Modelling and Controlling the Kinetic and Dynamic of a Bicycle

En este trabajo, se presenta el modelado y control posterior de una mini-bicicleta autónoma, que se utilizará para la enseñanza de sistemas de control. El modelo mecánico se construye inicialmente a partir de un diseño CAD y posteriormente se integra en Simulink, conjuntamente con los módulos de control. Se lleva a cabo el modelado del sistema completo, incluyendo las partes mecánicas, sensores, actuadores y la fricción de las ruedas con el suelo, consiguiéndose el mismo comportamiento que con la bicicleta física. A partir de las ecuaciones matemáticas que definen el comportamiento del sistema se diseña un controlador PID y un controlador LQG en el espacio de estados. Para verificar el modelo, los controladores diseñados se prueban también con los mismos parámetros en la mini-bicicleta física, obteniéndose un resultado idéntico.In this work, the modeling and subsequent control of an autonomous mini-bicycle is presented, which will be used for the teaching of control systems. The mechanical model is initially built from a CAD design and then integrated into Simulink, together with the control modules. The modeling of the complete system is carried out, including the mechanical parts, sensors, actuators and the friction of the wheels with the ground, achieving the same behavior as with the physical bicycle. From the mathematical equations that define the behavior of the system, a PID controller and an LQG controller are designed in the state space. To verify the model, the designed controllers are also tested with the same parameters in the physical mini-bicycle, obtaining an identical result.Universidad de Granada: Departamento de Arquitectura y Tecnología de Computadore

The properties of the brightest Lyα emitters at z ∼ 5.7

We use deep Very Large Telescope (VLT) optical and near-infrared spectroscopy and deep Spitzer/IRAC imaging to examine the properties of two of the most luminous Lyα emitters at z= 5.7. The continuum redward of the Lyα line is clearly detected in both objects, thus facilitating a relatively accurate measurement (10-20 per cent uncertainties) of the observed rest-frame equivalent widths, which are around 160 Å for both objects. Through detailed modelling of the profile of the Lyα line with a 3D Monte Carlo radiative transfer code, we estimate the intrinsic rest-frame equivalent width of Lyα and find values that are around 300 Å, which is at the upper end of the range allowed for very young, moderately metal-poor star-forming galaxies. However, the uncertainties are large and values as high as 700 Å are permitted by the data. Both Lyα emitters are detected at 3.6 m in deep images taken with the Spitzer Space Telescope. We use these measurements, the measurement of the continuum redward of Lyα and other photometry to constrain the spectral energy distributions of these very luminous Lyα emitters and to compare them with three similar Lyα emitters from the literature. The contribution from nebular emission is included in our models: excluding it results in significantly higher masses. Four of the five Lyα emitters have masses of the order of ∼109 M⊙ and fairly high specific star formation rates (≳10-100 Gyr−1). While our two Lyα emitters appear similar in terms of the observed Lyα rest-frame equivalent width, they are quite distinct from each other in terms of age, mass and star formation history. Evidence for dust is found in all objects, and emission from nebular lines often makes a dominant contribution to the rest-frame 3.6 m flux. Rich in emission lines, these objects are prime targets for the next generation of extremely large telescopes, the James Webb Space Telescope (JWST) and the Atacama Large Millimeter Array (ALMA

Modelling high redshift Lyman-alpha Emitters

We present a new model for high redshift Lyman-Alpha Emitters (LAEs) in the cosmological context which takes into account the resonant scattering of Ly-a photons through expanding gas. The GALICS semi-analytic model provides us with the physical properties of a large sample of high redshift galaxies. We implement a gas outflow model for each galaxy based on simple scaling arguments. The coupling with a library of numerical experiments of Ly-a transfer through expanding or static dusty shells of gas allows us to derive the Ly-a escape fractions and profiles. The predicted distribution of Ly-a photons escape fraction shows that galaxies with a low star formation rate have a f_esc of the order of unity, suggesting that, for those objects, Ly-a may be used to trace the star formation rate assuming a given conversion law. In galaxies forming stars intensely, the escape fraction spans the whole range from 0 to 1. The model is able to get a good match to the UV and Ly-a luminosity function (LF) data at 3 < z < 5. We find that we are in good agreement with both the bright Ly-a data and the faint population observed by Rauch et al. (2008) at z=3. Most of the Ly-a profiles of our LAEs are redshifted by the diffusion in the outflow which suppresses IGM absorption. The bulk of the observed Ly-a equivalent width (EW) distribution is recovered by our model, but we fail to obtain the very large values sometimes detected. Predictions for stellar masses and UV LFs of LAEs show a satisfactory agreement with observational estimates. The UV-brightest galaxies are found to show only low Ly-a EWs in our model, as it is reported by many observations of high redshift LAEs. We interpret this effect as the joint consequence of old stellar populations hosted by UV-bright galaxies, and high HI column densities that we predict for these objects, which quench preferentially resonant Ly-a photons via dust extinction.Comment: 17 pages, 12 figures, 3 tables, accepted for publication in MNRA

