1,976 research outputs found
The principle of symmetric bracket invariance as the origin of first and second quantization
The principle of invariance of the c-number symmetric bracket is used to
derive both the quantum operator commutator relation
and the time-dependent Schr\"odinger equation. A c-number dynamical equation is
found which leads to the second quantized field theory of bosons and fermions.Comment: 14 pages. Contributed Paper: XIX International Symposium on Lepton
and Photon Interactions at High Energies, Stanford University, August 9-14,
199
The Excess Far-Infrared Emission of AGN in the Local Universe
We have cross-correlated the Sloan Digital Sky Survey (SDSS) second data
release spectroscopic galaxy sample with the IRAS faint-source catalogue (FSC).
Optical emission line ratios are used to classify the galaxies with reliable
IRAS 60 and 100 microns detections into AGN and normal star-forming galaxies.
We then create subsamples of normal galaxies and AGN that are very closely
matched in terms of key physical properties such as stellar mass, redshift,
size, concentration and mean stellar age (as measured by absorption line
indicators in the SDSS spectra). We then quantify whether there are systematic
differences between the IR luminosities of the galaxies and the AGN in the
matched subsamples. We find that the AGN exhibit a significant excess in far-IR
emission relative to the star-forming galaxies in our sample. The excesses at
60 and 100 microns are 0.21 +/- 0.03 dex and 0.12 +/- 0.035 dex in
log[L(60)/M*] and log[L(100)/M*], respectively. We then discuss whether the
far-IR excess is produced by radiation from the active nucleus that is absorbed
by dust or alternatively, by an extra population of young stars that is not
detectable at optical wavelengths.Comment: 12 pages, 14 figures, accepted by MNRA
The Relationship of Hard X-ray and Optical Line Emission in Low Redshift Active Galactic Nuclei
In this paper we assess the relationship of the population of Active Galactic
Nuclei (AGN) selected by hard X-rays to the traditional population of AGN with
strong optical emission lines. First, we study the emission-line properties of
a new hard X-ray selected sample of 47 local AGN (classified optically as both
Type 1 and Type 2 AGN). We find that the hard X- ray (3-20 keV) and
[OIII]5007 optical emission-line luminosities are well-correlated over
a range of about four orders-of-magnitude in luminosity (mean luminosity ratio
2.15 dex with a standard deviation of = 0.51 dex). Second, we study
the hard X-ray properties of a sample of 55 local AGN selected from the
literature on the basis of the flux in the [OIII] line. The correlation between
the hard X-ray (2-10 keV) and [OIII] luminosity for the Type 1 AGN is
consistent with what is seen in the hard X-ray selected sample. However, the
Type 2 AGN have a much larger range in the luminosity ratio, and many are very
weak in hard X-rays (as expected for heavily absorbed AGN). We then compare the
hard X-ray (3-20 keV) and [OIII] luminosity functions of AGN in the local
universe. These have similar faint-end slopes with a luminosity ratio of 1.60
dex (0.55 dex smaller than the mean value for individual hard X-ray selected
AGN). We conclude that at low redshift, selection by narrow optical emission-
lines will recover most AGN selected by hard X-rays (with the exception of BL
Lac objects). However, selection by hard X-rays misses a significant fraction
of the local AGN population with strong emission lines
Production and Evolution of Perturbations of Sterile Neutrino Dark Matter
Sterile neutrinos, fermions with no standard model couplings [SU(2)
singlets], are predicted by most extensions of the standard model, and may be
the dark matter. I describe the nonthermal production and linear perturbation
evolution in the early universe of this dark matter candidate. I calculate
production of sterile neutrino dark matter including effects of Friedmann
dynamics dictated by the quark-hadron transition and particle population, the
alteration of finite temperature effective mass of active neutrinos due to the
presence of thermal leptons, and heating of the coupled species due to the
disappearance of degrees of freedom in the plasma. These effects leave the
sterile neutrinos with a non-trivial momentum distribution. I also calculate
the evolution of sterile neutrino density perturbations in the early universe
through the linear regime and provide a fitting function form for the transfer
function describing the suppression of small scale fluctuations for this warm
dark matter candidate. The results presented here differ quantitatively from
previous work due to the inclusion here of the relevant physical effects during
the production epoch.Comment: v4: matches version in Phys. Rev.
