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I will review recent progress in the modeling of the stellar spectral energy distributions of star-forming galaxies. I will cover the full relevant wavelength range from the near-infrared to the extreme ultraviolet, with an emphasis on the ultraviolet long- and shortward of the Lyman break where most of the stellar luminosity is emitted. Uncertainties in stellar atmosphere and evolution models will be critically examined, and the impact on the total panchromatic luminosity will be highlighted. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The search for the most distant galaxies is bursting with new discoveries and theoretical excitement. The topic is not only plainly interesting in itself, it also has profound implications for the study of cosmic reionization, the intergalactic medium, and cosmic enrichment. Such observations also provide a stringent benchmark for cosmological models. The following is a very concise attempt to review the present status of the field and its challenges from a theoretical perspective. [ABSTRACT FROM AUTHOR]

Gamma-ray bursts have been proved to be detectable up to distances much larger than any other astrophysical object, providing the most effective way, complementary to ordinary surveys, to study the high redshift universe. To this end, we present here the results of an observational campaign devoted to the study of the high-z GRB 090205 that led to the detection of the optical afterglow and host galaxy and to the first measure of its redshift, z = 4.65. Photometric observations of the GRB 090205 host galaxy argue in favor of a starburst galaxy with a stellar population younger than ∼150 Myr. Moreover, the metallicity of Z>0.27 Z⊙ derived from the GRB afterglow spectrum is among the highest derived from GRB afterglow measurement at high-z, suggesting that the burst occured in a rather enriched envirorment. Finally, a detailed analysis of the afterglow spectrum shows the existence of a line corresponding to Lyman-α emission at the redshift of the burst. GRB 090205 is thus hosted in a typical Lyman-α emitter (LAE) at z = 4.65. This makes the GRB 090205 host the farthest GRB host galaxy, spectroscopically confirmed, detected to date. [ABSTRACT FROM AUTHOR]

Contrary to the classical “cold” view of star formation, star forming clouds and YSOs abound with high energy phenomena. YSOs of almost all masses are intense sources of X-rays, with luminosities well above those of main sequence stars. Most of this emission originates in coronae, qualitatively similar to those of the Sun and of other main sequence stars. X-rays are also emitted in shocks at the base of mass accretion funnels and in jets. Diffuse X-ray emission from high mass star forming cloud has also been detected. I discuss the current status of observations with regard to these X-ray emission mechanisms, and the influence of X-rays from YSOs on circumstellar disks. [ABSTRACT FROM AUTHOR]

The various methods for studying in detail relevant stellar population parameters throught the integrated light are reviewed. The emphasis is given to the analysis based on absorption line-strength indices. The state-of-the-art of the stellar population synthesis models and methodologies is summarized. Finally some of the various uncertainties and limitations, which are lurking these studies are shown and discussed. [ABSTRACT FROM AUTHOR]

Recently there has been mounting observational evidence in favour of Luminous Blue Variables (LBVs) being the ‘direct’ progenitors of some core-collapse supernovae in stark contrast to theoretical predictions. Here we give an outline of these events and present, possibly, the most convincing evidence to date for LBV supernovae progenitors: the intriguing case of SN 2005 gj. We will connect this to our current understanding of massive star evolution and highlight the potential problems this causes. [ABSTRACT FROM AUTHOR]

Colliding winds of massive stars in binary systems are viable candidates for non-thermal high-energy photon emission. Long since, coincidences between massive star systems/associations and γ-ray sources have been noted. Now, with the sensitivity of the Fermi Gamma Ray Observatory and current very-high-energy (VHE) Cherenkov instruments, will it be possible to sensibly probe these systems as high-energy emitters. We will summarize the characteristics and broadband predictions of generic optically thin emission models in the observables accessible at GeV and TeV energies. The ability to constrain orbital parameters of massive star-star binaries through GeV-to-TeV observations is discussed. As an example we will present orbital parameter constraints for the nearby Wolf-Rayet binary system WR 147 based on recently published VHE flux limits. Combining our broadband emission model with the cataloged binaries systems and their individual parameters allows us to conclude on the population of massive star-star systems at high-energy γ-rays. [ABSTRACT FROM AUTHOR]

