196 research outputs found
New constructions of homogeneous operators
New examples of homogeneous operators involving infinitely many parameters are constructed. They are realized on Hilbert spaces of holomorphic functions with reproducing kernels which are computed explicitly. All the examples are irreducible and belong to the Cowen-Douglas class. Even though the construction is completely explicit, it is based on certain facts about Hermitian holomorphic homogeneous vector bundles. These facts also make possible a description of all homogeneous Cowen-Douglas operators, in a somewhat less explicit way
Testing the Hubble Law with the IRAS 1.2 Jy Redshift Survey
We test and reject the claim of Segal et al. (1993) that the correlation of
redshifts and flux densities in a complete sample of IRAS galaxies favors a
quadratic redshift-distance relation over the linear Hubble law. This is done,
in effect, by treating the entire galaxy luminosity function as derived from
the 60 micron 1.2 Jy IRAS redshift survey of Fisher et al. (1995) as a distance
indicator; equivalently, we compare the flux density distribution of galaxies
as a function of redshift with predictions under different redshift-distance
cosmologies, under the assumption of a universal luminosity function. This
method does not assume a uniform distribution of galaxies in space. We find
that this test has rather weak discriminatory power, as argued by Petrosian
(1993), and the differences between models are not as stark as one might expect
a priori. Even so, we find that the Hubble law is indeed more strongly
supported by the analysis than is the quadratic redshift-distance relation. We
identify a bias in the the Segal et al. determination of the luminosity
function, which could lead one to mistakenly favor the quadratic
redshift-distance law. We also present several complementary analyses of the
density field of the sample; the galaxy density field is found to be close to
homogeneous on large scales if the Hubble law is assumed, while this is not the
case with the quadratic redshift-distance relation.Comment: 27 pages Latex (w/figures), ApJ, in press. Uses AAS macros,
postscript also available at
http://www.astro.princeton.edu/~library/preprints/pop682.ps.g
Adsorption and diffusion of selenite on Boda Claystone Formation
This study provides adsorption and diffusion data of selenite on Boda Claystone Formation (BCF) which is a potential host rock of a deep geological disposal of high-level radioactive waste. The experiments were performed on two diverse core samples: one albitic claystone sample characteristic for the entire BCF and one pyrite containing sample sparsely occurring in BCF. The experiments were carried out under atmospheric conditions. Batch experiments were carried out to study the kinetics of adsorption at a high initial concentration (1.2 Ă 10â3 M), the adsorption isotherms and reversibility were investigated in the 10â10â10â3 M concentration range. Adsorption onto petrographic thin sections was done to study the elemental distribution on the microscale and the oxidation state of selenium. The maximum of the distribution coefficient was found as Kd â 200 L/kg and a decrease was experienced around 10â6â10â7 M equilibrium concentration, which showed similarities to other argillaceous rocks. Isotopic exchange experiments revealed reversibility of selenite adsorption. Diffusion was studied with through-diffusion and in-diffusion experiments. Using X-ray fluorescence, despite a low initial concentration of 2.3 Ă 10â5 M in the in-diffusion experiment, a meaningful diffusion profile of selenium could be obtained, from which the selenite apparent diffusion coefficient Dappselenite = (1.5â4.3) Ă 10â14 m2/s and the selenite rock capacity factor αselenite = 1.4â2.2 were determined. As selenium species are redox sensitive the oxidation state of adsorbed species was studied with X-ray absorption near edge structure spectroscopy on SeâK edge. Adsorbed selenium remained in +IV oxidation state, however reduction was experienced on the pyritic sample
A Photometric and Kinematic Study of AWM 7
We have measured redshifts and Kron-Cousins R-band magnitudes for a sample of
galaxies in the poor cluster AWM 7. We have measured redshifts for 172
galaxies; 106 of these are cluster members.
We determine the luminosity function from a photometric survey of the central
1.2 h^{-1} x 1.2 h^{-1} Mpc. The LF has a bump at the bright end and a
faint-end slope of \alpha = -1.37+-0.16, populated almost exclusively by
absorption-line galaxies.
The cluster velocity dispersion is lower in the core (\sim 530 km/s) than at
the outskirts (\sim 680 km/s), consistent with the cooling flow seen in the
X-ray. The cold core extends \sim 150 h^{-1} kpc from the cluster center. The
Kron-Cousins R-band mass-to-light ratio of the system is 650+-170 h
M_\odot/L_\odot, substantially lower than previous optical determinations, but
consistent with most previous X-ray determinations.
