for the star-forming complexes and higher σ and [ N II ]/ H-alpha surrounding the radio emission region , supporting interaction between the radio plasma and ambient gas . The two OH masers detected in IRAS F23199E are observed in the vicinity of these enhanced σ regions , supporting their association with the active nucleus and its interaction with the surrounding gas . The gas velocity field can be partially reproduced by rotation in a disk , with residuals along the north-south direction being tentatively attributed to emission from the front walls of a bipolar outflow .
The combination of HST images , VLA line spectroscopy , and Gemini IFU spectroscopy strongly indicates that , in this system , the OH megamaser sources are associated with the AGN rather than star formation .
Analysis of the inner regions of OH megamaser galaxies can contribute to our understanding the origin of these systems and provide insights into the star formation and galaxy evolution processes . Further adaptive optics observations with Gemini ’ s Nearinfrared Integral Field Spectrograph , as well as spectroscopic observations with integral field units of next generation telescopes , will allow a better understanding of the role AGN play in the gas emission of OH megamaser galaxies .
July 2018
Hekatelyne Carpes is a recent PhD graduate at Universidade Federal de Santa Maria - UFSM , Brazil . She can be reached at : hekatelyne . carpes @ gmail . com
Rogemar A . Riffel is an associate professor at Universidade Federal de Santa Maria - UFSM , Brazil . He can be reached at rogemar @ ufsm . br
References
Skinner , C . J ., “ A starburst origin of the OHmegamaser emission from the galaxy Arp220 ,” Nature , 386 : 472 , 1997
Lo , K . Y ., “ Mega-masers and Galaxies ,” Annual Review of Astronomy and Astrophysics , 43 : 625 , 2005
Huang , Yong , et al ., “ OH Megamaser : dense gas & the infrared radiation field ,” Journal of Astrophysics and Astronomy , 39 : 34 , 2018
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Figure 5 .
Observed H-alpha velocity field ( left ), rotating disk model ( center ), and residual between the two ( right ). The central cross marks the position of the nucleus , the white regions are masked locations where we were not able to fit the emission-line profiles , and the dotted lines represent the orientation of the line of nodes . The black contours in the residual map are from the 3-cm radio image with the same flux levels as shown in Figure 1 , and the white contours show radio contours at the 1.5 sigma level . The black asterisks labeled OH1 and OH2 mark the position of the maser sources .