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U. C. Joshi

Publications and source records attributed to U. C. Joshi.

20 records · Page 2Linked to original sources

Star formation along a misaligned bar in the peculiar starburst galaxy Mkn 439

We report the detection of massive star formation along a bar in the peculiar starburst galaxy Mkn 439. We present optical B, R and H_alpha + [NII] emission line images as well as H band images to show that the signature of the bar becomes progressively weak at longer wavelengths. Moreover, this bar is misaligned with the main body of the galaxy. The peak H_alpha emission does not coincide with the bluest regions seen in the colour maps. We infer that the starburst is young since the stars in the burst have not started influencing the light in the near infrared. There are indications of dust in the inner regions of this galaxy.

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Photometric studies of some starburst galaxies

We present the results of a detailed morphological analysis of ten starburst galaxies selected from the Markarian catalogue of uv-excess objects. CCD surface photometry of these galaxies was carried out based on observations made in B, V (Johnson) and R, I (Kron-Cousins) band passes. We present the radial variations of surface brightness, ellipticity, position angle and the colour indices for each galaxy obtained using ellipse fitting isophotal analysis. The residual images constructed for extracting the fine structure are also presented. A variety of morphological types are found to host the starburst phenomenon. The star formation activity is not confined to the nuclear region alone, but it also occurs at various locations in the galaxy and is seen as clumpy regions. The colour index and the residual images are used for deriving information about the sites of enhanced star formation activity and the triggers of the starburst. The luminosity profiles show an exponential behaviour in the outer region. The disk scale lengths and the half-light radii are derived. The contribution of the burst component has been estimated and the colours of the burst component are presented. Strong isophotal twisting is detected in all the S0 and E galaxies: Mrk 1002, Mrk 1308 and Mrk 14, in the sample. This is accompanied by boxiness in some cases, suggesting that a merger is responsible for the starburst activity in these galaxies. In case of isolated spirals, a bar or a central oval distortion appear to be the likely trigger for the starburst.

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