Dust properties in Early-type Galaxies

Abstract

We have carried out optical and near-IR photometric analysis of some of the early-type galaxies with the objective of studying of studying their dust properties, and to see how different these are from the properties of the dust in the Milky Way. In this paper we present results on some of the galaxies (NGC1172, NGC1439, NGC2672 and NGC3489) from this programme. In this paper a detailed study of wavelength dependent properties of dust in four early-type galaxies ( NGC1172, NGC1439, NGC2672, NGC3489) is presented. Optical observations of the sample galaxies were carried out in Johnson broad band filters B, V, R & I during December 1999 using 1m telescope of the State Observatory at Naini Tal, equipped with 2Kх2K TEK CCD, while near-IR observations in J, H & K' bands were carried out during January 2001 using 1.2m telescope, equipped with 256х256 HgCdTe NICMOS camera at Mt. Abu. Typical exposure times devoted were B(3600s), V(2700s), R(1800s), I(1200s), J(600s), H(600s), K'(300s). In order to obtain sky subtracted, geometrically aligned slean images, standard reduction prodedures (such as bias subtraction, flat fielding etc.) were applied to the galaxy images in optical (Goudfrooij et al. 1994) as well as in near-IR (Hunt et al. 1998) using the tasks available within the IRAF and the STSDAS packages.