Narrowband CCD Photometry of Giant HII Regions

We have obtained accurate CCD narrow band H_beta and H_alpha photometry of Giant HII Regions in M 33, NGC 6822 and M 101. Comparison with previous determinations of emission line fluxes show large discrepancies; their probable origins are discussed. Combining our new photometric data with global velocity dispersion (sigma) derived from emission line widths we have reviewed the L(H_beta)-sigma relation. A reanalysis of the properties of the GEHRs included in our sample shows that age spread and the superposition of components in multiple regions introduce a considerable spread in the regression. Combining the information available in the literature regarding ages of the associated clusters, evolutionary footprints on the interstellar medium, and kinematical properties of the knots that build up the multiple GEHRs, we have found that a subsample - which we refer to as young and single GEHRs - do follow a tight relation in the L-sigma plane.Comment: Accepted for publication in MNRAS, large figures available on a separate tarfil

A linear model for valuating preferences of freshwater inflows into forty selected estuaries along the South African coastline

According to the National Water Act of 1998, an estuary is an enclosed body of water that is either periodically or permanently open to the ocean. Within an estuary, the seawater is diluted to a measurable degree, creating a unique aquatic environment for animals and plants. Estuaries are environmental and economic assets to the population. The health status of our local estuaries, however, is being compromized due to a steady decrease in the freshwater inflow and supply. Tides and climatic conditions do have an impact upon the dynamics of an estuary, but these factors remain relatively constant throughout each year. The freshwater inflow and supply, however, are highly variable and are directly influenced by human involvement. Upstream abstraction for industrial and domestic use, for example, could lead to mouth closure where the ocean meets the river. The National Water Act of 1998 was established to address the lack of research and predominant mismanagement of freshwater inflow into South Africa’s estuaries (Allanson and Baird, 1999). To ensure proper water resource management, different water allocation costs and benefits need to be compared and analyzed to secure an optimum solution (Mlangeni, 2007). Like many environmental services yielded to man, estuary services are not traded in any markets. Alternative markets are thus sought to allow the estimation of the values of such services. Among the available valuation techniques are the Contingent Valuation Method (CVM), Travel Cost Method (TCM) and Hedonic Pricing Method (HPM). The involved benefits of water allocations are predicted in this study by use of the CVM which elicits respondents’ willingness to pay (WTP) towards predetermined changes in freshwater inflow into estuaries. The CVM was applied throughout the Water Research Commission’s (WRC) Project K5/1413 from 2000 to 2008 (Hosking, 2010). Each individual study employed specialized surveys which ideally created a close correspondence between the answers provided by respondents to the supposed scenarios and their voluntary exchanges in markets should money actually have been handled (Mlangeni, 2007). Much criticism has been directed towards the CVM, but careful use and application of the method has been shown to produce significant and satisfactory results (Hosking, 2010). The primary aim of this study was to collectively analyze the collated data provided by the WRC and compare the results with the findings of previous studies. Each variable was analyzed separately in order to reveal any discrepancies between the respective findings. A supplementary objective of this study was to add to the body of knowledge pertaining to South Africa’s estuaries and guide management in the distribution of freshwater towards proficient levels (Du Preez and Hosking, 2010). The associated change in the cumulative consumer surplus with an increased freshwater supply into forty selected estuaries was therefore investigated. The subsequent benefits due to a superior freshwater supply are therefore reflected (Du Preez and Hosking, 2010). The data gathered by each of the individual researchers throughout their studies (supported by the WRC) were combined to form a single dataset including all recorded information supplied by the corresponding respondents. As the investigation progressed, improvements were made upon the questionnaires posed to the considered estuary populations. Consequently, some of the data in the combined dataset were “missing”, since previous studies did not include certain questions, while later studies omitted others. Data imputation was employed to create an imputed dataset, enabling the modeling of the public’s WTP through regression techniques. A linear model was utilized in this study, also incorporating interaction between the predictor variables. The double-log functional form was implemented to estimate the public’s WTP. The population’s total willingness to pay (TWTP) was further estimated by aggregation. A summary of the respective results is displayed in in Table 1

A linear model for valuating preferences of freshwater inflows into forty selected estuaries along the South African coastline

