Digital Literary and Cultural Studies: State of the Art and Perspectives

Over the last decade Digital Humanities has ceased being a “niche discipline” and have become a major phenomenon in academic and cultural debate. Significant scientific results and outcomes have been achieved, and fundamental research infrastructures have been realized. Despite these far-reaching outcomes, Digital Humanities still does not have a satisfactory influence in the traditional disciplinary fields. We need to find new methods to deal with cultural artifacts and texts. Amongst the many emerging research fields in the DH, two come forth as the most promising and interesting: Big Data and distant reading; Semantic Web and Linked Open Data. In my paper I will argue that Big Data in the Humanities, although very promising, have some critical issues, and I will propose the idea of a Semantic Cultural and Literary Web, a collaborative infrastructure based on ontology driven semantic annotation of primary resources

The effect of stellar migration on Galactic chemical evolution: a heuristic approach

In the last years, stellar migration in galactic discs has been the subject of several investigations. However, its impact on the chemical evolution of the Milky Way still needs to be fully quantified. In this paper, we aim at imposing some constraints on the significance of this phenomenon by considering its influence on the chemical evolution of the Milky Way thin disc. We do not investigate the physical mechanisms underlying the migration of stars. Rather, we introduce a simple, heuristic treatment of stellar migration in a detailed chemical evolution model for the thin disc of the Milky Way, which already includes radial gas flows and reproduces several observational constraints for the solar vicinity and the whole Galactic disc. When stellar migration is implemented according to the results of chemo-dynamical simulations by Minchev et. al. (2013) and finite stellar velocities of 1 km s$^{-1}$ are taken into account, the high-metallicity tail of the metallicity distribution function of long-lived thin-disc stars is well reproduced. By exploring the velocity space, we find that the migrating stars must travel with velocities in the range 0.5 -2 km s$^{-1}$ to properly reproduce the high-metallicity tail of the metallicity distribution. We confirm previous findings by other authors that the observed spread in the age-metallicity relation of solar neighbourhood stars can be explained by the presence of stars which originated at different Galactocentric distances, and we conclude that the chemical properties of stars currently observed in the solar vicinity do suggest that stellar migration is present to some extent.Comment: Accepted for publication by Ap

Distant reading in literary studies: a methodology in quest of theory

Since Franco Moretti coined the successful term distant reading, quantitative/computational text analysis methods have gained wide circulation in literary studies. The diffusion of distant reading approaches has raised a lively debate and has attracted various criticisms, both from “traditional literary scholars” and from self-critical adopters. One important reason underlying these critical positions is the fact that it lacks sound and coherent rationales from the point of view of the theory: distant reading is the first methodology in literary studies that does not come with a theory of literature embedded in it. Consequently, all distant reading studies derive their theoretical frameworks and terms from literary theories that mostly rely on the notion that literary texts can be explained only by the way of interpretation. On what grounds, then, can we construct a theory of literature amenable to distant reading methods? I think that the better theoretical frameworks are the cognitive and bio-evolutionistic approaches to literature and cultural evolution studies. These theoretical approaches require a change in the level of description of the literary domain and justify the move from "interpretation" to "explanation" as the real aim of the scholarly inquiry

La rappresentazione digitale del testo: il paradigma del markup e i suoi sviluppi

La codifica elettronica dei testi rappresenta uno dei temi fondamentali della riflessione e della sperimentazione nel dominio dell’Informatica umanistica. Come è noto la soluzione considerata teoricamente ottimale e ampiamente diffusa nella pratica dalla comunità scientifica consiste nell’adozione dei markup language descrittivi basati su XML . Lo sviluppo e la diffusione della Text Encoding Initiative ha sancito questa scelta. XML può essere considerato sia un formalismo sia un modello di dati espresso da quel formalismo, e tale (meta)modello è appunto un albero ordinato etichettato. In altri termini XML considerato come linguaggio di modellizzazione può esprimere solo modelli la cui struttura è un albero. Il modello gerarchico si presta naturalmente a descrivere la struttura di numerosi livelli testuali scientificamente rilevanti: i livelli editoriale, morfosintattico, metrico, tanto per fare alcuni esempi, sono in linea generale descrivibili come strutture gerarchiche ordinate. I problemi emergono si pensa di eleggere XML a formalismo generale per la rappresentazione complessa dei testi in ambito umanistico e letterario. Le manifestazioni di queste difficoltà sono state comunemente rubricate come il problema delle gerarchie sovrapposte (overlapping hierarchies). Negli ultimi venti anni, proprio in parallelo con la diffusione di XML nel mondo dell’elaborazione testuale e della TEI nella comunità umanistica si sono moltiplicati i tentativi di trovare delle soluzioni definitive al problema. Le soluzioni proposte si possono dividere in due classi: soluzioni interne e soluzioni esterne al paradigma XML. Questo lavoro propone una analisi approfondita di queste soluzioni innovative e ne valuta la praticabilità in confronto a XML

Galactic fountains and gas accretion

Star-forming disc galaxies such as the Milky Way need to accrete \gsim 1 $M_{\odot}$ of gas each year to sustain their star formation. This gas accretion is likely to come from the cooling of the hot corona, however it is still not clear how this process can take place. We present simulations supporting the idea that this cooling and the subsequent accretion are caused by the passage of cold galactic-fountain clouds through the hot corona. The Kelvin-Helmholtz instability strips gas from these clouds and the stripped gas causes coronal gas to condense in the cloud's wake. For likely parameters of the Galactic corona and of typical fountain clouds we obtain a global accretion rate of the order of that required to feed the star formation.Comment: 2 pages, 1 figure, to appear in "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista & C.C. Popescu, AIP Conf. Se

