From blue star-forming to red passive: galaxies in transition in different environments

Exploiting a mass complete (M_*>10^(10.25)M_sun) sample at 0.03<z<0.11 drawn from the Padova Millennium Galaxy Group Catalog (PM2GC), we use the (U-B)_rf color and morphologies to characterize galaxies, in particular those that show signs of an ongoing or recent transformation of their star formation activity and/or morphology - green galaxies, red passive late types, and blue star-forming early types. Color fractions depend on mass and only for M_*<10^(10.7)M_sun on environment. The incidence of red galaxies increases with increasing mass, and, for M_*<10^(10.7)M_sun, decreases toward the group outskirts and in binary and single galaxies. The relative abundance of green and blue galaxies is independent of environment, and increases monotonically with galaxy mass. We also inspect galaxy structural parameters, star-formation properties, histories and ages and propose an evolutionary scenario for the different subpopulations. Color transformations are due to a reduction and suppression of SFR in both bulges and disks which does not noticeably affect galaxy structure. Morphological transitions are linked to an enhanced bulge-to-disk ratio due to the removal of the disk, not to an increase of the bulge. Our modeling suggests that green colors might be due to star formation histories declining with long timescales, as an alternative scenario to the classical "quenching" processes. Our results suggest that galaxy transformations in star formation activity and morphology depend neither on environment nor on being a satellite or the most massive galaxy of a halo. The only environmental dependence we find is the higher fast quenching efficiency in groups giving origin to post-starburst signatures.Comment: 20 pages, 12 figures, accepted for publication in Ap

The star formation history of galaxies: the role of galaxy mass, morphology and environment

We analyze the star formation history (SFH) of galaxies as a function of present-day environment, galaxy stellar mass and morphology. The SFH is derived by means of a non-parametric spectrophotometric model applied to individual galaxies at z ~ 0.04- 0.1 in the WINGS clusters and the PM2GC field. The field reconstructed evolution of the star formation rate density (SFRD) follows the values observed at each redshift (Madau & Dickinson 2014), except at z > 2 where our estimate is ~ 1.7x higher than the high-z observed value. The slope of the SFRD decline with time gets progressively steeper going from low mass to high mass haloes. The decrease of the SFRD since z = 2 is due to 1) quenching - 50% of the SFRD in the field and 75% in clusters at z > 2 originated in galaxies that are passive today - and 2) the fact that the average SFR of today's star-forming galaxies has decreased with time. We quantify the contribution to the SFRD(z) of galaxies of today's different masses and morphologies. The current morphology correlates with the current star formation activity but is irrelevant for the past stellar history. The average SFH depends on galaxy mass, but galaxies of a given mass have different histories depending on their environment. We conclude that the variation of the SFRD(z) with environment is not driven by different distributions of galaxy masses and morphologies in clusters and field, and must be due to an accelerated formation in high mass haloes compared to low mass ones even for galaxies that will end up having the same galaxy mass today.Comment: 16 pages, 10 figures. Published on MNRA

Present day background of nitrate as a methodology in the surface water - groundwater interaction applied in southeastern Buenos Aires province, Argentina

