3,960 research outputs found
A Last Look at the Microwave Haze/Bubbles with WMAP
The microwave "haze" was first discovered with the initial release of the
full sky data from the Wilkinson Microwave Anisotropy Probe. It is diffuse
emission towards the center of our Galaxy with spectral behavior that makes it
difficult to categorize as any of the previously known emission mechanisms at
those wavelengths. With now seven years of WMAP data publicly available, we
have learned much about the nature of the haze, and with the release of data
from the Fermi Gamma-Ray Space Telescope and the discovery of the gamma-ray
haze/bubbles, we have had a spectacular confirmation of its existence at other
wavelengths. As the WMAP mission winds down and the Planck mission prepares to
release data, I take a last look at what WMAP has to tell us about the origin
of this unique Galactic feature. Much like the gamma-rays, the microwave
haze/bubbles is elongated in latitude with respect to longitude by a factor of
roughly two, and at high latitudes, the microwave emission cuts off sharply
above ~35 degrees (compared to ~50 degrees in the gammas). The hard spectrum of
electrons required to generate the microwave synchrotron is consistent with
that required to generate the gamma-ray emission via inverse Compton
scattering, though it is likely that these signals result from distinct regions
of the spectrum (~10 GeV for the microwaves, ~1 TeV for the gammas). While
there is no evidence for significant haze polarization in the 7-year WMAP data,
I demonstrate explicitly that it is unlikely such a signal would be detectable
above the noise.Comment: 9 pages, 6 figures; accepted in ApJ; matches published version with
significantly enhanced figure
Microlensing of Lensed Supernovae
Given the number of recently discovered galaxy-galaxy lens systems, we
anticipate that a gravitationally lensed supernova will be observed within the
next few years. We explore the possibility that stars in the lens galaxy will
produce observable microlensing fluctuations in lensed supernova light curves.
For typical parameters, we predict that ~70% of lensed SNe will show
microlensing fluctuations > 0.5 mag, while ~25% will have fluctuations > 1 mag.
Thus microlensing of lensed supernova will be both ubiquitous and observable.
Additionally, we show that microlensing fluctuations will complicate
measurements of time delays from multiply imaged supernovae: time delays
accurate to better than a few days will be difficult to obtain. We also
consider prospects for extracting the lens galaxy's stellar mass fraction and
mass function from microlensing fluctuations via a new statistical measure, the
time-weighted light curve derivative.Comment: 13 pages, emulateapj format; accepted in ApJ; expanded discussion of
time delay uncertaintie
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