In this proceedings, we connect studies of accreting binary populations in nearby galaxies to the study of galaxies in the more distant reaches of the Universe. We focus on a population of GALEX-selected Ultraviolet-Luminous Galaxies (UVLGs) that appear to include an interesting subset that are analogs to the distant (3

Spitzer in the warm phase will provide a unique opportunity for large-field and deep observations of nearby galaxies to address a number of fundamental science questions that cannot be adequately answered within the confines of current sample sizes/depths as produced by regular general observer, or even Legacy, proposals. Potential science goals include the morphological classification of galaxies, the investigation of the edges of galaxy disks and of intragroup/intracluster environments, the use of hot dust emission to trace star formation and AGNs, the monitoring of supernovae and of other variable sources, and the calibration of stellar population models in the mid-IR. The local Universe is the only available benchmark against which distant galaxies can be compared, and every effort should be made to ensure that the properties of nearby galaxies are fully investigated by the ‘warm’ Spitzer. [ABSTRACT FROM AUTHOR]

Dwarf galaxies are important to study because they potentially provide a direct connection to the earliest epochs of galaxy formation. They also allow us to study the star formation process at relatively low abundances. Our understanding of the origins and evolution of dwarf galaxies has been changing very rapidly. New observations are giving better insight into the relationship between the two main families of dwarf galaxies, the dwarf ellipticals and the dwarf irregulars. Here I review a broad range of topics related to the formation and evolution of dwarf galaxies. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

