Abstract Details
| Name: Arun Kumar Diwakar Affiliation: ITM Uuniversity Raipur Conference ID: ASI2017_1086 Title : Shape and orientation of elliptical galaxy by photometry Authors and Co-Authors : D. K. Chakraborty, S.O.S. in Physics and Astrophysics, Pt. R. S. University, Raipur, C.G. Abstract Type : Poster Abstract Category : Extragalactic astronomy Abstract : Use of kinematical data, along with photometric data to study the shape of individual elliptical galaxy was initiated by Binney (1985) and Tenjes (1993). A rigorous method, using Bayesian statistics was taken up by Statler and his coworkers. We have followed the basic methodology developed by Statler. However, we used the photometric data alone, contrary to Statler who use kinematical data as well. Previously, Ryden used photometric data alone, and Statler (1994) re-analysed Ryden’s data to obtain a different fit. Statler (1994), thus makes a point-blank remark “The distribution of intrinsic shapes can not be determined from photometry aloneâ€. We worked on constraining the shape and orientation of elliptical galaxies, using photometry alone. Strong arguments in our favour are (i) number of galaxies with good photometry is many more than those with good kinematics and (ii) alternative models and approaches are necessary to make a cross-check of the results. We found that triaxialities T0 and T∞ at small and large radii, respectively, are not constrained. It shows that almost all values of T0 and T∞ are allowed within 1σ level. However, flattening q0 and q∞ at small and large radii, respectively, are well constrained. We made several attempts to find if triaxialities T0 and T∞ can be constrained, even under some spacial conditions, e.g. assuming a spacial situation wherein galaxies may have T0 = T∞ . Such conditions can not be justified, in general, but for the sake of a problem, we just assumed it. All our attempts to constrain triaxiality through photometry failed. What we found that, at the most, the absolute value of the triaxiality difference |Td| ≡ |T∞ − T0|, along with q0 and q∞ are constrained through photometry. In the light of above results, we can very well conclude that our work is complementary, and not contradictory, to that of Statler and his coworker. We continued to apply photometry to elliptical galaxies and analysed (i) orientations of NGC 1407 (θ = 13.5, φ= 127.5), NGC 2986(θ = 31.5, φ = 118.5) and NGC 4374 (θ = 67.5, φ = 175.5) rounder galaxies (ii) shapes of 3 very flat galaxies NGC 720 (q0 , q∞ = 0.68, 0.38), NGC 2768 (q0 , q∞ = 0.68, 0.28) and NGC 3605 (q0 , q∞ = 0.68, 0.43). |