Advanced search


Knowledge area




52 results, page 1 of 6

Evolución de cúmulos de galaxias empleando el efecto Sunyaev-Zel’dovich

DAVID OMAR SANCHEZ ARGUELLES (2009)

This work contains a brief description of the features of the Sunyaev-Zel’dovich effect

and its applications for recovering the properties of galaxy clusters through millimeter

wavelength observations. Observations taken at 1.1mm with the AzTEC camera

towards galaxy clusters in the near universe are described, as well as the contamination

and confusion sources in this type of observations.

The understanding of galaxy cluster properties will allow the design and running

(as a PhD. project) of a study about galaxy clusters that will be identified through the

Sunyaev-Zel’dovich effect by the telescopes ACT, SPT and Planck. Once installed on

the Large Millimeter Telescope, the AzTEC camera will take observations to improve

the constraints on large scale structure evolution models.

El presente trabajo contiene una breve descripción de las características del efecto

Sunyaev-Zel’dovich y su aplicación para recuperar las propiedades de cúmulos de galaxias

empleando observaciones en la región milimétrica del espectro electromagnético.

Se describen las observaciones realizadas con la cámara AzTEC instalada en el telescopio

ASTE a 1.1mm sobre cúmulos de galaxias en el universo cercano. A su vez, se

describen las fuentes de contaminación y confusión que afectan este tipo de observaciones.

La comprensión de estos efectos permitirá diseñar y realizar (como proyecto a realizar

en el Doctorado en Ciencias con especialidad en Astrofísica) un estudio de los

cúmulos de galaxias que serán identificados mediante el efecto Sunyaev-Zel’dovich por

los telescopios ACT,SPT y Planck. Las observaciones que se realizarán con la cámara

AzTEC, una vez instalada en el Gran Telescopio Milimétrico, permitirán realizar

fuertes restricciones a los modelos de evolución de la estructura a gran escala.

Master thesis

Cosmology Cluster of galaxy Submillimeter astronomy CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA RADIOASTRONOMÍA

Numerical models of galactic collitions

JORGE VILLA VARGAS (2009)

This thesis is devoted to the study of the formation and evolution of collisional

ring galaxies using N-body simulations. Two main subjects are developed: a

study of the morphological properties of the produced rings and their dependency

on the conditions of the collision, and the elaboration of a N-body model of the

Cartwheel galaxy.

After a review of the mechanisms involved in the formation of ring galaxies

and of some numerical techniques we present a number of simulations elaborated

to study the effect of the orbit of the perturber, its mass and structure as well

as the structure of the target disk on the large scale structure of the produced

rings and on other morphological features formed in the disk. We also analyse

the kinematic changes induced in the disk by the perturbation, in particular the

radial, tangential and vertical velocity components of the particles of the target

disk.

The model of the Cartwheel galaxy is then presented in detail: the physical

properties of the initial conditions, the history of the collision, the comparisons

of the best fit with the relevant observational data and the future evolution of

this system.

Esta tésis está dedicada al estudio de la formación y evolución de las galaxias

de anillo colisionales usando simulaciones de N-cuerpos. Dos temas principales

han sido desarrollados: en un primer tiempo, se realizamos un estudio de las

propiedades morfológicas de los anillos formados y de la dependencia de éstas en

las condiciones de la colisión; en seguida elaboramos un modelo de N-cuerpos de

la galaxia conocida como la “Rueda de Carreta”.

Después de un análisis de los mecanismos implicados en la formación de

galaxias de anillo colisionales y de algunas técnicas numéricas presentamos un

conjunto de simulaciones que han sido diseñadas para estudiar el efecto de dos

elementos: el de la órbita de la galaxia perturbadora y el de la estructura inicial de

las galaxias implicadas. Estudiamos el efecto producido por estos dos elementos

en la estructura de los anillos formados y en otros rasgos morfológicos formados

en el disco. También estudiamos los cambios producidos por la perturbación en

la cinemática del disco, en particular, en las componentes radial, tangencial y

vertical de las partículas del disco de la galaxia principal.

