Searching and fixating: scale-invariance vs. characteristic timescales in attentional processes

In an experiment involving semantic search, the visual movements of sample populations subjected to visual and aural input were tracked in a taskless paradigm. The probability distributions of saccades and fixations were obtained and analyzed. Scale-invariance was observed in the saccadic distributions, while the fixation distributions revealed the presence of a characteristic (attentional) time scale for literate subjects. A detailed analysis of our results suggests that saccadic eye motions are an example of Levy, rather than Brownian, dynamics.Comment: Accepted to Europhysics Letters (2011

Near-Infrared and Star-forming properties of Local Luminous Infrared Galaxies

We use HST NICMOS continuum and Pa-alpha observations to study the near-infrared and star-formation properties of a representative sample of 30 local (d ~ 35-75Mpc) luminous infrared galaxies (LIRGs, infrared 8-1000um luminosities of L_IR=11-11.9[Lsun]). The data provide spatial resolutions of 25-50pc and cover the central ~3.3-7.1kpc regions of these galaxies. About half of the LIRGs show compact (~1-2kpc) Pa-alpha emission with a high surface brightness in the form of nuclear emission, rings, and mini-spirals. The rest of the sample show Pa-alpha emission along the disk and the spiral arms extending over scales of 3-7kpc and larger. About half of the sample contains HII regions with H-alpha luminosities significantly higher than those observed in normal galaxies. There is a linear empirical relationship between the mid-IR 24um and hydrogen recombination (extinction-corrected Pa-alpha) luminosity for these LIRGs, and the HII regions in the central part of M51. This relation holds over more than four decades in luminosity suggesting that the mid-IR emission is a good tracer of the star formation rate (SFR). Analogous to the widely used relation between the SFR and total IR luminosity of Kennicutt (1998), we derive an empirical calibration of the SFR in terms of the monochromatic 24um luminosity that can be used for luminous, dusty galaxies.Comment: Accepted for publication in ApJ. Contact first author for high qualitity version of figure

CALIFA : a diameter-selected sample for an integral field spectroscopy galaxy survey

JMA acknowledges support from the European Research Council Starting Grant (SEDmorph; P.I. V. Wild).We describe and discuss the selection procedure and statistical properties of the galaxy sample used by the Calar Alto Legacy Integral Field Area (CALIFA) survey, a public legacy survey of 600 galaxies using integral field spectroscopy. The CALIFA "mother sample" was selected from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalogue to include all galaxies with an r-band isophotal major axis between 45 '' and 79 : 2 '' and with a redshift 0 : 005 M-r > -23 : 1 and over a stellar mass range between 10(9.7) and 10(11.4) M-circle dot. In particular, within these ranges, the diameter selection does not lead to any significant bias against - or in favour of - intrinsically large or small galaxies. Only below luminosities of M-r = -19 (or stellar masses <10(9.7) M-circle dot) is there a prevalence of galaxies with larger isophotal sizes, especially of nearly edge-on late-type galaxies, but such galaxies form <10% of the full sample. We estimate volume-corrected distribution functions in luminosities and sizes and show that these are statistically fully compatible with estimates from the full SDSS when accounting for large-scale structure. For full characterization of the sample, we also present a number of value-added quantities determined for the galaxies in the CALIFA sample. These include consistent multi-band photometry based on growth curve analyses; stellar masses; distances and quantities derived from these; morphological classifications; and an overview of available multi-wavelength photometric measurements. We also explore different ways of characterizing the environments of CALIFA galaxies, finding that the sample covers environmental conditions from the field to genuine clusters. We finally consider the expected incidence of active galactic nuclei among CALIFA galaxies given the existing pre-CALIFA data, finding that the final observed CALIFA sample will contain approximately 30 Sey2 galaxies.Peer reviewe

Analysis of the Interaction Effects in the Southern Galaxy Pair Tol1238-364 and ESO381-G009

In the context of the connection among galaxy-galaxy interaction, starbursts and nuclear activity, we present and discuss a quantitative morphological analysis based on BVR images and a detailed spectroscopic investigation of two interacting galaxies, the Seyfert 2 Tol1238-364 (IC 3639) and its companion ESO381-G009, forming a triple system with ESO381-G006. Broad-band optical photometry is complemented by Halpha imaging, which provides information about the distribution of star forming regions across the galaxies. Long-slit spectroscopic data obtained at different position angles of the slit are employed to determine the physical conditions of circumnuclear and extranuclear regions. A mixture of thermal and non-thermal ionizing radiation is found in the surroundings of the nucleus of Tol1238-364 and the energy budget supports the presence of a circumnuclear starburst.Several regions in both the galaxies show anomalous line ratios: additional ionization by shock-heating and low ionization of some extranuclear HII regions are suggested as possible explanations. An analysis of the emission-line profiles reveals the presence of a broad Halpha component in the nuclear region of Tol1238-364. Independent estimates of the star formation rates (SFR) were obtained through flux-calibrated Halpha-images and FIR emission in the four IRAS bands. Overall SFR densities have been compared with the SFR densities derived from Halpha emission in the individual regions of the galaxies sampled by long-slit spectra. In both galaxies an enhancement of the star formation activity with respect to isolated galaxies is revealed. The prevalence of starburst or nuclear activity has been examined through FIR color indices. The interaction scenario is discussed on the basis of the observed galaxy properties.Comment: Tentatively scheduled for publication in ApJS, v184 n2 October 2003 issue. A version with full resolution figures is available as unedited preprint at http://www.journals.uchicago.edu/ApJ/future.htm

CALIFA, the Calar Alto Legacy Integral Field Area survey: I. Survey presentation

We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction.We summarize the survey goals and design, including sample selection and observational strategy.We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of $\sim600$ galaxies in the Local Universe (0.005< z <0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK Integral Field Unit (IFU), with a hexagonal field-of-view of \sim1.3\sq\arcmin', with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 {\AA}, using two overlapping setups (V500 and V1200), with different resolutions: R\sim850 and R\sim1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis. We conclude from this first look at the data that CALIFA will be an important resource for archaeological studies of galaxies in the Local Universe.Comment: 32 pages, 29 figures, Accepted for publishing in Astronomy and Astrophysic

The Pierre Auger Observatory III: Other Astrophysical Observations

Astrophysical observations of ultra-high-energy cosmic rays with the Pierre Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference, Beijing, China, August 201

Operations of and Future Plans for the Pierre Auger Observatory

Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200

Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies $E>E_{th}=5.5\times 10^{19}$ eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at $E>E_{th}$ are heavy nuclei with charge $Z$, the proton component of the sources should lead to excesses in the same regions at energies $E/Z$. We here report the lack of anisotropies in these directions at energies above $E_{th}/Z$ (for illustrative values of $Z=6,\ 13,\ 26$). If the anisotropies above $E_{th}$ are due to nuclei with charge $Z$, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies

Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV

We describe the measurement of the depth of maximum, Xmax, of the longitudinal development of air showers induced by cosmic rays. Almost four thousand events above 10^18 eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/- 0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.Comment: Accepted for publication by PR