By the time, in 1937, the Swiss astronomer Zwicky measured the velocity dispersion of the Coma cluster of galaxies, astronomers somehow got acquainted with the idea that the universe is filled by some kind of dark matter. After almost a century of investigations, we have learned two things about dark matter, (i) it has to be non-baryonic — that is, made of something new that interact with normal matter only by gravitation— and, (ii) that its effects are observed in stellar systems when and only when their internal acceleration of gravity falls below a fix value a0=1.2×10-8 cm s-2. Being completely decoupled dark and normal matter can mix in any ratio to form the objects we see in the universe, and indeed observations show the relative content of dark matter to vary dramatically from object to object. This is in open contrast with point (ii). In fact, there is no reason why normal and dark matter should conspire to mix in just the right way for the mass discrepancy to appear always below a fixed acceleration. This systematic, more than anything else, tells us we might be facing a failure of the law of gravity in the weak field limit rather then the effects of dark matter. Thus, in an attempt to avoid the need for dark matter many modifications of the law of gravity have been proposed in the past decades. The most successful — and the only one that survived observational tests — is the Modified Newtonian Dynamics. MOND posits a breakdown of Newton’s law of gravity (or inertia) below a0, after which the dependence with distance became linear. Despite many attempts, MOND resisted stubbornly to be falsified as an alternative to dark matter and succeeds in explaining the properties of an impressively large number of objects without invoking the presence of non-baryonic dark matter. This suggests MOND is telling us something important about gravity in the weak field limit. In this paper, I will review the basics of MOND and its ability to explain observations without the need of dark matter. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report on the first 1D radiation-hydrodynamics simulations aimed at exploring the metallicity dependance of the evolution of planetary nebulae. Using scaled mean abundances, based on Galactic disk objects, we found that for lower metallicities the nebulae become more dilute and prone to departures from thermal equilibrium because of the reduced wind power of the central star and the reduced cooling efficiency of the nebular gas. At selected evolutionary phases we ‘switched off’ the hydrodynamic terms and computed equilibrium models for the fixed density structure and radiation field. This enabled us to study how the electron temperature and the emission of important diagnostic lines is influenced by hydrodynamics. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This is a paper version of the poster presented at this meeting in which we discuss some recent results of our analysis of the luminosity — emission line width relation found in HII galaxies, possible interpretation of the observed supersonic motions, the presence of second parameters in the relation and the validity of the application of these empirical relations to determinig extragalactic distances. A full analysis of these results will be presented in a forthcoming paper. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The recent starburst in the nearby dwarf galaxy NGC 1569 has had a deep impact on the interstellar medium of the whole galaxy. In this paper, we discuss the consequences of this event for the distribution and kinematics of the neutral atomic hydrogen and demonstrate how strong star formation influences the properties of the surrounding molecular gas. The detection of a complex halo structure leads us to propose the accretion of an intergalactic cloud as the trigger and the gas reservoir of the remarkably strong starburst. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Dwarf galaxies with active star formation play a significant role in the family of starburst galaxies. They share a number of properties with their giant brethren, while their lower mass leads to some charateristics that are specific to star forming dwarfs. To see both similarities and differences, in this brief review, we focus on the different phases of the interstellar medium in dwarfs. The hot gas, typically observed in X-rays, can, least in some cases, blow out of the galaxies. This phenomenon, still visible today, also provides an important mechanism for the metal enrichment of the intergalactic medium (IGM) in the early universe. The neutral gas, HI, sometimes extends into huge halos surrounding the optical galaxies. HI companions seem to be frequent, possibly pointing to infall and interaction as necessary means of feeding the starburst. On small scales, some dwarf galaxies show numerous HI holes, implying propagating star formation and allowing the investigation of early phases of what later may become a blow-out of the gas. Molecular gas, the site of actual star formation, is notoriously difficult to detect in dwarfs. The reasons for this are well understood and not related to a dearth of molecular material, but rather the low metallicity environment chracteristic for dwarf galaxies. Sensitive observations have provided a number of maps of molecular gas in dwarfs and the determination of gas properties is slowly becoming possible. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Galactic winds are expected to be nearly omnipresent in dwarf galaxies based on theoretical considerations and several indirect observational evidences. The direct observational proof for their presence is far more elusive, contrary to the widespread expectation that dwarf galaxies are very favourable places to observe galactic winds. Interstingly, there is much better direct observational evidence for galactic winds from massive galaxies. I review critically the different methods, their relative sucesses to detect galactic winds in dwarf galaxies, and also comment on the future observational possibilities. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present results from near-infrared integral-field spectroscopy of the circumnuclear starburst in M83, using the CIRPASS instrument on Gemini South. The combination of Paβ, CO (6,3), and [Fe II] equivalent width measurements over large contiguous regions allows us to track the spatial propagation of star formation across the ringlet, which is too heavily obscured to be properly analysed at optical wavelengths. We find the clearest evidence yet for an age gradient, with the youngest clusters found closest to where the dust lane crosses the ringlet. We discuss the implications for gas fueling by the bar. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nuclear rings are characterized by their high star formation rates, and are believed to be the products of gas inflow towards the inner regions of spiral galaxies. We present first results from a statistical survey of these rings, aimed to provide an insight into their triggering mechanisms and star formation properties. We gathered photometric data for 22 nuclear star-forming rings from a larger Hα survey of nearby spirals, of which we highlight three interesting cases (NGC 1343, NGC 1530, and NGC 5953). The high-quality images reveal that the rings are comprised of several distinct star-forming clusters within a few kiloparsecs of the nucleus. We analyzed each nuclear ring to obtain morphological parameters such as ellipticity, position angle, and size. We then compute the equivalent widths of each Hα emitting (HII) region forming the nuclear ring. Using modern population synthesis models, we convert the equivalent widths into an estimate of the age of each cluster. In general, ages range from 1 Myr to 10 Myrs throughout the rings. We compare the ages to the positions along each ring to detect possible age-related patterns. Where a bar exists in the host galaxy, we determine the approximate intersection points of the bar to the ring to probe whether the youngest hotspots occur near this intersection. We find that three rings from the sample show age gradients or bisymmetries along the plane of the ring, and in one case the youngest cluster does indeed intersect with one of the bar’s interaction points to the ring. