2,035 research outputs found
Three-dimensional structure of the Upper Scorpius association with the Gaia first data release
Using new proper motion data from recently published catalogs, we revisit the
membership of previously identified members of the Upper Scorpius association.
We confirmed 750 of them as cluster members based on the convergent point
method, compute their kinematic parallaxes and combined them with Gaia
parallaxes to investigate the 3D structure and geometry of the association
using a robust covariance method. We find a mean distance of ~pc
and show that the morphology of the association defined by the brightest (and
most massive) stars yields a prolate ellipsoid with dimensions of
~pc, while the faintest cluster members define a more
elongated structure with dimensions of ~pc. We
suggest that the different properties of both populations is an imprint of the
star formation history in this region.Comment: 5 pages, 1 figure, MNRAS letters (in press
Molecular Gas Properties of the Giant Molecular Cloud Complexes in the Arms and Inter-arms of the Spiral Galaxy NGC 6946
Combining observations of multiple CO lines with radiative transfer modeling
is a very powerful tool to investigate the physical properties of the molecular
gas in galaxies. Using new observations as well as literature data, we provide
the most complete CO ladders ever generated for eight star-forming regions in
the spiral arms and inter-arms of the spiral galaxy NGC 6946, with observations
of the CO(1-0), CO(2-1), CO(3-2), CO(4-3), CO(6-5), 13CO(1-0) and 13CO(2-1)
transitions. For each region, we use the large velocity gradient assumption to
derive beam-averaged molecular gas physical properties, namely the gas kinetic
temperature (T_K), H2 number volume density n(H2) and CO number column density
N(CO). Two complementary approaches are used to compare the observations with
the model predictions: chi-square minimisation and likelihood. The physical
conditions derived vary greatly from one region to the next: T_K=10-250 K,
n(H2)=10^2.3-10^7.0 cm^-3 and N(CO)=10^15.0-10^19.3 cm^-2. The spectral line
energy distribution (SLED) of some of these extranuclear regions indicates a
star-formation activity that is more intense than that at the centre of our own
Milky Way. The molecular gas in regions with a large SLED turnover transition
(J_max>4) is hot but tenuous with a high CO column density, while that in
regions with a low SLED turnover transition (J_max<=4) is cold but dense with a
low CO column density. We finally discuss and find some correlations between
the physical properties of the molecular gas in each region and the presence of
young stellar population indicators (supernova remnants, HII regions, HI holes,
etc.)Comment: 23 pages, 11 figures, MNRAS, Accepte
ISM chemistry in metal rich environments: molecular tracers of metallicity
In this paper we use observations of molecular tracers in metal rich and
alpha-enhanced galaxies to study the effect of abundance changes on molecular
chemistry. We selected a sample of metal rich spiral and star bursting objects
from the literature, and present here new data for a sample of early-type
galaxies (ETGs). We conducted the first survey of CS and methanol emission in
ETGs, detecting 7 objects in CS, and 5 in methanol emission. We find evidence
to support the hypothesis that CS is a better tracer of dense star-forming gas
than HCN. We suggest that the methanol emission in these sources is driven by
dust mantle destruction due to ionisation from high mass star formation, but
cannot rule out shocks dominating in some sources. The derived source averaged
CS/methanol column densities and rotation temperatures are similar to those
found in normal spiral and starburst galaxies, suggesting dense clouds are
little affected by the differences between galaxy types. Finally we used the
total column density ratios for our galaxy samples to show for the first time
that some molecular tracers do seem to show systematic variations that appear
to correlate with metallicity, and that these variations roughly match those
predicted by chemical models. Using this fact, the chemical models of Bayet et
al. (2012b), and assumptions about the optical depth we are able to roughly
predict the metallicity of our spiral and ETG sample, with a scatter of ~0.3
dex. We provide the community with linear approximations to the relationship
between the HCN and CS column density ratio and metallicity. Further study will
clearly be required to determine if this, or any, molecular tracer can be used
to robustly determine gas-phase metallically, but that a relationship exists at
all suggests that in the future it may be possible to calibrate a metallicity
indicator for the molecular interstellar medium (abridged).Comment: 14 pages, 9 figures. MNRAS, accepte
Lateral Transistor Gain Calculations
The gain of lateral transistors is calculated with a program entitled LATERAL . This program uses a profile generated with SUPREM II, and calculates the depletion region edges and the built in potential for the diffused junctions. The effects included are the base width narrowing due to the applied bias and. recombination in the base. The results are compared with measured gains, and show good agreement. The effects of lifetime in the base are seen to show a large affect on the calculated gain
Interview with Estelle Lavoie by Andrea L’Hommedieu
Biographical NoteEstelle Lavoie was born in Lewiston, Maine, on November 23, 1949, and grew up there, the youngest of three children. Her father worked as a building contractor until his death in 1964, after which her mother worked part-time as a bank teller. Estelle attended Lewiston public schools and was graduated from Bates College (class of 1971), spending her junior year studying in Switzerland. At the end of 1972, she went to work for Governor Ken Curtis. By September of 1973, she had been hired as part of Senator Ed Muskie’s staff, working first as a caseworker and eventually as his legislative assistant. She attended law school at American University from 1978 to 1981 and transitioned to Senator Mitchell’s staff when he assumed Muskie’s Senate seat. She left Mitchell’s staff in the fall of 1983 and joined the law firm of Preti, Flaherty, Beliveau & Pachios the following June. Her practice has evolved from health law to other political practice issues. She served on the Democratic State Committee from 1986 to 1990 and was a delegate to the 1988 National Convention.
SummaryInterview includes discussions of: meeting Senator Mitchell; Mitchell’s appointment to the Senate; Indian Land Claims Settlement case and its importance to the State of Maine; other colleagues on the Mitchell staff and their job responsibilities; Mitchell’s retention of Senator Muskie’s staff; leadership styles of Senators Muskie and Mitchell; conceptualizing and forming the George Mitchell Scholarship and Research Institute; and Mitchell’s strengths including: intelligence, compassion, gratitude, modesty, speaking ability, hard work, and dedication
Engendering Accountability: Gender Crimes Under International Criminal Law
Gender crimes, such as rape, sexual assault, sexual slavery, and forced prostitution, have always been perpetrated during war, yet the laws of war have been slow to acknowledge these crimes and to bring their perpetrators to justice. This article examines the response of the International Criminal Tribunals for the Former Yugoslavia and Rwanda to this lacuna in international law, and analyzes the mainly positive developments they have made in this area in relation to the definition of rape and to the prosecution of gender crimes as crimes against humanity, war crimes, grave breaches of the Geneva Conventions, and genocide. It also traces the procedural safeguards instituted to facilitate the prosecution of gender crimes. The authors consider the way in which these advances have been taken forward in the Statute of the International Criminal Court, and the usefulness of other responses, such as the truth commissions in Bosnia and Yugoslavia, and the gacaca courts in Rwanda
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