The cold gas in cluster galaxies can be traced by the absorption features they imprint in background luminous QSOs, just as in the field. We will present our first results in a systematic study of the QSO absorption systems whose line of sight goes near massive galaxy clusters.

Star formation on galactic scales is the process driving the evolution of galaxies. The discovery of XUV galaxies by GALEX (Thilker et al. 2005, Gil de Paz et al. 2005) shows that outer part of galaxies may be more active than it was once thought. Star formation seems indeed to proceed at low gaseous surface densities. We will present recent empirical results on the star formation at low densities in the outer disks of normal spirals; and in a set of low surface brightness galaxies.

NUclei of GAlaxies (NUGA) project is a combined effort to undertake a high resolution (1”-2”) and high-sensitivity CO survey, made with the Plateau de Bure IRAM interferometer, for a sample of nearby AGN spirals, which span the whole sequence of activity types. We study the distribution and dynamics of molecular gas in the inner 1 kpc of the nuclei with resolutions of 30-100 pc, and analyse systematically the different mechanisms for gas fuelling of the AGN. The large variety of observed dynamical instabilities (nuclear bars, spirals, warps, ...) are interpreted with the help of N-body numerical simulations. We present CO(1-0) and CO(2-1) maps of the Seyfert 2 galaxy NGC3147 of the NUGA sample at 1.8”x1.6” and 1.4”x1.2” resolution, respectively. Two nuclear rings dominate the CO maps at r=10” and r=20” (1”=180 pc). We discuss the correlation between this particular distribution of the molecular gas and the far-ultraviolet emission using GALEX satellite images and infrared emission with SPITZER images to infer conclusions on the star information.

The goal of this work is to develop spectral diagnostics of stellar populations in the near-infrared (NIR), for unresolved stellar populations of galaxies. Accurate abundance determinations through optical spectroscopy are not possible when investigating heavily reddened evolved stellar populations such as dusty spheroids or bulge-embedded globular clusters (cf. Stephens & Frogel 2004). This is partly due to the attenuation by dust of the visible light. Furthermore, the visible may not be representative of the typical older stellar populations in the galaxies. There are promising near-IR counterparts of some important visible diagnostics. For instance, in stars, the optical age indicator H? correlates well with Br? while the metallicity indicators Mg_b and Mg₂ correlate with MgI 1.50 (µm and CO 1.62 (µm, respectively. We use a sample of elliptical and bulge-dominate galaxies that have reliable Lick-indices from Bender et al. (1993) to test if the correlation between Mg2 and CO 1.62 (µm remain valid in galaxies and to calibrate it as spectral abundance indicator.

For disc galaxies at intermediate redshifts in the Hubble Deep Field North, age and metallicity gradients and dust extinction are investigated using the colour gradients in the disc region. The data are compared with model simulations of dusty galaxies with various age and metallicity gradients. We find that the sample galaxies contain some dust, but are not optically thick, and that the colour gradients in the stellar disc are dominated by populations that become younger and less metal-rich with increasing distance from the centre.

We present results about the star formation process in the giant HII region NGC5471 in the outskirts of M101. From resolved HST/WPFC2 photometry we find that star formation has been going for the last 70 Myr. We further compare previous results from integrated infrared-optical photometry with the stellar resolved CMD and we discuss the star formation properties of this region and its individual knots, as well as characterizing the different stellar content. This result has very important consequences in our understanding of the burst versus continuous star formation activity in spiral galaxies.

We have developed a grid of chemical evolution models of dwarf galaxies using low and intermediate mass stars yields from Gavilan et al. (2005). We study the metallicity, the gas fraction and the star formation rate. We also obtain the effective yield and study the implications of these results in the gas losses.

