96 research outputs found
Ultracold dense gas of deeply bound heteronuclear molecules
Recently, the quest for an ultracold and dense ensemble of polar molecules
has attracted strong interest. Polar molecules have bright prospects for novel
quantum gases with long-range and anisotropic interactions, for quantum
information science, and for precision measurements. However, high-density
clouds of ultracold polar molecules have so far not been produced. Here, we
report a key step towards this goal. Starting from an ultracold dense gas of
heteronuclear 40K-87Rb Feshbach molecules with typical binding energies of a
few hundred kHz and a negligible dipole moment, we coherently transfer these
molecules into a vibrational level of the ground-state molecular potential
bound by >10 GHz. We thereby increase the binding energy and the expected
dipole moment of the 40K-87Rb molecules by more than four orders of magnitude
in a single transfer step. Starting with a single initial state prepared with
Feshbach association, we achieve a transfer efficiency of 84%. While dipolar
effects are not yet observable, the presented technique can be extended to
access much more deeply bound vibrational levels and ultimately those
exhibiting a significant dipole moment. The preparation of an ultracold quantum
gas of polar molecules might therefore come within experimental reach.Comment: 5 pages, 5 figure
Strong molecular hydrogen emission and kinematics of the multiphase gas in radio galaxies with fast jet-driven outflows
Observations of ionized and neutral gas outflows in radio-galaxies (RGs)
suggest that AGN radio jet feedback has a galaxy-scale impact on the host ISM,
but it is still unclear how the molecular gas is affected. We present deep
Spitzer IRS spectroscopy of 8 RGs that show fast HI outflows. All of these
HI-outflow RGs have bright H2 mid-IR lines that cannot be accounted for by UV
or X-ray heating. This suggests that the radio jet, which drives the HI
outflow, is also responsible for the shock-excitation of the warm H2 gas. In
addition, the warm H2 gas does not share the kinematics of the ionized/neutral
gas. The mid-IR ionized gas lines are systematically broader than the H2 lines,
which are resolved by the IRS (with FWHM up to 900km/s) in 60% of the detected
H2 lines. In 5 sources, the NeII line, and to a lesser extent the NeIII and NeV
lines, exhibit blue-shifted wings (up to -900km/s with respect to the systemic
velocity) that match the kinematics of the outflowing HI or ionized gas. The H2
lines do not show broad wings, except tentative detections in 3 sources. This
shows that, contrary to the HI gas, the H2 gas is inefficiently coupled to the
AGN jet-driven outflow of ionized gas. While the dissipation of a small
fraction (<10%) of the jet kinetic power can explain the dynamical heating of
the molecular gas, our data show that the bulk of the warm molecular gas is not
expelled from these galaxies.Comment: 26 pages, 15 figures, Accepted for ublication in Ap
Starbursts and the triggering of the activity in nearby powerful radio galaxies
We present high quality long-slit spectra for three nearby powerful radio
galaxies 3C293, 3C305, PKS1345+12. These were taken with the aim of
characterising the young stellar populations (YSP), and thereby investigating
the evolution of the host galaxies, as well as the events that triggered the
activity. Isochrone spectral synthesis modelling of the wide wavelength
coverage spectra of nuclear and off-nuclear continuum-emitting regions have
been used to estimate the ages, masses and luminosities of the YSP component,
taking full account of reddening effects and potential contamination by
activity-related components. We find that the YSP make a substantial
contribution to the continuum flux in the off-nuclear regions on a radial scale
of 1 - 20kpc in all three objects. Moreover, in two objects we find evidence
for reddened post-starburst stellar populations in the near-nuclear regions of
the host galaxies. The YSP are relatively old (0.1- 2Gyr), massive and make up
a large proportion (~1 - 50%) of the total stellar mass in the regions of
galaxies sampled by the observations. Overall, these results are consistent
with the idea that AGN activity in some radio galaxies is triggered by major
gas-rich mergers. Therefore, these radio galaxies form part of the subset of
early-type galaxies that is evolving most rapidly in the local universe.
