IUCAA Preprints

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Author: search.filters.author.Kembhavi, A.K.Has files: Yes

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    Correlations among global photometric properties of disk galaxies
    (2015-03-01) Khosroshahi, Habib G.; Wadadekar, Yogesh; Kembhavi, A.K.
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    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.
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    Effective radii and color gradients in radio galaxies
    (2015-03-01) Mahabal, Ashish; Kembhavi, A.K.; Mccarthy, P.J
    We present de Vaucouleurs' effective radii in B and R bands for a sample of Molonglo Reference Catalogue radio galaxies and a control sample of normal galaxies. We use the ratio of the scale lengths in the two bands as an indicator to show that the radio galaxies tend to have excess of blue color in their inner region much more frequently than the control galaxies. We show that the scale length ratio is a useful indicator of radial color variation even when the conventional color gradient is too noisy to serve the purpose.
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    A dust lane in the radio galaxy 3C270
    (2015-02-18) Mahabal, A; Kembhavi, A.K.; Singh, K. P.; Bhatt, P.N.; Prabhu, T.P.
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    A Sptzer Study Of Pseudobulges In so Galaxies - Secular Evoution of disk
    (IUCAA, 2015-02) Vaghmare, Kaustubh; Barway, Sudhanshu; Kembhavi, A.K.
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    On the origin of the featureless soft X-ray excess emission from the Seyfert 1 galaxy ESO 198–G24
    (IUCAA, 2015-02) Laha, Sibasish; Dewangan, Gulab Chand; Kembhavi, A.K.
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    The soft x-ray excess in quasars
    (2014-11-22) Kembhavi, A.K.; Fabian, A.C.
    A soft x-ray excess in the energy range of a few tenths of a ke V has been detected in some quasars , and there are indications in the x-ray data which point to the excess being a feature universal to all quasars. The poor energy resolution in the concerned energy band make it impossible at the present to observationally constrain the excess quantitatively. We show in this paper that the shape of the excess sensitively determines the surface density therefore allows an assessment of the nature of the excess
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    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.
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    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.
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    Multicolor surface photometry of lenticulars galaxies I. The Data
    (2011-07-06) Barway, Sudhanshu; Mayya, Y. D.; Kembhavi, A.K.; et al.
    We present in this paper multicolor surface and aperture photometry in the B, V,R and K′ bands for a sample of 34 lenticular galaxies from the UGC catalogue. From surface photometric analysis, we obtain radial profiles of surface brightness, colors, ellipticity, position angle and the Fourier coefficients which describe the departure of isophotal shapes from purely elliptical form and find the presence of dust lanes, patches and ring like structure in several galaxies in the sample. We obtain total integrated magnitudes and colors and find that these are in good agreement with the values from the RC3 catalogue. Isophotal colors are correlated with each other, following the sequence expected for early- type galaxies. The color gradients in lenticulars are more negative than the corresponding gradients in ellipticals. There is a good correlation between B − V and B − R color gradients, and the mean gradient in the B−V,B−R and V −K′ colors are −0.13±0.06, −0.18±0.06, −0.25±0.11 magnitude per dex in radius respectively.