We adopt H_0 = 100 h km/s/Mpc throughout this paper; at the mean cluster
redshift, (5247+-76 km/s), 1 h^{-1} Mpc subtends 65\farcm5.Comment: 37 pages, LaTeX, including 12 Figures and 1 Table. Accepted for
publication in the Astronomical Journa
The 1.4 GHz light curve of GRB 970508
We report on Westerbork 1.4 GHz radio observations of the radio counterpart
to -ray burst GRB~970508, between 0.80 and 138 days after this event.
The 1.4 GHz light curve shows a transition from optically thick to thin
emission between 39 and 54 days after the event. We derive the slope of the
spectrum of injected electrons () in two
independent ways which yield values very close to . This is in agreement
with a relativistic dynamically near-adiabatic blast wave model whose emission
is dominated by synchrotron radiation and in which a significant fraction of
the electrons cool fast.Comment: Paper I. Accepted for publication in the Astrophysical Journal
Letter
The VIRMOS deep imaging survey II: CFH12K BVRI optical data for the 0226-04 deep field
(abridged) In this paper we describe in detail the reduction, preparation and
reliability of the photometric catalogues which comprise the 1.2 deg^2
CFH12K-VIRMOS deep field. The survey reaches a limiting magnitude of BAB~26.5,
VAB~26.2, RAB~25.9 IAB~25.0 and contains 90,729 extended sources in the
magnitude range 18.0<IAB<24.0. We demonstrate our catalogues are free from
systematic biases and are complete and reliable down these limits. We estimate
that the upper limit on bin-to-bin systematic photometric errors for the I-
limited sample is ~10% in this magnitude range. We estimate that 68% of the
catalogues sources have absolute per co-ordinate astrometric uncertainties less
than ~0.38" and ~0.32" (alpha,delta). Our internal (filter-to-filter) per
co-ordinate astrometric uncertainties are 0.08" and 0.08" (alpha,delta). We
quantify the completeness of our survey in the joint space defined by object
total magnitude and peak surface brightness. Finally, we present numerous
comparisons between our catalogues and published literature data: galaxy and
star counts, galaxy and stellar colours, and the clustering of both point-like
and extended populations. In all cases our measurements are in excellent
agreement with literature data to IAB<24.0. This combination of depth and areal
coverage makes this multi-colour catalogue a solid foundation to select
galaxies for follow-up spectroscopy with VIMOS on the ESO-VLT and a unique
database to study the formation and evolution of the faint galaxy population to
z~1 and beyond.Comment: 18 pages, 23 figures, accepted for publication in A&
The Effect of Environment on Shear in Strong Gravitational Lenses
Using new photometric and spectroscopic data in the fields of nine strong
gravitational lenses that lie in galaxy groups, we analyze the effects of both
the local group environment and line-of-sight galaxies on the lens potential.
We use Monte Carlo simulations to derive the shear directly from measurements
of the complex lens environment, providing the first detailed independent check
of the shear obtained from lens modeling. We account for possible tidal
stripping of the group galaxies by varying the fraction of total mass
apportioned between the group dark matter halo and individual group galaxies.
The environment produces an average shear of gamma = 0.08 (ranging from 0.02 to
0.17), significant enough to affect quantities derived from lens observables.
However, the direction and magnitude of the shears do not match those obtained
from lens modeling in three of the six 4-image systems in our sample (B1422,
RXJ1131, and WFI2033). The source of this disagreement is not clear, implying
that the assumptions inherent in both the environment and lens model approaches
must be reconsidered. If only the local group environment of the lens is
included, the average shear is gamma = 0.05 (ranging from 0.01 to 0.14),
indicating that line-of-sight contributions to the lens potential are not
negligible. We isolate the effects of various theoretical and observational
uncertainties on our results. Of those uncertainties, the scatter in the
Faber-Jackson relation and error in the group centroid position dominate.
