Issue |
A&A
Volume 587, March 2016
|
|
---|---|---|
Article Number | A45 | |
Number of page(s) | 7 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201527644 | |
Published online | 15 February 2016 |
The spatially resolved correlation between [NII] 205 μm line emission and the 24 μm continuum in nearby galaxies
1
Instituto de Física y Astronomía, Universidad de Valparaíso,
Avda. Gran Bretaña 1111,
Valparaíso,
Chile
e-mail:
thomas.hughes@uv.cl
2
Sterrenkundig Observatorium, Universiteit Gent,
Krijgslaan 281-S9, 9000
Gent,
Belgium
3
Department of Physics & Astronomy, McMaster
University, Hamilton, Ontario
L8S 4M1,
Canada
4
Department of Astronomy, the University of Tokyo,
Bunkyo-ku, 113-0033
Tokyo,
Japan
5
UK ALMA Regional Centre Node, Jodrell Bank Centre for
Astrophysics, School of Physics and Astronomy, University of Manchester,
Oxford Road, Manchester
M13 9PL,
UK
6
Laboratoire d’Astrophysique de Marseille, Université
d’Aix-Marseille and CNRS, UMR7326, 13388
Marseille Cedex 13,
France
7
Institut für theoretische Astrophysik, Zentrum für Astronomie der
Universität Heidelberg, Albert-Ueberle 2, 69120
Heidelberg,
Germany
8
Department of Physics & Astronomy, University of
Sussex, Brighton,
BN1 9QH,
UK
9
Infrared Processing and Analysis Center, California Institute of
Technology, MS
100-22, Pasadena,
CA
91125,
USA
10
Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via
Fosso del Cavaliere 100, 00133
Roma,
Italy
Received: 26 October 2015
Accepted: 30 December 2015
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.
Key words: galaxies: star formation / galaxies: spiral / galaxies: ISM / infrared: galaxies / ISM: lines and bands
© ESO, 2016
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.