Effects of galaxy interactions in different environments

We analyse star formation rates derived from photometric and spectroscopic data of galaxies in pairs in different environments using the 2dF Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey (SDSS). The two samples comprise several thousand pairs, suitable to explore into detail the dependence of star formation activity in pairs on orbital parameters and global environment. We use the projected galaxy density derived from the fifth nearest neighbour of each galaxy, with convenient luminosity thresholds to characterise environment in both surveys in a consistent way. Star formation activity is derived through the $\eta$ parameter in 2dFGRS and through the star formation rate normalised to the total mass in stars, $SFR/M^*$, given by Brinchmann et al. (2004) in the second data release SDSS-DR2. For both galaxy pair catalogs, the star formation birth rate parameter is a strong function of the global environment and orbital parameters. Our analysis on SDSS pairs confirms previous results found with the 2dFGRS where suitable thresholds for the star formation activity induced by interactions are estimated at a projected distance r_{\rm p} = 100 \kpc and a relative velocity $\Delta V = 350$ km $s^{-1}$. We observe that galaxy interactions are more effective at triggering important star formation activity in low and moderate density environments with respect to the control sample of galaxies without a close companion. Although close pairs have a larger fraction of actively star-forming galaxies, they also exhibit a greater fraction of red galaxies with respect to those systems without a close companion, an effect that may indicate that dust stirred up during encounters could be affecting colours and, partially, obscuring tidally-induced star formation.Comment: accepted MNRA

The orientation of galaxy pairs with filamentary structures: dependence on morphology

Aims. With the aim of performing an analysis of the orientations of galaxy pair systems with respect to the underlying large-scale structure, we study the alignment between the axis connecting the pair galaxies and the host cosmic filament where the pair resides. In addition, we analyze the dependence of the amplitude of the alignment on the morphology of pair members as well as filament properties. Methods. We build a galaxy pair catalog requiring r_p < 100\kpc and \Delta V < 500 \kms within redshift $z<0.1$ from the Sloan Digital Sky Survey (SDSS). We divided the galaxy pair catalog taking into account the morphological classification by defining three pair categories composed by elliptical-elliptical (E-E), elliptical-spiral (E-S) and spiral-spiral (S-S) galaxies. We use a previously defined catalog of filaments obtained from SDSS and we select pairs located closer than 1\mpc from the filament spine, which are considered as members of filaments. For these pairs, we calculate the relative angle between the axis connecting each galaxy, and the direction defined by the spine of the parent filament. Results. We find a statistically significant alignment signal between the pair axes and the spine of the host filaments consistent with a relative excess of $\sim$ 15\% aligned pairs. We obtain that pairs composed by elliptical galaxies exhibit a stronger alignment, showing a higher alignment signal for pairs closer than 200 \kpc to the filament spine. In addition, we find that the aligned pairs are associated with luminous host filaments populated with a high fraction of elliptical galaxies. The findings of this work show that large scale structures play a fundamental role in driving galactic anisotropic accretion as induced by galaxy pairs exhibiting a preferred alignment along the filament direction.Comment: 8 pages, 6 figures. Accepted for publication in A&

AGNs and galaxy interactions

We perform a statistical analysis of AGN host characteristics and nuclear activity for AGNs in pairs and without companions. Our study concerns a sample of AGNs derived from the SDSS-DR4 data by Kauffmann et al (2003) and pair galaxies obtained from the same data set by Alonso et al. (2006). An eye-ball classification of images of 1607 close pairs ($r_p<25$ kpc $h^{-1}$, $\Delta V<350$ km $s^{-1}$) according to the evidence of interaction through distorted morphologies and tidal features provides us with a more confident assessment of galaxy interactions from this sample. We notice that, at a given luminosity or stellar mass content, the fraction of AGNs is larger for pair galaxies exhibiting evidence for strong interaction and tidal features which also show sings of strong star formation activity. Nevertheless, this process accounts only for a $\sim 10$ increase of the fraction of AGNs. As in previous works, we find AGN hosts to be redder and with a larger concentration morphological index than non-AGN galaxies. This effect does not depend whether AGN hosts are in pairs or in isolation. The OIII luminosity of AGNs with strong interaction features is found to be significantly larger than that of other AGNs, either in pairs or in isolation. Estimations of the accretion rate, $L[OIII]/M_{BH}$, show that AGNs in merging pairs are actively feeding their black holes, regardless of their stellar masses. We also find that the luminosity of the companion galaxy seems to be a key parameter in the determination of the black hole activity. At a given host luminosity, both the OIII luminosity and the $L[OIII]/M_{BH}$ are significantly larger in AGNs with a bright companion ($M_r < -20$) than otherwise.Comment: 9 pages, 9 figures, accepted MNRA