La contaminación con nitrato en agua superficial y subterránea es un problema mundial vinculado especialmente con la intensa actividad agrícola. Las concentraciones elevadas afectan la calidad de las aguas y resulta ser un indicador importante de la influencia del hombre. En un acuífero libre de una cuenca de llanura en el sudeste bonaerense en Argentina se midieron 4-235 mg/L en octubre 2013 y 5,7-250 mg/L en julio 2014. Respecto a los tenores en el agua superficial se midieron concentraciones de 7–79,6 mg/L durante octubre 2013-julio 2014 y 1–120 mg/L de julio 2014 a abril 2015. Se calcularon los valores de Fondo Actual del acuífero mediante un análisis estadístico y se los comparó para monitorear sus variaciones. En cuanto al agua superficial, se calcularon sus variaciones de Fondo Actual en los dos periodos para cotejarlos con el acuífero. A partir de los resultados se propone una nueva metodología para analizar la vinculación agua superficial-subterránea.Nitrate contamination of surface and groundwater is a global problem which is related to the intense agricultural activity. The high concentrations affect the waters quality and it turns out to be an important indicator of the human influence. In the phreatic aquifer in a plain basin in southeastern Buenos Aires province of Argentina, nitrate has values between 4 and 235 mg/L measured in October 2013 and 5.7-250 mg/L in July 2014. Respect to the values in surface water, were measured concentrations of 7-79, 6 mg/L during October 2013-July 2014 and 1-120 mg/L from July 2014 to April 2015. The present day background values found in the aquifer were calculated through a statistical analysis and compared to monitor their variations. Also, were calculated in the two periods the present day background superficial water to compare them with the aquifer. Based on the results, a new methodology is proposed to analyze the surface-groundwater linkage.Fil: Calvi, Carolina Maria Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Dapeña, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Martinez, Daniel Emilio. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Geología de Costas y del Cuaternario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Geología de Costas y del Cuaternario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Slowly expanding lesions relate to persisting black-holes and clinical outcomes in relapse-onset multiple sclerosis

Black holes; Chronic active lesions; Volumetric MRIAgujeros negros; Lesiones activas crónicas; Resonancia magnética volumétricaForats negres; Lesions actives cròniques; Ressonància magnètica volumètricaBackground Slowly expanding lesions (SELs) are MRI markers of chronic active lesions in multiple sclerosis (MS). T1-hypointense black holes, and reductions in magnetization transfer ratio (MTR) are pathologically correlated with myelin and axonal loss. While all associated with progressive MS, the relationship between these lesion’s metrics and clinical outcomes in relapse-onset MS has not been widely investigated. Objectives To explore the relationship of SELs with T1-hypointense black holes, and longitudinal T1 intensity contrast ratio and MTR, their correlation to brain volume, and their contribution to MS disability in relapse-onset patients. Methods 135 patients with relapsing-remitting MS (RRMS) were studied with clinical assessments and brain MRI (T2/FLAIR and T1-weighted scans at 1.5/3 T) at baseline and two subsequent follow-ups; a subset of 83 patients also had MTR acquisitions. Early-onset patients were defined when the baseline disease duration was ≤ 5 years (n = 85). SELs were identified using deformation field maps from the manually segmented baseline T2 lesions and differentiated from the non-SELs. Persisting black holes (PBHs) were defined as a subset of T2 lesions with a signal below a patient-specific grey matter T1 intensity in a semi-quantitative manner. SELs, PBH counts, and brain volume were computed, and their associations were assessed through Spearman and Pearson correlation. Clusters of patients according to low (up to 2), intermediate (3 to 10), or high (more than 10) SEL counts were determined with a Gaussian generalised mixture model. Mixed-effects and logistic regression models assessed volumes, T1 and MTR within SELs, and their correlation with Expanded Disability Status Scale (EDSS) and confirmed disability progression (CDP). Results Mean age at study onset was 35.5 years (73% female), disease duration 5.5 years and mean time to last follow-up 6.5 years (range 1 to 12.5); median baseline EDSS 1.5 (range 0 to 5.5) and a mean EDSS change of 0.31 units at final follow-up. Among 4007 T2 lesions, 27% were classified as SELs and 10% as PBHs. Most patients (n = 65) belonged to the cluster with an intermediate SEL count (3 to 10 SELs). The percentage of PBHs was higher in SELs than non-SELs (up to 61% vs 44%, p < 0.001) and within-patient SEL volumes positively correlated with PBH volumes (r = 0.53, p < 0.001). SELs showed a decrease in T1 intensity over time (beta = -0.004, 95%CI −0.005 to −0.003, p < 0.001), accompanied by lower cross-sectional baseline and follow-up MTR. In mixed-effects models, EDSS worsening was predicted by the SEL log-volumes increase over time (beta = 0.11, 95%CI 0.03 to 0.20, p = 0.01), which was confirmed in the sub-cohort of patients with early onset MS (beta = 0.14, 95%CI 0.04 to 0.25, p = 0.008). In logistic regressions, a higher risk for CDP was associated with SEL volumes (OR = 5.15, 95%CI 1.60 to 16.60, p = 0.006). Conclusions SELs are associated with accumulation of more destructive pathology as indicated by an association with PBH volume, longitudinal reduction in T1 intensity and MTR. Higher SEL volumes are associated with clinical progression, while lower ones are associated with stability in relapse-onset MS

