Sampling, Intervention, Prediction, Aggregation: A Generalized Framework for Model-Agnostic Interpretations

Model-agnostic interpretation techniques allow us to explain the behavior of any predictive model. Due to different notations and terminology, it is difficult to see how they are related. A unified view on these methods has been missing. We present the generalized SIPA (sampling, intervention, prediction, aggregation) framework of work stages for model-agnostic interpretations and demonstrate how several prominent methods for feature effects can be embedded into the proposed framework. Furthermore, we extend the framework to feature importance computations by pointing out how variance-based and performance-based importance measures are based on the same work stages. The SIPA framework reduces the diverse set of model-agnostic techniques to a single methodology and establishes a common terminology to discuss them in future work

Wide Field Imaging. I. Applications of Neural Networks to object detection and star/galaxy classification

[Abriged] Astronomical Wide Field Imaging performed with new large format CCD detectors poses data reduction problems of unprecedented scale which are difficult to deal with traditional interactive tools. We present here NExt (Neural Extractor): a new Neural Network (NN) based package capable to detect objects and to perform both deblending and star/galaxy classification in an automatic way. Traditionally, in astronomical images, objects are first discriminated from the noisy background by searching for sets of connected pixels having brightnesses above a given threshold and then they are classified as stars or as galaxies through diagnostic diagrams having variables choosen accordingly to the astronomer's taste and experience. In the extraction step, assuming that images are well sampled, NExt requires only the simplest a priori definition of "what an object is" (id est, it keeps all structures composed by more than one pixels) and performs the detection via an unsupervised NN approaching detection as a clustering problem which has been thoroughly studied in the artificial intelligence literature. In order to obtain an objective and reliable classification, instead of using an arbitrarily defined set of features, we use a NN to select the most significant features among the large number of measured ones, and then we use their selected features to perform the classification task. In order to optimise the performances of the system we implemented and tested several different models of NN. The comparison of the NExt performances with those of the best detection and classification package known to the authors (SExtractor) shows that NExt is at least as effective as the best traditional packages.Comment: MNRAS, in press. Paper with higher resolution images is available at http://www.na.astro.it/~andreon/listapub.htm

Spectroscopic and photometric studies of low-metallicity star-forming dwarf galaxies. I. SBS 1129+576

Spectroscopy and V,I CCD photometry of the dwarf irregular galaxy SBS 1129+576 are presented for the first time. The CCD images reveal a chain of compact H II regions within the elongated low-surface-brightness (LSB) component of the galaxy. Star formation takes place mainly in two high-surface-brightness H II regions. The mean (V-I) colour of the LSB component in the surface brightness interval between 23 and 26 mag/sq.arcsec is relatively blue ~0.56+/-0.03 mag, as compared to the (V-I)~0.9-1.0 for the majority of known dwarf irregular and blue compact dwarf (BCD) galaxies. Spectroscopy shows that the galaxy is among the most metal-deficient galaxies with an oxygen abundance 12+log(O/H)= 7.36+/-0.10 in the brightest H II region and 7.48+/-0.12 in the second brightest H II region, or 1/36 and 1/28 of the solar value, respectively. Hbeta and Halpha emission lines and Hdelta and Hgamma absorption lines are detected in a large part of the LSB component. We use two extinction-insensitive methods based on the equivalent widths of (1) emission and (2) absorption Balmer lines to put constraints on the age of the stellar populations in the galaxy. In addition, we use two extinction-dependent methods based on (3) the spectral energy distribution (SED) and (4) the (V-I) colour. The observed properties of the LSB component can be reproduced by a stellar population forming continuously since 10 Gyr ago, provided that the star formation rate has increased during the last 100 Myr by a factor of 6 to 50 and no extinction is present. However, the observational properties of the LSB component can be reproduced equally well by continuous star formation which started not earlier than 100 Myr ago and stopped at 5 Myr, if some extinction is assumed.(Abridged)Comment: 17 pages, 12 figures, Accepted for publication in A&

