Theory of Spin-Dependent Electron Transfer Dynamics at Ar/Co(0001) and Ar/Fe(110) Interfaces

Recent core-hole-clock experiments [Phys. Rev. Lett. $\textbf{112}$, 086801 (2014)] showed that the spin dependence of electron injection times at Ar/Co(0001) and Ar/Fe(110) interfaces is at variance with the expectations based on previous calculations for related systems. Here we reconcile theory and experiment, and demonstrate that the observed dependence is rooted in the details of the spin-split surface band structures. Our ab initio calculations back that minority electrons are injected significantly faster than majority electrons in line with the experimentally reported ultrashort injection times. The dynamics is particularly sensitive to the size (in reciprocal-space) of the projected band gaps around $\overline{\Gamma}$ for both substrates at the resonance energies. A simple tunneling model incorporating the spin-dependent gap sizes further supports these findings.Comment: 5+6 pages, 4+4 figure

The Herschel PACS photometer calibration - A time dependent flux calibration for the PACS chopped point-source photometry AOT mode

We present a flux calibration scheme for the PACS chopped point-source photometry observing mode based on the photometry of five stellar standard sources. This mode was used for science observations only early in the mission. Later, it was only used for pointing and flux calibration measurements. Its calibration turns this type of observation into fully validated data products in the Herschel Science Archive. Systematic differences in calibration with regard to the principal photometer observation mode, the scan map, are derived and amount to 5-6%. An empirical method to calibrate out an apparent response drift during the first 300 Operational Days is presented. The relative photometric calibration accuracy (repeatability) is as good as 1% in the blue and green band and up to 5% in the red band. Like for the scan map mode, inconsistencies among the stellar calibration models become visible and amount to 2% for the five standard stars used. The absolute calibration accuracy is therefore mainly limited by the model uncertainty, which is 5% for all three bands.Comment: 20 pages, 7 pages of appendix, 11 figures, accepted to appear in Experimental Astronomy, Special Issue for Herschel Calibrations based on the "Herschel Calibration Workshop: Only the Best Data Products for the Legacy Archive", held at ESAC, 25 - 27 March 2013, http://herschel.esac.esa.int/CalibrationWorkshop5.shtm

Broad-band and Hα surface photometry of the central regions of nearby active galaxies - I. Observations

This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Sánchez-Portal, M., Díaz, A.I., Terlevich, R., Terlevich, E., Álvarez Álvarez, M. and I. Aretxaga. Broad-band and Hα surface photometry of the central regions of nearby active galaxies - I. Observations. Monthly Notices of the Royal Astronomical Society 312 (2000): 2-3

Filter-induced bias in Lyα emitter surveys: a comparison between standard and tunable filters. gran telescopio Canarias preliminary results

Lyα emitter (LAE) surveys have successfully used the excess in a narrowband filter compared to a nearby broadband image to find candidates. However, the odd spectral energy distribution (SED) of LAEs combined with the instrumental profile has important effects on the properties of the candidate samples extracted from these surveys. We investigate the effect of the bandpass width and the transmission profile of the narrowband filters used for extracting LAE candidates at redshifts z sime 6.5 through Monte Carlo simulations, and we present pilot observations to test the performance of tunable filters to find LAEs and other emission-line candidates. We compare the samples obtained using a narrow ideal rectangular filter, the Subaru NB921 narrowband filter, and sweeping across a wavelength range using the ultra-narrow-band tunable filters of the instrument OSIRIS, installed at the 10.4 m Gran Telescopio Canarias. We use this instrument for extracting LAE candidates from a small set of real observations. Broadband data from the Subaru, Hubble Space Telescope, and Spitzer databases were used for fitting SEDs to calculate photometric redshifts and to identify interlopers. Narrowband surveys are very efficient in finding LAEs in large sky areas, but the samples obtained are not evenly distributed in redshift along the filter bandpass, and the number of LAEs with equivalent widths <60 Å can be underestimated. These biased results do not appear in samples obtained using ultra-narrow-band tunable filters. However, the field size of tunable filters is restricted because of the variation of the effective wavelength across the image. Thus, narrowband and ultra-narrow-band surveys are complementary strategies to investigate high-redshift LAEs.This research has been partially funded by the UNAMDGAPA-PAPIIT IN110013 Program. J.A.D. and M.A.D. are grateful for support from CONACyT grant CB-128556. J.A.D. is grateful for support from grant SAB2010-0011 awarded by the Spanish MIED through the “Programa Nacional de Movilidad de Recursos Humanos” included in the Plan Nacional de I-D+i 2008-2011. T.V. acknowledges support from CONACYT grant 165365 through the program “Estancias posdoctorales y sabáticas al extranjero para la consolidación de grupos de investigación.” This work has been partially funded by the Spanish Ministry of Science and Innovation (MICINN) under the Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC (http://www.iac.es/consolider-ingenio-gtc), AYA2011-29517-C03-01, and AYA2011-29517-C03-02. Observations presented in this paper were made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma. The authors are thankful to the anonymous referee for the critical and constructive suggestion

