Star Formation in a Stellar Mass Selected Sample of Galaxies to z=3 from the GOODS NICMOS Survey (GNS)

We present a study of the star-forming properties of a stellar mass-selected sample of galaxies in the GOODS NICMOS Survey (GNS), based on deep Hubble Space Telescope imaging of the GOODS North and South fields. Using a stellar mass selected sample, combined with HST/ACS and Spitzer data to measure both UV and infrared derived star formation rates (SFR), we investigate the star forming properties of a complete sample of ~1300 galaxies down to log M*=9.5 at redshifts 1.5<z<3. Eight percent of the sample is made up of massive galaxies with M*>10^11 Msun. We derive optical colours, dust extinctions, and ultraviolet and infrared SFR to determine how the star formation rate changes as a function of both stellar mass and time. Our results show that SFR increases at higher stellar mass such that massive galaxies nearly double their stellar mass from star formation alone over the redshift range studied, but the average value of SFR for a given stellar mass remains constant over this 2 Gyr period. Furthermore, we find no strong evolution in the SFR for our sample as a function of mass over our redshift range of interest, in particular we do not find a decline in the SFR among massive galaxies, as is seen at z < 1. The most massive galaxies in our sample (log M*>11) have high average SFRs with values, SFR(UV,corr) = 103+/-75 Msun/yr, yet exhibit red rest-frame (U-B) colours at all redshifts. We conclude that the majority of these red high-redshift massive galaxies are red due to dust extinction. We find that A(2800) increases with stellar mass, and show that between 45% and 85% of massive galaxies harbour dusty star formation. These results show that even just a few Gyr after the first galaxies appear, there are strong relations between the global physical properties of galaxies, driven by stellar mass or another underlying feature of galaxies strongly related to the stellar mass.Comment: 18 pages, 10 figures, accepted for publication in MNRA

Spectroscopy of the Lens Galaxy of Q0957+561A,B. Implications of a possible central massive dark object

We present new long-slit William Herschel Telescope spectroscopic observations of the lens galaxy G1 associated with the double-imaged QSO 0957+561A,B. The obtained central stellar velocity dispersion, sigma_l = 310 +/- 20 km/s, is in reasonable agreement with other measurements of this dynamical parameter. Using all updated measurements of the stellar velocity dispersion in the internal region of the galaxy (at angular separations < 1".5) and a simple isotropic model, we discuss the mass of a possible central massive dark object. It is found that the data of Falco et al. (1997) suggest the existence of an extremely massive object of (0.5-2.1) x 10E10/h M_\odot (80% confidence level), whereas the inclusion of very recent data (Tonry & Franx 1998, and this paper) substantially changes the results: the compact central mass must be $\le$ 6 x10E9/h M_\odot at the 90% confidence level. We note that, taking into account all the available dynamical data, a compact nucleus with a mass of 10E9/h M_\odot (best fit) cannot be ruled out.Comment: 20 pages, 10 figures ApJ, in pres

Direct Evidence Of Porosity In Carbon-rich Hydrogenated Amorphous Silicon Carbide Films

Infrared absorption spectroscopy was used to study the oxidation of hydrogenated amorphous silicon carbide (a-Si:C:H) films prepared by the glow-discharge decomposition of gaseous mixtures of silane and methane. It has been found that carbon-rich samples incorporate oxygen when exposed to air, as detected by an increased absorption of the Si-O-Si stretching vibration band. The analysis of the infrared spectra of samples annealed in air at room temperature and at 200 °C indicates that, except for their oxidation rate, no appreciable difference exists in the mechanisms of oxygen incorporation in the films at the two temperatures. The oxidation kinetics suggests an open porous structure for these carbon-rich films. On the contrary, samples having a low carbon content appear to oxidize on the surface only, in a way similar to amorphous silicon.6694544454

The structures and total (minor + major) merger histories of massive galaxies up to z = 3 in the HST GOODS NICMOS Survey: A possible solution to the size evolution problem