An Atlas of Warm AGN and Starbursts from the IRAS Deep Fields

We present 180 AGN candidates based on color selection from the IRAS slow-scan deep observations, with color criteria broadened from the initial Point-Source Catalog samples to include similar objects with redshifts up to z=1 and allowing for two-band detections. Spectroscopic identifications have been obtained for 80 (44%); some additional ones are secure based on radio detections or optical morphology, although yet unobserved spectroscopically. These spectroscopic identifications include 13 Sy 1 galaxies, 17 Sy 2 Seyferts, 29 starbursts, 7 LINER systems, and 13 emission-line galaxies so heavily reddened as to remain of ambiguous classification. The optical magnitudes range from R=12.0-20.5; counts suggest that incompleteness is important fainter than R=15.5. Redshifts extend to z=0.51, with a significant part of the sample at z>0.2. The sample includes slightly more AGN than star-forming systems among those where the spectra contain enough diagnostic feature to make the distinction. The active nuclei include several broad-line objects with strong Fe II emission, and composite objects with the absorption-line signatures of fading starbursts. These AGN with warm far-IR colors have little overlap with the "red AGN" identified with 2MASS; only a single Sy 1 was detected by 2MASS with J-K > 2. Some reliable IRAS detections have either very faint optical counterparts or only absorption-line galaxies, potentially being deeply obscured AGN. The IRAS detections include a newly identified symbiotic star, and several possible examples of the "Vega phenomenon", including dwarfs as cool as type K. Appendices detail these candidate stars, and the optical-identification content of a particularly deep set of high-latitude IRAS scans (probing the limits of optical identification from IRAS data alone).Comment: ApJ Suppl, in press. Figures converted to JPEG/GIF for better compression; PDF with full-resolution figures available before publication at http://www.astr.ua.edu/keel/aoagn.pd

Collisional excitation of hydrogen and the determination of the primordial helium abundance from H II regions

This paper investigates the effect of collisional enhancement of the hydrogen lines on the derivation of the helium abundances in low metallicity H II regions. For this, we have constructed a grid of photoionization models relevant for the analysis of giant \hii regions in blue compact galaxies. We show that the effect of collisional excitation on the Halpha/Hbeta ratio can be quite important (up to 8% or more). The impact of this effect on the determination of the helium mass fraction has been tracked on four low-metallicity blue compact galaxies for which Keck spectra are available and which are among the best objects for the quest of the pregalactic helium abundance. We find that taking into account the effects of collisional excitation of hydrogen results in an upward correction of the helium mass fraction Y by up to 5%. However, combining with other systematic effects usually not considered in the determination of the helium abundance in low-metallicity galaxies, the resulting uncertainty should be much less.Comment: 10 pages, 6 Postscript figures, accepted for publication in the Astronomy and Astrophysic

The effect of social interactions in the primary life cycle of motion pictures

We model the consumption life cycle of theater attendance for single movies by taking into account the size of the targeted group and the effect of social interactions. We provide an analytical solution of such model, which we contrast with empirical data from the film industry obtaining good agreement with the diverse types of behaviors empirically found. The model grants a quantitative measure of the valorization of this cul- tural good based on the relative values of the coupling between agents who have watched the movie and those who have not. This represents a measurement of the observed quality of the good that is extracted solely from its dynamics, independently of critics reviews.Comment: 9 Pages, 3 figure

Fashion showcases design: perceptions of the showcase in the brazilian popular market

The present work aims to present the showcase, its relation with the building, with fashion and with the observer. The importance of this exhibition space extends from the aesthetic and communication functions to be part of a wide textile and clothing chain. This role integrates the whole cycle of creation, textiles, clothing and fashion accessories. For this article we used bibliographical references of design and fashion, as well as methodologies of photographic and ethnographic documentation, with application of focus groups. From the focus groups were identified descriptors related to emotional design. Such descriptors point to the emotions arising from memories, tastes and attitudes. These factors can lead to decisions and assist the wider knowledge of the target audience.- This work is supported by CNPq funding on the Programa Ciencias Sem Fronteiras - CSF by national funds within the scope of the project Processo no 203068/2014-9.info:eu-repo/semantics/publishedVersio

Study of DDO 68: nearest candidate for a young galaxy?

We present the results of optical spectroscopy and imaging with the SAO 6m telescope for the dwarf galaxy DDO 68 (UGC 5340 = VV 542), falling into the region of very low density of luminous (L > L*) galaxies (Lynx-Cancer void). Its deep images in V,R bands and in the narrow H-alpha-filter show that the galaxy has the very irregular morphology, with a long curved tail on the South and a ring-like structure at the Northern edge. The latter consists of 5 separate regions, in three of which we could measure O/H by the classical T_e method. Their weighted mean oxygen abundance corresponds to 12+log(O/H)=7.21+-0.03, coincident within uncertainties with those for IZw18. The (V-R) colour of DDO 68 is rather blue all over the galaxy, indicating the youth of its stellar populations. Comparing the (V-R)_0 colour of the underlying exponential disk of 0.12+-0.04 with the PEGASE.2 models for the evolving stellar clusters, we give the first estimate of the ages of the oldest stellar population, which needs confirmation by the other colours and the photometry of resolved stars. These ages are in the range of 200-900 Myr for continuous star formation law, and 100-115 Myr for the instantaneous starburst. We discuss the properties and the possible youth of this nearby object (2.3 times closer than the famous young galaxy IZw18) in the context of its atypical environment.Comment: 13 pages, including 7 tables and 3 postscript figures. Accepted for publication in Astron.Astrophys. Small language corrections are made after the A&A Language Edito