K-band images of grand-design spiral galaxies frequently display bright knots aligned along their arms (Grosbol & Patsis 1998). The nature of such knots was investigated by Grosbol et al. (2006) using medium resolution K-band spectra of grand-design spiral galaxy NGC2997 obtained by ISAAC/VLT. This revealed that they were very young stellar cluster (ages <10 Myr) possibly formed through interactions between gas and a density wave. Whereas observations of such young clusters in visual bands are troubled by high, varying attenuation by dust in the arm regions, near-infrared bands offer an almost unbiased view of their distribution. Thus, we obtained deep JHK-Brg photometry of the southern arm of NGC2997 with ISAAC/VLT to characterize the distribution of the young stellar cluster. A preliminary analysis of the data indicates that the young clusters are high concentrated to the arm region and have a magnitude distribution with a well defined low luminosity cutoff. This would suggest that the clusters are disrupted as a faint tail of aging clusters is not observed. A fainter population of somewhat more centrally concentrated sources is observed. They are likely globular clusters as they display a uniformed distribution over the field.

The stellar population of Starburst galaxies, the nature of their interstellar medium (ISM), and the interplay between the two, are the fundamental issues in understanding the nature of Starburst galaxies and how they affect the galaxy evolution. Blue Compact Dwarfs (BCDs), as extreme cases, have particular interests as their metal-poor environments are the closest resemblence to that of the primordial galaxies. We present the mid-IR excitation studies of a large sample of local Starbursts and BCD candidates observed by the Spitzer Space Telescope high resolution modules. We show a full range of infrared emission line properties. [NeV] emission are detected in half a dozen sources in the sample and they are all related with AGN activities. [OIV]25.89 are however ubiquitous in Starbursts and BCDs. The ratio of [OIV]25.89/[SIII]33.4 can successfully separate Starbursts with possible hidden AGN components from the pure Starbursts.

I will present radio continuum and linear polarization observations of spiral galaxies of different morphological types, inclinations and star formation rates (SFR). From our observations we found that the fraction of nonthermal (synchrotron) emission in galaxies with low SFR is smaller than in normally star-forming galaxies and -as expected- also the magnetic field strengths are smaller than usual. The low degree of linear polarization indicates that the magnetic fields are also less ordered in galaxies with low SFR. These observations support the view that star formation plays a significant role for the large-scale magnetic field amplification and its structure formation. This is also indicated for the magnetic field configuration in the halos of spiral galaxies as observed in edge-on galaxies.

We estimate a characteristic time-scale for spiral arm driven star formation, going from atomic hydrogen (HI) to dust enshrouded massive stars. Drawing on high-resolution HI data from THINGS and 24 (µm images from SINGS for a sample of 14 nearby disk galaxies, we measure the average angular offset between the HI and 24 m(µm peaks as a function of radius. We model these offsets assuming a characteristic pattern speed, Ω_p for the spiral density perturbation and a time-scale, t_HI->24(µm, for the characteristic time-span between the dense HI phase and the existence of massive stars that heat the surrounding dust. Fitting for ?p and t_HI->24(µm, we find that the radial dependence of this angular offset is consistent with this simple model, and that the resulting co-rotation radii of the spiral patterns are typically R_corot~2.5-3R_exp, consistent with methodologically independent estimates. Values of t_HI->24(µm for the sample are typically only 1-3 Myr. This implies a very rapid time-scale for star-formation in spiral arms, and an upper limit on the lifetime of the molecular clouds in spiral arms of only 1-2 Myr.

The process of star formation on the galactic scale is thought to be driven primarily by the available reservoir of molecular gas, but it has become increasingly clear that the local/global dynamical properties of the galaxies also affect the star formation law (Kennicutt-Schmidt law, KS hereafter). Using recently obtained CO(J=1-0) data from the NRO 45-m telescope, we categorize the KS law between the central regions of nearby galaxies according to its morphology. Barred galaxies are found to dominate the denser regime of the KS law than non-barred galaxies, but are found to share a common law, without marked difference in the star formation efficiency. The relation of the KS law to Hubble type and the Toomre's Q value is also explored.