El modelo de la galaxia de Rueda de Carreta es presentado en detalle. El

modelo describe las condiciones físicas de las condiciones iniciales y la historia

de la colisión. Hacemos algunas comparaciones entre el mejor ajuste y los datos

observacionales. También presentamos la evolución futura de éste sistema.

Doctoral thesis

Astronomy Galaxies Collision processes Numerical analysis CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA

Blast: the mass function, lifetimes, and properties of intermediate mass cores from a 50 deg² submillimeter galactic survey in vela (ℓ ≈265º)

David Hughes (2009)

We present first results from an unbiased 50 deg² submillimeter Galactic survey at 250, 350, and 500 μm from the 2006 flight of the Balloon-borne Large Aperture Submillimeter Telescope. The map has resolution ranging from 36′′ to 60′′ in the three submillimeter bands spanning the thermal emission peak of cold starless cores.We determine the temperature, luminosity, and mass of more than 1000 compact sources in a range of evolutionary stages and an unbiased statistical characterization of the population. From comparison with C¹⁸O data, we find the dust opacity per gas mass, κr = 0.16 cm² gˉ¹ at 250 μm, for cold clumps. We find that 2% of the mass of the molecular gas over this diverse region is in cores colder than 14 K, and that the mass function for these cold cores is consistent with a power law with index α = −3.22±0.14 over the mass range

Article

Clouds Stars: formation Submillimeter CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

The balloon-borne large aperture submillimeter telescope (BLAST) 2006: calibration and flight performance

David Hughes (2009)

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) operated successfully during a 250 hr flight over Antarctica in 2006 December (BLAST06). As part of the calibration and pointing procedures, the red hypergiant star VY CMa was observed and used as the primary calibrator. Details of the overall BLAST06 calibration procedure are discussed. The 1σ uncertainty on the absolute calibration is accurate to 9.5%, 8.7%, and 9.2% at the 250, 350, and 500 μm bands, respectively. The errors are highly correlated between bands resulting in much lower errors for the derived shape of the 250–500 μm continuum. The overall pointing error is <5′′ rms for the 36′′, 42′′, and 60′′ beams. The performance of optics and pointing systems is discussed.

Article

Balloons Submillimeter Telescopes CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

The blast survey of the vela molecular cloud: physical properties of the dense cores in vela-D

David Hughes (2009)

The Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) carried out a 250, 350 and 500μm survey of the galactic plane encompassing the Vela Molecular Ridge, with the primary goal of identifying the coldest dense cores possibly associated with the earliest stages of star formation. Here we present the results from observations of the Vela-D region, covering about 4 deg², in which we find 141 BLAST cores. We exploit existing data taken with the Spitzer MIPS, IRAC and SEST-SIMBA instruments to constrain their (single-temperature) spectral energy distributions, assuming a dust emissivity index β = 2.0. This combination of data allows us to determine the temperature, luminosity and mass of each BLAST core, and also enables us to separate starless from proto-stellar sources. We also analyze the effects that the uncertainties on the derived physical parameters of the individual sources have on the overall physical properties of starless and proto-stellar cores, and we find that there appear to be a smooth transition from the pre- to the proto-stellar phase. In particular, for proto-stellar cores we find a correlation between the MIPS24 flux, associated with the central protostar, and the temperature of the dust envelope. We also find that the core mass function of the Vela-D cores has a slope consistent with other similar (sub)millimeter surveys.

Article

Submillimeter Stars: formation ISM: clouds Balloons CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Blast: the redshift survey

David Hughes (2009)