According to the National Water Act of 1998, an estuary is an enclosed body of water that is either periodically or permanently open to the ocean. Within an estuary, the seawater is diluted to a measurable degree, creating a unique aquatic environment for animals and plants. Estuaries are environmental and economic assets to the population. The health status of our local estuaries, however, is being compromized due to a steady decrease in the freshwater inflow and supply. Tides and climatic conditions do have an impact upon the dynamics of an estuary, but these factors remain relatively constant throughout each year. The freshwater inflow and supply, however, are highly variable and are directly influenced by human involvement. Upstream abstraction for industrial and domestic use, for example, could lead to mouth closure where the ocean meets the river. The National Water Act of 1998 was established to address the lack of research and predominant mismanagement of freshwater inflow into South Africa’s estuaries (Allanson and Baird, 1999). To ensure proper water resource management, different water allocation costs and benefits need to be compared and analyzed to secure an optimum solution (Mlangeni, 2007). Like many environmental services yielded to man, estuary services are not traded in any markets. Alternative markets are thus sought to allow the estimation of the values of such services. Among the available valuation techniques are the Contingent Valuation Method (CVM), Travel Cost Method (TCM) and Hedonic Pricing Method (HPM). The involved benefits of water allocations are predicted in this study by use of the CVM which elicits respondents’ willingness to pay (WTP) towards predetermined changes in freshwater inflow into estuaries. The CVM was applied throughout the Water Research Commission’s (WRC) Project K5/1413 from 2000 to 2008 (Hosking, 2010). Each individual study employed specialized surveys which ideally created a close correspondence between the answers provided by respondents to the supposed scenarios and their voluntary exchanges in markets should money actually have been handled (Mlangeni, 2007). Much criticism has been directed towards the CVM, but careful use and application of the method has been shown to produce significant and satisfactory results (Hosking, 2010). The primary aim of this study was to collectively analyze the collated data provided by the WRC and compare the results with the findings of previous studies. Each variable was analyzed separately in order to reveal any discrepancies between the respective findings. A supplementary objective of this study was to add to the body of knowledge pertaining to South Africa’s estuaries and guide management in the distribution of freshwater towards proficient levels (Du Preez and Hosking, 2010). The associated change in the cumulative consumer surplus with an increased freshwater supply into forty selected estuaries was therefore investigated. The subsequent benefits due to a superior freshwater supply are therefore reflected (Du Preez and Hosking, 2010). The data gathered by each of the individual researchers throughout their studies (supported by the WRC) were combined to form a single dataset including all recorded information supplied by the corresponding respondents. As the investigation progressed, improvements were made upon the questionnaires posed to the considered estuary populations. Consequently, some of the data in the combined dataset were “missing”, since previous studies did not include certain questions, while later studies omitted others. Data imputation was employed to create an imputed dataset, enabling the modeling of the public’s WTP through regression techniques. A linear model was utilized in this study, also incorporating interaction between the predictor variables. The double-log functional form was implemented to estimate the public’s WTP. The population’s total willingness to pay (TWTP) was further estimated by aggregation. A summary of the respective results is displayed in in Table 1

Expansive components in H II regions

We study the presence of low intensity high velocity components, which we have termed wing features in the integrated Halpha emission line profiles of the HII region populations of the spiral barred galaxies NGC 1530, NGC 3359 and NGC 6951. We find that more than a third of the HII region line profiles in each galaxy show these components. The highest fraction is obtained in the galaxy whose line profiles show the best S:N, which suggests that wing features of this type may well exist in most, if not all, HII region line profiles. Applying selection criteria to the wing features, we obtain a sample of HII regions with clearly defined high velocity components in their profiles. Deconvolution of a representative sample of the line profiles eliminates any doubt that the wing features could possibly be due to instrumental effects. We present an analysis of the high velocity low intensity features fitting them with Gaussian functions; the emission measures, central velocities and velocity dispersions for the red and blue features take similar values. We interpret the features as signatures of expanding shells inside the HII regions. Up to a shell radius of R(shell)~0.2R(reg), the stellar winds from the central ionizing stars appear to satisfy the energy and momentum requirements for the formation and driving the shell. Several examples of the most luminous HII regions show that the shells appear to have larger radii; in these cases additional mechanisms may well be needed to explain the kinetic energies and momenta of the shells.Comment: 16 pages, 9 figures, accepted for publication in A&