Differences between the inferred star formation histories (SFHs) of star clusters and field stars have been giving rise to the impression that two distinct star formation processes are at work in galaxies. However, from population synthesis models it can be shown that a uniform SFH for which all mass is formed in clusters leads to different present day age distributions for clusters and field stars. The Small Magellanic Cloud (SMC) is an example of a galaxy where a discrepancy between the two is observed. It therefore provides an ideal opportunity to study the association of cluster and field star populations. We explain the age distributions by fitting the population synthesis code SPACE to SMC observations. This allows for a derivation of several properties of the SMC, like the cluster disruption timescale, infant mortality rate and star formation history, and a better understanding of the relation between cluster and field star populations.

In this poster we introduce the Local Volume Legacy (LVL) - a Spitzer Cycle 4 IRAC and MIPS Legacy survey of a volume-complete sample of 258 galaxies within 11 Mpc. The broad goal of LVL is to provide critical insight into two of the primary processes that shape the growth of galaxies: star formation and its interaction with the interstellar medium. This goal will be achieved by investigating the spatially- resolved star formation, dust, and red stellar populations of galaxies that have been drawn from a statistically robust local sample, in which the full diversity of galaxy properties (e.g., luminosities, surface brightnesses, metallicities) are represented. Our tiered sample includes: (1) all known galaxies inside a sub-volume bounded by 3.5 Mpc, and (2) an unbiased sample of S-Irr galaxies within the larger, and more representative, 11 Mpc sphere. LVL will produce a multi-wavelength census of the Galactic neighborhood, extending to the faintest limits of the galactic luminosity function and exploiting the highest spatial resolution and absolute depth achievable with Spitzer. Our rich suite of ancillary data includes H? and UV imaging from the GALEX 11HUGS and NGS surveys, stellar population mapping from the HST ANGST Treasury survey, HI mapping with the VLA and GMRT, optical broad-band imaging and spectroscopy. By homogeneously filling in critical gaps in the current Spitzer coverage of the Local Volume, and extending SED coverage from the ultraviolet to the far-infrared, LVL will provide an enduring archival dataset on the Galactic neighbourhood and the present-day galaxy population.

We have computed a series of realistic and self-consistent models of the emitted spectra of HII galaxies. Our models combine different codes of chemical evolution, evolutionary population synthesis and photoionization. The emitted spectrum of HII galaxies is reproduced by means of the photoionization code CLOUDY, using as ionizing spectrum the spectral energy distribution of the modelled HII galaxy, which in turn is calculated according to a Star Formation History (SFH) and a metallicity evolution given by a chemical evolution model that follows the abundances of 15 different elements. The results of our code were compared with photometric and spectral data of HII and BCD galaxies. Our technique reproduces observed diagnostic diagrams, equivalent width-colour and equivalent width-metallicity relations for local HII galaxies.

We have derived oxygen and nitrogen abundances for a sample of late-type, low surface brightness (LSB) galaxies found in the Sloan Digital Sky Survey (SDSS) as well as dwarf and irregular LSB galaxies where data were taken from the literature. Furthermore, we have computed a large grid (~5000 models) of chemical evolution models (CEMs), testing various time-scales for infall, baryon densities and several power-law initial mass functions (IMFs) as well. Because of the rather stable N/O-trends found both in the CEMs (for a given IMF) and in observations, we find that the hypotheses that LSB galaxies have stellar populations dominated by low-mass stars, i.e., very bottom-heavy IMFs (see Lee et al. 2004), can be ruled out. Such models predict much too high N/O-ratios and generally too low O/H-ratios. We also conclude that LSB galaxies probably have the same ages as their high surface brightness counterparts, although the rate of star formation may be considerably lower in these galaxies.

In this poster we present an extensive project aimed at studying the stellar population of bulges in spiral galaxies to understand their chemical properties and if these properties differ from those of elliptical galaxies. To achieve these goals, we observed a sample of disk galaxies in field and in cluster. We measured the main Lick indices (H-beta, Mg₂, <Fe>, MgFe) and the principal kinematical parameters (velocity, velocity dispersion) as function of the galactocentric radius, in order to determine the age, metallicity and alpha-enhancement for all the sample galaxies. alpha/Fe supersolar and constant value along the radial profile, in most of the galaxies, suggest that the star formation in these objects has been fast and occur at the same time in the whole bulge.

