2,746 research outputs found
The effect of interest on reserves on monetary policy
In October 2008 the Federal Reserve began paying banks interest on the reserves they hold. This action was intended to remove the implicit, distortionary tax that reserve requirements impose on banks, as well as help the Fed maintain the fed funds rate at its target. Going forward, interest on reserves is likely to simplify monetary policy implementation, as well as allow the Fed to pursue separate monetary and credit policies.Inflation (Finance) ; Monetary policy
Visualization of structures and cosmic flows in the Local Universe
A visualization of three-dimensional structures and cosmic flows is presented
using information from the Extragalactic Distance Database V8k redshift catalog
and peculiar velocities from the Cosmicflows-1 survey. Structures within a
volume bounded at 8000 km/s on the cardinal Supergalactic axes are explored in
terms of both the display of the positions of the 30124 galaxies of the catalog
and its reconstructed luminosity density field, corrected to account for
growing incompleteness with distance. Cosmography of the Local Universe is
discussed with the intent to identify the most prominent structures, including
voids, galaxy clusters, filaments and walls. The mapping also benefits from
precise distance measures provided through the Cosmicflows-1 observational
program. Three-dimensional visualizations of the coherent flows of galaxies in
the nearby universe are presented using recent results obtained on the
reconstruction of cosmic flows with the Wiener Filter approach. The three major
components of the Milky Way motion, namely the expulsion from the Local Void,
the infall toward the Virgo Cluster, and the bulk flow of the historic Local
Supercluster toward the Great Attractor are illustrated using different
visualization techniques and analyzed in the light of the cosmography derived
from the V8k redshift and Cosmicflows-1 distance catalogs.Comment: Advancing the physics of cosmic distances Proceedings IAU Symposium
No. 289, 2012 R. de Grijs, G. Bono 2012 International Astronomical Unio
Derivation of Distances with the Tully-Fisher Relation: The Antlia Cluster
The Tully-Fisher relation is a correlation between the luminosity and the HI
21cm line width in spiral galaxies (LLW relation). It is used to derive galaxy
distances in the interval 7 to 100 Mpc. Closer, the Cepheids, TRGB and Surface
Brightness Fluctuation methods give a better accuracy. Further, the SNIa are
luminous objects still available for distance measurement purposes, though with
a dramatically lower density grid of measurements on the sky. Galaxies in
clusters are all at the same distance from the observer. Thus the distance of
the cluster derived from a large number of galaxies (N) has an error reduced
according to the square root of N. However, not all galaxies in a cluster are
suitable for the LLW measurement. The selection criteria we use are explained
hereafter; the important point being to avoid Malmquist bias and to not
introduce any systematics in the distance measurement.Comment: Moriond0
Cosmic Bulk Flow and the Local Motion from Cosmicflows-2
Full sky surveys of peculiar velocity are arguably the best way to map the
large scale structure out to distances of a few times 100 Mpc/h. Using the
largest and most accurate ever catalog of galaxy peculiar velocities
"Cosmicflows-2", the large scale structure has been reconstructed by means of
the Wiener filter and constrained realizations assuming as a Bayesian prior
model the LCDM model with the WMAP inferred cosmological parameters. The
present paper focuses on studying the bulk flow of the local flow field,
defined as the mean velocity of top-hat spheres with radii ranging out to R=500
Mpc/h. The estimated large scale structures, in general, and the bulk flow, in
particular, are determined by the tension between the observational data and
the assumed prior model. A prerequisite for such an analysis is the requirement
that the estimated bulk flow is consistent with the prior model. Such a
consistency is found here. At R=50(150) Mpc/h the estimated bulk velocity is
250+/-21 (239+/-38) km/s. The corresponding cosmic variance at these radii is
126(60)km/s, which implies that these estimated bulk flows are dominated by the
data and not by the assumed prior model. The estimated bulk velocity is
dominated by the data out to R~200 Mpc/h, where the cosmic variance on the
individual Supergalactic Cartesian components (of the r.m.s. values) exceeds
the variance of the Constrained Realizations by at least a factor of 2. The
supergalactic SGX and SGY components of the CMB dipole velocity are recovered
by the Wiener filter velocity field down to a very few km/s. The SGZ component
of the estimated velocity, the one that is most affected by the Zone of
Avoidance, is off by 126 km/s (an almost 2 sigma discrepancy).Comment: 10 pages, accepted for MNRA
The Mid-Infrared Tully-Fisher Relation: Calibration of the SNIa Scale and Ho
This paper builds on a calibration of the SNIa absolute distance scale begun
with a core of distances based on the correlation between galaxy rotation rates
and optical Ic band photometry. This new work extends the calibration through
the use of mid-infrared photometry acquired at 3.6 microns with Spitzer Space
Telescope. The great virtue of the satellite observations is constancy of the
photometry at a level better than 1% across the sky. The new calibration is
based on 39 individual galaxies and 8 clusters that have been the sites of well
observed SNIa. The new 3.6 micron calibration is not yet as extensively based
as the Ic band calibration but is already sufficient to justify a preliminary
report. Distances based on the mid-infrared photometry are 2% greater in the
mean than reported at Ic band. This difference is only marginally significant.