We investigate the total major (> 1:4 by stellar mass) and minor (> 1:100 by stellar mass) merger history of a population of 80 massive (M_* > 10^11 M_sol) galaxies at high redshifts (z = 1.7 - 3). We utilize extremely deep and high resolution HST H-band imaging from the GOODS NICMOS Survey (GNS), which corresponds to rest-frame optical wavelengths at the redshifts probed. We find that massive galaxies at high redshifts are often morphologically disturbed, with a CAS deduced merger fraction f_m = 0.23 +/- 0.05 at z = 1.7 - 3. We find close accord between close pair methods (within 30 kpc apertures) and CAS methods for deducing major merger fractions at all redshifts. We deduce the total (minor + major) merger history of massive galaxies with M_* > 10^9 M_sol galaxies, and find that this scales roughly linearly with log-stellar-mass and magnitude range. We test our close pair methods by utilizing mock galaxy catalogs from the Millennium Simulation. We compute the total number of mergers to be (4.5 +/- 2.9) / from z = 3 to the present, to a stellar mass sensitivity threshold of ~ 1:100 (where \tau_m is the merger timescale in Gyr which varies as a function of mass). This corresponds to an average mass increase of (3.4 +/- 2.2) x 10^11 M_sol over the past 11.5 Gyrs due to merging. We show that the size evolution observed for these galaxies may be mostly explained by this merging.Comment: 19 pages, 10 figures, re-submitted to ApJ after a positive referee report, originally submitted on Sept 20 201

On the nature of the hard X-ray sources SWIFTJ1907.3-2050, IGRJ12123-5802 and IGRJ19552+0044

The INTEGRAL and Swift hard X-ray surveys have identified a large number of new sources, among which many are proposed as Cataclysmic Variables (CVs). Here we present the first detailed study of three X-ray selected CVs, Swift J1907.3-2050, IGRJ12123-5802, and IGRJ19552+0044 based on XMM-Newton, Suzaku, Swift observations and ground based optical and archival nIR/IR data. Swift J1907.3-2050 is highly variable from hours to months-years at all wavelengths. No coherent X-ray pulses are detected but rather transient features. The X-ray spectrum reveals a multi-temperature optically thin plasma absorbed by complex neutral material and a soft black body component arising from a small area. These characteristics are remarkably similar to those observed in magnetic CVs. A supra-solar abundance of nitrogen could arise from nuclear processed material from the donor star. Swift J1907.3-2050 could be a peculiar magnetic CV with the second longest (20.82 h) binary period. IGRJ12123-5802 is variable in the X-rays on a timescale of ~7.6 h. No coherent pulsations are detected, but its spectral characteristics suggest that it could be a magnetic CV of the Intermediate Polar (IP) type. IGRJ19552+0044 shows two X-ray periods, 1.38 h and 1.69 h and a X-ray spectrum characterized by a multi-temperature plasma with little absorption.We derive a low accretion rate, consistent with a CV below the orbital period gap. Its peculiar nIR/IR spectrum suggests a contribution from cyclotron emission. It could either be a pre-polar or an IP with the lowest degree of asynchronism.Comment: Accepted for publication in MNRAS. 14 pages, 11 figures, 5 table

Prevalence of chagas disease in Colombia : a systematic review and meta-analysis

Q2Artículo de investigación1-18Background Despite the adoption of campaigns to interrupt the main vector and to detect Trypanosoma cruzi in blood banks, millions of people are still chronically infected; however, the prevalence data are limited, and the epidemiology of Chagas disease has not been systematically evaluated. This study aimed to estimate the prevalence of Chagas disease in Colombia. Methods A systematic literature review and meta-analysis was conducted to select all observational studies reporting the prevalence of Chagas disease in Colombia, based on serological diagnosis in participants of any age and published between January 2007 and November 2017. Pooled estimates and 95% confidence intervals (95% CIs) were calculated using randomeffects models. In addition, the I 2 statistic was calculated. Results The literature search yielded a total of 1,510 studies; sixteen articles with relevant prevalence data were included in the systematic review. Of these, only 12 articles were included for entry in the meta-analysis. The pooled prevalence of Chagas disease across studies was 2.0% (95% CI: 1.0–4.0). A high degree of heterogeneity was found among studies (I2 > 75%; p < 0.001). The publication bias was not statistically significant (Egger’s test, p = 0.078). The highest pooled prevalences were found in the adult population (3.0%, 95% CI: 1.0–4.0), pregnant women (3.0%, 95% CI: 3.0–4.0) and the Orinoco region (7.0%, 95% CI: 2.2–12.6). Conclusions The results indicate that the T. cruzi-infected population is aging, the adult population, pregnant women and that the Orinoco region (department of Casanare) have the highest prevalences. These results highlight the need to maintain screening and surveillance programs to identify people with chronic T. cruzi infections

