We have developed a method for finding dynamical resonances in disk galaxies using the change in sense of the radial component of the in-plane velocity at a resonance radius. Using simulations we ...show that we would expect to find these changes at corotation radii with a weaker effect at the Lindblad resonances. The method works well with observations at high spectral and angular resolutions, and is suited to the analysis of two-dimensional velocity fields in He alpha from Fabry-Perot spectroscopy. We find clear indications of resonance effects in the disk velocity fields of virtually all of the 104 galaxies. The number of resonance radii detected ranges from one to seven, with a median of four. The frequency curves Omega, Omega + or - Kappa /2, Omega + or - Kappa /4 against radius for all the galaxies led us to discover a pattern in over 70% of the sample: given two pattern speeds, say Omega sub(1) and Omega sub(2), the OLR of Omega sub(1) coincides with the corotation of Omega sub(2), and the inner 4:1 resonance of Omega sub(2) coincides with the corotation of Omega sub(1). Although the second coincidence has been predicted, a prediction of this double coincidence is not found in the literature. This pattern is found once in 42 of the galaxies, twice in a further 26, three times in 5, and even four times in 1 galaxy. We also compute the ratio of corotation radius to bar length where we have sufficient image quality, finding a mean value of 1.3, and a shallow increase toward later type galaxies.
We present the integrated Hα emission line profile for 157 H ii regions in the central 3.4 × 3.4 arcmin2 of the galaxy M83 (NGC 5236). Using the Fabry–Perot interferometer GHαFaS, on the 4.2-m ...William Herschel Telescope on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity–velocity dispersion relation is also studied, and in the log(L)–log(σ) plane we do not find a linear relation, but an upper envelope with equation log(LHα) = 0.9 log(σ) + 38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity L= 1038.5 erg s−1, in full agreement with previous studies of other galaxies, reinforcing the idea of using H ii regions as standard candles.
Using velocity tagging we have detected hydrogen from NGC 5426 falling onto its interacting partner NGC 5427. Our observations, with the GHaFaS Fabry-Perot spectrometer, produced maps of the two ...galaxies in H Delta *a surface brightness and radial velocity. We found emission with the range of velocities associated with NGC 5426 along lines of sight apparently emanating from NGC 5427, superposed on the velocity map of the latter. After excluding instrumental effects we assign the anomalous emission to gas pulled from NGC 5426 during its passage close to NGC 5427. Its distribution, more intense between the arms and just outside the disk of NGC 5427, and weak, or absent, in the arms, suggests that the infalling gas is behind the disk, ionized by Lyman continuum photons escaping from NGC 5427. Modeling this, we estimate the distances of these gas clouds behind the plane: a few hundred parsecs to a few kiloparsecs. We also estimate the mass of the infalling (ionized plus neutral) gas, finding an infall rate of 10 M per year, consistent with the high measured star formation rate across the disk of NGC 5427 and with the detected circumnuclear galactic wind.
The understanding of the formation and evolution of galaxies will not be complete until we understand the physical processes that trigger and regulate starformation in them. This work is about star ...formation on several size scales. It includes the kinematic study of 157 H II regions in the spiral galaxy M83, in order to test the relation, if any, between luminosity (L) and velocity dispersion(s), indicative of virialization. We found that there is no strong correlation between the mentioned variables, but only an upper envelope with a maximum luminosity for a given velocity dispersion. We demonstrated that this envelope has a slope that is strongly dependent on an accurate correction of instrumental broadening. Using our experience in H II regions, we moved to star formation at larger scales. Thus, the bulk of this thesis is on starburst galaxies and their evolutionary descendants, the postburst galaxies. A starburst is a galaxy that is suddenly creating large amounts of stars, at a rate that is not sustainable for long periods.We performed a kinematic study of a sample of 11 such objects, showing that they are, in general, not supported by rotation and that many of them are consistent with a recent merger which affected their morphology and kinematics.Furthermore, from Sloan Digital Sky Survey (SDSS) we extracted a robust sample of 1006 starbursts and 240 postbursts at redshift 0.010<z<0.083. We performed a comparative study of their structural parameters, such as effective radius, sersic index, asymmetry and absolute magnitude. We have found that the majority of starbursts and postbursts in the nearby Universe are disky galaxies, with a tendency for starbursts to have shorter effective radii and larger asymmetries.
At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 2: Manuscript; Paper 3: Manuscript.