We will present azimuthally-averaged Spectral Energy Distributions (SEDs) from FUV to FIR, as a function of radius, for all disk galaxies included in the SINGS sample. Changes in these SEDs with the galactocentric distance will be interpreted in terms of the radial variation of the relative contribution of stars (of different ages), dust, and gas. This will be done by making use of the predictions of models for the chemical and spectro-photometric evolution of disk galaxies. As part of this analysis we will improve our determination of the growth rate of nearby disks recently carried out using GALEX UV and 2MASS near-infrared data alone (Munoz-Mateos et al. 2007) and study its dependence on the galaxy size/mass and environment.

We examined a correlation of CO(3-2)/CO(1-0) ratios and star formation efficiencies (SFEs) for the whole inner disk region of the nearby barred spiral galaxy M83. When CO(3-2)/CO(1-0) ratios are lower than 0.8, the correlation between CO(3-2)/CO(1-0) ratios and SFEs is not clearly seen. However, CO(3-2)/CO(1-0) ratios and SFEs show a positive correlation when CO(3-2)/CO(1-0) ratios exceed 0.8. According to Large Velocity Gradient (LVG) calculation, molecular gas density would be around 104 cm-3 at CO(3-2)/CO(1-0)~0.8. These results suggest that the critical density of molecular gas for which star formation occur is about 10⁴ cm^-3, and suggest that SFEs sharply increase in dense molecular gas exceeding critical density.

Wide field and high spatial resolution CO molecular emission line mapping observations toward NGC253 were performed. NGC253 is a very nearby (D=3.4 Mpc) and archetypal starburst galaxy. CO(1-0) and (3-2) emission line mapping observations were carried out using the Nobeyama 45-m telescope and the Atacama Submillimeter Telescope Experiment (ASTE), respectively. The maps cover about 10x3 arcmin (=7.3x2.1 kpc) for both transitions, and the spatial resolutions are 15 arcsec (=182 pc) and 24 arcsec (=290 pc) for (1-0) and (3-2), respectively. The CO(3-2) map is the first large area map which includes the galactic bar, the bar-end, and the starburst (2 kpc) ring. Strong CO(3-2) emissions are detected not only at the galactic center but also at the bar-end and the starburst ring. Moderate to high (3-2)/(1-0) ratio (r31 = 0.6-1.0) areas which suggest there are large amount of dense (n(H2) > 10^3-4 cm^-3) molecular gas agree well with massive star-forming regions.

The origin and distribution of r-process elements in the Milky Way are poorly understood. To unravel the chemical evolution history of the Galaxy, we measure the abundance of europium and other r-process elements in Galactic thin disk stars. With nearly one thousand Keck I HIRES spectra for stars that have 0.5

We report an analysis of stellar populations based on color gradients for a large sample of nearby S0 and early-type spiral galaxies. The color gradients are constructed from deep near-IR (JH bands) and optical (ugriz) images. The IR images were collected with ULBCAM at the UH 2.2-m telescope. The optical photometric data are taken from the Sloan Digital Sky Survey (SDSS). Deep surface brightness profiles, extending out to 3-4 disk scale lengths, were extracted from the ULBCAM and SDSS images. The galaxy colors are compared to the stellar population synthesis models of Bruzual & Charlot, revealing radial trends of ages and metallicities of stellar populations in the bulge and disk. This is the largest study of its kind to date (for S0 galaxies).

We present UV spectra of the edge on galaxy NGC3079 obtained with the GALEX slitless grism. We derived the dust attenuation across the main axes of the galaxy and discuss the use of different extinction curves to correct the observed UV fluxes.