Intriguingly, the results also suggest that the radio jets are triggered
relatively late in the merger sequence, and that there is an evolutionary link
between radio galaxies and luminous/ultra-luminous infrared galaxies.Comment: 17 pages, 13 figures, accepted for publication in MNRA
CSSs in a sample of B2 radio sources of intermediate strength
We present radio observations of 19 candidate compact steep-spectrum (CSS)
objects selected from a well-defined, complete sample of 52 B2 radio sources of
intermediate strength. These observations were made with the VLA A-array at
4.835 GHz. The radio structures of the entire sample are summarised and the
brightness asymmetries within the compact sources are compared with those of
the more extended ones, as well as with those in the 3CRR sample and the CSSs
from the B3-VLA sample. About 25 per cent of the CSS sources exhibit large
brightness asymmetries, with a flux density ratio for the opposing lobes of
5, possibly due to interaction of the jets with infalling material. The
corresponding percentage for the larger-sized objects is only about 5 per cent.
We also investigate possible dependence of the flux density asymmetry of the
lobes on redshift, since this might be affected by more interactions and
mergers in the past. No such dependence is found. A few individual objects of
interest are discussed in the paper.Comment: 10 pages, 7 figures, 2 tables; accepted for publication in Astronomy
and Astrophysic
Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?
We present the results of a comparison between the optical morphologies of a
complete sample of 46 southern 2Jy radio galaxies at intermediate redshifts
(0.05<z<0.7) and those of two control samples of quiescent early-type galaxies:
55 ellipticals at redshifts z<0.01 from the Observations of Bright Ellipticals
at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2<z<0.7 in
the Extended Groth Strip (EGS). Based on these comparisons, we discuss the role
of galaxy interactions in the triggering of powerful radio galaxies (PRGs). We
find that a significant fraction of quiescent ellipticals at low and
intermediate redshifts show evidence for disturbed morphologies at relatively
high surface brightness levels, which are likely the result of past or on-going
galaxy interactions. However, the morphological features detected in the galaxy
hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2
magnitudes brighter than those present in their quiescent counterparts. Indeed,
if we consider the same surface brightness limits, the fraction of disturbed
morphologies is considerably smaller in the quiescent population (53% at z<0.2
and 48% at 0.2<z<0.7) than in the PRGs (93% at z<0.2 and 95% at 0.2<z<0.7
considering strong-line radio galaxies only). This supports a scenario in which
PRGs represent a fleeting active phase of a subset of the elliptical galaxies
that have recently undergone mergers/interactions. However, we demonstrate that
only a small proportion (<20%) of disturbed early-type galaxies are capable of
hosting powerful radio sources.Comment: 20 pages, 7 figures, accepted for publication in MNRA
A near-IR study of the host galaxies of 2Jy radio sources at 0.03 < z < 0.5: I - the data
We present the results of a program of K- and Ks-band imaging of a sample of
2Jy radio galaxies with redshifts 0.03 < z < 0.5, for which the host galaxy
morphologies and structural parameters (effective radius, Sersic index and
unresolved nuclear point source contribution) have been determined using
GALFIT. Two-thirds of our sample are best modelled as being hosted by massive
elliptical galaxies with Sersic indices of n=4-6, with the remainder being
better suited either by a mixture of morphological components (usually a bulge
plus a small, less luminous, disk component) or by more disky galaxy models
with n=1-2. Our measured galaxy sizes are generally in very good agreement with
other imaging programs, both space- and ground-based. We also determine a
slightly higher average nuclear point source contribution than similar
HST-based programs. This is due to our inability to separate the AGN emission
from compact circum-nuclear stellar emission, but does not bias our modelling
of the remainder of the host galaxies and our results remain robust. We also
observe that roughly half of the objects in our sample are either undergoing
major or minor merger activity or are clearly morphologically disturbed.Comment: Accepted for publication in MNRAS. 31 pages, 9 figures, 6 tables.
