43,373 research outputs found
Piezoelectric transducer
Transducer consists of a hybrid thin film and a piezoelectric transistor that acts as a stress-sensitive device with built-in gain. It provides a stress/strain transducer that incorporates a signal amplification stage and sensor in a single package
Isotopic ratios at z=0.68 from molecular absorption lines toward B 0218+357
Isotopic ratios of heavy elements are a key signature of the nucleosynthesis
processes in stellar interiors. The contribution of successive generations of
stars to the metal enrichment of the Universe is imprinted on the evolution of
isotopic ratios over time. We investigate the isotopic ratios of carbon,
nitrogen, oxygen, and sulfur through millimeter molecular absorption lines
arising in the z=0.68 absorber toward the blazar B 0218+357. We find that these
ratios differ from those observed in the Galactic interstellar medium, but are
remarkably close to those in the only other source at intermediate redshift for
which isotopic ratios have been measured to date, the z=0.89 absorber in front
of PKS1830-211. The isotopic ratios in these two absorbers should reflect
enrichment mostly from massive stars, and they are indeed close to the values
observed toward local starburst galaxies. Our measurements set constraints on
nucleosynthesis and chemical evolution models.Comment: Accepted for publication in Astronomy & Astrophysics; 10 pages, 9
figure
Implications of Alternative Emission Trading Plans: Experimental Evidence
Two approaches to emissions trading are cap-and-trade, in which an aggregate cap on emissions is distributed in the form of emission allowances and baseline-and-credit, in which firms earn emission reduction credits for emissions below their baselines. Theoretical considerations suggest the long-run equilibria of the two plans will differ if baselines are proportional to output, because a variable baseline is equivalent to an output subsidy. To test this prediction we have developed a computerized environment in which subjects representing firms can adjust both their emission rates (per unit output) and capacity levels. Subjects buy or sell emission rights (allowances or credits) in a sealed bid call auction. The demand for output is simulated. All decisions are tracked through a double-entry bookkeeping system. This environment is to be used to compare short and long run responses to the alternative trading methods. Initial experiments in this environment will alternately hold emission rate and capacity choice constant. We report on six experimental sessions with variable emissions rates but fixed capacity and two pilot sessions with variable capacity but fixed emission rates.
Deep ALMA imaging of the merger NGC1614 - Is CO tracing a massive inflow of non-starforming gas?
Observations of the molecular gas over scales of 0.5 to several kpc provide
crucial information on how gas moves through galaxies, especially in mergers
and interacting systems, where it ultimately reaches the galaxy center,
accumulates, and feeds nuclear activity. Studying the processes involved in the
gas transport is an important step forward to understand galaxy evolution.
12CO, 13CO and C18O1-0 high-sensitivity ALMA observations were used to assess
properties of the large-scale molecular gas reservoir and its connection to the
circumnuclear molecular ring in NGC1614. The role of excitation and abundances
were studied in this context. Spatial distributions of the 12CO and 13CO
emission show significant differences. 12CO traces the large-scale molecular
gas reservoir, associated with a dust lane that harbors infalling gas. 13CO
emission is - for the first time - detected in the large-scale dust lane. Its
emission peaks between dust lane and circumnuclear molecular ring. A
12CO-to-13CO1-0 intensity ratio map shows high values in the ring region (~30)
typical for the centers of luminous galaxy mergers and even more extreme values
in the dust lane (>45). This drop in ratio is consistent with molecular gas in
the dust lane being in a diffuse, unbound state while being funneled towards
the nucleus. We find a high 16O-to-18O abundance ratio in the starburst region
(>900), typical of quiescent disk gas - by now, the starburst is expected to
have enriched the nuclear ISM in 18O relative to 16O. The massive inflow of gas
may be partially responsible for the low 18O/16O abundance since it will dilute
the starburst enrichment with unprocessed gas from greater radii. The
12CO-to-13CO abundance is consistent with this scenario. It suggests that the
nucleus of NGC1614 is in a transient phase of evolution where starburst and
nuclear growth are fuelled by returning gas from the minor merger event.Comment: 10 pages, 9 figures, accepted for publication in A&
A survey of HC_3N in extragalactic sources: Is HC_3N a tracer of activity in ULIRGs?
Context. HC_3N is a molecule that is mainly associated with Galactic star-forming regions, but it has also been detected in extragalactic environments.
Aims. To present the first extragalactic survey of HC_3N, when combining earlier data from the literature with six new single-dish detections, and to compare HC_3N with other molecular tracers (HCN, HNC), as well as other properties (silicate absorption strength, IR flux density ratios, C_(II) flux, and megamaser activity).
Methods. We present mm IRAM 30 m, OSO 20 m, and SEST observations of HC_3N rotational lines (mainly the J = 10–9 transition) and of the J = 1–0 transitions of HCN and HNC. Our combined HC_3N data account for 13 galaxies (excluding the upper limits reported for the non-detections), while we have HCN and HNC data for more than 20 galaxies.
