Advanced search


Knowledge area




9 results, page 1 of 1

Submm/mm Galaxy Counterpart Identification Using a Characteristic Density Distribution

Itziar Aretxaga David Hughes (2013)

We present a new submm/mm galaxy counterpart identification technique whichbuilds on the use of Spitzer IRAC colors as discriminators between likely counter-parts and the general IRAC galaxy population. Using 102 radio- and SMA-confirmedcounterparts to AzTEC sources across three fields (GOODS-N, GOODS-S, and COSMOS), we develop a non-parametric IRAC color-color characteristic density distribution (CDD), which, when combined with positional uncertainty information vialikelihood ratios, allows us to rank all potential IRAC counterparts around SMGsand calculate the significance of each ranking via the reliability factor. We reportall robust and tentative radio counterparts to SMGs, the first such list available forAzTEC/COSMOS, as well as the highest ranked IRAC counterparts for all AzTECSMGs in these fields as determined by our technique. We demonstrate that the technique is free of radio bias and thus applicable regardless of radio detections. For observations made with a moderate beamsize (∼18′′), this technique identifies ∼85 percent of SMG counterparts. For much larger beamsizes (≳30′′), we report identificationrates of 33-49 per cent. Using simulations, we demonstrate that this technique is animprovement over using positional information alone for observations with facilities such as AzTEC on the LMT and SCUBA-2 on JCMT.

Article

Submillimetre: galaxies Radio continuum: galaxies Infrared: galaxies Galaxies: high redshift Techniques: photometric Methods: data analysis CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA RADIOASTRONOMÍA RADIOASTRONOMÍA

A Spitzer-IRS Spectroscopic atlas of early-type galaxies in the Revised Shapley-Ames Catalog

OLGA MERCEDES VEGA CASANOVA (2013)

We produce an atlas of homogeneously reduced and calibrated low resolution IRS spectra of the nuclear regions of nearby early-type galaxies (i.e. Es and S0s, ETGs), in order to build a reference sample in the mid-infrared window. From the Spitzer Heritage Archive we extract ETGs in the Revised Shapley-Ames Catalog of Bright Galaxies having an IRS SL and/or LL spectrum. We recover 91 spectra out of 363 galaxies classified as ETGs in the catalog: 56 E (E0-E6), 8 mixed E/S0+S0/E, 27 S0 (both normal and barred - SB0) plus mixed types SB0/Sa+SB0/SBa. For each galaxy, we provide the fully reduced and calibrated spectrum, the intensity of nebular and molecular emission lines as well as of the Polycyclic Aromatic Hydrocarbons (PAHs) after a template spectrum of a passively evolving ETG has been subtracted. Spectra are classified into five mid-infrared classes, ranging from AGN (class-4) and star forming nuclei (class-3), transition class-2 (with PAHs) and class-1 (no-PAHs) to passively evolving nuclei (class-0). A demographic study of mid-infrared spectra shows that Es are significantly more passive than S0s:46⁺¹¹₋₁₀% of Es and 20⁺¹¹₋₇ % of S0s have a spectrum of class-0. Emission lines are revealed in 64⁺¹²₋₆ % of ETGs. The H₂S(1) line is found with similar rate in Es (34⁺¹⁰₋₈ %) and in S0s (51⁺¹⁵₋₁₂%). PAHs are detected in 47⁺⁸₋₇% of ETGs, but only 9⁺⁴₋₃% have PAHs ratios typical of star forming galaxies. Several indicators, such as peculiar morphologies and kinematics, dust–lane irregular shape, radio and X-ray properties, suggest that mid-infrared spectral classes are connected to phases of accretion/feedback phenomena occurring in the nuclei of ETGs.

Article

Infrared: galaxies Galaxies: elliptical and lenticular, cD Galaxies: fundamental parameters Techniques: spectroscopic CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

α Centauri A in the far infrared*: First measurement of the temperature minimum of a star other than the Sun

Carlos del Burgo Díaz (2013)

Context. Chromospheres and coronae are common phenomena on solar-type stars. Understanding the energy transfer to these heatedatmospheric layers requires direct access to the relevant empirical data. Study of these structures has, by and large, been limited to theSun thus far.

Aims. The region of the temperature reversal can be directly observed only in the far infrared and submillimetre spectral regime. Weaim at determining the characteristics of the atmosphere in the region of the temperature minimum of the solar sister star α Cen A. Asa bonus this will also provide a detailed mapping of the spectral energy distribution, i.e. knowledge that is crucial when searching forfaint, Kuiper belt-like dust emission around other stars.

