Integral field optical spectroscopy of a representative sample of ULIRGs: II. Two-dimensional kpc-scale extinction structure

We investigate the two-dimensional kpc-scale structure of the extinction in a representative sample of local ULIRGs using the Halpha/Hbeta line ratio.We use optical integral field spectroscopy obtained with the INTEGRAL instrument at the William Herschel Telescope. Complementary optical and near-IR high angular resolution HST images have also been used. The extinction exhibits a very complex and patchy structure in ULIRGs on kpc scales, from basically transparent regions to others deeply embedded in dust (Av~0.0 to Av~8.0 mag). Nuclear extinction covers a broad range in Av from 0.6 to 6 mag, 69% of the nuclei having Av>2.0 mag. Extinction in the external regions is substantially lower than in the nuclei with 64% of the ULIRGs in the sample having median Av of less than 2 mag for the entire galaxy. While post-coalescence nuclei tend to cluster around Av values of 2 to 3 mag, pre-coalescence nuclei appear more homogeneously distributed over the entire 0.4 mag <Av< 7.7 mag range. For the average extinction (Av~2.0 derived for the ULIRGs of the sample, the ratio of the de-reddened to observed SFR values is 6. The extinction-corrected, Halpha-based SFR ranges from 10 to 300 Msun/yr. For only 28% of the cases the de-reddened SFR is <20 Msun/yr, whereas for the observed SFR this percentage increases to 72%. The IR-based SFR is always higher than the optical-based one, with differences ranging from about 2 to up to 30. The nuclear observed SFR has an average contribution to the total one of 16% for the entire sample. Once corrected for extinction, the average value becomes 31%. Because of mostly extinction effects, the optical (I-band) half-light radius in the sample galaxies is on average a factor 2.3 larger than the corresponding near-IR (H-band) value.Comment: To appear in A&

Family and Internet

El desarrollo de la Humanidad nos dibuja un aumento en las capacidades de comunicación del ser humano. Esta situación viene de la mano, fundamentalmente, del gran avance que los nuevos medios de comunicación, caso de Internet, están experimentando. Según las autoras, esta situación reclama un entendimiento entre la familia y este medio (Internet), exige el establecimiento de unas líneas de comunicación que ayude a los miembros de la familia en su crecimiento y socializaciónThe progress of Humanity shows an increase in the communication capacities of the human being. This situation is bound to the great advance that the new media, such as Internet, are experiencing and it claims for a new understanding between the family and the new media. The authors think that the establisment of some communication lines which would help the families in their growth and socialization are completely necessary

Los videojuegos y su capacidad didáctico-formativa

Hoy las máquinas ocupan un lugar privilegiado en nuestra vida. Podemos destacar la presencia de los videojuegos dentro de la dinámica familiar y escolar. Los videojuegos pueden ser considerados como otra forma de enseñar, si esta se desarrolla a través de una correcta supervisión. Esta situación demanda la intervención directa de la familia y de los docentes como referentes socializadores de los niños de hoy, hombres del mañanaToday the machines occupy a privileged place in our life. We can emphasize the presence of the video games within the familiar and scholastic dynamics. The video games can be considered as other form of teaching, if this is developed through a correct supervision. This demand situation the direct intervention of the family and of the educational as referring of the children of today, men of the tomorrow

Thermal diagnostic of the Optical Window on board LISA Pathfinder

Vacuum conditions inside the LTP Gravitational Reference Sensor must comply with rather demanding requirements. The Optical Window (OW) is an interface which seals the vacuum enclosure and, at the same time, lets the laser beam go through for interferometric Metrology with the test masses. The OW is a plane-parallel plate clamped in a Titanium flange, and is considerably sensitive to thermal and stress fluctuations. It is critical for the required precision measurements, hence its temperature will be carefully monitored in flight. This paper reports on the results of a series of OW characterisation laboratory runs, intended to study its response to selected thermal signals, as well as their fit to numerical models, and the meaning of the latter. We find that a single pole ARMA transfer function provides a consistent approximation to the OW response to thermal excitations, and derive a relationship with the physical processes taking place in the OW. We also show how system noise reduction can be accomplished by means of that transfer function.Comment: 20 pages, 14 figures; accepted for publication in Class. Quantum Gra

Line and Continuum Variability in Active Galaxies

We compared optical spectroscopic and photometric data for 18 AGN galaxies over 2 to 3 epochs, with time intervals of typically 5 to 10 years. We used the Multi-Object Double Spectrograph (MODS) at the Large Binocular Telescope (LBT) and compared the spectra to data taken from the SDSS database and the literature. We find variations in the forbidden oxygen lines as well as in the hydrogen recombination lines of these sources. For 4 of the sources we find that, within the calibration uncertainties, the variations in continuum and line spectra of the sources are very small. We argue that it is mainly the difference in black hole mass between the samples that is responsible for the different degree of continuum variability. In addition we find that for an otherwise constant accretion rate the total line variability (dominated by the narrow line contributions) reverberates the continuum variability with a dependency $\Delta L_{line} \propto (\Delta L_{cont.})^{\frac{3}{2}}$. Since this dependency is prominently expressed in the narrow line emission it implies that the luminosity dominating part of the narrow line region must be very compact with a size of the order of at least 10 light years. A comparison to literature data shows that these findings describe the variability characteristics of a total of 61 broad and narrow line sources.Comment: 30 pages including the appendix, 18 figures including the appendix. Accepted 2015 September 3. Received 2015 August 24; in original form 2015 July 3 in Monthly Notices of the Royal Astronomical Societ

Rapid colour changes in Euglena sanguinea (Euglenophyceae) caused by internal lipid globule migration

The accumulation of red pigments under chronic stress is a response observed in most groups of oxygenic photoautotrophs. It is thought that the red pigments in the cell shield the chlorophyll located underneath from the light. Among these red pigments, the accumulation of carotenoids is one of the most frequent cases. However, the synthesis or degradation of carotenoids is a slow process and this response is usually only observed when the stress is maintained over a period of time. In the Euglenophyte Euglena sanguinea, this is due to the accumulation of a large amount of free and esterified astaxanthin (representing 80% of the carotenoid pool). While reddening is a slow and sometimes irreversible process in other phototrophs, reducing the efficiency of light harvesting by chlorophyll, in E. sanguinea it is highly dynamic, capable of shifting from red to green (and vice-versa) in 10-20 min. This change is not due to de novo carotenogenesis, but to the relocation of cytoplasmic lipid globules where astaxanthin accumulates. Thus, red globules migrate from the centre of the cell to peripheral locations when photoprotection is demanded. This protective system seems to be so efficient that other classical mechanisms are not operative in this species. For example, despite the presence and operation of the diadino-diatoxanthin cycle, nonphotochemical quenching (NPQ) is almost undetectable. Since E. sanguinea forms extensive floating colonies, reddening can be observed at much greater scale than at a cellular level, the mechanism described here being one of the fastest and most dramatic colour changes attributable to photosynthetic organisms at cell and landscape level. In sum, these data indicate an extremely dynamic and efficient photoprotective mechanism based on organelle migration more than on carotenoid biosynthesis that prevents excess light absorption by chlorophylls reducing the need for other protective processes related to energy dissipation.This work was supported by the Basque Government [UPV/EHU-GV IT-1018-16] [UPV/EHU PPG17/67 – GV IT-1040-16], and by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Research and Development Foundation (FEDER) through (i) [CTM2014-53902-C2-2-P] national grant and (ii) a “Juan de la Cierva-Incorporación” postdoctoral grant [IJCI-2014-22489] to BFM