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The central regions of disk galaxies are hosts to supermassive black holes whose masses show a tight correlation with the properties of surrounding stellar bulges. While the exact origin of this dependency is not clear, it can be related to the very basic properties of dark matter halos and the associated gas and stellar dynamics in the central kpc of host galaxies. In this review we discuss some of the recent developments in modeling the wide spectrum of dynamical processes which can be affiliated with the above phenomena, such as the structure of molecular tori in AGN, structure formation in triaxial halos, and dissipative and non-dissipative dynamics in nested bar systems, with a particular emphasis on decoupling of gaseous nuclear bars. We also briefly touch on the subject of fueling the nuclear starbursts and AGN. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We review the ages of starbursts and the methods used to obtain this information. We emphasize that the measurement of this parameter is non-trivial because of observational biases and the complex time-dependent behavior of a starburst. Star clusters probably provide the best estimates of starburst ages which are then in the range 10–100 Myr, although the short lifetimes of some clusters must introduce a bias against longer lived events. From studies of stellar populations in nearby dwarf galaxies, the burst frequency is found to be ∼ 15%. Stellar population synthesis modeling of unresolved galaxies provides starburst ages of a few Myr up to 100 Myr, consistent with ages derived using star clusters. Overall, the likely duration of a starburst event of ≤ 100 Myr suggests that they evolve on a time scale which is consistent with the internal dynamical time scale of a galaxy. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We review the properties of galaxies at z > 5, specifically those selected using the Lyman break technique. We show that these sources are typically young starbursts with relatively dust-free star formation regions. They are resolved on scales of 1 – 2 kpc, sometimes with multiple components seperated by a few kpc. They are smaller than z = 3 Lyman break galaxies (LBGs). As a population, they show no evidence of hosting AGN, obscured or otherwise. Approximately half of the photometrically-selected LBGs at IAB ∼ 26 show Lyα emission with luminosities of 1042–43 erg s-1. The comoving number density of Lyman break galaxies at z > 5 with M AB(1700Å) < -21 is a factor ∼ 3 lower than that for similar LBGs at z = 3 – 4. The integrated UV emission from z ∼ 5 LBGs brighter than MAB(1700Å) < -17.5 is sufficient to ionize their local volume. A similar population at much higher redshift would not be able to keep its local volume ionized. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Emission line diagnostics provide a powerful tool for extracting fundamental global properties of galaxies. In this paper, we review the common optical emission-line diagnostics for star-formation and discuss our recent progress in this area. We focus on our recent results using H-alpha and [OII] as star formation rate (SFR) indicators for local and high-z samples. In local samples, correction of the SFR(H-alpha) for extinction using the Balmer decrement and a classical reddening curve reduces the scatter and discrepancy between SFR(H-alpha) and reddening-insensitive SFR estimates. Using a combination of stellar population synthesis and photoionization models, we investigate the cause of the systematic discrepancy between SFRs derived from [OII] and those derived from H-alpha. There are two significant effects which produce strong disagreement between SFR([OII]) and SFR(H-alpha): reddening and metallicity. Such a disagreement can appear as a function of redshift, contaminating cosmic star formation history studies. We discuss our new theoretical SFR([OII]) calibration which does not contain a reddening assumption, and includes an optional correction for metallicity. This new SFR([OII]) calibration removes the previously observed discrepancy between the SFR([OII]) and SFR(Hα) for both nearby and high redshift samples. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We give an overview of the factors shaping the ultraviolet (UV)/optical — far-infrared (FIR)/submillimeter (submm) spectral energy distributions (SEDs) of normal (non-starburst) galaxies. Particular emphasis is placed on the influence of the geometry of dust and stars on the propagation of light through the interstellar medium. Although strong constraints can be placed on the amount and large scale distribution of dust in disks from the appearance of the galaxies in the optical/UV range, this dust does not account for the observed amplitude and colour of the FIR/submm radiation. Additional, optically thick components of dust associated with the young stellar population on large and small scales are required to account for the complete UV/optical — FIR/submm SEDs. Self-consistent models for the calculation of SEDs of spiral galaxies are reviewed, and their predictions for the dust emission and the attenuation of starlight are compared and contrasted. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper reviews the theoretical modelling of starburst galaxies with particular emphasis on the importance of the gas-phase physics in determining the form of the continuum SED and the emission line spectrum. Both line and continuum diagnostics have been used as star formation indicators. Here, we examine from the point of view of the theory how reliable each of these indicators may be, and to what physics of the galaxy they are sensitive, with the aim of decreasing the errors associated with measuring the star formation history of the universe. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Narrow line regions (NLR) are a major component of active galaxies, and commonly used as an indicator of the presence of an active galactic nucleus (AGN). Most of the analysis and theoretical work into NLRs so far has concentrated only on the narrow emission lines. However, NLRs show strong evidence of containing dust and will likely emit strongly in the infrared. Here, we model this radiation from NLRs, examining the effects of pressure and ionization parameter, and demonstrate that a large fraction of the NLR emission is emerges in the IR. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Our ability to correct the observational photometry of galaxies depends upon our knowledge of the attenuation of light produced by the dust contained in the interstellar medium. We will present a model based on the statistical properties of the local density in isothermal turbulence which might be appropriate to calculate the radiative transport through the diffuse interstellar medium. The model will be applied to study the attenuation caused by a distant foreground screen and a non scattering slab where the sources are mixed within the turbulent medium. It will be shown how the turbulent structure affects the attenuation curve and how the attenuation curve varies with the thickness of a foreground screen. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