Fountain-driven gas accretion by the Milky Way

Accretion of fresh gas at a rate of ~ 1 M_{sun} yr^{-1} is necessary in star-forming disc galaxies, such as the Milky Way, in order to sustain their star-formation rates. In this work we present the results of a new hydrodynamic simulation supporting the scenario in which the gas required for star formation is drawn from the hot corona that surrounds the star-forming disc. In particular, the cooling of this hot gas and its accretion on to the disc are caused by the passage of cold galactic fountain clouds through the corona.Comment: 2 pages, 1 figure. To appear in the proceedings of the conference "Assembling the Puzzle of the Milky Way", Le Grand-Bornand 17-22 April 2011, European Physical Journal, editors C. Reyl\'e, A. Robin and M. Schulthei

Hydrostatic models for the rotation of extra-planar gas in disk galaxies

We show that fluid stationary models are able to reproduce the observed, negative vertical gradient of the rotation velocity of the extra-planar gas in spiral galaxies. We have constructed models based on the simple condition that the pressure of the medium does not depend on density alone (baroclinic instead of barotropic solutions: isodensity and isothermal surfaces do not coincide). As an illustration, we have successfully applied our method to reproduce the observed velocity gradient of the lagging gaseous halo of NGC 891. The fluid stationary models discussed here can describe a hot homogeneous medium as well as a "gas" made of discrete, cold HI clouds with an isotropic velocity dispersion distribution. Although the method presented here generates a density and velocity field consistent with observational constraints, the stability of these configurations remains an open question.Comment: 12 pages, 9 figures. Accepted for publication in Astronomy and Astrophysic

The Tilt of the Fundamental Plane: Three-quarters Structural Nonhomology, One-quarter Stellar Population

The variation of the mass-to-light ratios M/L of early type galaxies as function of their luminosities L is investigated. It is shown that the tilt beta=0.27 (in the B--band) of the fundamental plane relation M/L ~ L^{beta} can be understood as a combination of two effects: about one-quarter (i.e. dbeta =0.07) is a result of systematic variations of the stellar population properties with increasing luminosity. The remaining three-quarters (i.e. dbeta =0.2) can be completely attributed to nonhomology effects that lead to a systematic change of the surface brightness profiles with increasing luminosity. Consequently, the observed tilt in the K-band (beta=0.17) where stellar population effects are negligible, is explained by nonhomology effects alone. After correcting for nonhomology, the mean value of the mass-to-light ratio of elliptical galaxies (M/L_B) is 7.1+-2.8 (1 sigma scatter).Comment: 8 pages, 3 figures, ApJL, 600, 39, minor changes made to match the published versio

Loss of star forming gas in SDSS galaxies

Using the star formation rates from the SDSS galaxy sample, extracted using the MOPED algorithm, and the empirical Kennicutt law relating star formation rate to gas density, we calculate the time evolution of the gas fraction as a function of the present stellar mass. We show how the gas-to-stars ratio varies with stellar mass, finding good agreement with previous results for smaller samples at the present epoch. For the first time we show clear evidence for progressive gas loss with cosmic epoch, especially in low-mass systems. We find that galaxies with small stellar masses have lost almost all of their cold baryons over time, whereas the most massive galaxies have lost little. Our results also show that the most massive galaxies have evolved faster and turned most of their gas into stars at an early time, thus strongly supporting a downsizing scenario for galaxy evolution.Comment: 29 pages, 9 figures, ApJ, accepte

Chemical abundances and radial velocities in the extremely metal-poor galaxy DDO 68

We present chemical abundances and radial velocities of six HII regions in the extremely metal-poor star-forming dwarf galaxy DDO 68. They are derived from deep spectra in the wavelength range 3500 - 10,000 {\AA}, acquired with the Multi Object Double Spectrograph (MODS) at the Large Binocular Telescope (LBT). In the three regions where the [O III]$\lambda$4363 {\AA} line was detected, we inferred the abundance of He, N, O, Ne, Ar, and S through the "direct" method. We also derived the oxygen abundances of all the six regions adopting indirect method calibrations. We confirm that DDO 68 is an extremely metal-poor galaxy, and a strong outlier in the luminosity - metallicity relation defined by star-forming galaxies. With the direct-method we find indeed an oxygen abundance of 12+log(O/H)=7.14$\pm$0.07 in the northernmost region of the galaxy and, although with large uncertainties, an even lower 12+log(O/H)=6.96$\pm$0.09 in the "tail". This is, at face value, the most metal-poor direct abundance detection of any galaxy known. We derive a radial oxygen gradient of -0.06$\pm$0.03 dex/kpc (or -0.30 dex $R_{25}^{-1}$) with the direct method, and a steeper gradient of -0.12$\pm$0.03 dex/kpc (or -0.59 dex $R_{25}^{-1}$) from the indirect method. For the $\alpha$-element to oxygen ratios we obtain values in agreement with those found in other metal-poor star-forming dwarfs. For nitrogen, instead, we infer much higher values, leading to log(N/O)$\sim-1.4$, at variance with the suggested existence of a tight plateau at $-1.6$ in extremely metal poor dwarfs. The derived helium mass fraction ranges from Y=0.240$\pm$0.005 to Y=0.25$\pm$0.02, compatible with standard big bang nucleosynthesis. Finally, we measured HII region radial velocities in the range 479$-$522 km/s from the tail to the head of the "comet", consistent with the rotation derived in the HI.Comment: Accepted for publication in MNRA