101 research outputs found
Interaction of Gravitational Waves with Charged Particles
It is shown here that a cloud of charged particles could in principle absorb
energy from gravitational waves (GWs) incident upon it, resulting in wave
attenuation. This could in turn have implications for the interpretation of
future data from early universe GWs.Comment: Appears in Gravitational Wave Astrophysics, Editor C.F. Sopuerta,
Astrophysics and Space Science Proceedings, Volume 40. ISBN
978-3-319-10487-4. Springer International Publishing Switzerland, 2015, p.
29
Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies
Observations reveal that supermassive black holes (SMBHs) grow through the accretion of gas at the centers of galaxies as luminous active galactic nuclei (AGN), releasing radiation that drives powerful outflows of ionized and molecular gas. These winds are thought to play a critical role in galaxy evolution by regulating star formation and the growth of galaxies and their SMBHs. To test this model, we must quantify the dynamic impact of outflows by measuring their mass outflow rates and energetics. Using spatially resolved spectroscopy and imaging from the Hubble Space Telescope and Cloudy photoionization models we mapped the ionized gas kinematics and mass distributions of narrow line region (NLR) outflows in nearby active galaxies. We find that the outflows contain up to several million solar masses of ionized gas and are limited to distances of 1 - 2 kiloparsecs from the nucleus. The maximum mass outflow rates are M = 3 - 12 solar masses per year and the outflow gas mass, velocity, radial extent, and energetics are positively correlated with AGN luminosity. We use our results to test simplified techniques with less stringent data requirements and find that they significantly overestimate the gas mass. These results are crucial for modeling powerful outflows at higher redshift that may considerably influence star formation rates and the formation of galactic structure
Dense Continuity and Selections of Set-Valued Mappings
∗ The first and third author were partially supported by National Fund for Scientific Research at the Bulgarian Ministry of Science and Education under grant MM-701/97.A theorem proved by Fort in 1951 says that an upper or lower
semi-continuous set-valued mapping from a Baire space A into non-empty
compact subsets of a metric space is both lower and upper semi-continuous
at the points of a dense Gδ -subset of A.
In this paper we show that the conclusion of Fort’s theorem holds under
the weaker hypothesis of either upper or lower quasi-continuity. The
existence of densely defined continuous selections for lower quasi-continuous
mappings is also proved
The difference vectors for convex sets and a resolution of the geometry conjecture
The geometry conjecture, which was posed nearly a quarter of a century ago,
states that the fixed point set of the composition of projectors onto nonempty
closed convex sets in Hilbert space is actually equal to the intersection of
certain translations of the underlying sets.
In this paper, we provide a complete resolution of the geometry conjecture.
Our proof relies on monotone operator theory. We revisit previously known
results and provide various illustrative examples. Comments on the numerical
computation of the quantities involved are also presented
Jansky Very Large Array detections of CO(1-0) emission in HI-absorption-selected galaxies at
We report a Karl G. Jansky Very Large Array search for redshifted CO(1-0)
emission from three HI-absorption-selected galaxies at ,
identified earlier in their CO(3-2) or CO(4-3) emission. We detect CO(1-0)
emission from DLA B1228-113 at and DLA J0918+1636 at
; these are the first detections of CO(1-0) emission in
high- HI-selected galaxies. We obtain high molecular gas masses, , for the two
objects with CO(1-0) detections, which are a factor of lower
than earlier estimates. We determine the excitation of the mid CO
rotational levels relative to the level, r, in HI-selected
galaxies for the first time, obtaining r and r for DLA J0918+1636, and r for DLA
B1228-113. These values are consistent with thermal excitation of the
levels. The excitation of the level in the HI-selected galaxies is
similar to that seen in massive main-sequence and sub-mm galaxies at
, but higher than that in main-sequence galaxies at ;
the higher excitation of the galaxies at is likely to be due to
their higher star-formation rate (SFR) surface density. We use Hubble Space
Telescope Wide Field Camera 3 imaging to detect the rest-frame near-ultraviolet
emission of DLA B1228-113, obtaining an NUV SFR of M
yr, significantly lower than that obtained from the total infrared
luminosity, indicating significant dust extinction in the
galaxy.Comment: 9 pages, 4 figures, and 2 tables. Accepted for publication in ApJ
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