A Strategy to Measure the Dark Energy Equation of State using the HII galaxy Hubble Relation & X-ray AGN Clustering: Preliminary Results

We explore the possibility of setting stringent constraints to the Dark Energy equation of state using alternative cosmic tracers like: (a) the Hubble relation using HII galaxies, which can be observed at much higher redshifts (z~3.5) than those currently traced by SNIa samples, and (b) the large-scale structure using the clustering of X-ray selected AGN,which have a redshift distribution peaking at z~1. We use extensive Monte-Carlo simulations to define the optimal strategy for the recovery of the dark-energy equation of state using the high redshift (z~2) Hubble relation, but accounting also for the effects of gravitational lensing, which for such high redshifts can significantly affect the derived cosmological constraints. Based on a "Figure of Merit" analysis, we provide estimates for the number of 2<z<3.5 tracers needed to reduce the cosmological solution space, presently provided by the Constitution SNIa set, by a desired factor. We find that it is much more efficient to increase the number of tracers than to reduce their individual uncertainties. Finally, we propose a framework to put constraints on the dark energy equation of state by using the joint likelihood of the X-ray AGN clustering and of the Hubble relation cosmological analyses. A preliminary joint analysis using the X-ray AGN clustering of the 2XMM survey and the Hubble relation of the Constitution SNIa set provide: Omega_m= 0.31+-0.01 and w=-1.06+-0.05. We also find that the joint SNIa-2XMM analysis provides significantly more stringent cosmological constraints, increasing the Figure of Merit by a factor ~2, with respect to that of the joint SNIa-BAO analysis.Comment: MNRAS in press, 12 colour figure

The internal dynamical equilibrium of HII regions: a statistical study

We present an analysis of the integrated Halpha emission line profiles for the HII region population of the spiral galaxies NGC 1530, NGC 6951 and NGC 3359. We show that 70% of the line profiles show two or three Gaussian components. The relations between the Halpha luminosity and non-thermal line width for the HII regions of the three galaxies are studied and compared with the relation found taken all the HII regions of the three galaxies as a single distribution. A clearer envelope in non-thermal line width is found when only those HII regions with non-thermal line width bigger than 13kms are considered. The linear fit for the envelope is logL=36.8+2.0*log(sigma). The masses of the HII regions on the envelope using the virial theorem and the mass estimates from the Halpha luminosity are comparable, which offers evidence that the HII regions on the envelope are virialized systems, while the remaining regions, the majority, are not in virial equilibrium.Comment: 19 pages, 10 figures,accepted for publication in A&

An improved method for statistical studies of the internal kinematics of HII regions: the case of M 83

We present the integrated Halpha emission line profile for 157 HII regions in the central 3.4' x 3.4' of the galaxy M 83 (NGC 5236). Using the Fabry-Perot interferometer GHaFaS, on the 4.2 m William Herschel on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity-velocity dispersion relation is also studied, and in the log(L)-log(sigma) plane we do not find a linear relation, but an upper envelope with equation log(L)=0.9 *log(sigma)+38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity L=10^38.5 ergs, in full agreement with previous studies of other galaxies, reinforcing the idea of using HII regions as standard candles.Comment: 13 pages, 9 figures, accepted for publication in MNRA

VLBA Continuum and H I Absorption Observations of the Ultra-Luminous Infrared Galaxy IRAS 17208-0014

