17 research outputs found
Integral field spectroscopy of M1-67. A Wolf-Rayet nebula with LBVN appearance
This work aims to disentangle the morphological, kinematic, and chemical
components of the nebula M1-67 to shed light on its process of formation around
the central Wolf-Rayet (WR) star WR124. We have carried out integral field
spectroscopy observations over two regions of M1-67, covering most of the
nebula in the optical range. Maps of electron density, line ratios, and radial
velocity were created to perform a detailed analysis of the two-dimensional
structure. We studied the physical and chemical properties by means of
integrated spectra selected over the whole nebula. Photoionization models were
performed to confirm the empirical chemical results theoretically. In addition,
we analysed infrared spectroscopic data and the MIPS 24micron image of M1-67
from Spitzer. We find that the ionized gas of M1-67 is condensed in knots
aligned in a preferred axis along the NE-SW direction, like a bipolar
structure. Both electron density and radial velocity decrease in this direction
when moving away from the central star. From the derived electron temperature,
Te~8200 K, we have estimated chemical abundances, obtaining that nitrogen
appears strongly enriched and oxygen depleted. From the last two results, we
infer that this bipolarity is the consequence of an ejection of an evolved
stage of WR124 with material processed in the CNO cycle. The infrared study has
revealed that the bipolar axis is composed of ionized gas with a low ionization
degree that is well mixed with warm dust and of a spherical bubble surrounding
the ejection at 24micron. Taking the evolution of a 60 Mo star and the temporal
scale of the bipolar ejection into account, we propose that the observed gas
was ejected during an eruption in the luminous blue variable. The star has
entered the WR phase recently without apparent signs of interaction between
WR-winds and interstellar material.Comment: Accepted for publication in section 6 of Astronomy and Astrophysics.
The official date of acceptance is 15/03/2013. 17 pages, 14 figures and 8
table
Blue compact dwarf galaxies with nitrogen overabundance: a view from integral field spectroscopy
This is an electronic version of the poster presented at the IX Scientific Meeting of the Spanish Astronomical Society (SEA), held on September 13-17, 2010, in Madrid.The summary of the poster appears in Zapatero Osorio, M.R. et al. (eds.). Highlights of Spanish Astrophysics VI. Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society (SEA), held on September 13-17, 2010, in Madrid. Barcelona: Sociedad Española de Astronomía, 2011. 39
The short-duration GRB 050724 host galaxy in the context of the long-duration GRB hosts
We report optical and near-infrared broad band observations of the
short-duration GRB 050724 host galaxy, used to construct its spectral energy
distribution (SED). Unlike the hosts of long-duration gamma-ray bursts (GRBs),
which show younger stellar populations, the SED of the GRB 050724 host galaxy
is optimally fitted with a synthetic elliptical galaxy template based on an
evolved stellar population (age ~2.6 Gyr). The SED of the host is difficult to
reproduce with non-evolving metallicity templates. In contrast, if the short
GRB host galaxy metallicity enrichment is considered, the synthetic templates
fit the observed SED satisfactorily. The internal host extinction is low (A_v
\~< 0.4 mag) so it cannot explain the faintness of the afterglow. This short
GRB host galaxy is more massive (~5x10^10 Mo) and luminous (~1.1 L*) than most
of the long-duration GRB hosts. A statistical comparison based on the ages of
short- and long-duration GRB host galaxies strongly suggests that
short-duration GRB hosts contain, on average, older progenitors. These findings
support a different origin for short- and long-duration GRBs.Comment: A&A in pres
PPAK Integral Field Spectroscopy survey of the Orion Nebula: Data Release
We present a low-resolution spectroscopic survey of the Orion nebula which
data we release for public use. In this article, we intend to show the possible
applications of this dataset analyzing some of the main properties of the
nebula. We perform an integral field spectroscopy mosaic of an area of ~5' X 6'
centered on the Trapezium region of the nebula, including the ionization front
to the south-east. The analysis of the line fluxes and line ratios of both the
individual and integrated spectra allowed us to determine the main
characteristics of the ionization throughtout the nebula.The final dataset
comprises 8182 individual spectra, which sample each one a circular area of
\~2.7" diameter. The data can be downloaded as a single row-stacked spectra
fits file plus a position table or as an interpolated datacube with a final
sampling of 1.5"/pixel. The integrated spectrum across the field-of-view was
used to obtain the main integrated properties of the nebula, including the
electron density and temperature, the dust extinction, the Halpha integrated
flux (after correcting for dust reddening), and the main diagnostic line
ratios. The individual spectra were used to obtain line intensity maps of the
different detected lines. These maps were used to study the distribution of the
ionized hydrogen, the dust extinction, the electron density and temperature,
and the helium and oxygen abundance...Comment: 13 pages, 8 figures, accepted for publishing in Astronomy &
Astrophysic
The interplay between ionized gas and massive stars in the HII galaxy IIZw70: integral field spectroscopy with PMAS
We performed an integral field spectroscopic study for the HII galaxy IIZw70
in order to investigate the interplay between its ionized interstellar medium
(ISM) and the massive star formation (SF). Observations were taken in the
optical spectral range (3700-6800 A) with the Potsdam Multi-Aperture
Spectrophotometer (PMAS) attached to the 3.5 m telescope at CAHA. We created
and analysed maps of spatially distributed emission-lines, continuum emission
and properties of the ionized ISM (e.g. physical-chemical conditions, dust
extinction, kinematics). We investigated the relation of these properties to
the spatial distribution and evolutionary stage of the massive stars. For the
first time we have detected the presence of Wolf-Rayet (WR) stars in this
galaxy. The peak of the ionized gas emission coincides with the location of the
WR bump. The region of the galaxy with lower dust extinction corresponds to the
region that shows the lowest values of velocity dispersion and radial velocity.
