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Población estelar joven embebida en la nube molecular galáctica asociada a la fuente IRAS 18236-1205
Get PDFEn esta tesis presento una metodología de selección y estudio de la población estelar
embebida en la nube molecular galáctica asociada a la fuente IRAS 18236-1205. La
fuente IRAS posee colores de región Ultra Compacta HII (UCHII) y tiene detección
en monosulfuro de carbono (CS), trazador molecular de alta densidad, lo cual da la
posibilidad de definir la nube molecular asociada hacia esta región. Lo anterior muestra
que ésta es buena candidata a región de formación estelar masiva. La metodología de
selección de la población embebida, está basada por una parte, en la distribución del
gas molecular monóxido de carbono (13CO) asociado a la fuente IRAS, nube molecular
seleccionada del mapeo Galactic Ring Survey (GRS) realizado en 13CO. Otros pasos
de la selección, se basan en los diagramas color-color y color-magnitud con datos del
cercano infrarrrojo de 2MASS.
Para el estudio de la componente estelar se usaron los catálogos de fuentes puntuales en
el cercano, medio y lejano infrarrojo de 2MASS, SPITZER e IRAS, respectivamente.
De los diagramas color-color y color-magnitud, usando datos de 2MASS, se construy
ó un criterio fotométrico para identificar los objetos estelares joóvenes embebidos en
la región molecular. Aplicando modelos a la distribución espectral de energía (SED)
de algunos ellos, se encontraron parámetros estelares de objetos estelares jóvenes embebidos
de masa intermedia y alta. Adicionalmente, se encontró un objeto de masa
intermedia no identificado por el catálogo de 2MASS y su efecto sobre el medio interestelar,
emisión en la banda de [4.5]¹m de IRAC-Spitzer asociado a un outflow.
Dos de los objetos seleccionados por el criterio fotométrico resultaron ser objetos estelares
jóvenes de alta e intermedia masa (B1V/B2V y B8V/A0V respectivamente), los
cuales deben estar asociados a la emisión radiativa responsable de los colores de región
UC HII. Otro objeto estelar joven de baja masa (F0V/F5V) fue encontrado en la región
de estudio. Este parece estar asociado con la presencia de un disco circumestelar y material
excitado por choque (IRAC-Spitzer [4.5]¹m).
Se concluye que el escenario de región de formación estelar masiva factible para ésta
región molecular es el de una asociación estelar joven embebida en una densa región
molecular (AV . 30) hacia la fuente IRAS 18236-1205
Ley de formación estelar en nubes moleculares galácticas con formación estelar de alta masa.
Get PDFThe aim of this thesis is the study of the star formation rate distribution with respect to
the gas density named star formation law in the literature, in a sample of galactic molecular
clouds (GMCs) and infrared dark clouds (IRDCs) embedded in these, as well
other star formation activity parameters. The clouds are defined using the 13CO molecular
emission line and the young stellar objects (YSOs) are selecting from Spitzer
GLIMPSE y MIPSGAL 24µm databases.
For each cloud the mass function (MF) of the YSOs is obtained in the mass range from
0.1 M⊙ to 30 M⊙. The resulting MF have a log normal form for low masses and an
extended tail toward higher masses, resembling well to the Salpeter’s form. This MF
is consistent with the resulting mass distribution in protostellar cores and young star
clusters in recent studies.With the YSOs mass and cloud masses, the star formation rate
(SFR) and star formation efficiency (SFE) are determined for all the clouds. These have
a SFR range from 12.0 to 756.0 M⊙ Myr−1, whilst the SFEs varying from 0.5% to
3.8 %. These SFR/SFE values are comparable to Orion A/B values and other Galactic
star-forming regions.El presente trabajo de tesis aborda el estudio de la distribución de la tasa de formación
estelar respecto a la densidad del gas, llamado en la literatura ley de formación estelar,
en una muestra de 12 nubes moleculares gigantes (GMCs) galácticas y en nubes
infrarrojas oscuras (IRDCs) asociadas a las GMCs, así como otros parámetros de la
actividad de formación estelar en éstas. Las nubes son definidas usando la emisión del
gas molecular 13CO y se ha hecho el censo de objetos estelares jóvenes (YSOs) a partir
de los datos de GLIMPSE y MIPSGAL 24µm Spitzer.
En cada una de las nubes se ha obtenido la función de masa de los YSOs en el rango
de 0.1 M⊙ hasta 30 M⊙. La función de masa para la muestra de nubes sigue una distribución log normal más una ley de potencia tipo Salpeter, la cual es consistente con
resultados de estudios recientes de la función de masa de cores proto estelares y de
cúmulos jóvenes estelares. Usando la masa de los YSOs y la masa de cada nube molecular,
se obtuvieron la tasa de formación estelar (SFR) y la eficiencia de formación
estelar (SFE) para cada una de las nubes. Los valores de SFR obtenidos están en el
rango de 12.0 hasta 756.0 M⊙ Myr−1, los cuales son comparables a los que se presentan
en regiones galácticas de formación estelar, tales como Orión A y B. Los valores
obtenidos para la SFE están en el rango de 0.5% hasta 3.8 %, siendo comparables a los
reportados en Orión y en regiones galácticas que forman estrellas de baja masa
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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