We present phase-referenced VLBI observations of the radio continuum emission from, and the neutral hydrogen 21 cm absorption toward, the Ultra-Luminous Infrared Galaxy IRAS 17208-0014. The observations were carried out at 1362 MHz using the Very Long Baseline Array, including the phased Very Large Array as an element. The high-resolution radio continuum images reveal a nuclear starburst region in this galaxy, which is composed of diffuse emission approximately 670 x 340 pc on the plane of the sky, and a number of compact sources. These sources are most likely to be clustered supernova remnants and/or luminous radio supernovae. Their brightness temperatures range over (2.2-6.6) x 10^{5} K, with radio spectral luminosities between (1-10) x 10^{21} W Hz^{-1}. The total VLBI flux density of the starburst region is ~52 mJy, which is about 50% of the total flux density detected with the VLA at arcsecond resolution. For this galaxy, we derive a massive star formation rate of ~84pm13 M{_\odot} yr^{-1}, and a supernova rate of ~4pm1 yr^{-1}. H I absorption is detected in multiple components with optical depths ranging between 0.3 and 2.5, and velocity widths between 58 and 232 km s^{-1}. The derived column densities, assuming T_{s}=100 K, range over (10-26) x 10^{21} cm^{-2}. The H I absorption shows a strong velocity gradient of 453 km s^{-1} across 0.36 arcsec (274 pc). Assuming Keplerian motion, the enclosed dynamical mass is about 2.3 x 10^9 sin^{-2}i M{_\odot}, comparable to the enclosed dynamical mass estimated from CO observations.Comment: 26 pages total, 6 figures. ApJ accepted. To appear in the April 1, 2003 issue of ApJ. For a version with better images, see http://www.aoc.nrao.edu/~emomjian/IRAS.p

Gemini GMOS/IFU spectroscopy of NGC 1569 - I: Mapping the properties of a young star cluster and its environment

[Abridged] We present Gemini-North GMOS/IFU observations of a young star cluster (cluster 10) and its environment near the centre of the dwarf irregular starburst galaxy NGC 1569. This forms part of a larger and on-going study of the formation and collimation mechanisms of galactic winds, including three additional IFU pointings in NGC 1569 covering the base of the galactic wind which are analysed in a companion paper. The good spatial- and spectral-resolution of these GMOS/IFU observations, covering 4740-6860 A, allow us to probe the interactions between clusters and their environments on small scales. Combining our GMOS spectrum with HST imaging, we find that cluster 10 is composed of two very close components with ages of 5-7 Myr and <5 Myr, and a combined mass of 7 +/- 5 x 10^3 Msun. A detailed analysis of the H_alpha emission line profile shapes across the whole field-of-view shows them to be composed of a bright narrow feature (intrinsic FWHM ~ 50 km/s) superimposed on a fainter broad component (FWHM < 300 km/s). By mapping the properties of each individual component, we investigate the small-scale structure and properties of the ionized ISM, including reddening, excitation and electron densities, and for the first time find spatial correlations between the line component properties. We discuss in detail the possible mechanisms that could give rise to the two components and these correlations, and conclude that the most likely explanation for the broad emission is that it is produced in a turbulent mixing layer on the surface of the cool gas clumps embedded within the hot, fast-flowing cluster winds. We conclude we are sampling well within the outer bounding shocks of the expanding superbubbles and within the outflow 'energy injection zone'.Comment: 22 pages, 14 figures, 4 tables, accepted to MNRA

Physiological modeling of isoprene dynamics in exhaled breath

Human breath contains a myriad of endogenous volatile organic compounds (VOCs) which are reflective of ongoing metabolic or physiological processes. While research into the diagnostic potential and general medical relevance of these trace gases is conducted on a considerable scale, little focus has been given so far to a sound analysis of the quantitative relationships between breath levels and the underlying systemic concentrations. This paper is devoted to a thorough modeling study of the end-tidal breath dynamics associated with isoprene, which serves as a paradigmatic example for the class of low-soluble, blood-borne VOCs. Real-time measurements of exhaled breath under an ergometer challenge reveal characteristic changes of isoprene output in response to variations in ventilation and perfusion. Here, a valid compartmental description of these profiles is developed. By comparison with experimental data it is inferred that the major part of breath isoprene variability during exercise conditions can be attributed to an increased fractional perfusion of potential storage and production sites, leading to higher levels of mixed venous blood concentrations at the onset of physical activity. In this context, various lines of supportive evidence for an extrahepatic tissue source of isoprene are presented. Our model is a first step towards new guidelines for the breath gas analysis of isoprene and is expected to aid further investigations regarding the exhalation, storage, transport and biotransformation processes associated with this important compound.Comment: 14 page