The overall picture suggests that the ISM of this region is being disrupted via
photoionization and stellar winds, leading to a spatial decoupling between
gas+stars and dust clouds. The bulk of dust appears to be located at the
boundaries of the region occupied by the probable ionizing cluster. We also
found that this region is associated to the nebular emission in HeII4686 and to
the intensity maximum of most emission lines. This indicates that the hard
ionizing radiation responsible for the HeII4686 nebular emission can be related
to the youngest stars. Within 0.4 x 0.3 kpc^2 in the central burst, we
derived O/H using direct determinations of Te[OIII]. We found abundances in the
range 12+log(O/H)=7.65-8.05, yielding an error-weighted mean of
12+log(O/H)=7.86 0.05.Comment: 10 pages, 10 figures, accepted for publication in A&A, minor changes
adde
Integral field spectroscopy of nitrogen overabundant blue compact dwarf galaxies
We study the spatial distribution of the physical properties and of oxygen
and nitrogen abundances in three Blue Compact Dwarf Galaxiess (HS 0128+2832, HS
0837+4717 and Mrk 930) with a reported excess of N/O in order to investigate
the nature of this excess and, particularly, if it is associated with
Wolf-Rayet (WR) stars We have observed these BCDs by using PMAS integral field
spectroscopy in the optical spectral range (3700 - 6900 {\AA}), mapping their
physical-chemical properties, using both the direct method and appropriate
strong-line methods. We make a statistical analysis of the resulting
distributions and we compare them with the integrated properties of the
galaxies. Our results indicate that outer parts of the three galaxies are
placed on the "AGN-zone" of the [NII]/H{\alpha} vs. [OIII]/H{\beta} diagnostic
diagram most likely due to a high N/O combined with the excitation structure in
these regions. From the statistical analysis, it is assumed that a certain
property can be considered as spatially homogeneous (or uniform) if a normal
gaussian function fits its distribution in several regions of the galaxy.
Moreover, a disagreement between the integrated properties and the mean values
of the distribution usually appears when a gaussian does not fit the
corresponding distribution. We find that for Mrk 930, the uniformity is found
for all parameters, except for electron density and reddening. The rotation
curve together with the H{\alpha} map and UV images, reveal a perturbed
morphology and possible interacting processes. The N/O is found to be constant
in the three studied objects at spatial scales of the order of several kpc so
we conclude that the number of WR stars estimated from spectroscopy is not
sufficient to pollute the ISM and to produce the observed N/O excess in these
objectsComment: 17 pages, 14 figures, accepted for publication in Astronomy &
Astrophysic
Transcellular communication at the immunological synapse: A vesicular traffic-mediated mutual exchange
The cell's ability to communicate with the extracellular environment, with other cells, and with itself is a crucial feature of eukaryotic organisms. In the immune system, T lymphocytes assemble a specialized structure upon contact with antigen-presenting cells bearing a peptide-major histocompatibility complex ligand, known as the immunological synapse (IS). The IS has been extensively characterized as a signaling platform essential for T-cell activation. Moreover, emerging evidence identifies the IS as a device for vesicular traffic-mediated cell-to-cell communication as well as an active release site of soluble molecules. Here, we will review recent advances in the role of vesicular trafficking in IS assembly and focused secretion of microvesicles at the synaptic area in naïve T cells and discuss the role of the IS in transcellular communication
Ionization structure and chemical abundances of the Wolf-Rayet nebula NGC 6888 with integral field spectroscopy
Context. The study of nebulae around Wolf-Rayet (WR) stars gives us clues about the mass-loss history of massive stars, as well as about the chemical enrichment of the interstellar medium (ISM).
Aims. This work aims to search for the observational footprints of the interactions between the ISM and stellar winds in the WR nebula NGC 6888 in order to understand its ionization structure, chemical composition, and kinematics.
Methods. We have collected a set of integral field spectroscopy observations across NGC 6888, obtained with PPAK in the optical range performing both 2D and 1D analyses. Attending to the 2D analysis in the northeast part of NGC 6888, we have generated maps of the extinction structure and electron density. We produced statistical frequency distributions of the radial velocity and diagnostic diagrams. Furthermore, we performed a thorough study of integrated spectra in nine regions over the whole nebula.
Results. The 2D study has revealed two main behaviours. We have found that the spectra of a localized region to the southwest of this pointing can be represented well by shock models assuming n = 1000 cm-3, twice solar abundances, and shock velocities from 250 to 400 km s-1. With the 1D analysis we derived electron densities ranging from <100 to 360 cm-3. The electron temperature varies from ~7700 K to ~10 200 K. A strong variation of up to a factor 10 between different regions in the nitrogen abundance has been found: N/H appears lower than the solar abundance in those positions observed at the edges and very enhanced in the observed inner parts. Oxygen appears slightly underabundant with respect to solar value, whereas the helium abundance is found to be above it. We propose a scenario for the evolution of NGC 6888 to explain the features observed. This scheme consists of a structure of multiple shells: i) an inner and broken shell with material from the interaction between the supergiant and WR shells, presenting an overabundance in N/H and a slight underabundance in O/H; ii) an outer shell very intense in [OIII]λ5007 Å corresponding to the main sequence bubble broken up as a consequence of the collision between supergiant and WR shells. Nitrogen and oxygen do not appear enhanced here, but helium appears enriched; iii) and finally it includes an external and faint shell that surrounds the whole nebula like a thin skin representing the early interaction between the winds from the main sequence star with the ISM for which typical circumstellar abundances are derived