188 research outputs found
Integral field optical spectroscopy of a representative sample of ULIRGs: I. The Data
We present a project aimed at studying the structure, dust distribution,
ionization state, and kinematics of a representative sample of 22 ULIRGs. The
galaxies in the sample undergo different merger phases (they are evenly divided
between pre- and post-coalescence systems) and ionization stages (27% HII, 32%
LINER, 18% Seyfert, and 23% mixed classifications) over a wide infrared
luminosity range (11.8<Lir/Lsun<12.6), which also includes some galaxies of low
luminosity. The main aims of this paper are to present the sample and discuss
the structure of the stellar and ionized gas components. Our results imply that
evolution caused by a merger is occurring in the ionized gas structure of
ULIRGs. The present study relies on the use of integral field optical
spectroscopy data obtained with the INTEGRAL instrument at the 4.2 m William
Herschel Telescope.Comment: To appear in A&A. Paper with higher quality images can be found at
http://hera.ph1.uni-koeln.de/ftpspace/maca/Catalog
Studying the kinematic asymmetries of disks and post-coalescence mergers using a new `kinemetry' criterion
We have obtained VIMOS/VLT optical integral field spectroscopy (IFS) data for
a sample of 4 LIRGs which have been selected at a similar distance ( 70
Mpc) to avoid relative resolution effects. They have been classified in two
groups (isolated disk and post-coalescence mergers) according to their
morphology. The method (developed by Krajnovic and coworkers) is
used to characterize the kinematic properties of these galaxies and to discuss
new criteria for distinguishing their status. We present and discuss new
kinematic maps (i.e., velocity field and velocity dispersion) for these four
galaxies. The morphological and kinematic classifications of these systems are
consistent, with disks having lower kinematic asymmetries than post-coalescence
mergers. We then propose and discuss a new kinematic criterion to differentiate
these two groups. This criterion distinguishes better these two categories and
has the advantage of being less sensitive to angular resolution effects.
According to the previous criteria,the present post-coalescence systems would
have been classified as disks. This indicates that the separation of disks from
mergers is subjective to the definition of `merger'. It also suggests that
previous estimates of the merger/disk ratio could have been underestimated, but
larger samples are necessary to establish a firmer conclusion.Comment: 15 figures, 19 page
Search for Tidal Dwarf Galaxies Candidates in a Sample of Ultraluminous Infrared Galaxies
(ABRIDGED) Star-forming small galaxies made out of collisional debris have
been found in a variety of merging systems. So far only a few of them are known
in ULIRGs although they show clear signs of interactions. Whether external star
formation may take place in such objects is an open question. The aim of this
paper is to identify and characterise the physical and kinematic properties of
the external star forming regions in a sample of ULIRGs, including TDG
candidates, using optical IFS and high angular resolution HST imaging. We have
found that the presence of external star-forming regions is common with 12
objects being identified in 5 ULIRGs. These regions show a large range of
dynamical mass up to 1x10^{10} M_sun, with average sizes of ~750 pc. In
addition, the line ratios, metallicities and H\alpha equivalent widths are
typical of young bursts of star formation (age ~ 5-8 Myr), and similar to those
of other TDG candidates. Their extinction corrected H\alpha luminosities lead
to masses for the young stellar component of ~2x10^6 - 7x10^8 M_sun. The
likelihood of survival of these regions as TDGs is discussed based on their
structural and kinematic properties. Most of these systems follow the relation
between effective radius and velocity dispersion found for globular clusters
and Ellipticals, which suggests they are stable against internal motions. The
stability against forces from the parent galaxy have been studied and a
comparison of the data with the predictions of dynamical evolutionary models is
also performed. Five regions out of twelve show High-Medium or High likelihood
of survival. Our best candidate, which satisfy all the utilized criteria, is