Results. A preliminary definition “HC_3N-luminous galaxy” is made based upon the HC_3N/HCN ratio. Most (~80%) HC_3N-luminous galaxies seem to be deeply obscured galaxies and (U)LIRGs. A majority (~60% or more) of the HC3N-luminous galaxies in the sample present OH mega- or strong kilomaser activity. A possible explanation is that both HC_3N and OH megamasers need warm dust for their excitation. Alternatively, the dust that excites the OH megamaser offers protection against UV destruction of HC_3N. A high silicate absorption strength is also found in several of the HC_3N-luminous objects, which may help the HC3N to survive. Finally, we find that a high HC_3N/HCN ratio is related to a high dust temperature and a low C_(II) flux
Molecular tendrils feeding star formation in the Eye of the Medusa - The Medusa merger in high resolution 12CO 2-1 maps
Studying molecular gas properties in merging galaxies gives us important
clues to the onset and evolution of interaction-triggered starbursts. NGC4194
is particularly interesting to study since its FIR-to-CO luminosity ratio
rivals that of ULIRGs,despite its lower luminosity compared to ULIRGs, which
indicates a high star formation efficiency that is relative to even most
spirals and ULIRGs.We study the molecular medium at an angular resolution of
0.65"x .52" through our observations of CO2-1 emission using the SMA. We
compare our CO2-1 maps with optical HST and high angular resolution radio
continuum images to study the relationship between molecular gas and other
components of the starburst region. The molecular gas is tracing the
complicated dust lane structure of NGC4194 with the brightest emission being
located in an off-nuclear ring-like structure with ~320pc radius, the Eye of
the Medusa. The bulk CO emission of the ring is found south of the kinematical
center of NGC4194. The northern tip of the ring is associated with the galaxy
nucleus, where the radio continuum has its peak. A prominent, secondary
emission maximum in the radio continuum is located inside the molecular ring.
This suggests that the morphology of the ring is partially influenced by
massive supernova explosions. From the combined evidence, we propose that the
Eye of the Medusa contains a shell of swept up material where we identify a
number of giant molecular associations. We propose that the Eye may be the site
of an efficient starburst of 5-7M_sun/yr, but it would still constitute only a
fraction of the 30-50M_sun/yr SFR of NGC4194. Furthermore, we find that ~50% of
the molecular mass of NGC4194 is found in extended filamentary-like structures
tracing the minor and major axis dust lanes. We suggest that molecular gas is
transported along these lanes providing the central starburst region with fuel.Comment: accepted for publication in A&A, 12 pages, 9 figure
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Morphological evidence for a sea-ice origin for Elysium Planitia platy terrain
Abstract not available
Solvable senescence model with positive mutations
We build upon our previous analytical results for the Penna model of
senescence to include positive mutations. We investigate whether a small but
non-zero positive mutation rate gives qualitatively different results to the
traditional Penna model in which no positive mutations are considered. We find
that the high-lifespan tail of the distribution is radically changed in
structure, but that there is not much effect on the bulk of the population. Th
e mortality plateau that we found previously for a stochastic generalization of
the Penna model is stable to a small positive mutation rate.Comment: 3 figure
Exact Results for Evaporating Black Holes in Curvature-Squared Lovelock Gravity: Gauss-Bonnet Greybody Factors
Lovelock gravity is an important extension of General Relativity that
provides a promising framework to study curvature corrections to the Einstein
action, while avoiding ghosts and keeping second order field equations. This
paper derives the greybody factors for D-dimensional black holes arising in a
theory with a Gauss-Bonnet curvature-squared term. These factors describe the
non-trivial coupling between black holes and quantum fields during the
evaporation process: they can be used both from a theoretical viewpoint to
investigate the intricate spacetime structure around such a black hole, and for
phenomenological purposes in the framework of braneworld models with a low
Planck scale. We derive exact spectra for the emission of scalar, fermion and
gauge fields emitted on the brane, and for scalar fields emitted in the bulk,
and demonstrate how the Gauss-Bonnet term can change the bulk-to-brane emission
rates ratio in favour of the bulk channel in particular frequency regimes.Comment: 29 pages, Latex file, 11 figures, Data files (greybody factors)
available at http://lpsc.in2p3.fr/ams/greybody/, typos corrected, references
added, version to appear in Phys. Rev.
Major impact from a minor merger - The extraordinary hot molecular gas flow in the Eye of the NGC 4194 Medusa galaxy
Minor mergers are important processes contributing significantly to how
galaxies evolve across the age of the Universe. Their impact on supermassive
black hole growth and star formation is profound. The detailed study of dense
molecular gas in galaxies provides an important test of the validity of the
relation between star formation rate and HCN luminosity on different galactic
scales. We use observations of HCN, HCO+1-0 and CO3-2 to study the dense gas
properties in the Medusa merger. We calculate the brightness temperature ratios
and use them in conjunction with a non-LTE radiative line transfer model. The
HCN and HCO+1-0, and CO3-2 emission do not occupy the same structures as the
less dense gas associated with the lower-J CO emission. The only emission from
dense gas is detected in a 200pc region within the "Eye of the Medusa". No HCN
or HCO+ is detected for the extended starburst. The CO3-2/2-1 brightness
temperature ratio inside "the Eye" is ~2.5 - the highest ratio found so far.
The line ratios reveal an extreme, fragmented molecular cloud population inside
"the Eye" with large temperatures (>300K) and high gas densities (>10^4 cm^-3).
"The Eye" is found at an interface between a large-scale minor axis inflow and
the Medusa central region. The extreme conditions inside "the Eye" may be the
result of the radiative and mechanical feedback from a deeply embedded, young,
massive super star cluster, formed due to the gas pile-up at the intersection.
Alternatively, shocks from the inflowing gas may be strong enough to shock and
fragment the gas. For both scenarios, however, it appears that the HCN and HCO+
dense gas tracers are not probing star formation, but instead a post-starburst
and/or shocked ISM that is too hot and fragmented to form new stars. Thus,
caution is advised in linking the detection of emission from dense gas tracers
to evidence of ongoing or imminent star formation.Comment: 10 pages, 5 figures, 2 tables, accepted for publication in A&
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