Open AccessDiscovery of atomic and molecular mid‐infrared emission lines in off‐nuclear regions of NGC 1275 and NGC 4696 with the Spitzer Space Telescope
Author(s) -
Johnstone R. M.,
Hatch N. A.,
Ferland G. J.,
Fabian A. C.,
Crawford C. S.,
Wilman R. J.
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.12460.x
Subject(s) - physics , astrophysics , galaxy , astronomy , emission spectrum , spectral line , line (geometry) , molecular cloud , spitzer space telescope , infrared , centaurus a , telescope , active galactic nucleus , stars , geometry , mathematics
We present Spitzer high‐resolution spectra of off‐nuclear regions in the central cluster galaxies NGC 1275 and NGC 4696 in the Perseus and Centaurus clusters, respectively. Both objects are surrounded by extensive optical emission‐line filamentary nebulae, bright outer parts of which are the targets of our observations. The 10–37 μm spectra show strong pure‐rotational lines from molecular hydrogen revealing a molecular component to the filaments which has an excitation temperature of ∼300−400 K. The flux in the 0−0 S(1) molecular hydrogen line correlates well with the strength of the optical lines, having about 3 per cent of the Hα+[N ii ] emission. The 11.3‐μm polycyclic aromatic hydrocarbon feature is seen in some spectra. Emission is also seen from both low‐ and high‐ionization fine‐structure lines. Molecular hydrogen cooler than ∼400 K dominates the mass of the outer filaments; the nebulae are predominantly molecular.