The FORS Deep Field Spectroscopic Survey

We present a catalogue and atlas of low-resolution spectra of a well defined sample of 341 objects in the FORS Deep Field. All spectra were obtained with the FORS instruments at the ESO VLT with essentially the same spectroscopic set-up. The observed extragalactic objects cover the redshift range 0.1 to 5.0. 98 objects are starburst galaxies and QSOs at z > 2. Using this data set we investigated the evolution of the characteristic spectral properties of bright starburst galaxies and their mutual relations as a function of the redshift. Significant evolutionary effects were found for redshifts 2 < z < 4. Most conspicuous are the increase of the average C IV absorption strength, of the dust reddening, and of the intrinsic UV luminosity, and the decrease of the average Ly alpha emission strength with decreasing redshift. In part the observed evolutionary effects can be attributed to an increase of the metallicity of the galaxies with cosmic age. Moreover, the increase of the total star-formation rates and the stronger obscuration of the starburst cores by dusty gas clouds suggest the occurrence of more massive starbursts at later cosmic epochs.Comment: 24 pages, 25 figures (35 PS files), 4 tables, accepted for publication in A&A. v2: minor typos corrected and references update

3D Lya radiation transfer. II. Fitting the Lyman break galaxy MS 1512-cB58 and implications for Lya emission in high-z starbursts

Using our 3D Lya radiation transfer code, we compute the radiation transfer of Lya and UV continuum photons including dust. Observational constraints on the neutral gas (column density, kinematics, etc.) are taken from other analysis of this object. RESULTS: The observed Lya profile of MS 1512--cB58 is reproduced for the first time taking radiation transfer and all observational constraints into account. The observed absorption profile is found to result naturally from the observed amount of dust and the relatively high HI column density. Radiation transfer effects and suppresion by dust transform a strong intrinsic Lya emission with EW(Lya)>~ 60 Ang into the observed faint superposed Lya emission peak. We propose that the vast majority of LBGs have intrinsically EW(Lya)~60-80 Ang or larger, and that the main physical parameter responsible for the observed variety of Lya strengths and profiles in LBGs is N_H and the accompanying variation of the dust content. Observed EW(Lya) distributions, Lya luminosity functions, and related quantities must therefore be corrected for radiation transfer and dust effects. The implications from our scenario on the duty-cycle of Lya emitters are also discussed.Comment: Accepted for publication in A&

Physical properties of z~4 LBGs: differences between galaxies with and without Ly-alpha emission

We have analysed the physical properties of z~4 Lyman Break Galaxies observed in the GOODS-S survey, in order to investigate the possible differences between galaxies where the Ly-alpha is present in emission, and those where the line is absent or in absorption. The objects have been selected from their optical color and then spectroscopically confirmed by Vanzella et al. (2005). From the public spectra we assessed the nature of the Ly-alpha emission and divided the sample into galaxies with Ly-alpha in emission and objects without Ly-alpha line (i.e. either absent or in absorption). We have then used the complete photometry, from U band to mid infrared from the GOODS-MUSIC database, to study the observational properties of the galaxies, such as UV spectral slopes and optical to mid-infrared colors, and the possible differences between the two samples. Finally through standard spectral fitting tecniques we have determined the physical properties of the galaxies, such as total stellar mass, stellar ages and so on, and again we have studied the possible differences between the two samples. Our results indicate that LBG with Ly-alpha in emission are on average a much younger and less massive population than the LBGs without Ly-alpha emission. Both populations are forming stars very actively and are relatively dust free, although those with line emission seem to be even less dusty on average. We briefly discuss these results in the context of recent models for the evolution of Lyman break galaxies and Ly-alpha emitters.Comment: Accepted for publication in A&A. Uses aa.cls, 6 pages, 3 figure

The Great Observatories Origins Deep Survey. VLT/FORS2 Spectroscopy in the GOODS-South Field: Part III

