Browsing by Author "Wadadekar, Yogesh"
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Item Bar fraction in lenticular galaxies: Dependence on luminosity and environment(2010-10-15) Barway, Sudhanshu; Wadadekar, Yogesh; Kembhavi, A.K.We present a study of bars in lenticular galaxies based on a sample of 371 galaxies from the SDSS-DR 7 and 2MASS in optical and near-infrared bands, respectively. We found a bar in 15% of the lenticular galaxies in our sample, which is consistent with recent stud- ies. The barred galaxy fraction shows a luminosity dependence, with faint lenticular galaxies (MK > −24.5, total absolute magnitude in K band) having a larger fraction of bars than bright lenticular galaxies (MK < −24.5). A similar trend is seen when Mr = −21.5, the total absolute magnitude in SDSS r band is used to divide the sample into faint and bright lenticular galaxies.We find that faint galaxies in clusters show a higher bar fraction than their counterparts in the field. This suggests that the formation of bars in lenticular galaxies not only depends on the total luminosity of galaxy but also on the environment of the host galaxy.Item Correlations among global photometric properties of disk galaxies(2015-03-01) Khosroshahi, Habib G.; Wadadekar, Yogesh; Kembhavi, A.K.Item Difference boosting neural network for automated star-galaxy classification(2002-03-01) Philip, Ninan S.; Wadadekar, Yogesh; Kembhavi, A.K.; et al.In this paper we describe the use of a new artificial neural network, called the difference boosting neural network (DBNN), for automated classification problems in astronomical data analysis. We illustrate the capabilities of the network by applying it to star galaxy classification using recently released, deep imaging data. We have compared our results with classification made by the widely used Source Extractor (SExtractor) package. We show that while the performance of the DBNN in star-galaxy classification is comparable to that of SExtractor, it has the advantage of significantly higher speed and flexibility during training as well as classification.Item Lenticular Galaxy Formation - Possible Luminosity Dependence(2007-03-27) Barway, Sudhanshu; Kembhavi, A.K.; Wadadekar, Yogesh; et al.We investigate the correlation between the bulge effective radius (re) and disk scale length (rd), in the near-infrared K band for lenticular galaxies in the field and in clusters. We find markedly different relations between the two parameters as a function of luminosity. Lenticulars with total absolute magnitude fainter than MT = −24.5 show a positive correlation, in line with predictions of secular formation processes for the pseudo bulges of late-type disk galaxies. But brighter lenticulars with MT < −24.5 show an anti-correlation, indicating that they formed through a different mechanism. The available data are insufficient to reliably determine the effect of galaxy environment on this correlation.Item Luminosity dependent star-formation history of S0 galaxies: evidence from GALEX-SDSS-2MASS-WISE colours(IUCAA, 2015-02) Barway, Sudhanshu; Wadadekar, Yogesh; Vaghmare, KaustubhItem Near infrared photometric plane for ellipticals and bulges of spirals(2000-09-20) Khosroshahi, Habib G.; Wadadekar, Yogesh; Kembhavi, A.K.; et al.We report the existence of a single plane in the space of global photometric pa- rameters describing elliptical galaxies and the bulges of early type spiral galaxies. The three parameters which define the plane are obtained by fitting the Sersic form to the brightness distribution obtained from near-infrared K band images. We find, from the range covered by their shape parameters, that the elliptical galaxies form a more ho- mogeneous population than the bulges. Known correlations like the Kormendy relation are projections of the photometric plane. The existence of the plane has interesting implications for bulge formation models.Item PyMorph: Automated galaxy structural parameter rstimation using python(2010-07-20) Vikram, Vinu; et al.; Wadadekar, Yogesh; Kembhavi, A.K.We present a new software pipeline – PyMorph – for automated estimation of structural parameters of galaxies. Both parametric fits through a two dimensional bulge disk decomposition as well as structural parameter measurements like concentration, asymmetry etc. are supported. The pipeline is designed to be easy to use yet flexible; individual software modules can be replaced with ease. A find-and-fit mode is available so that all galaxies in a image can be measured with a simple command. A parallel version of the Pymorph pipeline runs on computer clusters and a Virtual Observatory compatible web enabled interface is under development.Item Quantitative measure of evolution of bright cluster galaxies at moderate redshifts(2010-01-01) Vikram, Vinu; et al.; Wadadekar, Yogesh; Kembhavi, A.K.Using archival data from the Hubble Space Telescope, we study the quantitative morphological evolution of spectroscopically confirmed bright galaxies in the core regions of nine clusters ranging in redshift from z = 0.31 to z = 0.84. We use morphological parameters derived from two dimensional bulge-disk decomposition to study the evolution. We find an increase in the mean bulge-to-total luminosity ratio B/T as the Universe evolves. We also find a corresponding increase in the fraction of early type galaxies and in the mean S´ersic index. We discuss these results and their implications to physical mechanisms for evolution of galaxy morphology.Item A study o f quasar radio emission from the VLA first survey(2015-03-01) Wadadekar, Yogesh; Kembhavi, A.K.Using the most recent (1998) version of the VLA FIRST survey radio catalog, we have searched for radio emission from 1704 quasars taken from the most recent (1993) version of the Hewitt and Burbidge quasar catalog. These quasars lie in the "'5000 square degrees of sky already covered by the VLA FIRST survey. Our work has resulted in positive detection of radio emission from 389 quasars of which 69 quasars have been detected for the first time at radio wavelengths. We find no evidence of correlation between optical and radio luminosities for optically selected quasars. We find indications of a bimodal distribution of radio luminosity, even at a low flux limit of 1 mJy. We show that radio luminosity is a good discriminant between radio loud and radio quiet quasar populations, and that it may be inappropriate to make such a division on the basis of the radio to optical luminosity ratio. We discuss the dependence of the radio loud fraction on optical luminosity and redshift.Item Two dimensional galaxy image decomposition(2015-03-13) Wadadekar, Yogesh; Robbason, Braxton; Kembhavi, A. K.