115 research outputs found
SHARDS: Constraints on the dust attenuation law of star-forming galaxies at z~2
We make use of SHARDS, an ultra-deep (<26.5AB) galaxy survey that provides
optical photo-spectra at resolution R~50, via medium band filters (FWHM~150A).
This dataset is combined with ancillary optical and NIR fluxes to constrain the
dust attenuation law in the rest-frame NUV region of star-forming galaxies
within the redshift window 1.5<z<3. We focus on the NUV bump strength (B) and
the total-to-selective extinction ratio (Rv), targeting a sample of 1,753
galaxies. By comparing the data with a set of population synthesis models
coupled to a parametric dust attenuation law, we constrain Rv and B, as well as
the colour excess, E(B-V). We find a correlation between Rv and B, that can be
interpreted either as a result of the grain size distribution, or a variation
of the dust geometry among galaxies. According to the former, small dust grains
are associated with a stronger NUV bump. The latter would lead to a range of
clumpiness in the distribution of dust within the interstellar medium of
star-forming galaxies. The observed wide range of NUV bump strengths can lead
to a systematic in the interpretation of the UV slope () typically used
to characterize the dust content. In this study we quantify these variations,
concluding that the effects are ~0.4.Comment: 13 pages, 11+2 figures, 3 tables. MNRAS, in pres
Low night temperatures during the early growth phase enhance flowering in primocane shoots of red raspberries ( Rubus idaeus L.)
n/
Optically-faint massive Balmer Break Galaxies at z>3 in the CANDELS/GOODS fields
We present a sample of 33 Balmer Break Galaxies (BBGs) selected as HST/F160W
dropouts in the deepest CANDELS/GOODS fields (~mag) but
relatively bright in {\it Spitzer}/IRAC (~mag), implying red
colors (median and quartiles: \,mag).
Half of these BBGs are newly identified sources. Our BBGs are massive () high redshift ()
dusty (~mag) galaxies. The SEDs of half of our
sample indicate that they are star-forming galaxies with typical specific SFRs
0.5-1.0~Gyr, qualifying them as main sequence (MS) galaxies at .
One third of those SEDs indicates the presence of prominent emission lines
(H+, H[NII]) boosting the IRAC fluxes and red colors.
Approximately 20\% of the BBGs are very dusty (~mag)
starbursts with strong mid-to-far infrared detections and extreme SFRs
() that place them above the MS. The rest,
30\%, are post-starbursts or quiescent galaxies located below the MS
with mass-weighted ages older than 700~Myr. Only 2 of the 33 galaxies are X-ray
detected AGN with optical/near-infrared SEDs dominated by stellar emission, but
the presence of obscured AGN in the rest of sources cannot be discarded. Our
sample accounts for 8\% of the total number density of
galaxies at , but it is a significant
contributor (30\%) to the general population of red
galaxies at . Finally, our results point
out that 1 of every 30 massive galaxies in the
local Universe was assembled in the first 1.5~Gyr after the Big Bang, a
fraction that is not reproduced by state-of-the-art galaxy formation
simulations.Comment: 38 pages, 18 figures, Accepted for publication in The Astrophysical
Journal 26/03/201
Probing the Star Formation Main Sequence down to M at
We investigate the star formation main sequence (MS) (SFR-M) down
to 10 using a sample of 34,061 newly-discovered
ultra-faint ( mag) galaxies at detected in
the GOODS-N field. Virtually these galaxies are not contained in previous
public catalogs, effectively doubling the number of known sources in the field.
The sample was constructed by stacking the optical broad-band observations
taken by the HST/GOODS-CANDELS surveys as well as the 25 ultra-deep medium-band
images gathered by the GTC/SHARDS project. Our sources are faint (average
observed magnitudes mag, mag), blue (UV-slope
), star-forming (rest-frame colors mag,
mag) galaxies. These observational characteristics are
identified with young (mass-weighted age Gyr)
stellar populations subject to low attenuations (
mag). Our sample allows us to probe the MS down to
at and at , around 0.6 dex deeper than
previous analysis. In the low-mass galaxy regime, we find an average value for
the slope of 0.97 at and 1.12 at . Nearly 60% of our
sample presents stellar masses in the range M between
. If the slope of the MS remained constant in this regime, the sources
populating the low-mass tail of our sample would qualify as starburst galaxies.Comment: 34 pages, 16 figures, 9 tables. Accepted for publication to Ap
SHARDS: A global view of the star formation activity at z~0.84 and z~1.23
In this paper, we present a comprehensive analysis of star-forming galaxies
(SFGs) at intermediate redshifts (z~1). We combine the ultra-deep optical
spectro-photometric data from the Survey for High-z Absorption Red and Dead
Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field.
Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we
select [OII] emission line galaxies at z~0.84 and z~1.23 and characterize their
physical properties. Their rest-frame equivalent widths
(EW([OII])), line fluxes, luminosities, star formation rates
(SFRs) and dust attenuation properties are investigated. The evolution of the
EW([OII]) closely follows the SFR density evolution of the
universe, with a trend of EW([OII])(1+z) up to
redshift z~1, followed by a possible flattening. The SF properties of the
galaxies selected on the basis of their [OII] emission are compared with
complementary samples of SFGs selected by their MIR and FIR emission, and also
with a general mass-selected sample of galaxies at the same redshifts. We
demonstrate observationally that the UVJ diagram (or, similarly, a cut in the
specific SFR) is only partially able to distinguish the quiescent galaxies from
the SFGs. The SFR-M relation is investigated for the different samples,
yelding a logarithmic slope ~1, in good agreement with previous results. The
dust attenuations derived from different SFR indicators (UV(1600), UV(2800),
[OII], IR) are compared and show clear trends with respect to both the stellar
mass and total SFR, with more massive and highly star-forming galaxies being
affected by stronger dust attenuation.Comment: Replaced to match the accepted version (24 pages, 1 table, 17
figures). Published in ApJ, 812, 155 (2015):
http://stacks.iop.org/0004-637X/812/15
Anti-Inflammatory (M2) Response Is Induced by a sp(2)-Iminosugar Glycolipid Sulfoxide in Diabetic Retinopathy
Diabetic retinopathy (DR) is one of the most common complications of Diabetes Mellitus (DM) and is directly associated with inflammatory processes. Currently, neuro-inflammation is considered an early event in DR and proceeds via microglia polarization. A hallmark of DR is the presence of retinal reactive gliosis. Here we report the beneficial effect of (S (S),1R)-1-docecylsulfiny-5N,6O-oxomethylidenenojirimycin ((Ss)-DS-ONJ), a member of the sp(2)-iminosugar glycolipid (sp(2)-IGL) family, by decreasing iNOS and inflammasome activation in Bv.2 microglial cells exposed to pro-inflammatory stimuli. Moreover, pretreatment with (Ss)-DS-ONJ increased Heme-oxygenase (HO)-1 as well as interleukin 10 (IL10) expression in LPS-stimulated microglial cells, thereby promoting M2 (anti-inflammatory) response by the induction of Arginase-1. The results strongly suggest that this is the likely molecular mechanism involved in the anti-inflammatory effects of (S (S))-DS-ONJ in microglia. (S (S))-DS-ONJ further reduced gliosis in retinal explants from type 1 diabetic BB rats, which is consistent with the enhanced M2 response. In conclusion, targeting microglia polarization dynamics in M2 status by compounds with anti-inflammatory activities offers promising therapeutic interventions at early stages of DR
Electronic structure analysis of the quasi-one-dimensional oxide Sr6Co5O15 within the LDA+U method
The quasi-one-dimensional cobalt oxide Sr6Co5O15 is studied using first-principles electronic-structure calculations and Boltzmann transport theory. We have been able to describe the electronic structure, characterized by the structural one-dimensionality and a particular type of charge ordering, with unexpected electronic structure of the different Co atoms. The origin of the large unquenched misaligned orbital angular momenta comes out naturally from a correct description of the different crystal-field environments. The evolution with the on-site Coulomb repulsion (U) of the electronic structure and the transport properties is discussed, with a best agreement with experiment found for the smallest value of U that allows to converge the correct in-chain ferrimagnetic ground stateThe authors thank the CESGA for the computing facilities, the Ministerio de Educación y Ciencia (MEC) for the financial support through the project MAT2009-08165, the Ministerio de Ciencia e Innovación (MICINN) for the project MAT2007-60536 and the Xunta de Galicia for the project INCITE08PXIB236052PR. A.S.B. thanks MEC for a FPU grant. M.P. and J.B. thank Isabel Barreto program and Deputación da Coruña, respectively, for financial supportS
Retrospective cohort study: Risk of gastrointestinal cancer in a symptomatic cohort after a complete colonoscopy: Role of faecal immunochemical test
BACKGROUND: Faecal immunochemical test (FIT) has been recommended to assess symptomatic patients for colorectal cancer (CRC) detection. Nevertheless, some conditions could theoretically favour blood originating in proximal areas of the gastrointestinal tract passing through the colon unmetabolized. A positive FIT result could be related to other gastrointestinal cancers (GIC).
AIM: To assess the risk of GIC detection and related death in FIT-positive symptomatic patients (threshold 10 µg Hb/g faeces) without CRC.
METHODS: Post hoc cohort analysis performed within two prospective diagnostic test studies evaluating the diagnostic accuracy of different FIT analytical systems for CRC and significant colonic lesion detection. Ambulatory patients with gastrointestinal symptoms referred consecutively for colonoscopy from primary and secondary healthcare, underwent a quantitative FIT before undergoing a complete colonoscopy. Patients without CRC were divided into two groups (positive and negative FIT) using the threshold of 10 µg Hb/g of faeces and data from follow-up were retrieved from electronic medical records of the public hospitals involved in the research. We determined the cumulative risk of GIC, CRC and upper GIC. Hazard rate (HR) was calculated adjusted by age, sex and presence of significant colonic lesion.
RESULTS: We included 2709 patients without CRC and a complete baseline colonoscopy, 730 (26.9%) with FIT = 10 µgr Hb/gr. During a mean time of 45.5 ± 20.0 mo, a GIC was detected in 57 (2.1%) patients: An upper GIC in 35 (1.3%) and a CRC in 14 (0.5%). Thirty-six patients (1.3%) died due to GIC: 22 (0.8%) due to an upper GIC and 9 (0.3%) due to CRC. FIT-positive subjects showed a higher CRC risk (HR 3.8, 95%CI: 1.2-11.9) with no differences in GIC (HR 1.5, 95%CI: 0.8-2.7) or upper GIC risk (HR 1.0, 95%CI: 0.5-2.2). Patients with a positive FIT had only an increased risk of CRC-related death (HR 10.8, 95%CI: 2.1-57.1) and GIC-related death (HR 2.2, 95%CI: 1.1-4.3), with no differences in upper GIC-related death (HR 1.4, 95%CI: 0.6-3.3). An upper GIC was detected in 22 (0.8%) patients during the first year. Two variables were independently associated: anaemia (OR 5.6, 95%CI: 2.2-13.9) and age = 70 years (OR 2.7, 95%CI: 1.1-7.0).
CONCLUSION: Symptomatic patients without CRC have a moderate risk increase in upper GIC, regardless of the FIT result. Patients with a positive FIT have an increased risk of post-colonoscopy CRC
Zn_2GeO_4/SnO_2 nanowire heterostructures driven by plateau-rayleigh instability
Herein, we report the formation of a particular core-shell structure, with a zinc germanate (Zn_2GeO_4) nanowire core and a discontinuous shell of SnO_2 nanocrystals, obtained in a single-step process. We propose a growth model that combines the Plateau-Rayleigh mechanism to produce a pattern of amorphous germanium oxide (a-GeO_2) particles along the Zn_2GeO_4 nanowire and the subsequent growth of well-faceted SnO_2 crystals when the nanowire orientation meets good lattice matching conditions. In this latter case, the linear array of a-GeO_2 particles acts as nucleation sites for the SnO_2 crystallites, leading to a skewer-like morphology that retains the periodicity of the Plateau-Rayleigh process. Otherwise, nanowires with different orientations appear decorated with a pattern of a-GeO_2 beads mimicking a necklace. Atomic resolution electron microscopy has been used to characterize the Zn_2GeO_4/SnO_2 nanoheterostructures. In addition, optical confinement effects have been observed in the luminescence maps and spectra, which have potential for further exploitation in the design of optical microcavities
Nuevos datos de carbones y maderas fósiles de Pinus pinaster Aiton en el Holoceno de la Península Ibérica
The study of ligneous fossil remains (charcoal and wood) corresponding to three sites located in the interior of the Iberian Peninsula is presented. The chronologies established by means of radiocarbon or relative dating (archaeological) situate all the samples in the last phase of the Holocene. In the three deposits Pinus pinaster has been identified and there have being made other taxonomic contributions. A review of previous Pinus pinaster findings registered in the Peninsula is exposed and other considerations are made on the importance of this taxon in the Iberian vegetal landscape during the end of the Quaternary.Se ha realizado un estudio de restos fósiles leñosos correspondientes a tres yacimientos del interior de la península Ibérica: Hontalbilla (Segovia), Yecla (Murcia) y Castillejos (Badajoz). Las cronologías establecidas mediante datación absoluta (radiocarbono) o relativa (arqueológica) sitúan todas las muestras en la última fase del Holoceno. En los tres yacimientos se ha identificado Pinus pinaster, realizándose además otras aportaciones taxonómicas. Se reúnen los datos conocidos de macrorrestos de P. pinaster registrados en la Península y se realizan consideraciones sobre la importancia de este taxon en el paisaje vegetal ibérico durante el final del Cuaternario
- …