The Ic band result is confirmed with only a small adjustment. Incorporating a
1% decrease in the LMC distance, the present study indicates Ho = 75.2 +/- 3.0
km/s/Mpc.Comment: Accepted for publication in The Astrophysical Journal Letters, 6
pages, 2 figure
Goodness-of-fit analysis of the Cosmicflows-2 database of velocities
The goodness-of-fit (GoF) of the Cosmicflows-2 (CF2) database of peculiar
velocities with the LCDM standard model of cosmology is presented. Standard
application of the Chi^2 statistics of the full database, of its 4,838 data
points, is hampered by the small scale nonlinear dynamics which is not
accounted for by the (linear regime) velocity power spectrum. The bulk velocity
constitutes a highly compressed representation of the data which filters out
the small scales non-linear modes. Hence the statistics of the bulk flow
provides an efficient tool for assessing the GoF of the data given a model. The
particular approach introduced here is to use the (spherical top-hat window)
bulk velocity extracted from the Wiener filter reconstruction of the 3D
velocity field as a linear low pass filtered highly compressed representation
of the CF2 data. An ensemble 2250 random linear realizations of the WMAP/LCDM
model has been used to calculate the bulk velocity auto-covariance matrix. We
find that the CF2 data is consistent with the WMAP/LCDM model to better than
the 2 sigma confidence limits. This provides a further validation that the CF2
database is consistent with the standard model of cosmology.Comment: submitted to MNRAS, V2 : solved page sizing proble
The Arrowhead Mini-Supercluster of Galaxies
Superclusters of galaxies can be defined kinematically from local evaluations
of the velocity shear tensor. The location where the smallest eigenvalue of the
shear is positive and maximal defines the center of a basin of attraction.
Velocity and density fields are reconstructed with Wiener Filter techniques.
Local velocities due to the density field in a restricted region can be
separated from external tidal flows, permitting the identification of
boundaries separating inward flows toward a basin of attraction and outward
flows. This methodology was used to define the Laniakea Supercluster that
includes the Milky Way. Large adjacent structures include Perseus-Pisces, Coma,
Hercules, and Shapley but current kinematic data are insufficient to capture
their full domains. However there is a small region trapped between Laniakea,
Perseus-Pisces, and Coma that is close enough to be reliably characterized and
that satisfies the kinematic definition of a supercluster. Because of its
shape, it is given the name the Arrowhead Supercluster. This entity does not
contain any major clusters. A characteristic dimension is ~25 Mpc and the
contained mass is only ~10^15 Msun.Comment: Accepted for publication in The Astrophysical Journal. Video can be
viewed at http://irfu.cea.fr/arrowhea
Bimodality of Galaxy Disk Central Surface Brightness Distribution in the Spitzer 3.6 micron band
We report on measurements of the disk central surface brightnesses (mu0) at
3.6 microns for 438 galaxies selected by distance and absolute magnitude
cutoffs from the 2350+ galaxies in the Spitzer Survey of Stellar Structure in
Galaxies (S4G), one of the largest and deepest homogeneous mid-infrared
datasets of nearby galaxies. Our sample contains nearly 3 times more galaxies
than the most recent study of the mu0 distribution. We demonstrate that there
is a bimodality in the distribution of mu0. Between the low and high surface
brightness galaxy regimes there is a lack of intermediate surface brightness
galaxies.
Caveats invoked in the literature from small number statistics to the
knowledge of the environmental influences, and possible biases from low signal
to noise data or corrections for galaxy inclination are investigated. Analyses
show that the bimodal distribution of mu0 cannot be due to any of these biases
or statistical fluctuations. It is highly probable that galaxies settle in two
stable modes: a dark matter dominated mode where the dark matter dominates at
all radii - this gives birth to low surface brightness galaxies - and a
baryonic matter dominated mode where the baryons dominate the dark matter in
the central parts - this gives rise to the high surface brightness disks. The
lack of intermediate surface brightness objects suggests that galaxies avoid
(staying in) a mode where dark matter and baryons are co-dominant in the
central parts of galaxies.Comment: Accepted for publication in MNRAS, 9 pages, 10 figures, 1 tabl
The mid-infrared Tully-Fisher relation: Spitzer Surface Photometry
The availability of photometric imaging of several thousand galaxies with the
Spitzer Space Telescope enables a mid-infrared calibration of the correlation
between luminosity and rotation in spiral galaxies. The most important
advantage of the new calibration in the 3.6 micron band, IRAC ch.1, is
photometric consistency across the entire sky. Additional advantages are
minimal obscuration, observations of flux dominated by old stars, and
sensitivity to low surface brightness levels due to favorable backgrounds.
Through Spitzer cycle 7 roughly 3000 galaxies had been observed and images of
these are available at the Spitzer archive. In cycle 8 a program called Cosmic
Flows with Spitzer has been initiated that will increase by 1274 the available
sample of spiral galaxies with inclinations greater than 45 degrees from
face-on suitable for distance measurements. This paper describes procedures
based on the photometry package Archangel that are being employed to analyze
both the archival and the new data in a uniform way. We give results for 235
galaxies, our calibrator sample for the Tully-Fisher relation. Galaxy
magnitudes are determined with uncertainties held below 0.05 mag for normal
spiral systems. A subsequent paper will describe the calibration of the [3.6]
luminosity-rotation relation.Comment: Accepted for publication in The Astronomical Journal, 12 pages, 9
figure
- …