located in the advanced merger IRAS15250+3609 and presents a velocity field
decoupled from the relatively distant parent galaxy.Comment: 14 pages, 7 figures; A&A accepte
Whole transcriptome approach to evaluate the effect of aluminium hydroxide in ovine encephalon
Aluminium hydroxide adjuvants are crucial for livestock and human vaccines. Few studies have analysed their effect on the central nervous system in vivo. In this work, lambs received three different treatments of parallel subcutaneous inoculations during 16Â months with aluminium-containing commercial vaccines, an equivalent dose of aluminium hydroxide or mock injections. Brain samples were sequenced by RNA-seq and miRNA-seq for the expression analysis of mRNAs, long non-coding RNAs and microRNAs and three expression comparisons were made. Although few differentially expressed genes were identified, some dysregulated genes by aluminium hydroxide alone were linked to neurological functions, the lncRNA TUNA among them, or were enriched in mitochondrial energy metabolism related functions. In the same way, the miRNA expression was mainly disrupted by the adjuvant alone treatment. Some differentially expressed miRNAs had been previously linked to neurological diseases, oxidative stress and apoptosis. In brief, in this study aluminium hydroxide alone altered the transcriptome of the encephalon to a higher degree than commercial vaccines that present a milder effect. The expression changes in the animals inoculated with aluminium hydroxide suggest mitochondrial disfunction. Further research is needed to elucidate to which extent these changes could have pathological consequences
VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies II. Evidence for shock ionization caused by tidal forces in the extra-nuclear regions of interacting and merging LIRGs
LIRGs are an important class of objects in the low-z universe bridging the
gap between normal spirals and the strongly interacting and starbursting
ULIRGs. Studies of their 2D physical properties are still lacking. We aim to
understand the nature and origin of the ionization mechanisms operating in the
extranuclear regions of LIRGs as a function of the interaction phase and L_IR
by using IFS data obtained with VIMOS. Our analysis is based on over 25300
spectra of 32 LIRGs covering all types of morphologies and the entire
10^11-10^12 L_sun range. We found strong evidence for shock ionization, with a
clear trend with the dynamical status of the system. Specifically, we
quantified the variation with interaction phase of several line ratios
indicative of the excitation degree. While the [NII]/Ha ratio does not show any
significant change, the [SII]/Ha and [OI]/Ha ratios are higher for more
advanced interaction stages. We constrained the main mechanisms causing the
ionization in the extra-nuclear regions using diagnostic diagrams. Isolated
systems are mainly consistent with ionization caused by young stars. Large
fractions of the extra-nuclear regions in interacting pairs and more advanced
mergers are consistent with ionization caused by shocks. This is supported by
the relation between the excitation degree and the velocity dispersion of the
ionized gas, which we interpret as evidence for shock ionization in interacting
galaxies and advanced mergers but not in isolated galaxies. This relation does
not show any dependence with L_IR. All this indicates that tidal forces play a
key role in the origin of the ionizing shocks in the extra-nuclear regions. We
also showed what appears to be a common [OI]/Ha-sigma relation for the
extranuclear ionized gas in interacting (U)LIRGs. This needs to be investigated
further with a larger sample of ULIRGs.Comment: Accepted for publication in Astronomy and Astrophysics. Some figures
were removed due to space limitations. A version with the whole set of
figures can be seen at
http://www.damir.iem.csic.es/extragalactic/publications/publications.htm
PMAS integral field spectroscopy of luminous infrared galaxies. I.- The atlas
In this paper we present PMAS optical (3800-7200A) IFS of the northern
hemisphere portion of a volume-limited sample of 11 LIRGs. The PMAS
observations typically cover the central ~5kpc and are complemented with
HST/NICMOS images. For most LIRGs in our sample, the peaks of the continuum and
