77 research outputs found
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
The nature of the Lyman-alpha emission region of FDF-4691
In order to study the origin of the strong Lyman-alpha emission of
high-redshift starburst galaxies we observed and modeled the emission of the z
= 3.304 galaxy FDF-4691 (rest-frame EW = 103 Angstroem). The observations show
that FDF-4691 is a young starburst galaxy with a (for this redshift) typical
metallicity. The broad, double-peaked profile of the Lyman-alpha emission line
can be explained assuming a highly turbulent emission region in the inner part
of the starburst galaxy, and a surrounding extended shell of low-density
neutral gas with a normal dust/gas ratio and with Galactic dust properties. The
detection of the Lyman-alpha emission line is explained by the intrinsic broad
Lyman-alpha emission and a low HI column density of the neutral shell. A low
dust/gas ratio in the neutral shell is not needed to explain the strong
Lyman-alpha line.Comment: Accepted for publication in A&A Letter
Constraining Dust and Molecular Gas Properties in Lyα Blobs at z ~ 3
In order to constrain the bolometric luminosities, dust properties, and molecular gas content of giant Lyα nebulae, the so-called Lyα blobs, we have carried out a study of dust continuum and CO line emission in two well-studied representatives of this population at z ~ 3: an Lyα blob discovered by its strong Spitzer Multiband Infrared Photometer 24 μm detection (LABd05) and the Steidel blob 1 (SSA22-LAB01). We find that the spectral energy distribution of LABd05 is well described by an active-galactic-nucleus-starburst composite template with L_(FIR) = (4.0 ± 0.5) × 10^(12) L_☉, comparable to high-z submillimeter galaxies and ultraluminous infrared galaxies. New Large APEX Bolometer Camera 870 μm measurements rule out the reported Submillimeter Common-User Bolometer Array detection of the SSA22-LAB01 (S_(850 μm) = 16.8 mJy) at the >4σ level. Consistent with this, ultradeep Plateau de Bure Interferometer observations with ~2'' spatial resolution also fail to detect any 1.2 mm continuum source down to ≈0.45 mJy beam^(–1) (3σ). Combined with the existing (sub)millimeter observations in the literature, we conclude that the FIR luminosity of SSA22-LAB01 remains uncertain. No CO line is detected in either case down to integrated flux limits of S_νΔV ≾ 0.25-1.0 Jy km s^(–1), indicating a modest molecular gas reservoir, M(H_2) < (1-3) × 10^(10) M_☉. The non-detections exclude, with high significance (12σ), the previous tentative detection of a CO J = 4-3 line in the SSA22-LAB01. The increased sensitivity afforded by the Atacama Large Millimeter/submillimeter Array will be critical in studying molecular gas and dust in these interesting systems
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
Medium-resolution spectroscopy of galaxies with redshifts 2.3 < z < 3.5
Using FORS2 at the ESO VLT we obtained medium resolution (R ~ 2000) spectra
of 12 galaxies with 2.37 < z < 3.40 in the FORS Deep Field. Two individual
spectra with good S/N and a composite of all 12 spectra were used to derive
properties of the stellar and interstellar absorption lines of galaxies in this
redshift range. Systematic differences between the individual spectra were
found for the strength and profiles of the intrinsic interstellar lines. For
eight spectra with sufficient S/N we measured the `1370' and `1425' metallicity
indices. From these indices we find for our sample that galaxies at z > 3 have
lower mean metallicity than galaxies at 2.5 < z < 3. However there remain
uncertainties concerning the absolute calibration of the metallicity tracers in
use for high-redshift galaxies. Additional modeling will be needed to resolve
these uncertainties.Comment: 10 pages, 4 figures. Accepted by 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
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
Lyman alpha emission in high-redshift galaxies
A significant fraction of the high-redshift galaxies show strong Lyman
emission lines. For redshifts z>5, most known galaxies belong to this class.
However, so far not much is known about the physical structure and nature of
these objects. Our aim is to analyse the Lyman alpha emission in a sample of
high-redshift UV-continuum selected galaxies and to derive the physical
conditions that determine the Lyman alpha profile and the line strength.
VLT/FORS spectra with a resolution of R ~ 2000 of 16 galaxies in the redshift
range of z = 2.7 to 5 are presented. The observed Lyman alpha profiles are
compared with theoretical models. The Lyman alpha lines range from pure
absorption (EW = -17 Angstroem) to strong emission (EW = 153 Angstroem). Most
Lyman alpha emission lines show an asymmetric profile, and three galaxies have
a double-peaked profile. Both types of profiles can be explained by a uniform
model consisting of an expanding shell of neutral and ionised hydrogen around a
compact starburst region. The broad, blueshifted, low-ionisation interstellar
absorption lines indicate a galaxy-scale outflow of the ISM. The strengths of
these lines are found to be determined in part by the velocity dispersion of
the outflowing medium. We find star-formation rates of these galaxies ranging
from SFR(UV) = 1.2 to 63.2 Msun uncorrected for dust absorption. The Lyman
alpha emission strength of our target galaxies is found to be determined by the
amount of dust and the kinematics of the outflowing material.Comment: 11 pages, 6 figures. A&A accepte
The Great Observatories Origins Deep Survey - VLT/VIMOS Spectroscopy in the GOODS-South Field: Part II
We present the full data set of the VIMOS spectroscopic campaign of the
ESO/GOODS program in the CDFS, which complements the FORS2 ESO/GOODS
spectroscopic campaign. The GOODS/VIMOS spectroscopic campaign is structured in
two separate surveys using two different VIMOS grisms. The VIMOS Low Resolution
Blue (LR-Blue) and Medium Resolution (MR) orange grisms have been used to cover
different redshift ranges. The LR-Blue campaign is aimed at observing galaxies
mainly at 1.8<z<3.5, while the MR campaign mainly aims at galaxies at z<1 and
Lyman Break Galaxies (LBGs) at z>3.5. The full GOODS/VIMOS spectroscopic
campaign consists of 20 VIMOS masks. This release adds 8 new masks to the
previous release (12 masks, Popesso et al. 2009). In total we obtained 5052
spectra, 3634 from the 10 LR-Blue masks and 1418 from the 10 MR masks. A
significant fraction of the extracted spectra comes from serendipitously
observed sources: ~21% in the LR-Blue and ~16% in the MR masks. We obtained
2242 redshifts in the LR-Blue campaign and 976 in the MR campaign for a total
success rate of 62% and 69% respectively, which increases to 66% and 73% if
only primary targets are considered. The typical redshift uncertainty is
estimated to be ~0.0012 (~255 km/s) for the LR-Blue grism and ~0.00040 (~120
km/s) for the MR grism. By complementing our VIMOS spectroscopic catalog with
all existing spectroscopic redshifts publicly available in the CDFS, we
compiled a redshift master catalog with 7332 entries, which we used to
investigate large scale structures out to z~3.7. We produced stacked spectra of
LBGs in a few bins of equivalent width (EW) of the Ly-alpha and found evidence
for a lack of bright LBGs with high EW of the Ly-alpha. Finally, we obtained
new redshifts for 12 X-ray sources of the CDFS and extended-CDFS.Comment: 22 pages, 20 figures, accepted for publication on Astronomy and
Astrophysics, catalogs and data products are available at
http://archive.eso.org/cms/eso-data/data-packages/goods-vimos-spectroscopy-data-release-version-2.0/,
for ESO-GOODS related material consult
http://www.eso.org/sci/activities/projects/goods
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