Methods. For the nearby binary system α Cen, stellar parameters are known with high accuracy from measurements. For the basicmodel parameters Teff, log g and [Fe/H], we interpolate stellar model atmospheres in the grid of Gaia/PHOENIX and compute the corresponding model for the G2V star α Cen A. Comparison with photometric measurements shows excellent agreement between observed photospheric data in the optical and infrared. For longer wavelengths, the modelled spectral energy distribution is compared to Spitzer-MIPS, Herschel-PACS, Herschel-SPIRE, and APEX-LABOCA photometry. A specifically tailored Uppsala model based on the MARCS code and extending further in wavelength is used to gauge the emission characteristics of α CenA in the far infared.

Results. Similar to the Sun, the far infrared (FIR) emission of α CenA originates in the minimum temperature region above the stellar photosphere in the visible. However, in comparison with the solar case, the FIR photosphere of α CenA appears marginally cooler, Tmin~T160μm = 3920±375 K. Beyond the minimum near 160 μm, the brightness temperatures increase, and this radiation very likely originates in warmer regions of the chromosphere of α Cen A.

Conclusions. To the best of our knowledge, this is the first time a temperature minimum has been directly measured on a main-sequencestar other than the Sun.

Article

Stars: individual: αCen Stars: atmospheres Stars: chromospheres Circumstellar matter Infrared: stars Submillimeter: stars CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

UNCOVERING THE DEEPLY EMBEDDED ACTIVE GALACTIC NUCLEUS ACTIVITY IN THENUCLEAR REGIONS OF THE INTERACTING GALAXY Arp 299

Itziar Aretxaga (2013)

We present mid-infrared (MIR) 8–13μm spectroscopy of the nuclear regions of the interacting galaxy Arp 299(IC 694+NGC 3690) obtained with CanariCam (CC) on the 10.4 m Gran Telescopio Canarias (GTC). The highangular resolution (∼0”.3–0”.6) of the data allows us to probe nuclear physical scales between 60 and 120 pc,which is a factor of 10 improvement over previous MIR spectroscopic observations ofthis system. The GTC/CCspectroscopy displays evidence of deeply embedded active galactic nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC 3690/Arp 299-B1 can be explained as emission from AGN-heated dustin a clumpy torus with both a high covering factor and high extinction along the line of sight. The estimatedbolometric luminosity of the AGN in NGC 3690 is 3.2 ± 0.6 × 10⁴⁴ erg s⁻¹. The nuclear GTC/CC spectrum ofIC 694/Arp 299-A shows 11.3μm polycyclic aromatic hydrocarbon emission stemming from a deeply embedded (Av∼ 24 mag) region of less than 120 pc in size. There is also a continuum-emitting dust component. If associatedwith the putative AGN in IC 694, we estimate that it would be approximately five times less luminous than the AGN in NGC 3690. The presence of dual AGN activity makes Arp 299 a good example to study such phenomena in the early coalescence phase of interacting galaxies.

Article

Galaxies: individual (Arp 299, IC 694, NGC 3690) Galaxies: nuclei Galaxies: Seyfert Infrared: galaxies CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Dust around NEarby Stars. The survey observational results

Carlos del Burgo Díaz (2013)

Context. Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar system counterparts are the asteroid and Edgeworth-Kuiper belts.

Aims. The DUNES survey aims at detecting extra-solar analogues to the Edgeworth-Kuiper belt around solar-type stars, putting in this way the Solar system into context. The survey allow sus to address some questions related to the prevalence and properties of planetesimal systems.

Methods. We used Herschel/PACS to observe a sample of nearby FGK stars. Data at 100 and 160 μm were obtained, complemented in some cases with observations at 70 μm, and at 250, 350 and 500 μm using SPIRE. The observing strategy was to integrate as deep as possible at 100 μm to detect the stellar photosphere.

Results. Debris discs have been detected at a fractional luminosity level down to several times that of the Edgeworth-Kuiper belt. The incidence rate of discs around the DUNES stars is increased from a rate of ∼12.1% ± 5% before Herschel to ∼20.2% ± 2%. A significant fraction (∼52%) of the discs are resolved, which represents an enormous step ahead from the previously known resolved discs. Some stars are associated with faint far-IR excesses attributed to a new class of cold discs. Although it cannot be excluded that these excesses are produced by coincidental alignment of background galaxies, statistical arguments suggest that at least some of them are true debris discs. Some discs display peculiar SEDs with spectral indexes in the 70–160 μm range steeper than the Rayleigh-Jeans one. An analysis of the debris disc parameters suggests that a decrease might exist of the mean black body radius from the F-type to the K-type stars. In addition, a weak trend is suggested for a correlation of disc sizes and an anticorrelation of disc temperatures with the stellar age.