We have used absorption line imaging to measure radial profiles of the Mg2 and Fe5270 line strengths in the stellar populations of disk galaxies, then followed this up with spectroscopy of the HII regions to derive the oxygen abundance gradients in these same galaxies. The stellar abundance gradients are a fossil record of the chemical enrichment up to a Gyr ago, while the gas-phase oxygen abundances reflect the cumulative massive star formation right up to the present day. Together, all these gradients provide powerful constraints on the possible evolutionary scenarios for individual galaxies.

Elemental abundance trends within the thin and thick disk stellar populations of the Milky Way argue for distinct large-scale evolution within those populations. Recent studies of the abundance trends of thin and thick disk stars argue for unique star formation histories (Reddy et al. 2006, Brewer & Carney 2006, Bensby et al. 2003). For example, the heavy element contributions differ such that the r-process element [Eu/Fe] is higher at a given [Fe/H] in thick disk stars. In the thick disk, the s-process/r-process ratio may be lower overall (Mashonkina & Gehren 2001, Bensby et al. 2005). This evidence of the varying contributions of low and high mass stars is of particular interest in light of the possibility of chemical substructure in the Galactic disk. Based on high resolution (R~50,000) and high signal-to-noise (S/N~100) spectra of 600 nearby dwarf stars, we will present the s-/r-process ratio in the local disk population as traced by the abundance ratio La/Eu. Stellar parameters have been derived from photometry. The sample covers 800 K in effective temperature (5400 K <T_eff< 6200 K) and 0.7 dex in metallicity (-0.5 dex <[Fe/H]< +0.2 dex). We have employed an abundance measurement technique based on minimizing the Chi-squared fit to synthetic template spectra, a procedure from which we can also measure rotational velocities. Stellar kinematics and population assignments have been calculated for the entire sample, which is composed primarily of thin disk stars. Europium abundance results from a sub-sample limited to stars with little or no detectable rotation reproduce the [Eu/Fe] trends found by other studies. We find some evidence for variation both in [Eu/Fe] and [Eu/La] at a given [Fe/H] in thin disk stars, such that a few stars show little to no s-process enhancement.

We present results of new ATCA HI emission and absorption observations of Centaurus A, the nearest large radio galaxy. We apply a new software (Jozsa et al. 2007) fitting tilted-rings directly to the 3 dimensional data cube. The resulting best model does not reproduce the warped disk structure and kinematics of the (HI) gas sufficiently. A qualitatively model with elliptical orbits is discussed as well. Our results will be briefly compared to the models of ionised and molecular gas in the literature (e.g. Nicholson et al. 1992, Sparke 1996, Quillen et al. 2006). In addition to these large scale investigations, we will report on the findings for the very central region and compare our HI results to the central molecular and ionised disks of a few arcsec e.g. found by Marconi et al. (2001), Krajnovic et al. (2006), and Liszt (2001).

We explore the elemental abundance features of metal-rich disk stars, highlighting the comparisons made with those of the recently revealed Galactic bulge stars. A similarity between two of the comparisons leads to a new theoretical picture of the bulge-disk connection in the Galaxy, where a supermassive black hole resides at the center. We postulate that a metal-rich outflow, triggered by feedback from a black hole, was generated and quenched the star formation, which had lasted several billion years in the bulge. The expelled gas cooled down in the Galactic halo without escaping from the gravitational potential of the Galaxy. The gas gradually started to accrete to the disk around five billion years ago, corresponding to the time of sun’s birth, and replaced a low-metallicity halo gas that had been accreting over nearly ten billion years. The metal-rich infalling gas, whose elemental abundance reflects that of metal-rich bulge stars, mixed with the interstellar gas already present in the disk. Stars formed from the mixture compose the metal-rich stellar disk. This scheme is incorporated into models for chemical evolution of the disk. The resultant elemental features are compatible with the observed abundance trends of metal-rich disk stars, including the upturning feature exhibited in some [X/Fe] ratios, whose interpretation was theoretically puzzling. Furthermore, the predicted abundance distribution function of disk stars covers all observational facts to be considered: (i) the deficiency of metal-poor stars, (ii) the location of peak, and (iii) the extended metal-rich tail up to [Fe/H]~+0.4.