San Pedro Martir observations of microvariability in obscured quasars

Fast brightness variations are a unique tool to probe the innermost regions of active galactic nuclei (AGN). These variations are called microvariability or intra-night variability, and this phenomenon has been monitored in samples of blazars and unobscured AGNs. Detecting optical microvariations in targets hidden by the obscuring torus is a challenging task because the region responsible for the variations is hidden from our sight. However, there have been reports of fast variations in obscured Seyfert galaxies in X-rays, which rises the question whether microvariations can also be detected in obscured AGNs in the optical regime. Because the expected variations are very small and can easily be lost within the noise, the analysis requires a statistical approach. We report the use of a one-way analysis of variance, ANOVA, with which we searched for microvariability. ANOVA was successfully employed in previous studies of unobscured AGNs. As a result, we found microvariable events during three observing blocks: in two we observed the same object (Mrk 477), and in another, J0759+5050. The results on Mrk 477 confirm previous findings. However, since Mrk 477 is quite a peculiar target with hidden broad-line regions, we cannot rule out the possibility that we have serendipitously chosen a target prone to variations.Comment: Research note, 5 pages, 2 figures, accepted for publication in Astronomy and Astrophysic

SPIRE Point Source Catalog Explanatory Supplement

The Spectral and Photometric Imaging Receiver (SPIRE) was launched as one of the scientific instruments on board of the space observatory Herschel. The SPIRE photometer opened up an entirely new window in the Submillimeter domain for large scale mapping, that up to then was very difficult to observe. There are already several catalogs that were produced by individual Herschel science projects. Yet, we estimate that the objects of only a fraction of these maps will ever be systematically extracted and published by the science teams that originally proposed the observations. The SPIRE instrument performed its standard photometric observations in an optically very stable configuration, only moving the telescope across the sky, with variations in its configuration parameters limited to scan speed and sampling rate. This and the scarcity of features in the data that require special processing steps made this dataset very attractive for producing an expert reduced catalog of point sources that is being described in this document. The Catalog was extracted from a total of 6878 unmodified SPIRE scan map observations. The photometry was obtained by a systematic and homogeneous source extraction procedure, followed by a rigorous quality check that emphasized reliability over completeness. Having to exclude regions affected by strong Galactic emission, that pushed the limits of the four source extraction methods that were used, this catalog is aimed primarily at the extragalactic community. The result can serve as a pathfinder for ALMA and other Submillimeter and Far-Infrared facilities. 1,693,718 sources are included in the final catalog, splitting into 950688, 524734, 218296 objects for the 250\mu m, 350\mu m, and 500\mu m bands, respectively. The catalog comes with well characterized environments, reliability, completeness, and accuracies, that single programs typically cannot provide

A morphological study of galaxies in ZwCl0024+1652, a galaxy cluster at redshift z ∼ 0.4

ABSTRACT: he well-known cluster of galaxies ZwCl0024+1652 at z ∼ 0.4 lacks an in-depth morphological classification of its central region. While previous studies provide a visual classification of a patched area, we used the public code called galaxy Support Vector Machine GALSVM) and HST/ACS data as well as the WFP2 master catalogue to automatically classify all cluster members up to 1 Mpc. GALSVM analyses galaxy morphologies through support vector machine (SVM). From the 231 cluster galaxies, we classified 97 as early types (ETs) and 83 as late types (LTs). The remaining 51 stayed unclassified (or undecided). By cross-matching our results with the existing visual classification, we found an agreement of 81 per cent. In addition to previous Zwcl0024 morphological classifications, 121 of our galaxies were classified for the first time in this work. In addition, we tested the location of classified galaxies on the standard morphological diagrams, colour–colour and colour–magnitude diagrams. Out of all cluster members, ∼20 per cent are emission-line galaxies, taking into account previous GLACE results. We have verified that the ET fraction is slightly higher near the cluster core and decreases with the clustercentric distance, while the opposite trend has been observed for LT galaxies. We found a higher fraction of ETs (54 per cent) than LTs (46 per cent) throughout the analysed central region, as expected. In addition, we analysed the correlation between the five morphological parameters (Abraham concentration, Bershady–Concelice concentration, asymmetry, Gini, and M20 moment of light) and the clustercentric distance, without finding a clear trend. Finally, as a result of our work, the morphological catalogue of 231 galaxies containing all the measured parameters and the final classification is available in the electronic form of this paper.MP also acknowledges support from the Spanish MINECO under projects AYA2013-42227-P and AYA2016-76682-C3-1-P- This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under the grants AYA2014-58861-C3-2-P, AYA2014-58861-C3-3-P, AYA2017-88007-C3-1-P, and AYA2017-88007-C3-2-P

Metallic thin films on stepped surfaces: lateral scattering of quantum well states

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.Quantum well states of Ag films grown on stepped Au(111) surfaces are shown to undergo lateral scattering, in analogy with surface states of vicinal Ag(111). Applying angle resolved photoemission spectroscopy we observe quantum well bands with zone-folding and gap openings driven by surface/interface step lattice scattering. Experiments performed on a curved Au(111) substrate allow us to determine a subtle terrace-size effect, i.e., a fine step-density-dependent upward shift of quantum well bands. This energy shift is explained as mainly due to the periodically stepped crystal potential offset at the interface side of the film. Finally, the surface state of the stepped Ag film is analyzed with both photoemission and scanning tunneling microscopy. We observe that the stepped film interface also affects the surface state energy, which exhibits a larger terrace-size effect compared to surface states of bulk vicinal Ag(111)crystals.This work was supported in part by the Spanish Ministry of Economy (MINECO) through grants MAT2013–46593-C6–2-P, MAT2013–46593-C6–4-P, MAT2013–46593-C6–5-P, and FIS2010–19609-C02–02, by the German Sonderforschungsbereich SFB 1083, and by the Basque Government through Projects IT-621–13 and IT-756–13. ICN2 acknowledges support from the Severo Orchoa Program (MINECO, Grant SEV-2013-0295).Peer Reviewe