Superdense galaxies and the mass-size relation at low redshift

We search for massive and compact galaxies (superdense galaxies, hereafter SDGs) at z=0.03-0.11 in the Padova-Millennium Galaxy and Group Catalogue, a spectroscopically complete sample representative of the local Universe general field population. We find that compact galaxies with radii and mass densities comparable to high-z massive and passive galaxies represent 4.4% of all galaxies with stellar masses above 3 X 10^10 M_sun, yielding a number density of 4.3 X 10^-4 h^3 Mpc^-3. Most of them are S0s (70%) or ellipticals (23%), are red and have intermediate-to-old stellar populations, with a median luminosity-weighted age of 5.4 Gyr and a median mass-weighted age of 9.2 Gyr. Their velocity dispersions and dynamical masses are consistent with the small radii and high stellar mass estimates. Comparing with the WINGS sample of cluster galaxies at similar redshifts, the fraction of superdense galaxies is three times smaller in the field than in clusters, and cluster SDGs are on average 4 Gyr older than field SDGs. We confirm the existence of a universal trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. On top of the well known dependence of stellar age on galaxy mass, the luminosity-weighted age of galaxies depends on galaxy compactness at fixed mass, and, for a fixed mass and radius, on environment. This effect needs to be taken into account in order not to overestimate the evolution of galaxy sizes from high- to low-z. Our results and hierarchical simulations suggest that a significant fraction of the massive compact galaxies at high-z have evolved into compact galaxies in galaxy clusters today. When stellar age and environmental effects are taken into account, the average amount of size evolution of individual galaxies between high- and low-z is mild, a factor ~1.6. (abridged)Comment: ApJ, in pres

The evolution of galaxy sizes

We present a study of galaxy sizes in the local Universe as a function of galaxy environment, comparing clusters and the general field. Galaxies with radii and masses comparable to high-z massive and compact galaxies represent 4.4% of all galaxies more massive than 3 X 10^{10} M_sun in the field. Such galaxies are 3 times more frequent in clusters than in the field. Most of them are early-type galaxies with intermediate to old stellar populations. There is a trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass. We show the relation between size and luminosity-weighted age for galaxies of different stellar masses and in different environments. We compare with high-z data to quantify the evolution of galaxy sizes. We find that, once the progenitor bias due to the relation between galaxy size and stellar age is removed, the average amount of size evolution of individual galaxies between high- and low-z is mild, of the order of a factor 1.6.Comment: to appear in the proceedings of the IAU S295: The intriguing life of massive galaxies, editors D. Thomas, A. Pasquali & I. Ferrera

Minerología de la fracción arcilla asociada a áreas de alteración en la zona "Bajada a Valle Hermoso" de la Ruta Provincial E-57

Fil: Cejas, Gabriela. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Ayala, Rosa. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Ferreyra, Francisco. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Calvi, Marcelo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.El presente trabajo fue realizado a lo largo de la transecta “Bajada a Valle Hermoso” de la ruta E-57, en la Cuenca del arroyo Vaquerías. En una primera instancia se recurrió a la recopilación bibliográfica de los trabajos realizados en el área. Posteriormente se procedió a una toma sistemática de muestras de suelos a lo largo de la transecta, especialmente en zonas alteradas y con desmoronamientos.Fil: Cejas, Gabriela. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Ayala, Rosa. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Ferreyra, Francisco. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Calvi, Marcelo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Otras Ciencias de la Tierra y relacionadas con el Medio Ambient

