A comparative study of star formation processes in different environments

In this thesis we have identified two star formation sites for star formation in galaxies which differ widely in metal content. We conclude that `massive' star formation that occurs in a high density, high metallicity environment, like that encountered in circumnuclear star-forming regions, takes place in systems that comply to the definition of super stellar clusters and that are arranged in star forming complexes. These complexes have Halpha luminosities, and therefore masses of ionizing stars, that overlap at the lower end with those found in HII galaxies, which have a much lower metallicity. The fact that their ionization structure and the temperature of their ionizing radiation field are very similar, point to stellar clusters in these two environments which have the same equivalent effective temperature. This is contrary to what is expected from stellar evolution models which predict lower stellar effective temperatures in high metallicity regions.Comment: PhD Thesis at Universidad Autonoma de Madrid, Sept. 200

The metal abundance of circumnuclear star forming regions in early type spirals. Spectrophotometric observations

We have obtained long-slit observations in the optical and near infrared of 12 circumnuclear HII regions (CNSFR) in the early type spiral galaxies NGC 2903, NGC 3351 and NGC 3504 with the aim of deriving their chemical abundances. Only for one of the regions, the [SIII] $\lambda$ 6312 \AA was detected providing, together with the nebular [SIII] lines at $\lambda\lambda$ 9069, 9532 \AA, a value of the electron temperature of T$_e$([SIII])= 8400$^{+ 4650}_{-1250}$K. A semi-empirical method for the derivation of abundances in the high metallicity regime is presented. We obtain abundances which are comparable to those found in high metallicity disc HII regions from direct measurements of electron temperatures and consistent with solar values within the errors. The region with the highest oxygen abundance is R3+R4 in NGC 3504, 12+log(O/H) = 8.85, about 1.5 solar if the solar oxygen abundance is set at the value derived by Asplund et al. (2005), 12+log(O/H)$_{\odot}$ = 8.66$\pm$0.05. Region R7 in NGC 3351 has the lowest oxygen abundance of the sample, about 0.6 times solar. In all the observed CNSFR the O/H abundance is dominated by the O$^+$/H$^+$ contribution, as is also the case for high metallicity disc HII regions. For our observed regions, however, also the S$^+$/S$^{2+}$ ratio is larger than one, contrary to what is found in high metallicity disc HII regions for which, in general, the sulphur abundances are dominated by S$^{2+}$/H$^+$...Comment: 24 pages, 19 figures, accepted by MNRA

Dry beans do respond to inoculation

Non-Peer ReviewedRhizobial strains were evaluated in TagTeam® peat and granular formulations for their effectiveness at increasing yields in dry beans. Five strains were formulated as TagTeam® peat and tested with Nighthawk black beans in 1999. Yield increases ranged from 3% to 46% over controls. Two strains were superior and were reevaluated in 2000 in both granular and peat formulations of TagTeam®. Two classes of beans were used and consisted of black bean (cv. Expresso) and pinto bean (cv. Camino). There was a strain response in the granule formulation, while both strains performed similarly in the peat. The formulation response was consistent in both bean classes. Overall the inoculant response was greater in the black bean (var. Express) than in the pinto bean (cv. Camino). In 2000, a second control was added that consisted of 40 lbs/acre additional nitrogen. This nitrogen control had the highest yield increases and demonstrated that even though there is a response to inoculation, fertilizer nitrogen is important for reaching top yields

Properties of the ionized gas of circumnuclear star-forming regions in early type spirals

(Abbr.) A study of cicumnuclear star-forming regions (CNSFRs) in several early type spirals has been made in order to investigate their main properties: stellar and gas kinematics, dynamical masses, ionising stellar masses, chemical abundances and other properties of the ionised gas. Both high resolution (R$\sim$20000) and moderate resolution (R ~ 5000) have been used. In some cases these regions, about 100 to 150 pc in size, are seen to be composed of several individual star clusters with sizes between 1.5 and 4.9 pc estimated from Hubble Space Telescope (HST) images. Stellar and gas velocity dispersions are found to differ by about 20 to 30 km/s with the H$\beta$ emission lines being narrower than both the stellar lines and the [OIII] $\lambda$ 5007 \AA lines. The twice ionized oxygen, on the other hand, shows velocity dispersions comparable to those shown by stars. We have applied the virial theorem to estimate dynamical masses of the clusters, assuming that systems are gravitationally bounded and spherically symmetric, and using previously measured sizes. The measured values of the stellar velocity dispersions yield dynamical masses of the order of 10$^7$ to 10$^8$ solar masses for the whole CNSFRs. ...Comment: 7 pages, 8 figures, proceeding of the meeting "Young massive star clusters - Initial conditions and environments", Granada, Spain, 200

