1,723,254 research outputs found
Herbig-Haro objects in the star formation region NGC-7129
No full textWe have obtained new deep I, H(alpha) and [SII] CCD images of several fields in the star formation region NGC 7129. The data are presented in the form of grey-level pictures or isocontour plots. A large and complex nebulosity has been discovered in the field around the HH objects GGD 32 and HH 103. The nebulosity is formed by a diffuse component and several 'streamers' or filament-like structures and many HH clumps, among which GGD 32 and HH 103 are just the two most outstanding ones. The large nebulosity coincides with the western blueshifted CO peak of the outflow associated with the southern far-infrared source in NGC 7129. In addition, our images reveal some new morphological details about the previously known objects GGD 33-35 and HH 105. A large variety of excitation conditions is suggested by the relative H(alpha), [SII] ratios observed in the HH nebulosities. As a whole, the data show that the outflow activity in NGC 7129 is much more complicated than we expected.Unidad Deptal. de Astronomía y GeodesiaFac. de Ciencias MatemáticasTRUEpu
[Central Cordoba Railway, Engine Drawing Card, Sketch No. 7129]
No full textThis engine drawing card was created for Ferrocarril Cordoba Central (Cordoba Central Railway), Class 14-40 1/4 F. Section H-14 1/4 F. Sketch 7129. Copy Spec. [field left blank]
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
A Chandra and Spitzer census of the young star cluster in the reflection nebula NGC 7129
No full textContext. The reflection nebula NGC 7129 has long been known to be a site of recent star formation
as shown, e.g., by the presence of deeply embedded protostars and HH objects. However, studies of the
stellar population produced in the star formation process have remained rudimentary. A major step forward
has been made with recent Spitzer imaging of the region.
Aims. This study represents the next step towards a systematic assessment of the pre-main sequence population
in NGC 7129. Completeness of the pre-main sequence sample is necessary for studying key features that
allow the star-forming process to be understood, such as disk evolution, dynamical evolution, and mass function.
At a presumed age of ~3 Myr, NGC 7129 is in the critical range where disks around young stars disappear.
Methods. We make use of X-ray and IR imaging observations to identify the pre-main sequence stars in NGC 7129.
We define a sample of young stellar objects based on color–color diagrams composed from
IR photometry between 1.6 and 8 μm, from 2 MASS and Spitzer, and based on X-ray detected sources from a Chandra observation.
Results. This sample is composed of 26 Class II and 25 Class III candidates.
It has been selected from infrared sources in the Chandra field
(287 objects with photometry in all four Spitzer/IRAC bands, 811 objects with near-IR photometry)
and the 59 X-ray sources detected with Chandra. The sample is estimated to be complete down to ~ 0.5 .
The most restricted and least biased subsample of pre-main sequence stars is composed of lightly absorbed
(AV < 5 mag) stars in the cluster core. This sample comprises 7 Class II and 14 Class III sources
and has a disk fraction of %
and a median X-ray luminosity of log [erg/s] = 30.3.
Conclusions. Despite the various uncertainties related to the sample selection, absorption, mass distribution, distance, and,
consequently in the computation of disk fraction and X-ray luminosities,
the data yield consistent results. In particular, we confirm the age of ∼3 Myr for the NGC 7129 cluster. The
derived disk fraction is similar to that of σ Orionis, smaller than for Cha I
(∼2 Myr),
and larger than for Upper Sco (5 Myr). The X-ray luminosity function is similar to that of NGC 2264
(2 Myr) but fainter than for the Orion Nebula Cluster (1 Myr).
The pre-main sequence census should be further refined and extended with optical photometric and spectroscopic
searches for cluster members
Molecular gas in NGC 7129
No full textThis paper reports new submillimeter molecular line observations of NGC 7129, a reÑection nebula and star-forming region. Maps of 12CO and 13CO 2-1 and 3-2 emission show a cavity surrounded by bright ridges of denser molecular gas. Known molecular outflows in the region issue from deeply embedded sources in these ridges. Only the red lobe of the most prominent outflow is seen clearly, but there is some evidence to suggest that a blue counterjet is escaping through the front of the cavity. We suggest a picture of the region’s evolution in which the oldest star, BD +65°1638, created the cavity by sweeping the surrounding interstellar gas into the surrounding ridges. This led to further star formation, as evidenced by the outflow sources found in the ridges. One of these sources, FIRS 2, thought to be an intermediate-mass analog of a Class 0 young stellar object, is coincident with a pointlike source seen in a near-IR (K’)image
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
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