Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope: Early Results on Markarian 1014, Markarian 463, and UGC 5101

September 2004 • 2004ApJS..154..178A

Authors • Armus, L. • Charmandaris, V. • Spoon, H. W. W. • Houck, J. R. • Soifer, B. T. • Brandl, B. R. • Appleton, P. N. • Teplitz, H. I. • Higdon, S. J. U. • Weedman, D. W. • Devost, D. • Morris, P. W. • Uchida, K. I. • van Cleve, J. • Barry, D. J. • Sloan, G. C. • Grillmair, C. J. • Burgdorf, M. J. • Fajardo-Acosta, S. B. • Ingalls, J. G. • Higdon, J. • Hao, L. • Bernard-Salas, J. • Herter, T. • Troeltzsch, J. • Unruh, B. • Winghart, M.

Abstract • We present spectra taken with the Infrared Spectrograph on the Spitzer Space Telescope covering the 5-38 μm region of three ultraluminous infrared galaxies (ULIRGs): Mrk 1014 (z=0.163), Mrk 463 (z=0.051), and UGC 5101 (z=0.039). The continua of UGC 5101 and Mrk 463 show strong silicate absorption suggesting significant optical depths to the nuclei at 10 μm. UGC 5101 also shows the clear presence of water ice in absorption. Polycyclic aromatic hydrocarbon (PAH) emission features are seen in both Mrk 1014 and UGC 5101, including the 16.4 μm line in UGC 5101. The fine-structure lines are consistent with dominant active galactic nucleus (AGN) power sources in both Mrk 1014 and Mrk 463. In UGC 5101 we detect the [Ne V] 14.3 μm emission line, providing the first direct evidence for a buried AGN in the mid-infrared. The detection of the 9.66 μm and 17.03 μm H2 emission lines in both UGC 5101 and Mrk 463 suggest that the warm molecular gas accounts for 22% and 48% of the total molecular gas masses in these galaxies.

Based on observations obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407.


IPAC Authors


Phil Appleton

Senior Scientist


Lee Armus

Senior Scientist


Carl Grillmair

Associate Scientist

Jim Ingalls

Associate Scientist


Harry Teplitz

Senior Scientist