From ISO [Ne v] 14.3/24.3 μm line flux ratios, we find that 10 out of 20 planetary nebulae (PNs) have measured ratios below the low-electron density (Ne) theoretical predicted limit. Such astronomical data serve to provide important tests of atomic data, collision strengths in this case. In principle, well-calibrated measurements of the [Ne v] 14.3/24.3 flux ratio could improve upon the existing atomic data.

We analyze CO and H2 absorption lines of the foreground molecular cloud in the Carina nebula. We use HST-STIS (Hubble Space Telescope - Space Telescope Imaging Spectrograph) & IUE (International Ultraviolet Explorer) INES data to analyze the A-X (v=0→2) absorption band of CO for several hot stars toward the Carina nebula, while 9 stars of them have FUSE (Far Ultraviolet Spectroscopic Explorer) spectra to analyze the (v=0→4) vibrational band in the Lyman series of H2. The column densities of CO and H2 varies in the vicinity of N(CO) ~ 1013cm−2 and N(H2) ~ 1019cm−2, respectively. The resultant CO-to-H2 abundance ratio is about 10−6. We investigate the variation of the abundance ratio according to the relative position of the target stars to morphology the molecular cloud in the Carina nebula.

We have compiled two new Galactic open cluster catalogues. The first one has 119 objects with age, distance and metallicity data, while the second one has 144 objects with both absolute proper motion and radial velocity data, of which 45 clusters also with metallicity data available. An iron radial gradient of about −0.063±0.008 dex kpc−1 is obtained from our sample. By dividing clusters into age groups, we show that iron gradient was steeper in the past. A disk age-metallicity relation could very probably exist based on the current sample.

We study the effect of different star formation regimes on the dynamical and chemical evolution of the Dwarf Galaxy IZw18. To do that, we make use of a 2-D hydrocode coupled with detailed chemical yields originating from SNeII, SNeIa and low- and intermediate-mass stars. The results of our simulations are that IZw18 is a pretty young galaxy (we do not need to invoke stars older than 300 Myr in order to reproduce the chemical properties of this object) and the last burst of star formation occurred at most 15 Myr ago.

We determine the Fe abundances for several blue compact and emission-line galaxies. The O/Fe abundance ratios are found to increase with the metallicity of the galaxy, and to decrease with its degree of ionization. These correlations are interpreted as reflecting a decrease for lower metallicities of the depletion of Fe atoms on to dust grains, probably arising from the harder radiation fields prevailing at low metallicities.

We briefly describe our on-going investigation of the near-IR luminosity-metallicity relationship for dwarf irregular galaxies in nearby groups of galaxies. The motivations of the project and the observational databases are introduced, and a preliminary result is presented. The 12 + log(O/H) vs. H plane must be populated with more low-luminosity galaxies before a definite conclusion can be drawn.

Whether the Fe/α enrichment is due to SN Ia explosions or massive objects is a key problem to be addressed in constructing our picture of galactic evolution in the Early Universe. Observations in the rest-frame of Mg II emission at 2800 Å and the broad emission complex of Fe II spanning 2000-3000 Å in high-z quasars should allow to determine the time in the Universe when increases in Fe abundance occur. This in turn provides us constraints on the stellar initial mass function and QSO formation and even the cosmological parameters. However a problem remains in developing a reliable model for this complex ion that accurately predicts the emission line spectra seen in luminous AGN at high redshift. The Fe II/Mg II emission ratios using new 830-level Fe II model are investigated with the intent to explain the observed Fe II/Mg II emission scatter.

We observed the H2 absorption lines in the far-UV band toward HD 37903, which is the central star of the reflection nebula NGC 2023, and ran the radiative-collisional equilibrium program CLOUDY to simulate the UV radiation process of NGC 2023. The input parameters are chosen to generate the same ionization and excitation distribution of atoms and molecules as observed, so that we can create a physical model for NGC 2023.

We present first results of our XMM-Newton study of the nearby dwarf galaxies IC 2574, Holmberg I and Sextans A. Soft X-ray emission has been detected in IC 2574 and X-ray point sources (presumably X-ray binaries) are detected in all three galaxies.

