The Bulletin of The Korean Astronomical Society (천문학회보)
- Volume 39 Issue 1
- /
- Pages.40.1-40.1
- /
- 2014
- /
- 1226-2692(pISSN)
A New Method to Find Bars
- Lee, Yun Hee (Kyungpook National University) ;
-
Ann, Hong Bae
(Pusan National University) ;
-
Park, Myeong-Gu
(Kyungpook National University)
- Published : 2014.04.10
Abstract
We have classified barred galaxies for 418 RC3 sample galaxies within z < 0.01 from SDSS DR7 using the visual inspection, ellipse fitting method and Fourier analysis. We found the bar fraction to be ~60%, 43% and 70% for each method and that the ellipse fitting method tends to miss the bar when a large bulge hides the transition from bar to disk in early spirals. We also confirmed that the Fourier analysis cannot distinguish between a bar and spiral arm structure. These systematic difficulties may have produced the long-time controversy about bar fraction dependence on Hubble sequence, mass and color. We designed a new method to fine bars by analyzing the ratio map of bar strength in polar coordinates, which yields the bar fraction of ~27% and ~32% for SAB and SB, respectively. The consistency with visual inspection reaches around 70%, and roughly 90% of visual strong bar are classified as SAB and SB in our classification. Although our method also has a weakness that a large bulge lowers the value of bar strength, the missing bar fraction in early spirals is reduced to the level of ~1/4 compared to the ellipse fitting method. Our method can make up for the demerits of the previous automatic classifications and provide a quantitative bar classification that agrees with visual classification.
Keywords