Infalling Faint [OII] Emitters in Abell 851. I. Spectroscopic Confirmation of Narrowband-Selected Objects
We report on a spectroscopic confirmation of narrowband-selected [OII]
emitters in Abell 851 catalogued by Martin et al. (2000). The optical spectra
obtained from the Keck I Low Resolution Imaging Spectrometer (LRIS) and Keck II
Deep Imaging Multi-Object Spectrograph (DEIMOS) have confirmed [OII]3727
emission in narrowband-selected cluster [OII] candidates at a 85% success rate
for faint (i <~ 25) blue (g-i < 1) galaxies. The rate for the successful
detection of [OII] emission is a strong function of galaxy color, generally
proving the efficacy of narrowband [OII] search supplemented with broadband
colors in selecting faint cluster galaxies with recent star formation. Balmer
decrement-derived reddening measurements show a high degree of reddening
[E(B-V) >~ 0.5] in a significant fraction of this population. Even after
correcting for dust extinction, the [OII]/Ha line flux ratio for the
high-E(B-V) galaxies remains generally lower by a factor of ~2 than the mean
[OII]/Ha ratios reported by the studies of nearby galaxies. The strength of
[OII] equivalent width shows a negative trend with galaxy luminosity while the
Ha equivalent width does not appear to depend as strongly on luminosity. This
in part is due to the high amount of reddening observed in luminous galaxies.
Furthermore, emission line ratio diagnostics show that AGN-like galaxies are
abundant in the high luminosity end of the cluster [OII]-emitting sample, with
only moderately strong [OII] equivalent widths, consistent with a scenario of
galaxy evolution connecting AGNs and suppression of star-forming activity in
massive galaxies.Comment: 11 pages (LaTeX emulateapj), 8 figures, to appear in ApJ. A version
with high resolution figures available from the lead autho
The Color-Magnitude Relation in Coma: Clues to the Age and Metallicity of Cluster Populations
We have observed three fields of the Coma cluster of galaxies with a narrow
band (modified Stromgren) filter system. Observed galaxies include 31 in the
vicinity of NGC 4889, 48 near NGC 4874, and 60 near NGC 4839 complete to
M_5500=-18 in all three subclusters. Spectrophotometric classification finds
all three subclusters of Coma to be dominated by red, E type (ellipticals/S0's)
galaxies with a mean blue fraction, f_B, of 0.10. The blue fraction increases
to fainter luminosities, possible remnants of dwarf starburst population or the
effects of dynamical friction removing bright, blue galaxies from the cluster
population by mergers. We find the color-magnitude (CM) relation to be well
defined and linear over the range of M_5500=-13 to -22. After calibration to
multi-metallicity models, bright ellipticals are found to have luminosity
weighted mean [Fe/H] values between -0.5 and +0.5, whereas low luminosity
ellipticals have [Fe/H] values ranging from -2 to solar. The lack of CM
relation in our continuum color suggests that a systematic age effect cancels
the metallicity effects in this bandpass. This is confirmed with our age index
which finds a weak correlation between luminosity and mean stellar age in
ellipticals such that the stellar populations of bright ellipticals are 2 to 3
Gyrs younger than low luminosity ellipticals.Comment: 26 pages AAS LaTeX, 6 figures, accepted for publication in A
A possible observational bias in the estimation of the virial parameter in virialized clumps
The dynamics of massive clumps, the environment where massive stars
originate, is still unclear. Many theories predict that these regions are in a
state of near-virial equilibrium, or near energy equi-partition, while others
predict that clumps are in a sub-virial state. Observationally, the majority of
the massive clumps are in a sub-virial state with a clear anti-correlation
between the virial parameter and the mass of the clumps ,
which suggests that the more massive objects are also the more gravitationally
bound. Although this trend is observed at all scales, from massive clouds down
to star-forming cores, theories do not predict it. In this work we show how,
starting from virialized clumps, an observational bias is introduced in the
specific case where the kinetic and the gravitational energies are estimated in
different volumes within clumps and how it can contribute to the spurious
anti-correlation in these data. As a result, the observed
effective virial parameter , and in some
circumstances it might not be representative of the virial state of the
observed clumps.Comment: A&A letter, accepte
Non-grassmann "classicization" of fermion dynamics
A carefully motivated symmetric variant of the Poisson bracket in ordinary (not Grassmann) phase space variables is shown to satisfy identities which are in algebraic correspondence with the anticommutation postulates for quantized Fermion systems. "Symplecticity" in terms of this symmetric Poisson bracket implies generalized Hamilton's equations that can only be of Schroedinger type (e.g., the Dirac equation but not the Klein-Gordon or Maxwell equations). This restriction also excludes the old "four-Fermion" theory of beta decay
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