Nuevos registros de Vespidae (Hymenoptera: Vespoidea) para la región de la Orinoquía colombiana

We analyzed 72 specimens from the Arauca (71) and Casanare (1) departments in the Orinoco region of Colombia. The specimens belong to 10 genera and 18 species of vespid wasps. Four species are reported for the first time for the region and 14 are new records for the Arauca department. There is a likely new record of Stenodynerus cf. australis for the Neotropical region.Analizamos 72 especímenes colectados de los departamentos de Arauca (71) y Casanare (1) en la región de la Orinoquía. Estos pertenecen a 10 géneros y 18 especies de avispas. Cuatro especies son nuevos registros para la región y 14 son nuevas para el departamento de Arauca. Hay también un posible nuevo registro de Stenodyneus cf. australis para la región Neotropical

Gonadal Hormones Rapidly Enhance Spatial Memory and Increase Hippocampal Spine Density in Male Rats

17β-estradiol (E(2)) rapidly, within minutes, activates behaviors and cognition by binding to membrane estrogen receptors, activating cell signaling cascades and increasing dendritic spines. In female rodents, E(2) enhances spatial memory within 2–4 hours, and spine density is increased in the CA1 area of the hippocampus within 30–60 minutes. Although chronic gonadal hormone treatments in male rats alter cognition and spines/spine synapses and acute hormone effects occur in hippocampal slices, effects of acute, in vivo hormone administration in males are unknown. Therefore, we assessed rapid effects of E(2) (20 μg/kg) and testosterone (T) (750 μg/kg) on spatial memory using the object placement task and on hippocampal spine density using Golgi impregnation. Orchidectomized rats received hormones immediately after the training trial and were tested for retention 2 hours later. Vehicle-injected orchidectomized males spent equal time exploring objects in the old and new locations, but E(2-) or T-treated subjects spent more time exploring objects at the new location, suggesting enhanced memory. Both hormones also increased spine density in CA1, but not the dentate gyrus, by 20%–40% at 30 minutes and 2 hours after injections. This report is the first, to our knowledge, to show E(2) and T enhancements of memory and spine density within such a short time frame in male rats

Los restos de Sus scrofa (Artiodactyla, Mammalia) del yacimiento Pleistoceno de Pinilla del Valle (Madrid, España)

A morphologic and biometric study has been carried out on the fossil remains of Suidae derived from the first phase of excavation (1980-1989) at the late Pleistocene paleontological site of Cueva del Camino near Pinilla del Valle, north of Madrid. The material consists in 47 remains belonging to a minimum of 6 individuals. The results allow identifying the presence of the wild boar Sus scrofa, whose anatomical characteristics are compared with material from various European Pleistocene sites as well as present-day specimens. From the material obtained is this first phase of excavation stands out several cranial remains, because they are very scarce in coeval European sites, and are not recorded so far in other Spanish sites. The record of Sus scrofa agrees with the palaeoecological and palaeoenvironmental inferences displayed by previous studies from the whole faunal assemblage of the Cueva del Camino site.Se ha llevado a cabo un estudio morfológico y biométrico de los restos fósiles de Suidos excavados en el yacimiento del Pleistoceno superior de la Cueva del Camino, en el término de Pinilla del Valle (Madrid), comparándolos con los restos de otros yacimientos y con especímenes actuales. El material extraído comprende 47 elementos pertenecientes a un mínimo de 6 individuos, destacando la presencia de restos craneales, muy poco frecuentes en los yacimientos europeos de esta época, y ausentes en yacimientos españoles. Se han comprobado en los restos los caracteres anatómicos típicos de Sus scrofa, confirmándose las condiciones paleoambientales obtenidas del conjunto de la fauna