Empirical Tests Of Optimal Cognitive Distance

This article provides empirical tests of the hypothesis of ‘optimal cognitive distance’, proposed by Nooteboom (1999, 2000), in two distinct empirical settings. Variety of cognition, needed for learning, has two dimensions: the number of agents with different cognition, and differences in cognition between them (cognitive distance). The hypothesis is that in interfirm relationships optimal learning entails a trade-off between the advantage of increased cognitive distance for a higher novelty value of a partner’s knowledge, and the disadvantage of less mutual understanding. If the value of learning is the mathematical product of novelty value and understandability, it has an inverse-U shaped relation with cognitive distance, with an optimum level that yields maximal value of learning. With auxiliary hypotheses, the hypothesis is tested on interfirm agreements between pharmaceutical companies and biotech companies, as well as on interfirm agreements in ICT industries.innovation;organizational learning;ICT;biotechnology;alliances

Probing Individual Star Forming Regions Within Strongly Lensed Galaxies at z > 1

Star formation occurs on physical scales corresponding to individual star forming regions, typically of order ~100 parsecs in size, but current observational facilities cannot resolve these scales within field galaxies beyond the local universe. However, the magnification from strong gravitational lensing allows us to measure the properties of these discrete star forming regions within galaxies in the distant universe. New results from multi-wavelength spectroscopic studies of a sample of extremely bright, highly magnified lensed galaxies are revealing the complexity of star formation on sub-galaxy scales during the era of peak star formation in the universe. We find a wide range of properties in the rest-frame UV spectra of individual galaxies, as well as in spectra that originate from different star forming regions within the same galaxy. Large variations in the strengths and velocity structure of Lyman-alpha and strong P Cygni lines such as C IV, and MgII provide new insights into the astrophysical relationships between extremely massive stars, the elemental abundances and physical properties of the nebular gas those stars ionize, and the galactic-scale outflows they power.Comment: 4 pages, 3 figures. To be published in the Proceedings of IAU Symposium 309. For more details and closely related work see also arXiv:1310.6695 and arXiv:1406.335

On the lack of correlation between Mg II 2796, 2803 Angstrom and Lyman alpha emission in lensed star-forming galaxies

We examine the Mg II 2796, 2803 Angstrom, Lyman alpha, and nebular line emission in five bright star-forming galaxies at 1.66<z<1.91 that have been gravitationally lensed by foreground galaxy clusters. All five galaxies show prominent Mg II emission and absorption in a P Cygni profile. We find no correlation between the equivalent widths of Mg II and Lyman alpha emission. The Mg II emission has a broader range of velocities than do the nebular emission line profiles; the Mg II emission is redshifted with respect to systemic by 100 to 200 km/s. When present, Lyman alpha is even more redshifted. The reddest components of Mg II and Lyman alpha emission have tails to 500-600 km/s, implying a strong outflow. The lack of correlation in the Mg II and Lyman alpha equivalent widths, the differing velocity profiles, and the high ratios of Mg II to nebular line fluxes together suggest that the bulk of Mg II emission does not ultimately arise as nebular line emission, but may instead be reprocessed stellar continuum emission.Comment: The Astrophysical Journal, in press. 6 pages, 2 figure

Tropical tree cover in a heterogeneous environment: a reaction-diffusion model

This is the final version. Available from Public Library of Science via the DOI in this record.Observed bimodal tree cover distribution sat particular environmental conditions and theoretical models indicate that some areas in the tropics can be in either of the alternative stable vegetation states forest or savanna.However,when including spatial interaction in nonspatial differential equation models of a bistable quantity, only the state with the lowest potential energy remains stable. Our recent reaction-diffusion model of Amazonian tree cover confirmed this and was able to reproduce the observed spatial distribution of forest versus savanna satisfactorily when forced by heterogeneous environmental and anthropogenic variables, even though bistability was underestimated. These conclusions were solely based on simulation results for one set of parameters. Here, we perform ananalytical and numerical analysis of the model. We derive the Maxwell point (MP) of the homogeneous reaction-diffusion equation without savanna trees as a function of rainfall and human impact and show that the front between forest and nonforest settles at this point as long as savanna tree cover near the front remains sufficiently low. For parameters resulting in higher savanna tree cover near the front, we also find irregular forest-savanna cycles and woodland-savanna bistability, which can both explain the remaining observed bimodality.EPSR

