What determines large scale galaxy clustering: halo mass or local density?

Using dark matter simulations we show how halo bias is determined by local density and not by halo mass. This is not totally surprising, as according to the peak-background split model, local density is the property that constraints bias at large scales. Massive haloes have a high clustering because they reside in high density regions. Small haloes can be found in a wide range of environments which determine their clustering amplitudes differently. This contradicts the assumption of standard Halo Occupation Distribution (HOD) models that the bias and occupation of haloes is determined solely by their mass. We show that the bias of central galaxies from semi-analytic models of galaxy formation as a function of luminosity and colour is not correctly predicted by the standard HOD model. Using local density instead of halo mass the HOD model correctly predicts galaxy bias. These results indicate the need to include information about local density and not only mass in order to correctly apply HOD analysis in these galaxy samples. This new model can be readily applied to observations and has the advantage that the galaxy density can be directly observed, in contrast with the dark matter halo mass.Comment: 11 pages, 9 figure

A disaggregated view of the cyclical developments in euro area investment

Artículo de revist

Development of the Red Sequence in Galaxy Clusters

We investigate the origin of the color-magnitude relation (CMR) observed in cluster galaxies by using a combination of a cosmological N-body simulation of a cluster of galaxies and a semi-analytic model of galaxy formation. The departure of galaxies in the bright end of the CMR with respect to the trend defined by less luminous galaxies could be explained by the influence of minor mergers.Comment: Proceedings IAU Symposium No. 267, 2009. Co-Evolution of Central Black Holes and Galaxie

Chess to work patterns in mathematics in Primary Education

Presentamos una propuesta para integrar algunos elementos del ajedrez en la enseñanza y aprendizaje de las matemáticas en segundo y tercer curso de Educación Prima- ria. En particular se orienta hacia el reconocimiento de patrones geométricos y numéricos

Collaboration and Citation Analysis Within Social Sciences: A Comparative Analysis Between Two Fields

The present study focuses on a collaboration of a citation analysis of the JCR journals of the categories Demography and Urban Studies indexed in Social Science Citation Index from the period 2000–2016. A total of 64 journals were covered (26 for Demography and 38 for Urban Studies). We found that the percentages of multi-authored documents in both categories are very similar; moreover, the citation distribution is shown to be increasing in both but behaves slightly different in the two samples analysed. It seems to be a relation between the number of citations a document received and the number of authors. Regarding international collaboration, both categories present a similar type of network with densities of the kind of social science networks. Anglo-Saxon countries are the most prolific ones and the biggest collaborators in both networks. Urban Studies shows a relative importance to countries of emerging economies since it indexed more journals in the sample with a wider regional scope

Credit allocation along the business cycle : evidence from the latest boom bust credit cycle in Spain

En este trabajo se explota una base de datos que fusiona la información sobre peticiones de crédito de la Central de Información de Riesgos con los estados contables de las empresas, mostrándose evidencia de que, durante la gran recesión que se inició en 2008, el acceso al crédito de las empresas españolas que presentaban una situación financiera más débil se deterioró en comparación con el del resto de empresas. Sin embargo, en contra de lo que indica la teoría del acelerador financiero, se encuentra que, durante la etapa de recuperación económica tras la última recesión, el acceso al crédito de las empresas con una situación financiera más débil no mejoró en relación con el del resto de compañías e incluso se deterioró algo. También se aporta evidencia empírica de que las políticas crediticias de los bancos con las empresas con las que mantenían relaciones crediticias previas son comparativamente menos sensibles a la información pública que aquellas aplicadas a las empresas con las que no mantenían relaciones previas. Este resultado, junto con la correlación positiva entre el acceso al crédito bancario de las empresas y el número de relaciones bancarias de estas, podría estar vinculado a la existencia de información privada adquirida por los bancos a lo largo de sus interacciones con sus deudores. Por último, también se encuentra que la existencia de estas relaciones entre deudores y acreedores habría contribuido a moderar la contracción del crédito durante la crisisUsing a dataset that merges information of loan applications from the Spanish CCR with firms’ financial accounts, we find that during the great recession access to credit of firms with weak balance sheets deteriorated relative to other firms. However, contrary to the financial accelerator theory, we find that during the recovery phase after the latest recession access to credit of weaker firms did not improve relative to other firms and it even further deteriorated somewhat. We also provide empirical evidence that lending policies of banks with firms they are exposed to before the lending decision is taken are comparatively less sensitive to public information than those applied to new firms. This result, together with the positive correlation we find between firms’ access to bank loans and the number of firms’ bank credit relationships, might be linked to the existence of private information developed by banks through their interaction with borrowers. We also find that this relationship lending contributed to smooth credit contraction during the crisi

Chemical feedback from SNIa in isolated galaxies. The Single Degenerate Scenario

The nature of the Supernova Ia progenitors remains unknown. This is amajor issue for galactic chemical evolution models since both chemicaland energy feedback influence the evolution of baryons. The progenitormodels for the supernovae Ia available in the literature proposedifferent shapes for the function which regulates the explosion times ofthe SNIa. In this work, we include for in hydrodynamical simulations theSingle Degenerate scenario for supernova type Ia. We analyse theimplications for the chemical enrichment of galaxies. Our best scenariocan reproduce the [alpha /Fe] ratios for bulge-dominated type galaxies,the observed SNIa rates and the observed correlation between the thestar formation and the supernova Ia rates in galaxies.Fil: Jiménez, Noelia. Istituto Nazionale Di Astrofisica; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tissera, Patricia Beatriz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Matteucci, Francesca. Istituto Nazionale Di Astrofisica; Itali

Evolución de galaxias en cúmulos revelada a través de la relación color magnitud

En este Trabajo de Tesis se investigan los procesos involucrados en el desarrollo de la Relación Color Magnitud (RCM) de galaxias en cúmulos. Esta relación comprende galaxias de tipo temprano y corresponde a la secuencia roja (SR) observada en el plano color magnitud. La distribución de galaxias en este plano es bimodal en los colores y parte de las galaxias se distribuyen en una zona difusa llamada “nube azul”. La SR está formada mayormente por galaxias pobres en gas con baja formación estelar, prototípicamente galaxias de tipo temprano. Estas galaxias constituyen el objeto de estudio de la presente investigación y la relación color magnitud que las caracteriza será referida como RCM.Facultad de Ciencias Astronómicas y Geofísica

A constant market share analysis of the euro area in the period 1994-2007

Artículo de revist