38,482 research outputs found
The dark matter halo density profile, spiral arm morphology and black hole mass of M33
In this paper, we investigate the dark matter halo density profile of M33. We
find that the HI rotation curve of M33 is best described by a NFW dark matter
halo density profile model, with a halo concentration of cvir = 4.0\pm1.0 and a
virial mass of Mvir = (2.2\pm0.1)\times10^11 Msun. We go on to use the NFW
concentration (cvir)of M33, along with the values derived for other galaxies
(as found in the literature), to show that cvir correlates with both spiral arm
pitch angle and supermassive black hole mass.Comment: 18 pages, accepted for publicatio
The connection between shear and star formation in spiral galaxies
We present a sample of 33 galaxies for which we have calculated (i) the
average rate of shear from publish rotation curves, (ii) the far-infrared
luminosity from IRAS fluxes and (iii) The K-band luminosity from 2MASS. We show
that a correlation exists between the shear rate and the ratio of the
far-infrared to K-band luminosity. This ratio is essentially a measure of the
star formation rate per unit mass, or the specific star formation rate. From
this correlation we show that a critical shear rate exists, above which star
formation would turn off in the disks of spiral galaxies. Using the correlation
between shear rate and spiral arm pitch angle, this shear rate corresponds to
the lowest pitch angles typically measured in near-infrared images of spiral
galaxies.Comment: Accepted for publication in MNRAS letters. 5 figures, 1 tabl
A Reanalysis of Small Scale Velocity Dispersion in the CfA1 Survey
The velocity dispersion of galaxies on scales of Mpc,
, may be estimated from the anisotropy of the galaxy-galaxy
correlation function in redshift space. We present a reanalysis of the CfA1
survey, correct an error in the original analysis of Davis and Peebles (1983),
and find that is extremely sensitive to the details of how
corrections for infall into the Virgo cluster are applied. We conclude that a
robust value of cannot be obtained from this survey. We also
discuss results from other redshift surveys, including the effect of removing
clusters.Comment: 12 pages, uuencoded(latex file + 2 Postscript figures), uses aas
macro
Geodesics and compression bodies
We consider hyperbolic structures on the compression body C with genus 2
positive boundary and genus 1 negative boundary. Note that C deformation
retracts to the union of the torus boundary and a single arc with its endpoints
on the torus. We call this arc the core tunnel of C. We conjecture that, in any
geometrically finite structure on C, the core tunnel is isotopic to a geodesic.
By considering Ford domains, we show this conjecture holds for many
geometrically finite structures. Additionally, we give an algorithm to compute
the Ford domain of such a manifold, and a procedure which has been implemented
to visualize many of these Ford domains. Our computer implementation gives
further evidence for the conjecture.Comment: 31 pages, 11 figures. V2 contains minor changes. To appear in
Experimental Mathematic
25-Year Quagmire: The "War On Drugs" and Its Impact on American Society
Analysis, based on an analysis of 25 years of government data regarding drugs and the criminal justice system, finds that the "war on drugs" has increasingly targeted low-level offenders for arrest and incarceration, and is largely failing to provide adequate treatment in prison. 33 pagesAnalysis, based on an analysis of 25 years of government data regarding drugs and the criminal justice system, finds that the "war on drugs" has increasingly targeted low-level offenders for arrest and incarceration, and is largely failing to provide adequate treatment in prison
The Myers-Steenrod theorem for Finsler manifolds of low regularity
We prove a version of Myers-Steenrod's theorem for Finsler manifolds under
minimal regularity hypothesis. In particular we show that an isometry between
-smooth (or partially smooth) Finsler metrics, with ,
, and is necessary a
diffeomorphism of class . A generalisation of this result to
the case of Finsler 1-quasiconformal mapping is given. The proofs are based on
the reduction of the Finlserian problems to Riemannian ones with the help of
the the Binet-Legendre metric.Comment: 14 page
Uneven Justice: State Rates of Incarceration by Race and Ethnicity
Examines racial and ethnic disparities by state, and finds substantial variation in the degree of black-to-white incarceration. The report finds that African Americans are incarcerated at nearly six times the rate of whites and Latinos at nearly double the rate. Five states, located in the Northeast and Midwest, incarcerate blacks at more than ten times the rate of whites. Recommended reforms include: addressing disparities through changes in drug policy, mandatory sentencing laws, reconsideration of "race neutral" policies, and changes in resource allocation
The development of apologies in the Japanese L2 of adult English native speakers
The present paper focuses on the use of seven apologies strategies in the Japanese of 20 adult, high-intermediate English learners/users of Japanese. Nine of these learners had spent a minimum of two years in Japan. The proportions of apology strategies produced by the two groups of learners in response to 8 situations presented to them in a Discourse Completion Test (DCT) were compared with data obtained from a control group of 14 Japanese L1 participants and a control group of 12 British English L1 participants. In total, 1999 tokens of apology strategies were collected. Statistical analyses and an analysis of lexical items allowed us to describe the learnersâ development and the effect of the stay in Japan
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