Radio properties of the OH megamaser galaxy IIZw 096

I: The HST-ACS F814W image (grey scale) for IIZw 096. The green crosses indicate the bright spots in this optical image. II: VLA (A configuration) contour map at 33 GHz (white line) are overlaid on the HST image; the contour levels are 0.0000441 × (1, 2, 4, 8) Jy/beam and the Beam FWHM: 82.4 × 59.5 (mas) at -69.1◦. The red circles stand for the regions around the D1 component and the radius is about 0.1 arcsec. The red contour stands for the OH megamaser emission (red) from EVN archival data (project ES064B). The details about image parameters of the OH emission are present in Fig. A.2. III: The zoomed map of D1 region from II. The yellow ellipses are the two regions where we extracted the integrated OH emission lines.

Wu Hong, Wu Zhongzu, Sotnikova Yu., Chen Yongjun, Zhang Bo, Mufakharov T., Shen Zhiqiang, Chen Xi, Mikhailov A., Mingaliev M., Han Xianming L., Misra Prabhakar

Based on the two epochs EVN archive data from OH line observations of IIZw 096, we confirm that the high-resolution OH emission in this source mainly comes from two spots (OH1 and OH2) of comp D1 of this merging system. We found no significant variations in the OH line emission. The OH 1665 MHz line emission is detected at about 6  σ  level in the OH1 region by combining two epoch EVN observations. We found that the comp D1 shows the brightest CO, HCO+ line emission, as well as multi-band radio continuum emission. The environment around D1 shows no clear velocity structure associated with circular motions, making it different from most other OHMs in the literature, which might have been caused by an effect during the merger stage. Meanwhile, we found that the CO emission shows three velocity structures around D1, including the central broad FWHM region, the double peak region where the CO line profile shows two separated peaks, and the region of the high-velocity clouds where the CO line peaks at a high velocity ( ∼  11000 \kms). \HI in absorption also show high-velocity clouds around the D1 region, which might be due to inflows caused by the merging of two or more galaxy components. Based on the high-resolution K-band VLA and L-band VLBA observations of the radio continuum emission, we derived the brightness temperature in the range  10^5 K to  10^6 K, which is consistent with other starburst dominant OHM sources in the literature. The multi-band VLA observations show that the radio continuum emission of comp D might also have contributions from free-free emission, besides synchrotron emission. As a concenquence, these results support a starburst origin for the OHMs, without the presence of an AGN. Original →