High resolution Brackett line spectroscopy with the Keck Telescope reveals relatively narrow recombination lines toward the embedded young super star cluster nebula in NGC 5253. The gas within this nebula is almost certainly gravitationally bound by the massive and compact young star cluster.

Young clusters are observed to form in a variety of interacting galaxies and violent starbursts, a substantial number resembling the progenitors of the well-studied globular clusters in mass and size. By studying young clusters in merger remnants and peculiar galaxies, we can therefore learn about the violent star formation history of these galaxies. We present a new set of evolutionary synthesis models of our GALEV code specifically developed to include the gaseous emission of presently forming star clusters, and a new tool that allows to determine individual cluster metallicities, ages, extinction values and masses from a comparison of a large grid of model Spectral Energy Distributions (SEDs) with multi-color observations. First results for the newly-born clusters in NGC 1569 are presented.

We present a 3D analysis based on Fabry-Perot data of some astronomical objects directly related to recycling processes within the irregular galaxies NGC4449 and IC1613.

We constructed a model of the infrared spectral energy distribution for very young galaxies by taking into account the dust size distribution in the early stage of galaxy evolution.

We present recent results from mid-infrared observations of a sample of nearby, infrared luminous starbursts and AGN made with the new mid-infrared instrument, “Michelle”, on UKIRT. Narrow band imaging in the 7-13 micron range with sub-arcsec resolution has been used to study the spatial distribution of polycyclic aromatic hydrocarbon (PAH) features. The comparison of these sub-arcsecond resolution data with radio continuum data at similar resolution can be used to determine, 1) the sources of excitation required for PAH emission, and 2) whether PAH features are a measure of the relative contribution of star formation and AGN to the bolometric energy output of a galaxy. Unlike the far-infrared emission from dust, that in the mid-infrared can be used to discriminate between different heating sources.

High-resolution multiwavelength studies of nearby galaxies are essential to understand the full cycle of star formation, and the balance between gas recycling and creation of compact objects. In particular, we study this cycle in the environment of ultra-luminous X-ray sources.

We are constructing the first complete unbiased control sample of the most isolated galaxies of the northern sky to serve as a template in the study of star formation and galaxy evolution in denser environments. Our goal is to compare and quantify the properties of different phases of the interstellar medium in this sample, as well as the level of star formation, both relevant parameters in the internal evolution of galaxies and strongly conditioned by the environment. To achieve this goal we are building a multiwavelength database for this sample to compare and quantify the properties of different phases of the ISM.

We report the first results of the ongoing survey using HST/WFPC2 (F300W) in parallel with ACS within the Chandra Deep Field South. A sample of 34 objects were identified in the WFPC2 images and their counterparts were found in the ACS images taken by the GOODS team; 6 of them are stars. Galaxies were classified as early-, late-types, and starbursts by template fitting which was also used to determine their photometric redshifts (z< 1). Analysis of the light concentration, asymmetry and clumpiness shows that this sample is a mixed bag, containing dwarf ellipticals, early- and late-spirals, and peculiar objects which resemble mergers in progress. This result has important implications for galaxy evolution since the intermediate redshifts are the epoch when the rise in the volume-averaged star formation rate occurs.

Using a set of 60 Tree-SPH simulations of the formation of an individual galaxy, including star formation physics, we quantitatively assess the numerical accuracy and convergence of these methods. For simulations using 24000 particles in total, the gross structures of the resultant galaxies are reliably resolved.

In many SPH simulations of galaxy formation a lower limit is imposed on the kernel radius h equal to the gravitational softening length ∈. It has been found that such a constraint can in some circumstances compromise the spatial resolution to which hydrodynamical quantities are evaluated to the extent that the evolution of the gross features of a numerical galaxies are affected. Such effects can be avoided by allowing h to evolve freely to maintain a roughly constant number of neighbours in SPH summations. Here we focus on how imposing a constraint on h may affect the velocity field.

In this work, we explore a simple method with few free parameters, which describes the global dynamical consequences on disk galaxies of a slow cycling of gas between the interstellar, almost collisionless very cold gas and the warm collisional phases, with a secular transformation of a fraction of warm gas into stars.