The mass-metallicity relation of interacting galaxies

We study the mass-metallicity relation of galaxies in pairs and in isolation taken from the SDSS-DR4 using the stellar masses and oxygen abundances derived by Tremonti et al. (2004). Close galaxy pairs, defined by projected separation r_p < 25kpc/h and radial velocity Delta_V < 350 km/s, are morphologically classified according to the strength of the interaction signs. We find that only for pairs showing signs of strong interactions, the mass-metallicity relation differs significantly from that of galaxies in isolation. In such pairs, the mean gas-phase oxygen abundances of galaxies with low stellar masses (Mstar ~< 10^9 Msun/h) exhibit an excess of 0.2 dex. Conversely, at larger masses (Mstar >~ 10^10 Msun/h) galaxies have a systematically lower metallicity, although with a smaller difference (-0.05 dex). Similar trends are obtained if g-band magnitudes are used instead of stellar masses. In minor interactions, we find that the less massive member is systematically enriched, while a galaxy in interaction with a comparable stellar mass companion shows a metallicity decrement with respect to galaxies in isolation. We argue that metal-rich starbursts triggered by a more massive component, and inflows of low metallicity gas induced by comparable or less massive companion galaxies, provide a natural scenario to explain our findings.Comment: Accepted for publication in MNRAS Letter

Galaxy Pairs in the 2dF Survey I. Effects of Interactions in the Field

We study galaxy pairs in the field selected from the 100 K public release of the 2dF galaxy redshift survey. Our analysis provides a well defined sample of 1258 galaxy pairs, a large database suitable for statistical studies of galaxy interactions in the local universe, $z \le 0.1$. Galaxy pairs where selected by radial velocity ($\Delta V$) and projected separation ($r_{\rm p}$) criteria determined by analyzing the star formation activity within neighbours (abridged). The ratio between the fractions of star forming galaxies in pairs and in isolation is a useful tools to unveil the effects of having a close companion. We found that about fifty percent of galaxy pairs do not show signs of important star formation activity (independently of their luminosities) supporting the hypothesis that the internal properties of the galaxies play a crucial role in the triggering of star formation by interactions.Comment: 9 pages, 11 Postscript figures. Submitted to MNRAS. Revised versio

The dilution peak, metallicity evolution, and dating of galaxy interactions and mergers

Strong inflows of gas from the outer disk to the inner kiloparsecs are induced during the interaction of disk galaxies. This inflow of relatively low-metallicity gas dilutes the metallicity of the circumnuclear gas. We have investigated several aspects of the process as the timing and duration of the dilution and its correlation with the induced star formation. We analysed major (1:1) gas-rich interactions and mergers, spanning a range of initial orbital characteristics. Star formation and metal enrichment from SNe are included in our model. Our results show that the strongest trend is between the star formation rate and the dilution of the metals in the nuclear region; i.e., the more intense the central burst of star formation, the more the gas is diluted. This trend comes from strong inflows of relatively metal-poor gas from the outer regions of both disks, which fuels the intense star formation and lowers the overall metallicity for a time. The strong inflows happen on timescales of about 10^8 years or less, and the most intense star formation and lowest gas phase metallicities are seen generally after the first pericentre passage. As the star formation proceeds and the merger advances, the dilution reduces and enrichment becomes dominant - ultimately increasing the metallicity of the circumnuclear gas to a level higher than the initial metallicities of the merging galaxies. The "fly-bys" - pairs that interact but do not merge - also cause some dilution. We even see some dilution early in the merger or in the "fly-bys" and thus do not observe a strong trend between the nuclear metallicities and separation in our simulations until the merger is well advanced. We also analyse the O and Fe enrichment of the ISM, and show that the evolution of the alpha/Fe ratios, as well as the dilution of the central gas metallicity, can be used as a clock for "dating" the interaction.Comment: 13 pages, 11 figures, A&A in press. Final version after language editin

Patient safety walkrounds with hospital managers: a tool for improving the care of critical patients

