B. R. Brandl et al. 2009 ApJ 699 1982 doi:10.1088/0004-637X/699/2/1982
B. R. Brandl1, L. Snijders1, M. den Brok2, D. G. Whelan3, B. Groves1, P. van der Werf1, V. Charmandaris4,5,6, J. D. Smith7, L. Armus8, R. C. Kennicutt Jr9 and J. R. Houck10
Show affiliationsUsing the Infrared Spectrograph on the Spitzer Space Telescope, we observed the Antennae galaxies obtaining spectral maps of the entire central region and high signal-to-noise 5-38 μm spectra of the two galactic nuclei and six infrared-luminous regions. The total infrared luminosity of our six IR peaks plus the two nuclei is L IR = 3.8 × 1010 L ☉, with their derived star formation rates ranging between 0.2 and 2 M ☉ yr–1, with a total of 6.6 M ☉ yr–1. None of the typical mid-IR tracers of active galactic nucleus activity is detected in either nucleus of the system, excluding the presence of a dust-enshrouded accretion disk. The hardest and most luminous radiation originates from two compact clusters in the southern part of the overlap region, which also have the highest dust temperatures. Polycyclic aromatic hydrocarbon (PAH) emission and other tracers of softer radiation are spatially extended throughout and beyond the overlap region, but regions with a harder and more intense radiation field show a reduced PAH strength. The strong H2 emission is rather confined around the nucleus of NGC 4039, where shocks appear to be the dominant excitation mechanism, and the southern part of the overlap region, where it traces the most recent starburst activity. The luminosity ratio between the warm molecular gas (traced by the H2 lines) and the total far-IR emission is ~ 1.6 × 10–4, similar to that found in many starbursts and ultraluminous infrared galaxies. The total mass of warm H2 in the Antennae is 2.5 × 107 M ☉, with a fraction of warm to total H2 gas mass of about 0.35%. The average warm H2 temperature is 302 ± 26 K and appears anticorrelated with the radiation field hardness, possibly due to an evolution of the photodissociation region (PDR) morphology. The previously reported tight correlation between the H2 and PAH emission was not found but higher total PAH emission to continuum ratios were found in PDRs with warmer gas.
galaxies: interactions; galaxies: ISM; galaxies: starburst; H II regions; infrared: galaxies; ISM: structure
Issue 2 (2009 July 10)
Received 2008 July 30, accepted for publication 2009 May 11
Published 2009 June 26
B. R. Brandl et al. 2009 ApJ 699 1982
Mark Keremedjiev et al. 2009 ApJ 690 1105
H. W. W. Spoon et al. 2009 ApJ 693 1223
J. Bernard-Salas et al. 2009 ApJS 184 230
Yanling Wu et al. 2009 ApJ 701 658
Almudena Alonso-Herrero et al. 2009 ApJ 697 660
Lucio Rossi 2010 Supercond. Sci. Technol. 23 034001
James Gray et al JHEP05(2008)099
Vijay Balasubramanian et al JHEP12(2005)006
Vijay Balasubramanian et al JHEP05(2008)067