Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...452..599l&link_type=abstract
Astrophysical Journal v.452, p.599
Astronomy and Astrophysics
Astronomy
27
Galaxies: Individual Name: Arp 220, Galaxies: Kinematics And Dynamics, Galaxies: Nuclei, Infrared: Galaxies
Scientific paper
We report spatially resolved near-infrared spectroscopy at a resolution (λ/Δλ) ˜ 1000 of the double nucleus of Arp 220 in the Paβ, Brγ, [Fe II] (λ = 1.2567 μm), and H2 (1-0 S1) (λ = 2.1218 μm) emission lines. The Brγ hydrogen recombination line is strongly peaked on the two nuclei, and the Paβ is centered on the western nucleus with emission across the eastern nucleus. Both lines show a velocity separation of ˜200 km s-1 between the eastern and western nuclei, the former being redshifted relative to the latter. Both the magnitude and the direction of this velocity shift are consistent with recent CO millimeter measurements of larger scale gas motions over the central 2". The implied rotation requires a central mass greater than 1.5 × 109 Msun. The extinction determined from the ratio of the Paβ and Brγ lines is found to be AV ˜ 10 mag for the western nucleus and AV ˜ 13 mag for the eastern nucleus. The [Fe II] and H2 lines show a different morphology than the hydrogen recombination lines, particularly the H2 line which shows significant flux between the two nuclei. The [Fe II] and H2 lines also do not show velocity splitting between the two nuclei. The difference in spatial and velocity structure between the [Fe II], H2, and ionized hydrogen lines implies multiple excitation processes are at work within the nucleus. The [Fe II] and H2 lines may have a significant contribution from extranuclear shocks related to either a starburst-driven wind or the ongoing merger process.
Armus Lee
Knop Rob A.
Larkin James E.
Matthews Keith
Soifer Thomas B.
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