Variación de parámetros físicos y químicos en suelos afectados por incendio en la reserva natural de Vaquerías, Valle Hermoso, Provincia de Córdoba

La persistencia de los incendios forestales incontrolados que progresivamente están destruyendo ecosistemas en las zonas serranas de Córdoba, constituye un serio problema ambiental derivado no solo de la pérdida de masa forestal sino también de procesos de degradación de suelo. El área de estudio se ubica en la porción central de las Sierras Chicas, comprendida entre los meridianos 64° 41 y 64° 47 de longitud Oeste y paralelos 31° 10 y 31° 13 de latitud Sur, coincidente con la Reserva Natural de Vaquerías de la Universidad Nacional de Córdoba, en Valle Hermoso, provincia de Córdoba. La ubicación y sus condiciones ambientales la hacen proclive al disturbio de fuego frecuente. Se analizan en este trabajo las características químicas y físico-químicas de suelos al año y 20 días del último incendio forestal registrado en la Reserva Natural de Vaquerías, comparándolas con las de suelos inalterados y las de suelos muestreados a los 20 días de haberse producido el incendio, con el fin de poner de manifiesto las repercusiones que ha tenido sobre el sistema edáfico. El muestreo al año siguiente de hacerse producido el evento se llevó a cabo respetando las zonas muestreadas en 2011, que se diferencian fundamentalmente por la cobertura vegetal original.Del análisis de los datos obtenidos se observa que sonlos sectores de pastizal y arbustal los más afectados por el incendio, lo que evidencia que es allí donde el incendio alcanzó mayor intensidad. Es por esto, que la revegetación natural, es decir, la reconstitución de la cubierta vegetal autóctona es el mejor medio de frenar la erosión. Diferentes situaciones post-incendio, pueden ocasionar cambios en las propiedades del suelo, permanentes o temporales, por esto es recomendable continuar con el monitoreo de los parámetros analizados en este trabajo de investigación. Palabras Clave: incendio forestal, erosión, Córdoba.Fil: Cejas, Gabriela. Universidad Nacional de Córdoba; Argentina.Fil: Ayala, Rosa. Universidad Nacional de Córdoba; Argentina.Fil: Calvi, Marcelo. Universidad Nacional de Córdoba; Argentina.Fil: Tissera, Germán. Universidad Nacional de Córdoba; Argentina.Otras Ciencias de la Tierra y relacionadas con el Medio Ambient

Análisis mineralógico en áreas de alteración de la zona "bajada a Valle Hermoso" de la ruta provincial E-57

El presente trabajo fue realizado a lo largo de la transecta "Bajada a Valle Hermoso" de la ruta E-57, en la Cuenca del arroyo Vaquerías. Se procedió a una toma sistemática de muestras de suelos a lo largo de la transecta, especialmente en zonas alteradas y con deslizamiento de suelo y roca. En laboratorio se limpiaron dichas muestras de modo tal de preservar la fracción arcilla y la fracción arena, las cuales fueron analizadas posteriormente. La fracción arcilla se evaluó a partir de los difractográmas de RX por el método del polvo, las cuales posteriormente fueron analizadas y comparadas con una base de datos, por lo que se pudo identificar los minerales mayoritarios presentes en dicha fracción, y comprobar la existencia de arcillas expansibles, que son generadoras de inestabilidad en las laderas. La fracción arena fue estudiada a través del método de estudio a grano suelto por microscopio de polarización, con el objetivo de identificar la mineralogía de dicha fracción presente. De este modo, los resultados sirvieron de sustento a las difracciones realizadas, se pudieron observar las alteraciones presentes y deducir los procesos actuantes. La presencia de minerales de arcilla del tipo illita mayoritariamente, y del tipo kaolinita que le siguen en abundancia son las causales del proceso de colapsibilidad diferencial, ya que dichas arcillas poseen diferentes comportamientos mecánicos.Fil: Cejas, Gabriela. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Ayala, Rosa. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Ferreyra, Francisco. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Calvi, Marcelo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Otras Ciencias de la Tierra y relacionadas con el Medio Ambient