Landscape table 4 added as extra included figur
Fundamental properties of Fanaroff-Riley II radio galaxies investigated via Monte Carlo simulations
[Abridged] Radio galaxies and quasars are among the largest and most powerful
single objects known and are believed to have had a significant impact on the
evolving Universe and its large scale structure. We explore the intrinsic and
extrinsic properties of the population of FRII objects (kinetic luminosities,
lifetimes, and the central densities of their environments). In particular, the
radio and kinetic luminosity functions of FRIIs are investigated using the
complete, flux limited radio catalogues of 3CRR and Best et al. We construct
multidimensional Monte Carlo simulations using semi-analytical models of FRII
radio source growth to create artificial samples of radio galaxies. Unlike
previous studies, we compare radio luminosity functions found with both the
observed and simulated data to explore the fundamental source parameters. We
allow the source physical properties to co-evolve with redshift, and we find
that all the investigated parameters most likely undergo cosmological
evolution. Strikingly, we find that the break in the kinetic luminosity
function must undergo redshift evolution of at least (1+z)^3. The fundamental
parameters are strongly degenerate, and independent constraints are necessary
to draw more precise conclusions. We use the estimated kinetic luminosity
functions to set constraints on the duty cycles of these powerful radio
sources. A comparison of the duty cycles of powerful FRIIs with those
determined from radiative luminosities of AGN of comparable black hole mass
suggests a transition in behaviour from high to low redshifts, corresponding to
either a drop in the typical black hole mass of powerful FRIIs at low
redshifts, or a transition to a kinetically-dominated, radiatively-inefficient
FRII population.Comment: Accepted to MNRAS. 30 pages, 18 figures, 4 tables + online material
(in appendix): 9 pages, 14 figure
Sharing and archiving nucleic acid structure mapping data
Nucleic acids are particularly amenable to structural characterization using chemical and enzymatic probes. Each individual structure mapping experiment reveals specific information about the structure and/or dynamics of the nucleic acid. Currently, there is no simple approach for making these data publically available in a standardized format. We therefore developed a standard for reporting the results of single nucleotide resolution nucleic acid structure mapping experiments, or SNRNASMs. We propose a schema for sharing nucleic acid chemical probing data that uses generic public servers for storing, retrieving, and searching the data. We have also developed a consistent nomenclature (ontology) within the Ontology of Biomedical Investigations (OBI), which provides unique identifiers (termed persistent URLs, or PURLs) for classifying the data. Links to standardized data sets shared using our proposed format along with a tutorial and links to templates can be found at http://snrnasm.bio.unc.edu
VLBA observations of GHz-Peaked-Spectrum radio sources at 15 GHz
We present VLBA observations at 15 GHz of ten GHz Peaked Spectrum (GPS) radio
sources. The cores are often difficult or impossible to locate. When likely
cores are found, they account for a small fraction of the flux density in GPS
galaxies - around or below 2%, while in GPS quasars they can account for more
than 20% of the total flux density. We detect low polarization in the GPS
sources -- i.e., typically less than a few percent and often less than one
percent. This establishes that low polarization in the parsec scale structure
is an important defining characteristic of the GPS sources. The dichotomy in
the radio morphology versus optical identification, i.e., galaxies are
symmetric and quasars are not, is basically confirmed from these new data,
which also indicate that the radio emission from GPS quasars is dominated by a
jet, with often a weak or hidden core, suggesting they are at moderate angles
to the line of sight, and so are only moderately beamed.Comment: 14 pages, 11 figures, to appear on A&A; complete ps draft with better
quality figures available at http://www.ira.noto.cnr.it/staff/carlo/1554.p
TRY plant trait database - enhanced coverage and open access
Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
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