88 research outputs found
Climate responsive spatial research by design â a case study analysis on the coastal area of Flanders
Climate responsive research by design â the opportunities of the âVlakte van de Raanâ within the coastal area of Flanders
HERschel Observations of Edge-on Spirals (HEROES). II: Tilted-ring modelling of the atomic gas disks
Context. Edge-on galaxies can offer important insights in galaxy evolution as
they are the only systems where the distribution of the different components
can be studied both radially and vertically. The HEROES project was designed to
investigate the interplay between the gas, dust, stars and dark matter (DM) in
a sample of 7 massive edge-on spiral galaxies.
Aims. In this second HEROES paper we present an analysis of the atomic gas
content of 6 out of 7 galaxies in our sample. The remaining galaxy was recently
analysed according to the same strategy. The primary aim of this work is to
constrain the surface density distribution, the rotation curve and the geometry
of the gas disks in a homogeneous way. In addition we identify peculiar
features and signs of recent interactions.
Methods. We construct detailed tilted-ring models of the atomic gas disks
based on new GMRT 21-cm observations of NGC 973 and UGC 4277 and re-reduced
archival HI data of NGC 5907, NGC 5529, IC 2531 and NGC 4217. Potential
degeneracies between different models are resolved by requiring a good
agreement with the data in various representations of the data cubes.
Results. From our modelling we find that all but one galaxy are warped along
the major axis. In addition, we identify warps along the line of sight in three
galaxies. A flaring gas layer is required to reproduce the data only for one
galaxy, but (moderate) flares cannot be ruled for the other galaxies either. A
coplanar ring-like structure is detected outside the main disk of NGC 4217,
which we suggest could be the remnant of a recent minor merger event. We also
find evidence for a radial inflow of 15 +- 5 km/s in the disk of NGC 5529,
which might be related to the ongoing interaction with two nearby companions.
(Abridged)Comment: 39 pages, 38 figures, Accepted for publication in Astronomy &
Astrophysic
THE INTERACTION OF TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) AND PACED BREATHING ON ACOUSTIC AND LEXICAL SPEECH FEATURES IN THE CONTEXT OF STRESS
THE INTERACTION OF TRANSCRANIAL DIRECT CURRENT STIMULATION (TDCS) AND PACED BREATHING ON ACOUSTIC AND LEXICAL SPEECH FEATURES IN THE CONTEXT OF STRESS
Five hemodynamic variables demonstrate that phenylephrine increases cardiac output by improving venous return in patients with anesthesia-induced hypotension
Metal sorption by biochars : a trade-off between phosphate and carbonate concentration as governed by pyrolysis conditions
Three feedstocks, pine wood, grass and cow manure, were pyrolyzed under various conditions and tested on their ability to sorb metals in aquatic systems. The feedstocks were pyrolyzed at 2 different temperatures (350 degrees C and 550 degrees C) and 2 different residence times (10 and 60 min) and resulting biochars were assessed on their capability to immobilize Pb, Cu, Cd and Zn.
Manure-based chars, and to a lesser extent grass-based chars, featured high concentrations of phosphates and carbonates, These anions play an important role in metal sorption because they form insoluble complexes with the metals. Washing reduced the concentration of these anions, leading to a reduced sorption of metals by the biochar.
The carbonate concentration on the biochars' surface increased at higher reactor temperature and longer residence times. The opposite trend was observed for the phosphate concentration and the cation exchange capacity. Accordingly, the optimal temperature-residence time combination for sorption was a trade-off between these properties. Biochar produced from cow manure and pyrolyzed at 550 degrees C for 10 min showed the best sorption for all metals considered
HERschel Observations of Edge-on Spirals (HEROES). I: Far-infrared morphology and dust mass determination
Context. Edge-on spiral galaxies with prominent dust lanes provide us with an
excellent opportunity to study the distribution and properties of the dust
within them. The HEROES project was set up to observe a sample of seven large
edge-on galaxies across various wavelengths for this investigation.
Aims. Within this first paper, we present the Herschel observations and
perform a qualitative and quantitative analysis on them, and we derive some
global properties of the far infrared and submillimetre emission.
Methods. We determine horizontal and vertical profiles from the Herschel
observations of the galaxies in the sample and describe the morphology.
Modified black-body fits to the global fluxes, measured using aperture
photometry, result in dust temperatures and dust masses. The latter values are
compared to those that are derived from radiative transfer models taken from
the literature.
Results. On the whole, our Herschel flux measurements agree well with
archival values. We find that the exponential horizontal dust distribution
model often used in the literature generally provides a good description of the
observed horizontal profiles. Three out of the seven galaxies show signatures
of extended vertical emission at 100 and 160 {\mu}m at the 5{\sigma} level, but
in two of these it is probably due to deviations from an exactly edge-on
orientation. Only for NGC 4013, a galaxy in which vertically extended dust has
already been detected in optical images, we can detect vertically extended
dust, and the derived scaleheight agrees with the value estimated through
radiative transfer modelling. Our analysis hints at a correlation between the
dust scaleheight and its degree of clumpiness, which we infer from the
difference between the dust masses as calculated from modelling of optical data
and from fitting the spectral energy distribution of Herschel datapoints.Comment: 21 pages, 12 figures. Accepted for publication in Astronomy &
Astrophysic
A resolved analysis of cold dust and gas in the nearby edge-on spiral NGC 891
We investigate the connection between dust and gas in the nearby edge-on
spiral galaxy NGC 891. High resolution Herschel PACS and SPIRE 70, 100, 160,
250, 350, and 500 m images are combined with JCMT SCUBA 850 m
observations to trace the far-infrared/submillimetre spectral energy
distribution (SED). Maps of the HI 21 cm line and CO(J=3-2) emission trace the
atomic and molecular hydrogen gas, respectively. We fit one-component modified
blackbody models to the integrated SED, finding a global dust mass of
8.510 M and an average temperature of 232 K. We
also fit the pixel-by-pixel SEDs to produce maps of the dust mass and
temperature. The dust mass distribution correlates with the total stellar
population as traced by the 3.6 m emission. The derived dust temperature,
which ranges from approximately 17 to 24 K, is found to correlate with the 24
m emission. Allowing the dust emissivity index to vary, we find an average
value of = 1.90.3. We confirm an inverse relation between the dust
emissivity spectral index and dust temperature, but do not observe any
variation of this relationship with vertical height from the mid-plane of the
disk. A comparison of the dust properties with the gaseous components of the
ISM reveals strong spatial correlations between the surface mass densities of
dust and the molecular hydrogen and total gas surface densities. Observed
asymmetries in the dust temperature, and the H-to-dust and total
gas-to-dust ratios hint that an enhancement in the star formation rate may be
the result of larger quantities of molecular gas available to fuel star
formation in the NE compared to the SW. Whilst the asymmetry likely arises from
dust obscuration due to the geometry of the line-of-sight projection of the
spiral arms, we cannot exclude an enhancement in the star formation rate in the
NE side of the disk.Comment: Accepted for publication in A&A. 21 pages, including 13 figures and 4
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