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Evidence for Shock-heated Gas in the Taffy Galaxies and Bridge from Optical Emission-line IFU Spectroscopy

Joshi, Bhavin A. and Appleton, Philip N. and Blanc, Guillermo A. and Guillard, Pierre and Rich, Jeffrey and Struck, Curtis and Freeland, Emily E. and Peterson, Bradley W. and Helou, George and Alatalo, Katherine (2019) Evidence for Shock-heated Gas in the Taffy Galaxies and Bridge from Optical Emission-line IFU Spectroscopy. Astrophysical Journal, 878 (2). Art. No. 161. ISSN 1538-4357. doi:10.3847/1538-4357/ab2124.

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We present optical integral field unit observations of the Taffy system (UGC 12914/15), named for the radio emission that stretches between the two galaxies. Given that these gas-rich galaxies are believed to have recently collided head-on, the pair exhibits a surprisingly normal total (sub-LIRG) IR luminosity (L_(FIR) ~ 4.5 × 10^(10) L_⊙). Previous observations have demonstrated that a large quantity of molecular and neutral gas has been drawn out of the galaxies into a massive multiphase bridge. We present, for the first time, spatially resolved spectroscopy of the ionized gas in the system. The results show that the ionized gas is highly disturbed kinematically, with gas spread in two main filaments between the two galaxies. The line profiles exhibit widespread double components in both the bridge and parts of the disks of the galaxies. We investigate the spatial distribution of the excitation properties of the ionized gas using emission-line diagnostic diagrams and conclude that a large quantity (up to 40%) of the emission from the entire system is consistent with gas heated in ~200 km s^(−1) shocks. While the shocked gas is mainly associated with the bridge, there is a significant amount of shocked gas associated with both galaxies. Confirming other multiwavelength indicators, the results suggest that the effects of shocks and turbulence can continue to be felt in a high-speed galaxy collision long after the collision has occurred. The persistence of shocks in the Taffy system may explain the relatively low current star formation rates in the system as a whole.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Joshi, Bhavin A.0000-0002-7593-8584
Appleton, Philip N.0000-0002-7607-8766
Guillard, Pierre0000-0002-2421-1350
Rich, Jeffrey0000-0002-5807-5078
Struck, Curtis0000-0002-6490-2156
Helou, George0000-0003-3367-3415
Alatalo, Katherine0000-0002-4261-2326
Additional Information:© 2019. The American Astronomical Society. Received 2018 December 18; revised 2019 April 28; accepted 2019 May 11; published 2019 June 25. B.A.J. would like to thank the Visiting Graduate Fellowship Program at IPAC/Caltech for six months of support toward work performed for this paper. B.A.J. is also grateful to Drs. Rogier Windhorst and Rolf Jansen for helpful discussions on work done in this paper. The authors thank the anonymous referee for their helpful review and suggestions. This research has made use of NASA's Astrophysics Data System. This research has made use of the Python programming language along with the Numpy, Scipy, and Matplotlib packages. This research has also made use of Astropy, a community-developed core Python package for Astronomy (The Astropy Collaboration 2018).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Infrared Processing and Analysis Center (IPAC)UNSPECIFIED
Subject Keywords:galaxies: individual (UGC 12914&5) ; galaxies: interactions; galaxies: ISM; galaxies: kinematics and dynamics
Issue or Number:2
Record Number:CaltechAUTHORS:20190625-125512734
Persistent URL:
Official Citation:Bhavin A. Joshi et al 2019 ApJ 878 161
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96701
Deposited By: George Porter
Deposited On:26 Jun 2019 14:30
Last Modified:16 Nov 2021 17:23

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