IUCAA Preprints
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Item 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 Fundamental plane distances to early-type field galaxies in the South Equatorial Strip(2000-07-25) Muller, K. R.; Wegner, G.; Freudling, W.Radial velocities and central velocity disper- sions are derived for 238 E/S0 galaxies from medium- resolution spectroscopy. New spectroscopic data have been obtained as part of a study of the Fundamental Plane distances and peculiar motions of early-type galaxies in three selected directions of the South Equatorial Strip, undertaken in order to investigate the reality of large- scale streaming motion; results of this study have been reported in M¨uller et al. (1998). The new APM South Equatorial Strip Catalog (−17◦.5 < δ < +2◦.5) was used to select the sample of field galaxies in three directions: (1) 15h10 – 16h10; (2) 20h30 – 21h50; (3) 00h10 – 01h30. The spectra obtained have a median S/N per ˚ A of 23, an in- strumental resolution (FWHM) of ∼ 4 ˚ A, and the spectro- graph resolution (dispersion) is ∼ 100 km s−1. The Fourier cross-correlation method was used to derive the radial ve- locities and velocity dispersions. The velocity dispersions have been corrected for the size of the aperture and for the galaxy effective radius. Comparisons of the derived radial velocities with data from the literature show that our values are accurate to 40 km s−1. A comparison with results from Jørgensen et al. (1995) shows that the derived central velocity dispersion have an rms scatter of 0.036 in log σ. There is no offset relative to the velocity dispersions of Davies et al. (1987).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 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.