Integral field spectroscopy of local LCBGs: NGC 7673, a case study. Physical properties of star-forming regions

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Physical properties of the star-forming regions in the local Luminous Compact Blue Galaxy (LCBG) NGC 7673 are studied in detail using 3D spectroscopic data taken with the PMAS fibre pack (PPAK) integral field unit at the 3.5-m telescope in the Centro Astronomico Hispano Aleman (CAHA). We derive integrated and spatially resolved properties such as extinction, star formation rate (SFR) and metallicity for this galaxy. Our data show an extinction map with maximum values located at the position of the main clumps of star formation showing small spatial variations [E(B - V)(t) = 0.12-0.21 mag]. We derive an H alpha-based SFR for this galaxy of 6.2 +/- 0.8M(circle dot) yr(-1) in agreement with the SFR derived from infrared and radio continuum fluxes. The star formation is located mainly in clumps A, B, C and F. Different properties measured in clump B make this region peculiar. We find the highest H alpha luminosity with an SFR surface density of 0.5 M-circle dot yr(-1) kpc(-2) in this clump. In our previous work, the kinematic analysis for this galaxy shows an asymmetrical ionized gas velocity field with a kinematic decoupled component located at the position of clump B. This region shows the absence of strong absorption features and the presence of a Wolf-Rayet stellar population indicating that this is a young burst of massive stars. Furthermore, we estimate a gas metallicity of 12 + log(O/H) = 8.20 +/- 0.15 (0.32 solar) for the integrated galaxy using the R23 index. The values derived for the different clumps with this method show small metallicity variations in this galaxy, with values in the range 8.12 (for clump A) to 8.23 (for clump B) for 12 + log(O/H). The analysis of the emission-line ratios discards the presence of any active galactic nuclei (AGN) activity or shocks as the ionization source in this galaxy. Between the possible mechanisms to explain the starburst activity in this galaxy, our 3D spectroscopic data support the scenario of an on-going interaction with the possibility for clump B to be the dwarf satellite galaxy.
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. © 2010 The Authors © 2010 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. We are grateful to the anonymous referee for his valuable comments which have led to an improvement in this paper. We acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2006-02358 and AYA2006-15698-C02-02. This work is partially funded by the Spanish MICINN under the Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC. ACM acknowledges support from the Juan de la Cierva Program financed by the Spanish MICINN. JPG acknowledges support from a University of Florida Alumni Fellowship and RG from NASA Grant LTSA NA65-11635. SFS thanks the sub-programs of Viabilidad, Diseño, Acceso y Mejora de ICTS ICTS-2009-10 and the PAI Proyecto de Excelencia P08-FWM-04319 and the funds of the PAI research group FQM360. SFS thanks the Spanish Plan Nacional de Astronomía program AYA2005-09413-C02-02.
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