The combination of spatial and spectral resolution allow us to use Chandra in the study regions of massive star formation which had been inaccessible even from the ground until the last decade. IRAC and MIPS data from Spitzer can be combined with the X–ray data to provide insight into the presence of a disk and the activity of the star. The total package allows us to better understand the evolution of the clusters. We have an ongoing program to study several young star forming clusters including distant clusters between 1-3 kpc which support O stars, RCW 38, NGC 281 and RCW 108 and well as clusters within a kpc including IRAS 20050+2720 and NGC 1579, which is a small cluster centered on the Be star LkHα101 and is of uncertain distance although the X-ray data help us refine the current distance estimates. Given the space constraints we only discuss RCW 108 below.

We present the results of a study of the evolution of the optical and near-IR colors and mass-to-light ratios (M/L) of early-type galaxies from z~ 1 to the present. This exercise is relevant for studies that use photometry of galaxies to infer properties such as stellar masses and star formation histories through comparison with stellar population models. We have dynamical M/L for a sample of 20 early types at z~ 1 with velocity dispersions from deep optical spectroscopy and structural parameters (size and surface brightness) from high-resolution HST imaging. We compare those with 23 early-type galaxies in the Coma Cluster at z=0.02. For both samples rest-frame optical/near-IR photometry is available, from HST and Spitzer in the case of the z~ 1 sample. We find that the M/L evolves faster in the near-IR than expected from most stellar population models, and also that predictions from different models can differ significantly in the near-IR. As a consequence, there is a systematic uncertainty of a factor of two in stellar mass estimates from near-IR photometry for evolved, high-z galaxies. Optical colors provide a less biased indicator of the M/L. Agreement among the models is required before near-IR photometry can be used as a robust tool to estimate galaxy masses without systematic uncertainties.

This talk charts the implementation of the resolutions of the IAU XXIV General Assembly in 2000 (IAU 2000) in The Astronomical Almanac (AsA).

We present a study of the morphologies and stellar content of the galaxies in the central ∼ 74”×64” region of the galaxy cluster Abell 2218 (see Fig. 1). The spectroscopic data were obtained with the integral field unit PMAS (Roth et al. 2005) in the PPAK mode (Verheijen et al. 2004; Kelz et al. 2006), at the 3.5 m telescope of the Calar Alto Observatory. The covered wavelength range was 4650–8000 Å, with a spectral resolution FWHM∼ 10Å. These data were combined with with deep HST/ACS F475W, F555W, F625W and F850LP imaging, and additional data from the literature.

In Fig. 2 we show the rest-frame B-V vs. MV colour-magnitude diagram for the identified cluster members. The data are segregated according to an objective morphological classification based on the Sérsic index. Contrary to previous results (e.g. Ziegler et al. 2001; Smail et al. 2001) there is a clear indication that the cluster population is not dominated by early-type galaxies, and that there exists an almost parity between early- and late-type objects. In addition, the late-type galaxies spread over a wider range of colours and luminosities with respect to the early-types. This indicates that early-type objects are more massive and have older stellar populations, while late-type galaxies are less massive and exhibit a wider range of stellar population properties.

The results agree with the two-steps scenario for the evolution of galaxies in clusters (e.g. Poggianti 2003), which explains the co-existence of a primordial population of early-type galaxies formed at early epochs, with an additional population of late-type galaxies that have been captured by the cluster, infalling, suffering a short enhancement of the star formation that is later quenched by the interaction with the environment, and that afterwards evolved passively, becoming redder and fainter. Finally, galaxy-galaxy interactions and dry merging processes were responsible for the building up of new massive spheroidal galaxies.

Full details are given in Sánchez et al. (2007).

We numerically model winds driven by super star clusters (SSC) using the hydrodynamic code ZEUS with the new radiative cooling procedure. The importance of cooling on the wind dynamics depends on the properties of the central cluster: the energy and mass deposition rates Lsc and Ṁsc, and the cluster radius Rsc. Low mass clusters behave adiabatically, and their winds are well described by the solution of Chevalier & Clegg (1985). However, for larger Lsc and Ṁsc and/or smaller Rsc, cooling becomes important, and the wind enters the radiative regime in which the wind temperature quickly drops to 104 K at a small distance away from the cluster (Silich et al., 2004). There is no stationary wind solution for very energetic and compact clusters. This is expressed by the line of the critical luminosity Lcrit shown by the left panel as a function of Rsc.