Future surveys of lens environments should prioritize spectroscopic sampling of
both the local lens environment and objects along the line of sight,
particularly those bright (I < 21.5) galaxies projected within 5' of the lens.Comment: Accepted for publication in The Astrophysical Journal; 28 pages, 9
figures, 5 table
SPT-CL J0546-5345: A Massive z > 1 Galaxy Cluster Selected Via the Sunyaev-Zel'dovich Effect with the South Pole Telescope
We report the spectroscopic confirmation of SPT-CL J0546-5345 at = 1.067.
To date this is the most distant cluster to be spectroscopically confirmed from
the 2008 South Pole Telescope (SPT) catalog, and indeed the first z > 1 cluster
discovered by the Sunyaev-Zel'dovich Effect (SZE). We identify 21 secure
spectroscopic members within 0.9 Mpc of the SPT cluster position, 18 of which
are quiescent, early-type galaxies. From these quiescent galaxies we obtain a
velocity dispersion of 1179^{+232}_{-167} km/s, ranking SPT-CL J0546-5345 as
the most dynamically massive cluster yet discovered at z > 1. Assuming that
SPT-CL J0546-5345 is virialized, this implies a dynamical mass of M_200 =
1.0^{+0.6}_{-0.4} x 10^{15} Msun, in agreement with the X-ray and SZE mass
measurements. Combining masses from several independent measures leads to a
best-estimate mass of M_200 = (7.95 +/- 0.92) x 10^{14} Msun. The spectroscopic
confirmation of SPT-CL J0546-5345, discovered in the wide-angle, mass-selected
SPT cluster survey, marks the onset of the high redshift SZE-selected galaxy
cluster era.Comment: ApJ, in pres
Two fossil groups of galaxies at z~0.4 in the COSMOS: accelerated stellar-mass build-up, different progenitors
We report on 2 fossil groups of galaxies at z=0.425 and 0.372 discovered in
the Cosmic Evolution Survey (COSMOS) area. Selected as X-ray extended sources,
they have total masses (M_200) of 1.9(+/-0.41)E13 and 9.5(+/-0.42)E13 M_sun,
respectively, as obtained from a recent X-ray luminosity-mass scaling relation.
The lower mass system appears isolated, whereas the other sits in a well-known
large-scale structure (LSS) populated by 27 other X-ray emitting groups. The
identification as fossil is based on the i-band photometry of all the galaxies
with a photo-z consistent with that of the group at the 2-sigma confidence
level and within a projected group-centric distance equal to 0.5R_200, and
i_AB<=22.5-mag limited spectroscopy. Both fossil groups exhibit high
stellar-to-total mass ratios compared to all the X-ray selected groups of
similar mass at 0.3<=z<=0.5 in the COSMOS. At variance with the composite
galaxy stellar mass functions (GSMFs) of similarly massive systems, both fossil
group GSMFs are dominated by passively evolving galaxies down to M^stars~1E10
M_sun (according to the galaxy broad-band spectral energy distributions). The
relative lack of star-forming galaxies with 1E10<=M^stars<=1E11 M_sun is
confirmed by the galaxy distribution in the b-r vs i color-magnitude diagram.
Hence, the 2 fossil groups appear as more mature than the coeval, similarly
massive groups. Their overall star formation activity ended rapidly after an
accelerated build up of the total stellar mass; no significant infall of
galaxies with M^stars>=1E10 M_sun took place in the last 3 to 6 Gyr. This
similarity holds although the 2 fossil groups are embedded in two very
different density environments of the LSS, which suggests that their galaxy
populations were shaped by processes that do not depend on the LSS. However,
their progenitors may do so. ...Comment: 12 pages, 5 color figures, 1 table; to be published in the MNRA
UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from
1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The
data set comprises 2190 observations and is the largest homogeneously observed
and reduced sample of SN Ia to date, nearly doubling the number of
well-observed, nearby SN Ia with published multicolor CCD light curves. The
large sample of U-band photometry is a unique addition, with important
connections to SN Ia observed at high redshift. The decline rate of SN Ia
U-band light curves correlates well with the decline rate in other bands, as
does the U-B color at maximum light. However, the U-band peak magnitudes show
an increased dispersion relative to other bands even after accounting for
extinction and decline rate, amounting to an additional ~40% intrinsic scatter
compared to B-band.Comment: 84 authors, 71 pages, 51 tables, 10 figures. Accepted for publication
in the Astronomical Journal. Version with high-res figures and electronic
data at http://astron.berkeley.edu/~saurabh/cfa2snIa
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