gas (e.g., Halpha, [NII]) emissions coincide, unlike what is observed in local,
strongly interacting ULIRGs. The only exceptions are galaxies with
circumnuclear rings of star formation where the most luminous Halpha emitting
regions are found in the rings rather than in the nuclei, and the displacements
are well understood in terms of differences in the stellar populations. A large
fraction of the nuclei of these LIRGs are classified as LINER and intermediate
LINER/HII, or composite objects. The excitation conditions of the integrated
emission depend on the relative contributions of HII regions and the diffuse
emission to the line emission over the PMAS FoV. Galaxies dominated by high
surface-brightness HII regions show integrated HII-like excitation. A few
galaxies show slightly larger integrated [NII]/Halpha and [SII]/Halpha line
ratios than the nuclear ones, probably because of more contribution from the
diffuse emission. The Halpha velocity fields over the central few kpc are
generally consistent, at least to first order, with rotational motions. The
velocity fields of most LIRGs are similar to those of disk galaxies, in
contrast to the highly perturbed fields of most local, strongly interacting
ULIRGs. The peak of the Halpha velocity dispersion coincides with the position
of the nucleus and is likely to be tracing mass. All these results are similar
to the properties of z~1 LIRGs, and they highlight the importance of detailed
studies of flux-limited samples of local LIRGs. (Abridged)Comment: Accepted for publication in Astronomy and Astrophysic
VLT-SINFONI integral field spectroscopy of low-z luminous and ultraluminous infrared galaxies
We present an atlas of a sample of local (z < 0.1) LIRGs (10) and ULIRGs (7) covering the luminosity range log(LIR/Lâ) = 11.1â12.4. The atlas is based on near-infrared H (1.45â1.85 ÎŒm) and K-band (1.95â2.45 ÎŒm) VLT-SINFONI integral field spectroscopy (IFS). The atlas presents the ionised, partially ionised, and warm molecular gas two-dimensional flux distributions and kinematics over an FoV of ~3âĂâ3âkpc (LIRGs) and ~12âĂâ12âkpc (ULIRGs) and with average linear resolutions of ~0.2âkpc and ~0.9âkpc, respectively. The different phases of the gas show a wide morphological variety with the nucleus as the brightest BrÎł source for ~33% of the LIRGs and ~71% of the ULIRGs, whereas all the LIRGs and ULIRGs have their maximum H2 emission in their nuclear regions. In LIRGs, the ionised gas distribution is dominated by the emission from the star-forming rings or giant HII regions in the spiral arms. The BrÎł and [FeII] line at 1.644âÎŒm trace the same structures, although the emission peaks at different locations in some of the objects, and the [FeII] seems to be more extended and diffuse. The ULIRG subsample is at larger distances and contains mainly pre-coalescence interacting systems. Although the peaks of the molecular gas emission and the continuum coincide in ~71% of the ULIRGs, regions with intense Paα (BrÎł) emission tracing luminous star-forming regions located at distances of 2â4âkpc away from the nucleus are also detected, usually associated with secondary nuclei or tidal tails. LIRGs have mean observed (i.e. uncorrected for internal extinction) SFR surface densities of about 0.4 to 0.9 Mââyr-1âkpc-2 over large areas (4â9 kpc2) with peaks of about 2â2.5 Mââyr-1âkpc-2 in the smaller regions (0.16âkpc2) associated with the nucleus of the galaxy or the brightest BrÎł region. ULIRGs do have similar average SFR surface densities for the integrated emitting regions of ~0.4âMââyr-1âkpc-2 in somewhat larger areas (100â200 kpc2) and for the Paα peak (~2âMââyr-1âkpc-2 in 4 kpc2). The observed gas kinematics in LIRGs is primarily due to rotational motions around the centre of the galaxy, although local deviations associated with radial flows and/or regions of higher velocity dispersions are present. The ionised and molecular gas share the same kinematics (velocity field and velocity dispersion) to first order, showing slight differences in the velocity amplitudes (peak-to-peak) in some cases, whereas the average velocity dispersions are compatible within uncertainties. As expected, the kinematics of the ULIRG subsample is more complex, owing to the interacting nature of the objects of the sample
Extranuclear Halpha-emitting complexes in low-z (U)LIRGs: Precursors of tidal dwarf galaxies?
