68,158 research outputs found
Limits on the luminosity function of Ly-alpha emitters at z = 7.7
The Ly-alpha luminosity function (LF) of high-redshift Ly-alpha emitters
(LAEs) is one of the few observables of the re-ionization epoch accessible to
date with 8-10 m class telescopes. The evolution with redshift allows one to
constrain the evolution of LAEs and their role in re-ionizing the Universe at
the end of the Dark Ages.
We have performed a narrow-band imaging program at 1.06 microns at the CFHT,
targeting Ly-alpha emitters at redshift z ~ 7.7 in the CFHT-LS D1 field. From
these observations we have derived a photometric sample of 7 LAE candidates at
z ~ 7.7.
We derive luminosity functions for the full sample of seven objects and for
sub-samples of four objects. If the brightest objects in our sample are real,
we infer a luminosity function which would be difficult to reconcile with
previous work at lower redshift. More definitive conclusions will require
spectroscopic confirmation.Comment: 12 pages, accepted to Astronomy and Astrophysic
BZBJ1058+5628: a new quasi-periodic BL Lac
We present the historic photographic light curves of three little known
Blazars (two BL Lacs and one FSRQ), BZB J1058+5628, BZQ J1148+5254 and BZB
J1209+4119 spanning a time interval of about 50 years, mostly built using the
Asiago plate archive. All objects show evident long-term variability, over
which short-term variations are superposed. One source, BZB J1058+5628, showed
a marked quasi-periodic variability of 1 mag on time scale of about 6.3 years,
making it one of the few BL Lac objects with a quasi-periodic behavior.Comment: Accepted by The Astronomical Journal; 7 figures; 7 table
Detecting the Most Distant (z>7) Objects with ALMA
Detecting and studying objects at the highest redshifts, out to the end of
Cosmic Reionization at z>7, is clearly a key science goal of ALMA. ALMA will in
principle be able to detect objects in this redshift range both from high-J
(J>7) CO transitions and emission from ionized carbon, [CII], which is one of
the main cooling lines of the ISM. ALMA will even be able to resolve this
emission for individual targets, which will be one of the few ways to determine
dynamical masses for systems in the Epoch of Reionization. We discuss some of
the current problems regarding the detection and characterization of objects at
high redshifts and how ALMA will eliminate most (but not all) of them.Comment: to appear in Astrophysics and Space Science, "Science with ALMA: a
new era for Astrophysics", ed. R. Bachille
On the Schroedinger Representation for a Scalar Field on Curved Spacetime
It is generally known that linear (free) field theories are one of the few
QFT that are exactly soluble. In the Schroedinger functional description of a
scalar field on flat Minkowski spacetime and for flat embeddings, it is known
that the usual Fock representation is described by a Gaussian measure. In this
paper, arbitrary globally hyperbolic space-times and embeddings of the Cauchy
surface are considered. The classical structures relevant for quantization are
used for constructing the Schroedinger representation in the general case. It
is shown that in this case, the measure is also Gaussian. Possible implications
for the program of canonical quantization of midisuperspace models are pointed
out.Comment: 11 pages, Revtex, no figure
VERITAS Observations of the Coma Cluster of Galaxies
Clusters of galaxies are one of the few prominent classes of objects
predicted to emit gamma rays not yet detected by satellites like EGRET or
ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs). The detection of
Very High Energy (VHE, E > 100 GeV) gamma rays from galaxy clusters would
provide insight into the morphology of non-thermal particles and fields in
clusters. VERITAS, an array of four 12-meter diameter IACTs, is ideally
situated to observe the massive Coma cluster, one of the best cluster
candidates in the Northern Hemisphere. This contribution details the results of
VERITAS observations of the Coma cluster of galaxies during the 2007-2008
observing season.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium
on High Energy Gamma-Ray Astronomy 2008
On the Relation Between Fock and Schroedinger Representations for a Scalar Field
Linear free field theories are one of the few Quantum Field Theories that are
exactly soluble. There are, however, (at least) two very different languages to
describe them, Fock space methods and the Schroedinger functional description.
In this paper, the precise sense in which the two representations are related
is reviewed. Several properties of these representations are studied, among
them the well known fact that the Schroedinger counterpart of the usual Fock
representation is described by a Gaussian measure. A real scalar field theory
is considered, both on Minkowski spacetime for arbitrary, non-inertial
embeddings of the Cauchy surface, and for arbitrary (globally hyperbolic)
curved spacetimes. As a concrete example, the Schroedinger representation on
stationary and homogeneous cosmological spacetimes is constructed.Comment: 23 pages. No figures. A new section on examples adde
- …