Article

Circumstellar matter Planetary systems Infrared: stars CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Alignment in star-debris disc systems seen by Herschel

Carlos del Burgo Díaz (2013)

Many nearby main-sequence stars have been searched for debris using the far-infrared Herschel satellite, within the DEBRIS, DUNES and Guaranteed-Time Key Projects.We discuss here 11 stars of spectral types A to M where the stellar inclination is known and can be compared to that of the spatially-resolved dust belts. The discsare found to be well aligned with the stellar equators, as in the case of the Sun’s Kuiper belt, and unlike many close-in planets seen in transit surveys. The ensemble of stars here can be fitted with a star-disc tilt of ≲10º. These results suggest that proposed mechanisms for tilting the star or disc in fact operate rarely. A few systems also host imaged planets, whose orbits at tens of AU are aligned with the debris discs, contrary to what might be expected in models where external perturbers induce tilts.

Article

Planetary systems Circumstellar matter Infrared: stars CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Herschel observations of the debris disc around HIP 92043*

Carlos del Burgo Díaz (2013)

Context. Typical debris discs are composed of particles ranging from several micron sized dust grains to km sized asteroidal bodies, and their infrared emission peaks at wavelengths 60–100 μm. Recent Herschel DUNES observations have identified several debris discs around nearby Sun-like stars (F, G and K spectral type) with significant excess emission only at 160 μm.

Aims.We observed HIP 92043 (110 Her, HD 173667) at far-infrared and sub-millimetre wavelengths with Herschel PACS and SPIRE. Identification of the presence of excess emission from HIP 92043 and the origin and physical properties of any excess was undertaken through analysis of its spectral energy distribution (SED) and the PACS images.

Methods. The PACS and SPIRE images were produced using the HIPE photProject map maker routine. Fluxes were measured using aperture photometry. A stellar photosphere model was scaled to optical and near infrared photometry and subtracted from the farinfared and sub-mm fluxes to determine the presence of excess emission. Source radial profiles were fitted using a 2D Gaussian and compared to a PSF model based on Herschel observations of α Boo to check for extended emission.

Results. Clear excess emission from HIP 92043 was observed at 70 and 100 μm. Marginal excess was observed at 160 and 250 μm. Analysis of the images reveals that the source is extended at 160 μm. A fit to the source SED is inconsistent with a photosphere and single temperature black body.

Conclusions. The excess emission from HIP 92043 is consistent with the presence of an unresolved circumstellar debris disc at 70 and 100 μm, with low probability of background contamination. The extended 160 μm emission may be interpreted as an additional cold component to the debris disc or as the result of background contamination along the line of sight. The nature of the 160 μm excess cannot be determined absolutely from the available data, but we favour a debris disc interpretation, drawing parallels with previously identified cold disc sources in the DUNES sample.

Article

Infrared: stars Circumstellar matter Stars: individual: HIP 92043 (110 Her, HD 173667) CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA ASTRONOMÍA Y ASTROFÍSICA ASTRONOMÍA Y ASTROFÍSICA

Selective photodeposition of zinc nanoparticles on the core of a single-mode optical fiber

RUBEN RAMOS GARCIA (2013)

An experimental and theoretical study about selective photodeposition of metallic zinc nanoparticles onto an optical fiber end is presented. It is well known that metallic nanoparticles possess a high absorption coefficient and therefore trapping and manipulation is more challenging than dielectric particles. Here, we demonstrate a novel trapping mechanism that involves laser-induced convection flow (due to heat transfer from the zinc particles) that partially compensates both absorption and scattering forces in the vicinity of the fiber end. The gradient force is too small and plays no role on the deposition process. The interplay of these forces produces selective deposition of particles whose size is directly controlled by the laser power. In addition, a novel trapping mechanism termed convective-optical trapping is demonstrated.