Metallicity evolution of AGNs from UV emission-lines based on a new index

We analyzed the evolution of the metallicity of the gas with the redshift for a sample of AGNs in a very wide redshift range (0<z<4) using ultraviolet emission-lines from the narrow-line regions (NLRs) and photoionization models. The new index C43=log(CIV+CIII])/HeII is suggested as a metallicity indicator for AGNs. Based on this indicator, we confirmed the no metallicity evolution of NLRs with the redshift pointed out by previous works. We found that metallicity of AGNs shows similar evolution than the one predicted by cosmic semi-analytic models of galaxy formation set within the Cold Dark Matter merging hierarchy (for z < 3). Our results predict a mean metallicity for local objects in agreement with the solar value (12+log(O/H)=8.69). This value is about the same that the maximum oxygen abundance value derived for the central parts of local spiral galaxies. Very low metallicity log(Z/Z_{\odot})~ -0.8 for some objects in the range 1.5 < z <3 is derived.Comment: 25 pages, 10 figures, accepted MNRA

Internal kinematic and physical properties in a BCD galaxy: Haro 15 in detail

We present a detailed study of the kinematic and physical properties of the ionized gas in multiple knots of the blue compact dwarf galaxy Haro 15. Using echelle and long slit spectroscopy data, obtained with different instruments at Las Campanas Observatory, we study the internal kinematic and physical conditions (electron density and temperature), ionic and total chemical abundances of several atoms, reddening and ionization structure. Applying direct and empirical methods for abundance determination, we perform a comparative analysis between these regions and in their different components. On the other hand, our echelle spectra show complex kinematics in several conspicuous knots within the galaxy. To perform an in-depth 2D spectroscopic study we complete this work with high spatial and spectral resolution spectroscopy using the Integral Field Unit mode on the Gemini Multi-Object Spectrograph instrument at the Gemini South telescope. With these data we are able to resolve the complex kinematical structure within star forming knots in Haro 15 galaxy.Comment: 6 pages, 2 figures, IX Scientific Meeting of the Spanish Astronomical Society held on September 13-17, 2010, in Madrid, Spai

Haro15: Is it actually a low metallicity galaxy?

We present a detailed study of the physical properties of the nebular material in multiple knots of the blue compact dwarf galaxy Haro 15. Using long slit and echelle spectroscopy, obtained at Las Campanas Observatory, we study the physical conditions (electron density and temperature), ionic and total chemical abundances of several atoms, reddening and ionization structure. The latter was derived by comparing the oxygen and sulphur ionic ratios to their corresponding observed emission line ratios (the eta and eta' plots) in different regions of the galaxy. Applying direct and empirical methods for abundance determination, we perform a comparative analysis between these regions.Comment: (Poster paper) 2 pages, 2 figure

Chickpeas respond well to inoculation with TagTeam®

Non-Peer ReviewedRhizobia strains were tested in TagTeam® peat and granule formulations for their effectiveness at increasing yields in chickpeas. Of the five strains tested in 1999, the top three were chosen on the basis of yields produced and were formulated in both peat and granular for testing in 2000. Desi (cv. Myles) and kabuli (cv. Chico) chickpeas were used to evaluate the strains in 2000. Results were consistent in both types of chickpeas with both varieties responding well to inoculation. In a peat formulation there was no difference between the strains but in the granular formulation there was a difference. One of the three strains survived poorly on the granules and was not used in the trials. Of the two remaining strains one showed a slight advantage over the other and this was consistent in both desi and kabuli chickpeas. The average response to inoculation over 4 locations ranged from 30% to 47% increase in yields in kabuli and 48% to 60% increase in yields in desi. The response in desi and kabuli chickpeas is site specific as Birsay gave the highest yields in desi chickpeas, while Milden was the most responsive with kabuli type chickpeas