Aims. We present the full data set of the spectroscopic campaign of the ESO/GOODS program in the GOODS-South field, obtained with the FORS2 spectrograph at the ESO/VLT. Method. Objects were selected as candidates for VLT/FORS2 observations primarily based on the expectation that the detection and measurement of their spectral features would benefit from the high throughput and spectral resolution of FORS2. The reliability of the redshift estimates is assessed using the redshift-magnitude and color-redshift diagrams, and comparing the results with public data. Results. Including the third part of the spectroscopic campaign (12 masks) to the previous work (26 masks, Vanzella et al. 2005, 2006), 1715 spectra of 1225 individual targets have been analyzed. The actual spectroscopic catalog provides 887 redshift determinations. The typical redshift uncertainty is estimated to be sigma(z) ~ 0.001. Galaxies have been selected adopting different color criteria and using photometric redshifts. The resulting redshift distribution typically spans two domains: from z=0.5 to 2 and z=3.5 to 6.3. The reduced spectra and the derived redshifts are released to the community through the ESO web page http://www.eso.org/science/goods/Comment: 11 pages, 11 figures; accepted for publication in Astronomy & Astrophysics. Data are available at http://www.eso.org/science/goods

On the dependence between UV luminosity and Lyman-alpha equivalent width in high redshift galaxies

We show that with the simple assumption of no correlation between the Ly-alpha equivalent width and the UV luminosity of a galaxy, the observed distribution of high redshift galaxies in an equivalent width - absolute UV magnitude plane can be reproduced. We further show that there is no dependence between Ly-alpha equivalent width and Ly-alpha luminosity in a sample of Ly-alpha emitters. The test was expanded to Lyman-break galaxies and again no dependence was found. Simultaneously, we show that a recently proposed lack of large equivalent width, UV bright galaxies (Ando et al. 2006) can be explained by a simple observational effect, based on too small survey volumes.Comment: 7 pages, 3 figures, 2 tables, accepted in MNRA

Lyman-alpha emission galaxies at a redshift of z = 5.7 in the FORS Deep Field

We present the results of a search for Lyman-alpha emission galaxies at z~ 5.7 in the FORS Deep Field. The objective of this study is to improve the faint end of the luminosity function of high-redshift Lyman-alpha emitting galaxies and to derive properties of intrinsically faint Lyman-alpha emission galaxies in the young universe. Using FORS2 at the ESO VLT and a set of special interference filters, we identified candidates for high-redshift Lyman-alpha galaxies. We then used FORS2 in spectroscopic mode to verify the identifications and to study their spectral properties. The narrow-band photometry resulted in the detection of 15 likely Lyman-alpha emission galaxies. Spectra with an adequate exposure time could be obtained for eight galaxies. In all these cases the presence of Lyman-alpha emission at z = 5.7 was confirmed spectroscopically. The line fluxes of the 15 candidates range between 3 and 16 * 10^-21 Wm^-2, which corresponds to star-formation rates not corrected for dust between 1 and 5 Msun/yr. The luminosity function derived for our photometrically identified objects extends the published luminosity functions of intrinsically brighter Lyman-alpha galaxies. With this technique the study of high-redshift Lyman-alpha emission galaxies can be extended to low intrinsic luminosities.Comment: 9 pages, 17 figures. Accepted by A&A. PDF version with higher resolution figures here: http://www.lsw.uni-heidelberg.de/users/jheidt/fdf/pubs/fdflae5_7_110406.pd

The physical properties of Lyalpha emitting galaxies: not just primeval galaxies?

We have analyzed a sample of LBGs from z =3.5 to z=6 selected from the GOODS-S field as B,V and i-dropouts, and with spectroscopic observations showing that they have the Lyalpha line in emission. Our main aim is to investigate their physical properties and their dependence on the emission line characteristics, to shed light on the relation between galaxies with Lyalpha emission and the general LBG population.The objects were selected from their continuum colors and then spectroscopically confirmed by the GOODS collaboration and other campaigns. From the spectra we derived the line flux and EW. We then used U-band to mid-IR photometry from GOODS-MUSIC to derive the physical properties of the galaxies, such as total stellar mass, age and so on, through standard SED fitting techniques.Although most galaxies are fit by young stellar populations, a small but non negligible fraction has SEDs that require considerably older stellar component, up to 1 Gyr. There is no apparent relation between age and EW: some of the oldest galaxies have large EW, and should be also selected in narrow band surveys. Therefore not all Lyalpha emitters are primeval galaxies in the very early stages of formation,as is commonly assumed. We also find a large range of stellar populations, with masses from 5x10^8 Msol to 5x10^10 Msol and SFR from few to 60 Msol/yr. Although there is no correlation between mass and EW, we find a significant lack of massive galaxies with high EW, which could be explained if the most massive galaxies were more dusty and/or contained more neutral gas than less massive objects. Finally we find that more than half of the galaxies contain small but non negligible amounts of dust: the mean E(B-V) and the EW are well correlated, although with a large scatter, as already found at lower redshiftComment: Accepted by Astronomy & Astrophysci