Invited Presentation
Enhancing the detection rate of megamasers based on optical and mid-infrared photometry
Presenter: Cheng-Yu Kuo (NSYSU)
H$_{2}$O megamasers from circumnuclear disks (disk masers) in active galaxies provide an unique way to probe active galactic nuclei and allow accurate measurement of the mass of supermassive black holes and determination of the Hubble constant. Nonetheless, the detection rates of H$_{2}$O megamasers and disk masers are typically $\le$2.6\% and $\le$1\%, respectively. The low detection rate significantly limit the extent of applying megamasers to solve important astrophysical questions. To enhance the detection rate of H$_{2}$O megamasers, we study the mid-infrared properties of maser host galaxies using photometry from the Wide-field Infrared Survey Explorer (WISE) and find that galaxies with megamaser emissions are enhanced in all mid-infrared wavelengths, with the enhancement strongest at 22$\micron$. In addition, the detection rate of megamasers depends substantially on all indicators of AGN strength in the mid-infrared, such as $W1-W2$, $W1-W4$, and the total mid-infrared luminosity of an AGN. The correlations between megamaser detection rate and the level of AGN activity allow us to boost the detection rate by a factor of 2$-$8. The resultant detection rate can range from 6\% to 17\%, depending on the chosen sample selection criteria. In addition to studying the mid-infrared properties, we also explore the correlations between megamasers and their optical properties. We find that adding the information of optical color and absolute g-band magnitude can help effectively boost the detection rate of disk masers with relatively high detection completeness.
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