Using velocity tagging we have detected hydrogen from NGC 5426 falling onto its interacting partner NGC 5427. Our observations, with the GHaFaS Fabry-Perot spectrometer, produced maps of the two ...galaxies in Halpha surface brightness and radial velocity. We found emission with the range of velocities associated with NGC 5426 along lines of sight apparently emanating from NGC 5427, superposed on the velocity map of the latter. After excluding instrumental effects we assign the anomalous emission to gas pulled from NGC 5426 during its passage close to NGC 5427. Its distribution, more intense between the arms and just outside the disk of NGC 5427, and weak, or absent, in the arms, suggests that the infalling gas is behind the disk., ionized by Lyman continuum photons escaping from NGC 5427. Modeling this, we estimate the distances of these gas clouds- behind the plane: a few hundred pc to a few kpc. We also estimate the mass of the infalling (ionized plus neutral) gas, finding an infall rate of 10 solar masses per year, consistent with the high measured SFR across the disk of NGC 5427 and with the detected circumnuclear galactic wind.
We analyse the internal dynamics of star-forming HII regions and their efficiency in interacting with the ISM. We use GHaFaS (Fabry-Perot) data of the nearby spiral galaxy M83 to perform ...multiple-Gaussian fitting to the integrated Halpha emission line for 136 HII regions, advanced instrumental response subtraction and to study the Luminosity-velocity dispersion relation. We find that the best way of dealing with instrumental response effects is convolving its actual shape with the Gaussian before fitting and that in our data almost none of the regions need a secondary Gaussian.
This paper presents a multiproxy palaeoenvironmental study from Abric del Pastor (Alcoy, Spain), a rock shelter which has yielded evidence for Middle Palaeolithic human occupation. The sedimentary ...sequence has been analysed for lipid biomarker n-alkane abundances (ACL, CPI), compound specific leaf wax δ2H and δ13C, and bulk organic geochemistry (TOC, %N, %S), providing a record of past climate and local vegetation dynamics. Site formation processes have been reconstructed through the application of soil micromorphology. Analyses of anthracological, microvertebrate and macrofaunal assemblages from selected subunits are also presented here. Our data indicates that a variable climate marked by predominantly cold conditions persisted through most of the sequence and that Neanderthal occupations in stratigraphic unit IVd, assigned to MIS 4 or late MIS 5, occurred in a landscape setting characterised by a mosaic of biotopes. The presence of key resources inside the ravine where the site is located suggests that the occupation of the rock shelter may have been strategically motivated by a subsistence and mobility strategy which focused on zones of localised ecological resilience, such as intra-mountainous valleys or ravines, during periods of global or regional environmental downturn.
•New palaeoenvironmental data for Neanderthal site of Abric del Pastor is presented.•Degradation of n-alkanes linked to anthropogenic fire.•Occupations in S.U. IVd occurred in generally cold and dry conditions.•The Barranc del Cinc acted as a vegetation refugium.•Occupation of rock shelter may have been strategically motivated by its location.
Purpose
Thrombotic events (TE) represent one of the major complications of SARS-CoV-2 infection. The objective is to evaluate vessel density (VD) and perfusion density (PD) by optical coherence ...tomography angiography (OCTA) in COVID-19 patients, and compare the findings with healthy controls. The secondary objective is to evaluate if there are differences in OCTA parameters between COVID-19 patients with and without associated TE.
Methods
Cross-sectional case–control study that included patients with laboratory-confirmed diagnosis of COVID-19 with and without TE related to the infection and age-matched healthy controls. Ophthalmological examination and OCTA were performed 12 weeks after diagnosis. Demographic data and medical history were collected. Macular OCTA parameters in the superficial retinal plexus were analyzed according to ETDRS sectors.
Results
Ninety patients were included, 19 (20%) COVID-19 patients with associated TE, 47 (49.5%) COVID-19 patients without TE, and 29 (30.5%) healthy controls. Fifty-three (55.7%) were male, mean age 54.4 (SD 10.2) years. COVID-19 patients presented significantly lower VD than healthy controls: central (
p
= 0.003), inner ring (
p
= 0.026), outer ring (
p
= 0.001). PD was also significantly decreased: outer ring (
p
= 0.003), full area (
p
= 0.001). No differences in OCTA parameters were found between COVID-19 patients with and without TE.
Conclusions
OCTA represents a promising tool for the in vivo assessment of microvascular changes in COVID-19. Patients with SARS-CoV-2 infection show lower VD and PD compared to healthy controls. However, no differences were found between COVID-19 when considering TE. Prospective studies are required to further evaluate the retinal microvascular involvement of SARS-CoV-2 and its impact on the vasculature of other organs.
We present the integrated Halpha emission line profile for 157 HII regions in the central 3.4' x 3.4' of the galaxy M 83 (NGC 5236). Using the Fabry-Perot interferometer GHaFaS, on the 4.2 m William ...Herschel on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity-velocity dispersion relation is also studied, and in the log(L)-log(sigma) plane we do not find a linear relation, but an upper envelope with equation log(L)=0.9 *log(sigma)+38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity L=10^38.5 ergs, in full agreement with previous studies of other galaxies, reinforcing the idea of using HII regions as standard candles.
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