1,721,003 research outputs found
Formation and evolution of galaxy disks
No full textThese are the proceedings of the international conference “Formation and Evolution of Galaxy Disks” organized by the Specola Vaticana (the Vatican Observatory). The meeting hosted 198 participants from 26 countries. The program consisted of 61 talks and about 130 poster papers.
In 2000 the Vatican Observatory organized a conference on Galaxy Disks and Disk Galaxies, the proceedings of which were published in ASP Conference Series Vol. 230. Since that time, a great amount of work has been done in this very active field. October 2007 was deemed an appropriate time to hold another similar conference where outstanding senior and junior astronomers in this field could air new results. The conference was focused on the formation and evolution of galaxy disks and covered the following topics: (1) properties of nearby galaxy disks; (2) interstellar medium, star formation, and chemical evolution; (3) disk edges, outskirts, and environment; (4) accretion onto disks, interactions, and mergers; (5) secular evolution of disks and bar/spiral driven evolution of galaxies; (6) evolution of disk structural properties; and (7) disk formation in a hierarchical universe. This books is of interest for researchers in extragalactic astronomy. It presents an overview of the relevant results and the progress made in the field in the last seven years
New Statistical Goodness of Fit Techniques Applied to the Recovery of the Milky Way Near-IR Luminosity Density Distribution - the 'Wild Bootstrap' Approach
No full textFitting models to regression data is an important part of astronomers everyday work. A common proceeding is based on the assumption, that a parametric class of functions describes the data structure sufficiently well. Then, for example, a least squares fit results in a parameter estimate. In a second step various kinds of χ2 goodness of fit measures are applied to assess whether the deviation between data and the model with the estimated parameters is due to random noise and not to systematic departures from the model. We present a new method which is applicable in noisy versions of Fredholm integral equations of the first kind. For the second step we suggest a bootstrap algorithm which allows an approximation of the distribution of the suggested test statistic
New Statistical Goodness of Fit Techniques Applied to the Recovery of the Milky Way Near-IR Luminosity Density Distribution - the 'Wild Bootstrap' Approach
No full textFitting models to regression data is an important part of astronomers everyday work. A common proceeding is based on the assumption, that a parametric class of functions describes the data structure sufficiently well. Then, for example, a least squares fit results in a parameter estimate. In a second step various kinds of χ2 goodness of fit measures are applied to assess whether the deviation between data and the model with the estimated parameters is due to random noise and not to systematic departures from the model. We present a new method which is applicable in noisy versions of Fredholm integral equations of the first kind. For the second step we suggest a bootstrap algorithm which allows an approximation of the distribution of the suggested test statistic
Morphology and Photometry of Isolated Seyfert Galaxies
No full textAn unresolved and intriguing problem about active galactic nuclei is the mechanism responsible for nuclear triggering and fueling. Until now there is not a unique solution that can completely explain this phenomenon. We present preliminary results about morphological and photometric analysis of a sample of 35 nearby (z<0.035) and isolated Seyfert galaxies, observed through broad-band BVR filters at the 1.8-m Vatican Telescope and the 2.2-m ESO-La Silla Telescope. We analyzed photometric and morphological parameters and, using GALFIT software, we obtained two-dimensional decomposition of the luminosity profiles
The circumnuclear ring of ionized gas in NGC 3593
Full text linkWe present the results of narrow-band Hα +[N II] imaging of the early-type spiral NGC 3593 in combination with a study of the flux radial profiles of the [N II] (lambda lambda 654.80, 658.34 nm), Hα, and [S II] (lambda lambda 671.65, 673.08 nm) emission lines along its major axis. The galaxy is known to contain two counterrotating stellar discs of different size and luminosity. We find that the Hα emission mainly derives from a small central region of 57 arcsec x 25 arcsec. It consists of a filamentary pattern with a central ring. This has a diameter of about 17 arcsec ( ~ 0.6 h^{-1} kpc) and it contributes about half of the total Hα flux. The ring is interpreted as the result of the interaction between the acquired retrograde gas which later formed the smaller counterrotating stellar disc and the pre-existing prograde gas of the galaxy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
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