In the case of SSC above the threshold line, the stagnation point Rst appears inside the cluster. It splits the cluster volume into two parts: the outer one with r > Rst where the wind velocity is always positive, and the inner one r < Rst where it has a complicated time-dependent profile. The mass inserted into the outer region leaves the cluster in a form of quasi-stationary wind, while most of the mass from the inner region either accumulates there or passes the inner boundary and eventually feeds further star formation. The middle figure shows that the stagnation point Rst asymptotically approaches the cluster radius Rsc with the increasing Lsc.

The right figure summarises several of our calculations for a cluster with an Rsc = 10 pc. It shows the amount of the mass Ṁout outflowing from the cluster depending on Lsc. It can be seen that Ṁout grows with Lsc following the power-law fit of the simulations Ṁout ≈ Lsc0.54. However, the fraction of the outflowing mass to the total mass deposited by the cluster Ṁsc decreases with Lsc from 100% for Lsc = Lcrit to several percent for Lsc = 5 × 1044 erg s−1.

The chronology of bulge and disk formation is a major unsolved issue in galaxy formation, which impacts on our global understanding of the Hubble sequence. We present colors of the nuclear regions of intermediate-redshift disk galaxies, with the aim of obtaining empirical information of ages of bulges at 0.1 < z < 1.3. We work with a sample of 248 galaxies (123 inclined + 125 face-on) from the HST Groth Strip Survey (Groth et al. 1994) and another one with 404 objects (214 inclined + 190 face-on) from the HST GOODS-N field (Giavalisco et al. 2004), covering redshifts 0.1 z < 1.3. Those samples are apparent-diameter limited at RF814W < 1.4”, and have inclination 50° < i < 70° for the inclined samples and i < 50° for the face-on ones. We find that, as in the Local Universe, the minor axis color profiles are negative (bluer outward), and fairly gentle, indicating that bulge colors are not distinctly different from disk colors. We apply a conservative criterion to identify bulges and potential precursors of present-day bulges, based on nuclear excess surface brightness above the exponential profile of the outer parts. For galaxies with central brightness excesses, rest-frame color distributions show a red sequence. In contrast, galaxies without central brightness excesses show typical colors of star-forming populations. Clearly, something had truncated star formation in many high-density cores, already at z = 1. The truncation epoch is uncertain, 1.5 < z < 10. The color-magnitude distribution of intermediate-z bulges shows more color dispersion than that of bulges in the Local Universe. Most of bulges are as red as local bulges, while the remainder are significantly bluer, a possible sign of late bulge formation.

We argue that with the refined definition of TDB to be adopted by the IAU, the transformation between TDB and TCB becomes trivial.

In this invited contribution I review the justifications for the attempts, currently very popular, to include in semi-analytic models of galaxy formation prescriptions to describe the mutual link between the star formation and nuclear activity in galaxies, which has been for surprisingly long time neglected.

We describe our results on multi-colour observations of extremely red galaxies found in two gravitational lensing clusters (Abell 1835 and AC114). Applying a colour criteria of R-K≥ 5.6 we have selected 12(10) EROs, of which 10(4) have no R-band detection. 5 of these objects have exceptional red colours (R-K>7.5). We compare their colours with other galaxy populations, like distant red galaxies and infrared detected extremely red galaxies, in order to differentiate between them.

Recent observations show that spiral galaxies are surrounded by massive and extended haloes of both neutral and ionized gas. These gaseous haloes have peculiar kinematics with respect to their discs: they rotate more slowly and they show an overall inflow motion. Theoretical models of the formation of these gaseous haloes show that they cannot originate solely from a galactic fountain (supernova outflows from the disk); substantial accretion of material from the Intergalactic Medium should play an important role.

Collision between molecular clouds is considered an efficient mechanism to trigger cloud collapse to form stars. Various observations show that the process is taking place in the universe (Vallee 1995; Wang et al. 2004).

With the present level of accuracy it may be necessary to use space borne atomic clocks to directly generate TCG, and to start addressing the limitations in the coordinate time transformations.

Blue compact dwarf (BCD) galaxies are gas-rich, low-luminosity (Mb≳-18 mag) and compact systems, currently undergoing violent star-formation burst (Sargent & Searle 1970). While it was initially hypothesized that they were very young galaxies (e.g. Sargent & Searle 1970, et al. 1988), the subsecuent detection of an extended, redder stellar host galaxy showed that the vast majority of them are old systems (e.g. Gil de Paz et al. 2003,2005). BCDs play an important role for understanding the process of galaxy formation and evolution.

