The spatially resolved correlation between [NII] 205μm line emission and the 24μm continuum in nearby galaxies
Abstract
A correlation between the 24 μm continuum and the [Nii] 205 μm line emission may arise if both quantities trace the star formation activity on spatially-resolved scales within a galaxy, yet has so far only been observed in the nearby edge-on spiral galaxy NGC 891. We therefore assess whether the [Nii] 205−24 μm emission correlation has some physical origin or is merely an artefact of line-of-sight projection effects in an edge-on disc. We search for the presence of a correlation in Herschel and Spitzer observations of two nearby face-on galaxies, M 51 and M 83, and the interacting Antennae galaxies NGC 4038 and 4039. We show that not only is this empirical relationship also observed in face-on galaxies, but also that the correlation appears to be governed by the star formation rate (SFR). Both the nuclear starburst in M 83 and the merger-induced star formation in NGC 4038/9 exhibit less [Nii] emission per unit SFR surface density than the normal star-forming discs. These regions of intense star formation exhibit stronger ionization parameters, as traced by the 70/160 μm far-infrared (FIR) colour. These observations suggest the presence of higher ionization lines that may become more important for gas cooling, thereby reducing the observed [Nii] 205 μm line emission in regions with higher star formation rates. Finally, we present a general relation between the [Nii] 205 μm line flux density and SFR density for normal star-forming galaxies, yet note that future studies should extend this analysis by including observations with wider spatial coverage for a larger sample of galaxies.
Additional Information
© 2016 ESO. Received 26 October 2015. Accepted 30 December 2015. We thank the anonymous referee for the useful comments and suggestions that helped to improve this paper. T.M.H. and E.I. acknowledge CONICYT/ALMA funding Program in Astronomy/PCI Project N°:31140020. T.M.H. also acknowledges the financial support from the Belgian Science Policy Office (BELSPO) in the frame of the PRODEX project C90370 (Herschel-PACS Guaranteed Time and Open Time Programs: Science Exploitation). M.B. and I.D.L. acknowledge the financial support of the Flemish Fund for Scientific Research (FWO-Vlaanderen). SPIRE was developed by a consortium of institutes led by Cardiff University (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); and Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA (UK); and NASA (USA). This research made use of APLpy, an open-source plotting package for Python hosted at http://aplpy.github.com.Attached Files
Published - aa27644-15.pdf
Submitted - 1601.01317v1.pdf
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Additional details
- Eprint ID
- 66619
- Resolver ID
- CaltechAUTHORS:20160503-111923243
- Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)
- 31140020
- Belgian Science Policy Office (BELSPO) PRODEX
- C90370
- Fonds Wetenschappelijk Onderzoek - Vlaanderen (FWO)
- Canadian Space Agency (CSA)
- National Astronomical Observatories of China
- Commissariat à l'Energie Atomique (CEA)
- Agenzia Spaziale Italiana (ASI)
- Ministerio de Ciencia e Innovación (MCINN)
- Swedish National Space Board (SNSB)
- Science and Technology Facilities Council (STFC)
- NASA
- United Kingdom Space Agency (UKSA)
- Centre National d'Études Spatiales (CNES)
- Centre National de la Recherche Scientifique (CNRS)
- Created
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2016-05-03Created from EPrint's datestamp field
- Updated
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2021-11-11Created from EPrint's last_modified field