We present optical and infrared spectroscopy of the Ðrst 2 months of evolution of the Type II supernova SN 1999em. We combine these data with high-quality optical/infrared photometry beginning only 3 days after shock breakout, in order to study the performance of the "" expanding photosphere method ÏÏ (EPM) in the determination of distances. With this purpose, we develop a technique to measure accurate photospheric velocities by cross-correlating observed and model spectra. The application of this technique to SN 1999em shows that we can reach an average uncertainty of 11% in velocity from an individual spectrum. Our analysis shows that EPM is quite robust to the e †ects of dust. In particular, the distances derived from the V I Ðlters change by only 7% when the adopted visual extinction in the host galaxy is varied by 0.45 mag. The superb time sampling of the BV IZJHK light curves of SN 1999em permits us to study the internal consistency of EPM and test the dilution factors computed from atmosphere models for Type II plateau supernovae. We Ðnd that, in the Ðrst week since explosion, the EPM distances are up to 50% lower than the average, possibly because of the presence of circumstellar material. Over the following 65 days, on the other hand, our tests lend strong credence to the atmosphere models, and conÐrm previous claims that EPM can produce consistent distances without having to craft speciÐc models to each supernova. This is particularly true for the V I Ðlters, which yield dis- tances with an internal consistency of 4%. From the whole set of BV IZJHK photometry, we obtain an average distance of 7.5^0.5 Mpc, where the quoted uncertainty (7%) is a conservative estimate of the internal precision of the method obtained from the analysis of the Ðrst 70 days of the supernova evolution.

We present BUDDA (Bulge/ Disk Decomposition Analysis), a new code devoted to perform a two-dimensional bulge/disk decomposition directly from the images of galaxies. The bulge component is fitted with a generalized Sérsic profile, whereas disks have an exponential profile. No other components are included. Bars and other substructures, like lenses, rings, inner bars, and inner disks, are studied with the residual images obtained through the subtraction of bulges and disks from the original images. This means that a detailed structural analysis of galaxies may be performed with a small number of parameters, and substructures may be directly studied with no a priori assumptions. As has been already shown by several studies, two-dimensional fitting is much more reliable than one-dimensional profile fitting. Moreover, our code has been thoroughly tested with artificial data, and we demonstrate it to be an accurate tool for determining structural parameters of galaxies. We also show that our code is useful in various kinds of studies, including galaxies of, e.g., different morphological types, and inclinations, which also may be observed at different spatial resolutions. Thus, the code has a broader range of potential applications than most of the previous codes, which are developed to tackle specific problems. To illustrate its usefulness, we present the results obtained with a sample of 51 mostly early-type galaxies (but covering the whole Hubble sequence). These results show some of the applications in which the code may be used: the determination of parameters for fundamental plane and structural studies, quantitative morphological classification of galaxies, and the identification and study of hidden substructures. We have determined the structural parameters of the galaxies in our sample and found many examples of hidden inner disks in ellipticals, secondary bars, nuclear rings and dust lanes in lenticulars and spirals, and also wrong morphological classification cases. We now make BUDDA generally available to the astronomical community.

We have obtained deep J and K s images of a sample of nine barred galaxies in order to collect a reliable and homogeneous set of images to which N-body simulations of barred galaxies will be compared. The observations were performed using the new near-infrared camera available at the 2.1-m telescope of the Observatorio Astrofísico Guillermo Haro (OAGH) in Cananea, Sonora, Mexico. We present the results of surface photometry techniques applied to the observed images, as well as to the deprojected images. These results include radial profiles of surface brightness (elliptically averaged), colour, position angle, ellipticity and the b 4 Fourier component. In addition, we present isophotal maps, colour maps, surface brightness profiles along the bar major and minor axes, characteristic radial scalelengths and bar length estimates. We discuss how projection effects can influence these measurements and the uncertainties introduced by deprojecting galaxy images. We show that analytical expressions can be used to obtain reliable estimates of deprojected bar lengths, ellipticities and position angles directly from the observed images. These expressions are based on the assumption that the outer parts of the bar are vertically thin, as shown by theoretical work. The usefulness of our data in addressing issues on bar formation and evolution is also discussed. In particular, we present results showing a steep drop in the ellipticity profile, as expected for bar formation processes in which the dark matter halo plays a fundamental role. Furthermore, we show that the location of this drop is a good indicator of the end of the bar in strongly barred galaxies, as predicted by numerical models.

Along with a brief analysis we present data obtained from BVRI and Ks images of a sample of 19 galaxies (18 barred and 1 unbarred) which will be further explored in a future paper. We measured the lengths and colors of the bars, created color maps and estimated global color gradients. Applying a method developed in a companion paper, we could distinguish for 7 galaxies in our sample those whose bars have been recently formed from the ones with already evolved bars. We estimated an average difference in the optical colors between young and evolved bars that may be translated to an age difference of the order of 10 Gyr, meaning that bars may be, at least in some cases, long standing structures. Moreover, our results show that, on average, evolved bars are longer than young bars. This seems to indicate that, during its evolution, a bar grows longer by capturing stars from the disk, in agreement with recent numerical and analytical results. Although the statistical significance of these results is low, and further studies are needed to confirm them, we discuss the implications from our results on the possibility of bars being a recurrent phenomenon. We also present isophotal contours for all our images as well as radial profiles of relevant photometric and geometric parameters.