Recent observations of stellar populations in barred galaxies have focused on the spatial distribution of stellar population ages and metallicities. However, barred galaxies are complex objects where dynamical instabilities play a leading role in shaping any spatial distribution. The age distribution of stellar populations should thus be analyzed from the two points of view of stellar population evolution and dynamical secular evolution. Chemodynamical simulations of single barred galaxies have been performed to produce face-on mass-weighted maps of stellar population ages and metallicities. Luminosity-weighted maps in V-band are also displayed after calibrating the simulation with mass-to-light ratios provided by a synthesis population model. Two different chemodynamical codes are used, one with simple star formation and feedback recipes (see Wozniak 2007), a second with a full treatment of stellar evolution effects, multi-phase ISM, multi-elements cooling, etc. Several important results for the interpretation of observations on barred galaxies will be discussed. For instance, it will be shown that inside a stellar bar two persistent diametrically opposed regions display a mean age lower than the surrounding average. These two low-age regions are due to the accumulation of young stellar populations trapped on elliptical-like orbits along the bar, near the ultra-harmonic resonance. Age gradients along the bar major-axis are comparable to recent observations. Another low-age region is the outer ring located near the Outer Lindblad Resonance, but the presence and strength of this structure is very time-dependent.

We describe the functioning, the tests and first results of a new galactic chemodynamical tool designed to be coupled with an N-body+SPH code (e.g. Gadget-2 or our own PM+SPH code). In the framework of non-instantaneous recycling approach, we follow the interaction between dynamics and chemistry due to star formation and feedback processes (winds, SNII, SNIa, UV background). One of the main original features of our code is that we record the abundance evolution of several chemical elements (H, He, C, N, O, Mg, Fe etc.). This allows us to build cooling functions dependent on the real abundances of individual elements. Star formation recipes are based on recent progress on molecular clouds fragmentation and stellar cluster formation. Other features include the presence of two phases (CNM at 100K and Warm/Hot medium) in pressure equilibrium (with condensation/evaporation and phase transition). We will also discuss the effects of adding a dusty component.

We have collected photometric and spectroscopic observations of thick disks in a sample of edge-on disk galaxies. We find that thick disks are more prominent in lower mass galaxies, to the point of dominating the total stellar mass. Kinematically, most thick disks (8 of 9) are comparable to the Milky Way thick disk showing a moderate rotational lag and are consistent with being a kinematically hot stellar population in equilibrium with the overall galaxy potential. However, we find one example of a thick disk which is counter-rotating when compared to the thin disk. We have derived ages and metallicities using the Lick spectral indices and confirm that thick disks are uniformly old and metal poor. Our observations support thick disk formation models where the thick disk is formed from the direct accretion of stars from infalling satellite galaxies.

We calculate the radial profiles of thickness and the volume density of gas layer for several spiral galaxies (MW, M33, M51, M100, M101, M106), using the model of isothermal equilibrium gaseous disk in a three-component galaxy. A relationship between the gas volume density in the plane of the disk and the star formation rate SFR (Schmidt law) is analyzed. It enables us to compare the galaxies by the efficiency of star formation at different radii. It is shown that the volume densities of gas and SFR are more tightly interconnected than the corresponding surface densities. The only galaxy which is strongly inconsistent with the Schmidt power law is the starburst galaxy M106.

We present the FIR size-dust temperature-luminosity 3D analysis of a complete sample of 225 local galaxies selected in the IRAS Bright Galaxy Sample radio continuum follow-ups at 1.4 GHz (Condon et al. 1990, 1996). We show that most of the dispersion of the 60-to-100um color versus FIR luminosity diagram can be attributed to the presence of a third parameter, namely the size of the star forming region. Using the IRAS 60-to-100um flux density ratio, the FIR luminosity and the radio continuum size of the star forming region, we explain the dispersion by a simple relation between these three parameters.
To explore the physical processes giving rise to this relation, we have constructed a simple model and shown that this relation that can be derived from the Schmidt law relating the SFR to the gas surface density.