The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) has recently surveyed ≃8.7 deg² centered on GOODS-South at 250, 350 and 500 μm. In Dye et al. (2009) we presented the catalogue of sources detected at 5σ in at least one band in this field and the probable counterparts to these sources in other wavebands. In this paper, we present the results of a redshift survey in which we succeeded in measuring redshifts for 82 of these counterparts. The spectra show that the BLAST counterparts are mostly star-forming galaxies but not extreme ones when compared to those found in the Sloan Digital Sky Survey. Roughly one quarter of the BLAST counterparts contain an active nucleus. We have used the spectroscopic redshifts to carry out a test of the ability of photometric redshift methods to estimate the redshifts of dusty galaxies, showing that the standard methods work well even when a galaxy contains a large amount of dust. We have also investigated the cases where there are two possible counterparts to the BLAST source, finding that in at least half of these there is evidence that the two galaxies are physically associated, either because they are interacting or because they are in the same large-scale structure. Finally, we have made the first direct measurements of the luminosity function in the three BLAST bands. We find strong evolution out to z = 1, in the sense that there is a large increase in the space-density of the most luminous galaxies. We have also investigated the evolution of the dust-mass function, finding similar strong evolution in the space-density of the galaxies with the largest dust masses, showing that the luminosity evolution seen in many wavebands is associated with an increase in the reservoir of interstellar matter in galaxies.

Article

Galaxies: evolution Surveys Submillimeter Galaxies: high-redshift CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Blast observations of resolved galaxies: temperature profiles and the effect of active galactic nuclei on fir to submillimeter emission

David Hughes (2009)

Over the course of two flights, the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) made resolved maps of seven nearby (<25 Mpc) galaxies at 250, 350, and 500 μm. During its 2005 June flight from Sweden, BLAST observed a single nearby galaxy, NGC 4565. During the 2006 December flight from Antarctica, BLAST observed the nearby galaxies NGC 1097, NGC 1291, NGC 1365, NGC 1512, NGC 1566, and NGC 1808. We fit physical dust models to a combination of BLAST observations and other available data for the galaxies observed by Spitzer. We fit a modified blackbody to the remaining galaxies to obtain total dust mass and mean dust temperature. For the four galaxies with Spitzer data, we also produce maps and radial profiles of dust column density and temperature. We measure the fraction of BLAST detected flux originating from the central cores of these galaxies and use this to calculate a “core fraction,” an upper limit on the “active galactic nucleus fraction” of these galaxies. We also find our resolved observations of these galaxies give a dust mass estímate 5–19 times larger than an unresolved observation would predict. Finally, we are able to use these data to derive a value for the dust mass absorption coefficient of κ = 0.29 ±0.03 m² kg⁻¹ at 250 μm. This study is an introduction to future higher-resolution and higher-sensitivity studies to be conducted by Herschel and SCUBA-2.

Article

Balloons Galaxies: photometry Submillimeter Telescopes CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Conos concentradores de radiación para astronomía en longitudes de onda milimétricas

VICTOR MAURICIO ALFONSO GOMEZ GONZALEZ (2012)

We present the design, simulations, 3D models and first prototypes of radiation

concentrator devices for millimeter wavelength astronomy applications.

Among the main features of these devices are: a great capacity for energy concentration,

high-pass filter behavior and detection of the incident radiation within

a calculated maximum angle. Results of electromagnetic analysis simulations are

presented, the S21 parameters were computed and they represent the radiation

transmitted from the entrance aperture to the exit aperture of the cones; the dominant

propagation mode is the transverse electric (TE11). There is a very wide

range of applications for these devices, including solar energy concentration, and

particularly in astronomical instruments to detect sources emitting at millimeter

wavelengths such as dust and cold gas, material that is at the origin of many

phenomena in astrophysics, from early galaxies to star and planet formation. The

devices shown in this work will be part of a detection system with bolometers

operating at cryogenic temperatures of 4 K; for the manufacturing stage we present

the mechanical designs and 3D models for these devices, their mounts and

the assemblies for the system where they will be installed.

Se presenta el diseño, simulaciones, modelos en 3D y fabricación de conos concentradores

de radiación para aplicaciones en astronomía en longitudes de onda

milimétricas. Entre las principales características de estos dispositivos se encuentran:

una gran capacidad de concentración de energía, funcionan como filtros

pasa-altas y sólo detectan la radiación que incide dentro del ángulo calculado. Se

presentan los resultados de transmisión contra frecuencia, obtenidos de las simulaciones

de análisis electromagnético, de donde se obtienen los parámetros S21, que

en este caso representan la radiación transmitida desde la apertura de entrada a

la apertura de salida de los conos; el modo de propagación dominante es el transversal

