We present extensive new spectroscopy and imaging of PNG 135.9+55.9. We use these data as constraints to photoionization models to derive limits on the oxygen abundance. We find that PNG 135.9+55.9 has an oxygen abundance less than 1/50 of the solar value. Our models favour a value of 12 + log O/H between 5.8 and 6.5 dex, confirming that PNG 135.9

We present optical broad- and narrow-band imaging of a sample of a dozen barred galaxies. These images are analysed in conjunction with our previously published near-infrared imaging of their central regions and with literature values for, e.g. bar strengths and the total star formation activity of the galaxies. We present B, I and Hα images, and

EMIR (Espectrógrafo Multiobjeto Infrarrojo) is a wide-field, near-infrared, multi-object spectrograph, with image capabilities, which will be located at the Nasmyth focus of GTC (Gran Telescopio Canarias). It will allow observers to obtain many intermediate resolution spectra simultaneously, in the nIR bands Z, J, H, K. A multi-slit mask unit will

The varying global distribution of stars, or specifically, their concentration Cr_e, within elliptical galaxies and spiral galaxy bulges is intimately related to the mass of their central supermassive black holes (Mbh), such that log (Mbh/Msun) = 6.81(±0.95)Cr_e + 5.03±0.41. This correlation has a Spearman correlation coefficient rs=0.91, and a

The aim of a data reduction process is to minimize the influence of data acquisition imperfections on the estimation of the desired astronomical quantity. For this purpose, one must perform appropriate manipulations with data and calibration frames. In addition, random-error frames (computed from first principles: expected statistical distribution

We have compiled a database of Chandra-HRC snapshot images covering most of the M31 disk. The database consists of 5 HRC fields. All fields were observed at 16 different epochs covering a baseline of nearly 2 years. The merged image has a mean total exposure time of 17 ks. These data were analyzed to measure the mean fluxes of ~130 sources, most of