NDLI: The origin of the near-IR line emission from molecular, low and high ionization gas in the inner kiloparsec of NGC 6240

Content Provider	Springer Nature Link
Author	Ilha, Gabriele da Silva Bianchin, Marina Riffel, Rogemar A.
Copyright Year	2016
Abstract	The understating of the origin of the $\mbox{H}_{2}$ line emission from the central regions of galaxies represents an important key to improve our knowledge about the excitation and ionization conditions of the gas in these locations. Usually these lines can be produced by Starburst, shocks and/or radiation from an active galactic nucleus (AGN). Luminous Infrared Galaxies (LIRG) represent ideal and challenging objects to investigate the origin of the $\mbox{H}_{2}$ emission, as all processes above can be observed in a single object. In this work, we use K-band integral field spectroscopy to map the emission line flux distributions and kinematics and investigate the origin of the molecular and ionized gas line emission from inner $1.4\times2.4~\mbox{kpc}^{2}$ of the LIRG NGC 6240, known to be the galaxy with strongest $\mbox{H}_{2}$ line emission. The emission lines show complex profiles at locations between both nuclei and surrounding the northern nucleus, while at locations near the southern nucleus and at $1^{\prime\prime}$ west of the northern nucleus, they can be reproduced by a single Gaussian component. We found that the $\mbox{H}_{2}$ emission is originated mainly by thermal processes, possible being dominated by heating of the gas by X-rays from the AGN at locations near both nuclei. For the region between the northern and southern nuclei shocks due to the interacting process may be the main excitation mechanism, as indicated by the high values of the $\mbox{H}_{2}\,\lambda2.12~μ \mbox{m}/\mbox{Br}\gamma$ line ratio. A contribution of fluorescent excitation may also be important at locations near $1^{\prime\prime}$ west of the northern nucleus, which show the lowest line ratios. The [Fe ii] $\lambda2.072~μ \mbox{m}/\mbox{Br}\gamma$ ratio show a similar trend as observed for $\mbox{H}_{2}\,\lambda2.12~μ \mbox{m}/\mbox{Br}\gamma$ , suggesting that [Fe ii] and $\mbox{H}_{2}$ line emission have similar origins. Finally, the [Ca viii] $\lambda2.32~μ \mbox{m}$ coronal line emission is observed mainly in regions next to the nuclei, suggesting it is originated gas ionized by the radiation from the AGN.
Starting Page	1
Ending Page	9
Page Count	9
File Format	PDF
ISSN	0004640X
Journal	Astrophysics and Space Science
Volume Number	361
Issue Number	6
e-ISSN	1572946X
Language	English
Publisher	Springer Netherlands
Publisher Date	2016-05-02
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Galaxies: active galaxies: ISM Infrared: galaxies Galaxies: individual (NGC 6240) Astrophysics and Astroparticles Astronomy, Observations and Techniques Cosmology Extraterrestrial Physics, Space Sciences Astrobiology
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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