2,578 research outputs found
The Statistical Properties of Galaxies Containing ULXs
We present a statistical analysis of the properties of galaxies containing
ultraluminous X-ray objects (ULXs). Our primary goal is to establish the
fraction of galaxies containing a ULX as a function of ULX luminosity. Our
sample is based on ROSAT HRI observations of galaxies. We find that ~ 12% of
galaxies contain at least one ULX with L_X > 10^39 erg/s and ~ 1% of galaxies
contain at least one ULX with L_X > 10^40 erg/s. These ULX frequencies are
lower limits since ROSAT HRI observation would miss absorbed ULXs (i.e., with
N_H >~ 10^21 cm^-2) and those within ~ 10" of the nucleus (due to the
positional error circle of the ROSAT HRI). The Hubble type distribution of
galaxies with a ULX differs significantly from the distribution of types for
nearby RC3 galaxies, but does not differ significantly from the galaxy type
distribution of galaxies observed by the HRI in general. We find no increase in
the mean FIR luminosity or FIR / K band luminosity ratio for galaxies with a
ULX relative to galaxies observed by the HRI in general, however this result is
also most likely biased by the soft bandpass of the HRI and the relatively low
number of high SFR galaxies observed by the HRI with enough sensitivity to
detect a ULX.Comment: Accepted by Apj. 5 pages with 4 figures formatted using emulateapj.
Version with just b/w figures available at
http://www.pha.jhu.edu/~ptak/paper
A Proposal to Measure the Quasiparticle Poisoning Time of Majorana Bound States
We propose a method of measuring the fermion parity lifetime of Majorana
fermion modes due to quasiparticle poisoning. We model quasiparticle poisoning
by coupling the Majorana modes to electron reservoirs, explicitly breaking
parity conservation in the system. This poisoning broadens and shortens the
resonance peak associated with Majorana modes. In a two lead geometry, the
poisoning decreases the correlation in current noise between the two leads from
the maximal value characteristic of crossed Andreev reflection. The latter
measurement allows for calculation of the poisoning rate even if temperature is
much higher than the resonance width.Comment: 5 pages, 5 figure
The magneto-optical Faraday effect in spin liquid candidates
We propose an experiment to use the magneto-optical Faraday effect to probe
the dynamic Hall conductivity of spin liquid candidates. Theory predicts that
an external magnetic field will generate an internal gauge field. If the source
of conductivity is in spinons with a Fermi surface, a finite Faraday rotation
angle is expected. We predict the angle to scale as the square of the frequency
rather than display the standard cyclotron resonance pattern. Furthermore, the
Faraday effect should be able to distinguish the ground state of the spin
liquid, as we predict no rotation for massless Dirac spinons. We give a
semiquantitative estimate for the magnitude of the effect and find that it
should be experimentally feasible to detect in both
-(ET)Cu(CN) and, if the spinons form a Fermi surface,
Herbertsmithite. We also comment on the magneto-optical Kerr effect and show
that the imaginary part of the Kerr angle may be measurable.Comment: 5 pages, 1 figur
Training in Citizenship
One hundred years ago, the township was the unit of government in this country. At its meetings, opinions were formed through neighborly discussion. Rapid grouth in population brought with it greater and greater complexity in form of government. The theory of democracy, identifying the functioning of government with the will of the people remained, however. Politicians were prone to refer to the wisdom of the people as though it were that of one person and to the wills of the people as though they formed one will. This is spite of the fact that centers of government were often at a distance where the actual work was done by unseen powers--politicians, office holders and influential men
The Bright Ages Survey. II. Evolution of Luminosity, Dust Extinction, and Star Formation from z = 0.5 to z = 2.5
The Bright Ages Survey is a K-band-selected redshift survey over six separate fields with UBVRIzJHK imaging covering a total of 75.6 arcmin(2) and reaching K = 20-20.5. Two fields have deep HST imaging, while all are centered on possible overdensities in the z similar to 2 range. Here we report photometric redshifts and spectroscopy for this sample, which has been described in Paper I. We find 18 galaxies with spectroscopic redshifts of z > 1:5. The derived rest-frame R-band luminosity functions show strong evolution out to z = 2. The luminosity function at z = 2 shows more bright galaxies than at any other epoch, even the extrapolated z = 3 luminosity function from Shapley et al. However, the R-band integrated luminosity density remains roughly constant from to z = 0:5 to z = 2. Evolved galaxies (E, S0, Sa) show a decreasing contribution to the total R-band luminosity density with redshift. The dust extinction in our K-selected sample is moderately larger [median z = 2 E(B - V) 0:30] than that found in Lyman break
galaxies, although not enough to make a significant impact on the total light or star formation found at high redshift. We measure the extinction-corrected star formation rate density at z 2, finding Ï_(SFR)(z = 1.5-2.5)= 0.093 M_â yr^(-1) Mpc^(-3), consistent with a relatively flat instantaneous star formation rate from z = 1-4
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