GALEX Spectroscopic observations in the Far UV and in the Near UV are complemented by Mid-/Far-IR data from ISO to analyze a sample of galaxies in the ELAIS S1 field. We show that the FUV-NUV cannot be used as a proxy for the UV slope β beyond a redshift z = 0.10 – 0.15. In addition, we estimate the UV dust attenuation from the FIR/FUV dust ratio and we compare it to the UV slope β which was proposed as a dust attenuation estimator. For this sample of MIR-selected galaxies, we find a large dispersion and the dust attenuation estimated from β could be wrong by several magnitudes. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

A new Monte-Carlo radiative-transfer code, Sunrise, is used to study the effects of dust in N-body/hydrodynamic simulations of interacting galaxies. Dust has a profound effect on the appearance of the simulated galaxies. At peak luminosities, ∼ 90% of the bolometric luminosity is absorbed, and the dust obscuration scales with luminosity in such a way that the brightness at UV/visual wavelengths remains roughly constant. A general relationship between the fraction of energy absorbed and the ratio of bolometric luminosity to baryonic mass is found. Comparing to observations, the simulations are found to follow a relation similar to the observed IRX-β relation found by Meurer et al. when similar luminosity objects are considered. The highest-luminosity simulated galaxies depart from this relation and occupy the region where local (U)LIRGs are found. This agreement is contingent on the presence of Milky-Way-like dust, while SMC-like dust results in far too red a UV continuum slope to match observations. The simulations are used to study the performance of star-formation indicators in the presence of dust. The far-infrared luminosity is found to be reliable. In contrast, the Hα and far-UV luminosity suffer severely from dust attenuation, and dust corrections can only partially remedy the situation. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

There are many ways in which observations with large telescopes are improving our understanding of evolution on the Asymptotic Giant Branch. Perhaps more importantly AGB stars also offer huge potential to probe the nature of low- and intermediate-mass populations over a very considerable range of distances and in a variety of environments. This review which is far from exhaustive, touches upon: the discovery of AGB stars in resolved stellar populations and their detailed investigation; the importance of abundances measurements — particularly those of technetium and lithium; the potential of kinematic studies and recent developments in interferometry. Finally the important role of AGB stars as probes of distant and unresolved populations is mentioned. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The infrared Spitzer Space Telescope is the last of NASA’s Great Observatories. Highlights of the first results from the Infrared Spectrograph (IRS) Extragalactic Team are given. The main focus of this paper is a demonstration of the unprecedented sensitivity of the IRS, which makes observations of distant, dust enshrouded galaxies possible. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]