Article

Fiber optics, infrared Photothermal effects Optical tweezers or optical manipulation Laser trapping CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Fotogrametría aérea aplicada a encinos (Quercus spp.) en Sierra La Laguna, B.C.S. Recomendaciones para su identificación y conservación

MARIANA RAMIREZ VARGAS (2020)

"Vegetation monitoring is essential to design strategies for forest management and conservation. As an efficient alternative for monitoring, precise methods have been developed such as airborne multispectral sensors, which process images through photogrammetry, technique which determines the shape, size and position of objects without being in contact with them. This option implies multiple benefits for vegetation monitoring because joined with vegetation indexes (VIs) estimation, it is possible to evaluate vegetation species thanks to the spectral signature that identifies each of them. The main objective of this work was to implement a supervised classification model using high resolution aerial images to identify, quantify and estimate the coverage and height of San Antonio oaks in BCS, where three species of Quercus develop. The methodological framework is applied in a 20.9 hectares polygon in which oaks were geo-positioned and identified, the height of 30% of the oaks was measured using an hypsometer. The imagery was acquired with an unmanned aerial vehicle equipped with two sensors to measure reflectance in the visible part of light (RGB) and in the near infrared (NIR). From the aerial images, VIs were estimated in the dry and rainy season. Besides the mosaics created with each sensor, the Digital Surface and Terrain Model were built and from those, the canopy height model (CHM), which contains the oak´s height data was built. The results suggest that by their own, VIs based on RGB bands on the dry season, show better performance (accuracy 50%, Kappa 0.25) than those based on the NIR band (accuracy 53%, kappa 0.15) or in the rainy season with an RGB index (accuracy 47%, kappa 0.18). Integrating the CHM to the algorithm, performance improves when it was evaluated by a VI based on RGB in the dry season (accuracy 72.7%, kappa 0.59), unlike the model with an NIR index (accuracy 62.4%, kappa 0.40) or in the rainy season with an RGB index (accuracy 66.3%, kappa 0.44). Once all the vegetation indexes (RGB and NIR) and the CHM are included in the classification algorithm, the RGB model achieves an accuracy of 81% in the dry season against the 74% obtained in the rainy season model and also the 71% with all the NIR indexes in the dry season..."

"El monitoreo de la vegetación resulta imprescindible para diseñar estrategias referentes al manejo y conservación forestal. Como alternativa eficiente se han desarrollado métodos precisos como sensores multiespectrales aerotransportados, que mediante fotogrametría procesan imágenes para conocer la forma, tamaño y posición de los objetos sin estar en contacto con ellos. Esta opción implica beneficios para el monitoreo de la vegetación ya que aunada a la estimación de índices de vegetación (IV) es posible evaluar a las especies vegetales gracias a la firma espectral que las identifica. En este sentido, el objetivo principal de este trabajo fue implementar un modelo de clasificación supervisada utilizando imágenes aéreas de alta resolución para identificar y estimar la cobertura y la altura de los encinos en San Antonio de la Sierra, B.C.S, localidad en la que se desarrollan tres especies del género Quercus. La metodología se aplicó en un polígono de 20.9 hectáreas, en el que se geo-posicionaron e identificaron los encinos; con un hipsómetro se midió la altura del 30% de los encinos. Para lo anterior, se obtuvieron imágenes con un vehículo aéreo no tripulado, equipado con dos sensores para medir la reflectancia en la parte visible de la luz (RGB) y en el infrarrojo cercano (NIR). A partir de las imágenes aéreas se estimaron los IV en la temporada seca y de lluvias. Además de los mosaicos creados de cada sensor, se construyó el Modelo digital de superficie, de terreno y a partir de estos el modelo de elevación del dosel (MED) que contenía los datos de altura de los encinos. Los resultados sugieren que por sí solos los IV basados en las bandas RGB en la temporada de estiaje, muestran un mejor desempeño (precisión 50%, kappa 0.25) que aquellos basados en el NIR (precisión 53%, kappa 0.15) o en la temporada de lluvias con IV RGB (precisión 47%, kappa 0.18). Al integrar los datos de altura de la vegetación, obtenidos mediante los modelos fotogramétricos, el desempeño mejora al evaluar un IV RGB en época seca (precisión 72.7%, kappa 0.59) a diferencia del modelo con un IV basado en el NIR (precisión 62.4%, kappa 0.40) o en época lluviosa con un IV RGB (precisión 66.3%, kappa 0.44)..."

Master thesis

Espectro de luz visible, infrarrojo cercano, fotogrametría aérea, clasificación supervisada, modelo de elevación del dosel Visible light spectrum, near infrared, aerial photogrammetry, supervisedclassification, canopy height model BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA BIOLOGÍA VEGETAL (BOTÁNICA) ECOLOGÍA VEGETAL ECOLOGÍA VEGETAL