2 Observations

2.1 Sample

Our sample is compiled from two different samples described by Rest et al. (2001) and Tran et al. (2001). The first sample was created by selecting E/S0 galaxies on their optical properties only from the Lyon/Meudon Extragalactic Database (LEDA). A randomly selected subset of 68 galaxies from this sample was observed with HST using WFPC2 in snapshot mode and thus this sample is referred to as the "snapshot'' sample. An additional sample of galaxies was assembled from archival HST images of nearby E/S0 galaxies selected for their 100 $\mu$m IRAS emission as these were likely to contain large amount of dust (Tran et al. 2001). This sample is referred to as the "IRAS sample''. From these two samples, we have selected 36 objects (18 from each) according to their optical/IR properties, with no regard to radio properties. The reason for this selection was to avoid biasing in picking a priori "interesting" objects and objects with strong radio fluxes. Galaxies in our sample are nearby ellipticals and lenticulars (E/S0), $cz<3200 \>{\rm km}~{\rm s}^{-1}$, at galactic latitude exceeding $20^{\circ}$ to minimize Galactic extinction, and with absolute V-band magnitude less then -17. Because of their optical/IR selection they tend to have low radio powers.

The global properties of galaxies in our sample are listed in Table 1 of Rest et al. (2001) and in Table 7 of Tran et al. (2001). In the list of 36 galaxies, 18 of them were chosen because they have dust in the form of disks or filaments. The other 18 non-dusty galaxies were selected to match dusty galaxies in optical properties, redshift, magnitude, and IRAS flux. However, after the initial selection, more detailed studies (Rest et al. 2001, Tran et al. 2001) showed that 6 of the "non-dusty'' galaxies showed faint dust structures and have here been included in the "dust'' class. We used H=80  $\>{\rm km}~{\rm s}^{-1}\>{\rm Mpc}^{-1}$ to be consistent with the papers defining the samples.

2.2 Data acquisition and reduction

The observations were undertaken with the VLA in C configuration at 3.6 cm wavelength. All sources were observed at two frequencies in the 8 GHz X-band (8.4351 and 8.4851 GHz) with a bandwidth of 50 MHz for each frequency. We observed 68 sources in total, 36 galaxies and 32 calibrators. Each galaxy was observed for 15 min while calibrators were observed for 130 seconds. Most of the calibrators had position code A (positional accuracy <0002), but four calibrators had B (0002-001) and three had C (001-015) as is indicated on the calibrator web page of the VLA. The radio positions of the detected sources are limited by this positional accuracy of the calibrators, as well as by the accuracy of the Gaussian fit to the source brightness distribution, which is dependent on the signal-to-noise ratios. Taking this in account the overall accuracy is about 50 mas for mJy sources and about 100 mas for 100 $\mu$Jy sources. The observations were taken on March 13, 2000.

We used the Astronomical Image Processing System (AIPS) to reduce the data using the standard procedures from the AIPS cookbook. After initial calibration, the data were imaged using the task IMGR. The data were self-calibrated in phases to improve the image dynamic range, using a model derived from the same data. In some cases amplitude self-calibration was performed on the data to improve the final images. For our astrometric purpose, the positions of the sources were extracted before self-calibration so that phase information was preserved. All the images were examined using the tasks JMFIT and IMSTAT.