Stellar Populations of Highly Magnified Lensed Galaxies: Young Starbursts at z~2

We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at z=1.70, MS1512-cB58 at z=2.73, SGAS J152745.1+065219 at z=2.76 and SGAS J122651.3+215220 at z=2.92. This includes new Spitzer imaging for RCSGA0327 as well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226. Lensing magnifications of 3-4 magnitudes allow a detailed study of the stellar populations and physical conditions. We compare star formation rates as measured from the SED fit, the H-alpha and [OII] emission lines, and the UV+IR bolometric luminosity where 24 micron photometry is available. The SFR estimate from the SED fit is consistently higher than the other indicators, which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z~2. Our analysis finds similar stellar population parameters for all four lensed galaxies: stellar masses 3-7*10^9 M_sun, young ages ~ 100 Myr, little dust content E(B-V)=0.10-0.25, and star formation rates around 20-100 M_sun/yr. Compared to typical values for the galaxy population at z~2, this suggests we are looking at newly formed, starbursting systems that have only recently started the build-up of stellar mass. These results constitute the first detailed, uniform analysis of a sample of the growing number of strongly lensed galaxies known at z~2.Comment: 13 pages, 8 figures, Accepted to Ap

Spatially Resolved Galactic Wind in Lensed Galaxy RCSGA 032727-132609

We probe the spatial distribution of outflowing gas along four lines of sight separated by up to 6 kpc in a gravitationally-lensed star-forming galaxy at z=1.70. Using MgII and FeII emission and absorption as tracers, we find that the clumps of star formation are driving galactic outflows with velocities of -170 to -250 km/sec. The velocities of MgII emission are redshifted with respect to the systemic velocities of the galaxy, consistent with being back-scattered. By contrast, the FeII fluorescent emission lines are either slightly blueshifted or at the systemic velocity of the galaxy. Taken together, the velocity structure of the MgII and FeII emission is consistent with arising through scattering in galactic winds. Assuming a thin shell geometry for the out owing gas, the estimated masses carried out by these outfows are large (> 30 - 50 $\rm{M_{\odot} yr^{-1}}$), with mass loading factors several times the star-formation rate. Almost 20% to 50% of the blueshifted absorption probably escapes the gravitational potential of the galaxy. In this galaxy, the outflow is "locally sourced", that is, the properties of the outflow in each line of sight are dominated by the properties of the nearest clump of star formation; the wind is not global to the galaxy. The mass outflow rates and the momentum flux carried out by outflows in individual star forming knots of this object are comparable to that of starburst galaxies in the local Universe.Comment: 19 pages, 10 figure, accepted for publication in MNRA

FIREWORKS U38-to-24 micron photometry of the GOODS-CDFS: multi-wavelength catalog and total IR properties of distant Ks-selected galaxies

We present a Ks-selected catalog, dubbed FIREWORKS, for the Chandra Deep Field South (CDFS) containing photometry in U_38, B_435, B, V, V_606, R, i_775, I, z_850, J, H, Ks, [3.6 um], [4.5 um], [5.8 um], [8.0 um], and the MIPS [24 um] band. The imaging has a typical Ks limit of 24.3 mag (5 sigma, AB) and coverage over 113 arcmin^2 in all bands and 138 arcmin^2 in all bands but H. We cross-correlate our catalog with the 1 Ms X-ray catalog by Giacconi et al. (2002) and with all available spectroscopic redshifts to date. We find and explain systematic differences in a comparison with the 'z_850 + Ks'-selected GOODS-MUSIC catalog that covers ~90% of the field. We exploit the U38-to-24 micron photometry to determine which Ks-selected galaxies at 1.5<z<2.5 have the brightest total IR luminosities and which galaxies contribute most to the integrated total IR emission. The answer to both questions is that red galaxies are dominating in the IR. This is true no matter whether color is defined in the rest-frame UV, optical, or optical-to-NIR. We do find however that among the reddest galaxies in the rest-frame optical, there is a population of sources with only little mid-IR emission, suggesting a quiescent nature.Comment: Accepted for publication in the Astrophysical Journal, 20 pages, 10 figures, reference to website correcte

The Mass Distribution of the Strong Lensing Cluster SDSS J1531+3414

We present the mass distribution at the core of SDSS J1531+3414, a strong-lensing cluster at z=0.335. We find that the mass distribution is well described by two cluster-scale halos with a contribution from cluster-member galaxies. New HST observations of SDSS J1531+3414 reveal a signature of ongoing star formation associated with the two central galaxies at the core of the cluster, in the form of a chain of star forming regions at the center of the cluster. Using the lens model presented here, we place upper limits on the contribution of a possible lensed image to the flux at the center region, and rule out that this emission is coming from a background source.Comment: 8 pages, 5 figures; Submitted to Ap