eléctrico (TE11). Las aplicaciones de estos dispositivos son muy amplias y

en diversas áreas, entre las que destacan la concentración de energía solar y particularmente

en instrumentos astronómicos para la detección de fuentes que emiten

en longitudes de onda milimétricas tales como el polvo y gas frío, material que

se encuentra en el origen de muchos fenómenos de la astrofísica, desde galaxias

primitivas hasta la formación estelar y planetaria. Los dispositivos presentados en

este trabajo formarán parte de un sistema de detección con bolómetros, operando

a temperaturas criogénicas de 4 K. Para la etapa de fabricación se realizaron los

diseños mecánicos y modelos 3D de estos dispositivos, monturas y ensambles para

el sistema en que operarán.

Master thesis

Optical couplers Millimetre wave antennas Astronomical instruments Astronomy CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA

Blast: correlations in the cosmic far-infrared background at 250, 350, and 500 μm reveal clustering of star-forming galaxies

David Hughes (2009)

We detect correlations in the cosmic far-infrared background due to the clustering of star-forming galaxies in

observations made with the Balloon-borne Large Aperture Submillimeter Telescope, at 250, 350, and 500μm.

We perform jackknife and other tests to confirm the reality of the signal. The measured correlations are well fitted by a power law over scales of 5´–25´, with ∆I/I = 15.1% ±1.7%. We adopt a specific model for submillimeter sources in which the contribution to clustering comes from sources in the redshift ranges 1.3≤ z≤ 2.2, 1.5 ≤ z ≤ 2.7, and 1.7 ≤ z ≤ 3.2, at 250, 350, and 500μm, respectively. With these distributions, our measurement of the power spectrum, P(kθ ), corresponds to linear bias parameters, b = 3.8 ±0.6, 3.9 ±0.6, and 4.4 ±0.7, respectively. We further interpret the results in terms of the halo model, and find that at the smaller scales, the simplest halo model fails to fit our results. One way to improve the fit is to increase the radius at which dark matter halos are artificially truncated in the model, which is equivalent to having some star-forming galaxies at z ≥ 1 located in the outskirts of groups and clusters. In the context of this model, we find a minimum halo mass required to host a galaxy is log(Mmin/M⊙) = 11.5⁺⁰˙⁴₋₀․₁, and we derive effective biases beff = 2.2 ±0.2, 2.4 ±0.2, and 2.6 ±0.2, and effective masses log(Meff/M⊙) = 12.9 ±0.3, 12.8 ±0.2, and 12.7 ±0.2, at 250, 350 and 500μm, corresponding to spatial correlation lengths of r₀ = 4.9, 5.0, and 5.2 ±0.7h⁻¹ Mpc, respectively. Finally, we discuss implications for clustering measurement strategies with Herschel and Planck.

Article

Galaxies: evolution Galaxies: high-redshift Infrared: galaxies Large-scale structure of universe Submillimeter CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

AzTEC millimetre survey of the COSMOS field – II. Source count overdensity and correlations with large-scale structure

ITZIAR ARETXAGA MENDEZ David Hughes (2009)

We report an overdensity of bright submillimetre galaxies (SMGs) in the 0.15 deg² AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z ≲ 1.1. This portion of the COSMOS field shows a ∼3σ overdensity of robust SMG detections when compared to a background, or ‘blank-field’, population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG overdensity is most significant in the number of very bright detections (14 sources with measured fluxes S₁․₁ₘₘ > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities and infers an overdensity significance of ≫ 4σ. We find that the overdensity and spatial correlation to optical-IR galaxy density are most consistent with lensing of a background SMG population by foreground mass structures along the line of sight, rather than physical association of the SMGs with the z ≲ 1.1 galaxies/clusters. The SMG positions are only weakly correlated with weak-lensing maps, suggesting that the dominant sources of correlation are individual galaxies and the more tenuous structures in the survey region, and not the massive and compact clusters. These results highlight the important roles cosmic variance and large-scale structure can play in the study of SMGs.

Article

Gravitational lensing Surveys Galaxies: evolution Cosmology: miscellaneous Infrared: galaxies Submillimeter CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA