281 research outputs found
Aperture-free star formation rate of SDSS star-forming galaxies
Large area surveys with a high number of galaxies observed have undoubtedly
marked a milestone in the understanding of several properties of galaxies, such
as star-formation history, morphology, and metallicity. However, in many cases,
these surveys provide fluxes from fixed small apertures (e.g. fibre), which
cover a scant fraction of the galaxy, compelling us to use aperture corrections
to study the global properties of galaxies. In this work, we derive the current
total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming
galaxies, using an empirically based aperture correction of the measured flux for the first time, thus minimising the uncertainties associated
with reduced apertures. All the fluxes have been
extinction-corrected using the ratio free from aperture
effects. The total SFR for 210,000 SDSS star-forming galaxies has been
derived applying pure empirical and aperture
corrections based on the Calar Alto Legacy Integral Field Area (CALIFA) survey.
We find that, on average, the aperture-corrected SFR is 0.65dex higher
than the SDSS fibre-based SFR. The relation between the SFR and stellar mass
for SDSS star-forming galaxies (SFR--) has been obtained, together
with its dependence on extinction and equivalent width. We
compare our results with those obtained in previous works and examine the
behaviour of the derived SFR in six redshift bins, over the redshift range . The SFR-- sequence derived here is in
agreement with selected observational studies based on integral field
spectroscopy of individual galaxies as well as with the predictions of recent
theoretical models of disc galaxies
The extended HeII4686-emitting region in IZw18 unveiled: clues for peculiar ionizing sources
New integral field spectroscopy has been obtained for IZw18, the nearby
lowest-metallicity galaxy considered our best local analog of systems forming
at high-z. Here we report the spatially resolved spectral map of the nebular
HeII4686 emission in IZw18, from which we derived for the first time its total
HeII-ionizing flux. Nebular HeII emission implies the existence of a hard
radiation field. HeII-emitters are observed to be more frequent among high-z
galaxies than for local objects. So investigating the HeII-ionizing source(s)
in IZw18 may reveal the ionization processes at high-z. HeII emission in
star-forming galaxies, has been suggested to be mainly associated with
Wolf-Rayet stars (WRs), but WRs cannot satisfactorily explain the
HeII-ionization at all times, in particular at lowest metallicities. Shocks
from supernova remnants, or X-ray binaries, have been proposed as additional
potential sources of HeII-ionizing photons. Our data indicate that conventional
HeII-ionizing sources (WRs, shocks, X-ray binaries) are not sufficient to
explain the observed nebular HeII4686 emission in IZw18. We find that the
HeII-ionizing radiation expected from models for either low-metallicity
super-massive O stars or rotating metal-free stars could account for the
HeII-ionization budget measured, while only the latter models could explain the
highest values of HeII4686/Hbeta observed. The presence of such peculiar stars
in IZw18 is suggestive and further investigation in this regard is needed. This
letter highlights that some of the clues of the early Universe can be found
here in our cosmic backyard.Comment: 6 pages, 3 figures. Accepted for publication in ApJ Letter
Local Anchor Based Location Management Schemes for Small Cells in HetNets
(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.[EN] Existing location management (LM) methods for macrocells in LTE-Advanced have tracking area list (TAL) granularity. Therefore, a user equipment (UE) triggers a location update (LU) whenever it leaves its current TAL, and it is searched through paging (PG) with TAL accuracy. However, these procedures are not well-suited for small cells (SCs). The reasons are twofold. First, dense deployments of SCs imply that paging has a low probability to be successful in the first attempt, increasing the signaling overhead in the core network (CN). Second, smaller coverage areas lead to a higher mobility among cells, increasing the signaling overhead in the CN due to LUs. In this work, two LM schemes with fine granularity are proposed. These schemes update UE's location to a local anchor (LA) in a SC or tracking area (TA) basis, respectively. By increasing the accuracy of UE's location, a significant reduction of signaling overhead in the CN due to PG is achieved. Moreover, LUs to the LA are performed through direct X2-interface links to avoid signaling overhead in the CN. A versatile mobility model is developed and closed-form expressions for UEs' mobility metrics are found to validate the proposed schemes through variations of critical parameters such as TA/TAL configuration, UE's mobility patterns and cell residence times.This work has been supported by European Commission under the FP7 S2EuNet project and the Spanish Government through project TIN2013-47272-C2-1-RPacheco-Paramo, DF.; Akyildiz, IF.; Casares Giner, V. (2016). Local Anchor Based Location Management Schemes for Small Cells in HetNets. IEEE Transactions on Mobile Computing. 15(4):883-894. https://doi.org/10.1109/TMC.2015.2431717S88389415
AKARI/IRC Broadband Mid-infrared data as an indicator of Star Formation Rate
AKARI/Infrared Camera (IRC) Point Source Catalog provides a large amount of
flux data at {\it S9W} () and {\it L18W} ()
bands. With the goal of constructing Star-Formation Rate(SFR) calculations
using IRC data, we analyzed an IR selected
GALEX-SDSS-2MASS-AKARI(IRC/Far-Infrared Surveyor) sample of 153 nearby
galaxies. The far-infrared fluxes were obtained from AKARI diffuse maps to
correct the underestimation for extended sources raised by the point-spread
function photometry. SFRs of these galaxies were derived by the spectral energy
distribution fitting program CIGALE. In spite of complicated features contained
in these bands, both the {\it S9W} and {\it L18W} emission correlate with the
SFR of galaxies. The SFR calibrations using {\it S9W} and {\it L18W} are
presented for the first time. These calibrations agree well with previous works
based on Spitzer data within the scatters, and should be applicable to
dust-rich galaxies.Comment: PASJ, in pres
Spatially resolved integral field spectroscopy of the ionized gas in IZw18
We present a detailed 2D study of the ionized ISM of IZw18 using new PMAS-IFU
optical observations. IZw18 is a high-ionization galaxy which is among the most
metal-poor starbursts in the local Universe. This makes IZw18 a local benchmark
for understanding the properties most closely resembling those prevailing at
distant starbursts. Our IFU-aperture (~ 1.4 kpc x 1.4 kpc) samples the entire
IZw18 main body and an extended region of its ionized gas. Maps of relevant
emission lines and emission line ratios show that higher-excitation gas is
preferentially located close to the NW knot and thereabouts. We detect a
Wolf-Rayet feature near the NW knot. We derive spatially resolved and
integrated physical-chemical properties for the ionized gas in IZw18. We find
no dependence between the metallicity-indicator R23 and the ionization
parameter (as traced by [OIII]/[OII]) across IZw18. Over ~ 0.30 kpc^2, using
the [OIII]4363 line, we compute Te[OIII] values (~ 15000 - 25000 K), and oxygen
abundances are derived from the direct determinations of Te[OIII]. More than
70% of the higher-Te[OIII] (> 22000 K) spaxels are HeII4686-emitting spaxels
too. From a statistical analysis, we study the presence of variations in the
ISM physical-chemical properties. A galaxy-wide homogeneity, across hundreds of
parsecs, is seen in O/H. Based on spaxel-by-spaxel measurements, the
error-weighted mean of 12 + log(O/H) = 7.11 +/- 0.01 is taken as the
representative O/H for IZw18. Aperture effects on the derivation of O/H are
discussed. Using our IFU data we obtain, for the first time, the IZw18
integrated spectrum.Comment: Accepted for publication in MNRAS, 13 pages, 10 figures, 4 table
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Latitudinal gradients in butterfly population variability are influenced by landscape heterogeneity
The variability of populations over time is positively associated with their risk of local extinction. Previous work has shown that populations at the high-latitude boundary of species’ ranges show higher inter-annual variability, consistent with increased sensitivity and exposure to adverse climatic conditions. However, patterns of population variability at both high- and low-latitude species range boundaries have not yet been concurrently examined. Here, we assess the inter-annual population variability of 28 butterfly species between 1994 and 2009 at 351 and 18 sites in the United Kingdom and Catalonia, Spain, respectively. Local population variability is examined with respect to the position of the species’ bioclimatic envelopes (i.e. whether the population falls within areas of the ‘core’ climatic suitability or is a climatically ‘marginal’ population), and in relation to local landscape heterogeneity, which may influence these range location – population dynamic relationships. We found that butterfly species consistently show latitudinal gradients in population variability, with increased variability in the more northerly UK. This pattern is even more marked for southerly distributed species with ‘marginal’ climatic suitability in the UK but ‘core’ climatic suitability in Catalonia. In addition, local landscape heterogeneity did influence these range location – population dynamic relationships. Habitat heterogeneity was associated with dampened population dynamics, especially for populations in the UK. Our results suggest that promoting habitat heterogeneity may promote the persistence of populations at high-latitude range boundaries, which may potentially aid northwards expansion under climate warming. We did not find evidence that population variability increases towards southern range boundaries. Sample sizes for this region were low, but there was tentative evidence, in line with previous ecological theory, that local landscape heterogeneity may promote persistence in these retracting low-latitude range boundary populations
Star Forming Objects in the Tidal Tails of Compact Groups
A search for star forming objects belonging to tidal tails has been carried
out in a sample of deep Halpha images of 16 compact groups of galaxies. A total
of 36 objects with Halpha luminosity larger than 10^38 erg s-1 have been
detected in five groups. The fraction of the total Halpha luminosity of their
respective parent galaxies shown by the tidal objects is always below 5% except
for the tidal features of HCG95, whose Halpha luminosity amounts to 65% of the
total luminosity. Out of this 36 objects, 9 star forming tidal dwarf galaxy
candidates have been finally identified on the basis of their projected
distances to the nuclei of the parent galaxies and their total Halpha
luminosities. Overall, the observed properties of the candidates resemble those
previously reported for the so-called tidal dwarf galaxies.Comment: 5 gif figures. Accepted for publication in Astrophysical Journa
Hemostatic markers in surgery: a different fibrinolytic activity may be of pathophysiological significance in orthopedic versus abdominal surgery
Without prophylaxis, patients subjected to major abdominal surgery have a risk of deep vein thrombosis of approximately 30%, while the rate varies between 40% and 60% in orthopedic surgery. The reasons for this discrepancy are not completely understood. The present study was designed to compare the pre- and postoperative behavior of different coagulation and fibrinolysis parameters in patients undergoing both types of surgery, receiving low molecular weight heparin prophylaxis. Samples were taken before operation and on postoperative days 1, 3, and 7. The following parameters were assessed: prothrombin fragment 1 + 2, thrombin-antithrombin III complexes, fibrinopeptide A, tissue plasminogen activator, plasminogen activator inhibitor, plasmin-alpha 2-antiplasmin complexes, and fibrin degradation products. We found a significant increase in the clotting markers postoperatively compared with preoperative values (P < 0.05), both in abdominal and orthopedic surgery, indicating a marked hemostatic activation which remained until postoperative day 7. A significant increase in plasminogen activator inhibitor (P < 0.01) and a decrease in tissue plasminogen activator and plasmin-alpha 2-antiplasmin complexes was also observed early after operation. The plasminogen activator inhibitor activity decreased, while tissue plasminogen activator and plasmin-alpha 2-antiplasmin levels increased significantly on days 3 and 7 (P < 0.05). Fibrin degradation products significantly increased throughout the postoperative period (P < 0.01). Preoperatively, we found higher plasminogen activator inhibitor activity and lower tissue plasminogen activator and plasmin-alpha 2-antiplasmin complexes (P < 0.05) in patients undergoing hip replacement compared with abdominal surgery. Fibrin degradation products were also significantly lower on postoperative day 3 in patients undergoing hip replacement (P < 0.01). We suggest that the lower preoperative fibrinolytic activation observed in patients undergoing orthopedic surgery compared with abdominal surgery might have pathophysiological consequences. Our results also indicate that the hemostatic activation persists beyond the 7th postoperative day despite prophylaxis
Randomized study of aprotinin and DDAVP to reduce postoperative bleeding after cardiopulmonary bypass surgery
BACKGROUND: Patients on cardiopulmonary bypass (CPB) have an increased susceptibility to postoperative bleeding. Previous reports using desmopressin acetate (DDAVP) for the prevention of postoperative bleeding have given contradictory results, whereas the protease inhibitor aprotinin has been shown to reduce blood loss after this type of surgery. This randomized study was performed to assess the efficacy of DDAVP versus aprotinin in the prevention of bleeding after CPB.
METHODS AND RESULTS: One hundred nine of 122 eligible patients were randomized to four different groups: Group A (n = 28) received aprotinin starting with a bolus of 2 x 10(6) KIU followed by a continuous infusion of 0.5 x 10(6) KIU/h until the end of surgery; group B (n = 25) received of DDAVP 0.3 micrograms/kg i.v. on completion of CPB; group C (n = 28) received two doses of DDAVP, the first as in group B and an additional dose 6 hours after surgery; group D (n = 28) received no treatment. There was a marked reduction of postoperative blood loss either at 12 hours (P < .01) or 72 hours (P < .02) in the aprotinin group compared with all other groups, whereas no significant effect was observed in either of the two DDAVP regimens. A significant reduction in the amount of blood used was observed only in the aprotinin group (P < .01). Of the plasma fibrinolytic components assayed, there was a significant reduction of the fibrin degradation product generation in the aprotinin group (P < .001), whereas a significant systemic hyperfibrinolysis was observed in both DDAVP-treated groups and the control group. No side effects related to the study drugs were observed in any patient.
CONCLUSIONS: Aprotinin inhibited fibrinolysis; this correlated with a significant reduction of postoperative blood loss and need for blood replacement after CPB. Neither one nor two doses of DDAVP had a beneficial effect. Aprotinin offers a better alternative than DDAVP in the prevention of bleeding after CPB
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