The structural properties of the low surface brightness stellar host in BCDs are often studied by fitting r1/n models to the outer regions of their radial profiles. The limitations imposed by the presence of a large starburst emission overlapping the underlying component makes this kind of analysis a difficult task.

We propose a two-dimensional fitting methodology in order to improve the extraction of the structural parameters of the LSB host Amorín et al. 2006, submitted). A set of ideal simulations are presented in order to test the reliability of the method and to determine its robustness and flexibility. We present the different steps of the method discussing its advantages and weaknesses. We compare the results for a sample of eight objects with those already obtained using a one-dimensional technique (Caon et al. 2005).

We fit a PSF convolved Sérsic model to the BVR images with the GALFIT publicly software (Peng et al. 2002). We restrict the fit to the stellar host by masking out the starburst region and take special care to minimize the sky-subtraction uncertainties. Consistency checks are performed to assess the reliability and accuracy of the derived structural parameters.

We obtain robust fits for all the sample galaxies, all of which, except one, show low Sérsic indices n—very close to 1—with good agreement in the three bands. These findings suggest that the stellar hosts in BCDs have near-exponential profiles. Since the Sérsic index n of host galaxies is important in the context of the possible structural and evolutionary connections among the different types of dwarf galaxies, we are currently extending the study to a larger sample of objects. This kind of studies will help us to understand the mechanisms that form and shape BCD galaxies, and how they relate to the other dwarf galaxy classes.

We examined observational characteristics of multi-phase turbulent flows in the diffuse interstellar medium (ISM) by calculating atomic and molecular carbon lines. Radiation field maps of C+, C0, and CO line emissions were generated by calculating the non-local thermodynamic equilibrium (nonLTE) level populations and high resolution hydrodynamic simulations of diffuse ISM. By analyzing synthetic line emission, we found a high ratio between the lines of high- and low-excitation energies in the diffuse multi-phase interstellar medium. Our results shows that simultaneous observations of the lines of warm- and cold-gas tracers will be useful in examining the thermal structure, and hence the origin of diffuse interstellar clouds.

Properties related to dust attenuation and star formation of an UV selected sample of intermediate redshift galaxies are presented in this work. We find hints of a decrease of the LIR/LFUV ratio with increasing redshift at low values of the total luminosity. Downsizing is observed at all redshifts, and the SSFR is found to increase with increasing redshift at all stellar masses.

Pulsars can be considered as very precise clocks if they are observed from the barycenter of the Solar system. Pulsar Timing Array (PTA) can be used to establish new astronomical reference frame which describes both space and time properties. Among these arrays most remarkable are the Parks Pulsar Timing Array (PPTA) and Kalyazin Pulsar Timing Array (KPTA).

Large-scale CO observations with the millimeter/submillimeter telescope NANTEN toward a whole FIR loop-like structure whose angular extent is ~20° × 20° around (l, b) ~(109°, − 45°) in Pegasus have been carried out in the 12CO (J = 1 − 0) at 4′ – 8′ grid spacing and the 12CO emitting region in the 13CO (J=1–0) at 2′ grid spacing. The diameter corresponds to ~25 pc at a distance of 100 pc, adopted from that of the star HD886(B2IV) near the center of the loop.

Spiral galaxies can be affected by interactions in clusters, that also may distort the internal velocity field. If unrecognized from single-slit spectroscopy, this could lead to a wrong determination of the maximum rotation velocity as pointed out by Ziegler et al. 2003. This parameter directly enters into the Tully--Fisher relation, an important tool to investigate the evolution of spiral galaxies. To overcome this problem, we measure the 2D-velocity fields by observing three different slit positions per galaxy using FORS2 at the VLT providing us with full coverage of each galaxy and an adequate spatial resolution. The kinematic properties are compared to structural features determined on the HST/ACS images to assess possible interaction processes. As a next step, the whole analysis will be performed for three more clusters, so that we will be able to establish a high-accuracy TFR for spirals at z∼0.5.

Motivated by the GALEX discovery of recent star formation in outermost regions of M83 and NGC4625, we have investigated the nature of the XUV disks with follow-up high resolution imaging and spectroscopy, and attempted to detect them at other wavelengths (IR, Hα). We searched for additional XUV-disk galaxies in the local universe, in order to quantify the incidence of the XUV-disk phenomenon, infer the causes of such extended star formation (SF), and place these systems in the context of disk galaxy evolution.

Current and near future all-sky astrometric catalogs on the ICRF are reviewed with the emphasis on reference star data at optical wavelengths for user applications.