Introducción y Objetivos: 1) Describir el proceso de implantación de las Rondas de Seguridad (RS) con Directivos en el área de Cuidados Intensivos de un hospital de tercer nivel; 2) Analizar si hubo diferencias entre las RS en la Unidad de Cuidados Intensivos de adultos (UCI) y la Unidad de Cuidados Intensivos pediátrica (UCIp); 3) Conocer las opiniones de los participantes sobre la herramienta utilizada. Metodología: Estudio analítico longitudinal realizado entre 2009 y 2011. Se utilizó una hoja de registro compuesta por 6 ítems: 1) Presencia de pulsera identificativa; 2) Apósitos de las vías en buen estado; 3) Cabecera de la cama elevada a 30º; 4) Colchón adaptado a paciente con úlcera por presión; 5) Hoja de tratamiento médico sin dudas para enfermería y 6) Hoja de Objetivos Diarios cubierta. Se empleó el estadístico U-Mann Whitney para muestras no paramétricas. Resultados: Se observaron un total de 167 pacientes en 7 RS. La inicial de la UCI los ítems “colchón para paciente con úlceras por presión” y “hoja de objetivos diarios cubierta” registraban un cumplimiento inferior al 60%. En el caso de la UCIp se encontró el 0% de cumplimiento para la pulsera identificativa. Hubo diferencias estadísticamente significativas entre la UCI y la UCIp para los ítems anteriormente citados. Conclusión: Las RS con Directivos aplicadas a las UCI del Hospital Universitario Central de Asturias mejoraron aspectos importantes de Seguridad del Paciente. La implicación de los Directivos fue lo mejor valorado por parte de los profesionales y garantizó el éxito en la implantación de la herramienta.Objectives: 1) To describe the process of implementation of walkrounds with hospital managers in the Intensive Care Unit (ICU) at a tertiary hospital ; 2) To examine whether there were differences between the WR in the Adult Intensive Care Unit (AICU) and the Pediatric Intensive Care Unit (PICU ); 3) To know the opinion of the participants about the tool. Methodology: It is an analytic and longitudinal study done between 2009 and 2011. It was used a sheet with 6 items: 1) Presence of wristband ; 2) Dressings roads in good condition; 3) Headboard at 30º; 4) Special mattress adapted to patients with pressure ulcers ; 5 ) Sheet for medical treatments without any doubts for nurses and 6) Daily goal sheet fulfilled. It was used Statistical U Mann – Whitney for nonparametric samples. Results: A total of 167 patients were seen in 7. walkrounds At the beginning, items “mattress for patients with pressure ulcers” and “daily goal sheet fulfilled” had less than 60% of compliance in AICU. For the PICU, we found 0 % of compliance in the presence of wristband. There were statistically significant differences between the AICU and the PICU for those items. Conclusion: Walkrounds with hospital managers applied to ICUs at our hospital improved important aspects of patient safety. The involvement of hospital managers was the most important thing for the rest of health care workers and it ensured the successful implementation of the tool

Prevalence and distribution of infectious and parasitic agents in roe deer from Spain and their possible role as reservoirs

In order to provide up-to-date information about the prevalence of infectious and parasitic agents in Spanish roe deer (Capreolus capreolus), samples from 93 animals hunted from January 2013 to April 2015 were collected and analysed by parasitological, serological and molecular techniques. Sampled animals came from four roe deer populations corresponding to Oceanic, Continental, Mediterranean and Mountainous ecosystems of Spain. Data regarding sex, age and year were also considered. A high percentage of roe deer (95.7%) resulted positive for at least one agent. Sarcocystis spp. was the most frequently diagnosed genus (88.8%), followed by gastrointestinal nematodes (62.9%) and Schmallenberg virus (53.5%). Varestrongylus capreoli (38%), Anaplasma phagocitophylum (34.2%), Eimeria spp. (29.2%), Toxoplasma gondii (25%) and Cephenemyia stimulator (23.8%) displayed medium prevalences and, finally low percentages were registered for Moniezia spp. (6.7%), Dictyocaulus noerneri (2.4%) and Mycobacterium avium subsp. paratuberculosis (1.5%). No infections by Neospora caninum, Bovine herpesvirus, pestivirus or Coxiella burnetii were found. Climate was significantly associated with the prevalence of T. gondii, C. stimulator and A. phagocitophylum, with higher prevalences in animals from Oceanic and Mediterranean areas. Our results suggest that infections affecting Spanish roe deer, especially those of parasitic aetiology, represent one of the causes of the descent in the abundance of this ungulate in the last years. Moreover, the high prevalence of zoonotic agents such as T. gondii and A. phagocitophylum could also have a great relevance in the environmental and/or Public Health.This research was supported by a Programme for consolidating and structuring competitive research groups (GRC2015/003, Xunta de Galicia) and by the Research Project ‘RUMIGAL: Rede de estudo multidisciplinar dos ruminantes en Galicia’ (R2014/005, Xunta de Galicia, Spain)S