopher Martin, Tom A. Barlow, Karl Forster, Peter G. Friedman, Patrick Morrissey, Susan G. Neff, David Schiminovich, Todd Small, Ted K. Wyder, José Donas, Timothy M. Heckman, Young-Wook Lee, Bruno Milliard, R. Michael Rich, Alex S. Szalay, Barry Y. Welsh, and Sukyoung K. Yi 2007 ApJS 173 572-596 doi: 10.1086/516646
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16869
Deposited On:06 Jan 2010 01:02
Last Modified:08 Nov 2021 23:30

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