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Article Dans Une Revue The Astrophysical Journal Année : 2021

Tracing the Ionization Structure of the Shocked Filaments of NGC 6240

1 Ritter Astrophysical Research Center
2 Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Australia National University, Cotter Road, Weston, ACT 2611, Australia
3 Cahill Center for Astronomy and Astrophysics
4 ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)
5 RSAA - Research School of Astronomy and Astrophysics [Canberra]
6 Department of Astronomy, University of Massachusetts, Amherst, Amherst, MA 01003, USA
7 NRAO - National Radio Astronomy Observatory [Charlottesville]
8 The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USA
9 Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
10 ObAS - Observatoire astronomique de Strasbourg
11 Nu ́cleo de Astronom ́ıa de la Facultad de Ingenier ́ıa y Ciencias, Universidad Diego Portales, Av. Eje ́rcito Libertador 441, Santiago, Chile
12 JHU - Johns Hopkins University
13 STSci - Space Telescope Science Institute
14 UC Santa Cruz - Department of Astronomy and Astrophysics [Univ California Santa Cruz]
15 Department of Physics, Rhodes College, Memphis, TN 38112, USA
16 Instituto de Astrof ́ısica, Facultad de F ́ısica, Pontificia Universidad Cato ́lica de Chile, Casilla 306, Santiago 22, Chile
17 Joint ALMA Observatory and European Southern Observatory, Alonso de Co ́rdova 3107, Casilla 19001, Vitacura, Santiago, Chile
18 Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
Mark G. Allen

Résumé

We study the ionization and excitation structure of the interstellar medium in the late-stage gas-rich galaxy merger NGC 6240 using a suite of emission line maps at $\sim$25 pc resolution from the Hubble Space Telescope, Keck NIRC2 with Adaptive Optics, and ALMA. NGC 6240 hosts a superwind driven by intense star formation and/or one or both of two active nuclei; the outflows produce bubbles and filaments seen in shock tracers from warm molecular gas (H$_2$ 2.12$\mu$m) to optical ionized gas ([O III], [N II], [S II], [O I]) and hot plasma (Fe XXV). In the most distinct bubble, we see a clear shock front traced by high [O III]/H$\beta$ and [O III]/[O I]. Cool molecular gas (CO(2-1)) is only present near the base of the bubble, towards the nuclei launching the outflow. We interpret the lack of molecular gas outside the bubble to mean that the shock front is not responsible for dissociating molecular gas, and conclude that the molecular clouds are partly shielded and either entrained briefly in the outflow, or left undisturbed while the hot wind flows around them. Elsewhere in the galaxy, shock-excited H$_2$ extends at least $\sim$4 kpc from the nuclei, tracing molecular gas even warmer than that between the nuclei, where the two galaxies' interstellar media are colliding. A ridgeline of high [O III]/H$\beta$ emission along the eastern arm aligns with the south nucleus' stellar disk minor axis; optical integral field spectroscopy from WiFeS suggests this highly ionized gas is centered at systemic velocity and likely photoionized by direct line-of-sight to the south AGN.
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Dates et versions

hal-03417420 , version 1 (06-11-2021)

Identifiants

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Anne M. Medling, Lisa J. Kewley, Daniela Calzetti, George C. Privon, Kirsten Larson, et al.. Tracing the Ionization Structure of the Shocked Filaments of NGC 6240. The Astrophysical Journal, 2021, 923, ⟨10.3847/1538-4357/ac2ebb⟩. ⟨hal-03417420⟩
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