(Abridged)This paper characterizes the physical and kinematic properties of
external massive star-forming regions in a sample of (U)LIRGs. We use high
angular resolution ACS images from the HST B and I bands, as well as
Halpha-line emission maps obtained with IFS. We find 31 external
Halpha-emitting (young star-forming) complexes in 11 (U)LIRGs. These complexes
have in general similar sizes, luminosities, and metallicities to extragalactic
giant HII regions and TDG candidates found in less luminous mergers and compact
groups of galaxies. We assess the mass content and the likelihood of survival
as TDGs of the 22 complexes with simple structures in the HST images based on
their photometric, structural, and kinematic properties. The dynamical tracers
used (radius-sigma and luminosity-sigma diagrams) indicate that most of the
complexes might be self-gravitating entities. The resistance to forces from the
parent galaxy is studied by considering the tidal mass of the candidate and its
relative velocity with respect to the parent galaxy. After combining the
results of previous studies of TDG searches in ULIRGs a total of 9 complexes
satisfy most of the applied criteria and thus show a high-medium or high
likelihood of survival, their total mass likely being compatible with that of
dwarf galaxies. They are defined as TDG candidates. We propose that they
probably formed more often during the early phases of the interaction.
Combining all data for complexes with IFS data where a significant fraction of
the system is covered, we infer a TDG production rate of 0.3 candidates with
the highest probabilities of survival per system for the (U)LIRGs class. This
rate, though, might decrease to 0.1 after the systems in (U)LIRGs have evolved
for 10 Gyr, for long-lived TDGs, which would imply that no more than 5-10 % of
the overall dwarf population could be of tidal origin.Comment: Accepted for publication in A&A, 21 pages, 8 figures. Typo corrected
(article 1111.0468
Gender differences in the plasma concentration of the GAS6-TAM system in COVID-19 patients
Resumen del trabajo presentado en el 4th European Congress on Thrombosis and Haemostasis, celebrado en Gante (BĂ©lgica), los dĂas 14 y 15 de octubre de 2021Background: SARS-CoV-2 induces an immune response with potentially harmful effects for the patient due to an uncontrolled release of inflammatory factors, specially at the capillary wall. The vitamin K-dependent plasma protein GAS6 and the TAM (TYRO3, AXL, and MERTK) receptors play a relevant role among restorative mechanisms that counterbalance pro-inflammatory responses at the endothelial interface.
Aims: To study the influence of gender on the effects of SARS-CoV-2 infection in the GAS6/TAM system, as reflected by plasma concentration at patient admittance at the emergency ward.
Methods: The plasma content of GAS6, AXL, and MERTK was analyzed in a first group of 132 patients, 68 females and 64 males consecutively admitted to the emergency ward during the first peak of COVID-19. A confirmatory group was studied from the second wave of contagions. An analysis of gender differences in relation to the GAS6/TAM concentrations in plasma was performed on this population.
Results: In accordance with recently published GAS6 levels, significantly higher in the SARS-CoV-2 positive than in negative patients, increased progressively with the severity of the disease in SARS-CoV-2 positive individual irrespective of the gender of the patient. In contrast, while soluble AXL exhibited higher plasma concentration in deceased patients and no significant differences were observed in MERTK concentration, differential gender analysis suggest differences in soluble TAM receptors. While a COVID-19 related increase in sAXL was observed in men, this was not the case in women. Oppositely, MERTK differences due to COVID-19 infection were only significant in women.
Summary/Conclusion: GAS6-TAM system of ligands and receptors is implicated in the immune response to SARS-CoV-2 in patients from both genders. Plasma GAS6 levels paralleled COVID-19 severity being an early marker of disease prognosis in both sexes. In contrast, soluble TAM receptors presented a gender-specific behavior. Sex-related differences in sAXL and sMERTK expression in COVID-19 patients could affect therapy efficacy deserving further investigation
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