760 research outputs found
Mergers and Acquisitions in the Colombian Financial Sector (Impact on Efficiency 1990-2005)
Colombia has witnessed a renewed interest in merging and acquiring financial institutions during 2003-2005. These have been âcomplementary mergersâ that seek to exploit economies scale and scope. This process contrasts favorably with those mergers & acquisitions that occurred during the mid-1990s, which involved mainly âtwin institutionsâ that lacked potential for gaining multiproduct efficiency. This document analyzes the need to remove some of the regulatory constraints that obstruct further exploitation of such economies of scale-scope and quantifies the âcost efficienciesâ shown by the Colombian banking sector (1994-2005). At the aggregate level, we found (absolute) banking efficiency to be around 63%, a similar value to those found in related studies post-crisis. This implies that banks operating in Colombia have been able to recover their efficiency levels during postcrisis 2003-2005, except for mortgage institutions. We highlight regulatory barriers that could be removed to help the banking system move closer to the optimal production frontier.Financial Institutions, Mergers and Acquisitions
The Molecular Gas in the Circumnuclear Region of Seyfert Galaxies
Sub-arcsecond IRAM Plateau de Bure mm-interferometric observations of the
12CO (2-1) line emission in the Seyfert~1 NGC 3227 and the Seyfert~2 NGC 1068
have revealed complex kinematic systems in the inner 100 pc to 300 pc that are
not consistent with pure circular motion in the host galaxies. Modeling of
these kinematic systems with elliptical orbits in the plane of the host galaxy
(representing gas motion in a bar potential) is a possible solution but does
not reproduce all features observed. A better description of the complex
kinematics is achieved by circular orbits which are tilted out of the plane of
the host galaxy. This could indicate that the thin circumnuclear gas disk is
warped. In the case of NGC 1068 the warp model suggests that at a radius of
about 70 pc, the gas disk is oriented edge-on providing material for the
obscuration of the AGN nucleus. The position-velocity diagrams show rising
rotation curves at r 2
x 10^7 M_solar for NGC 3227 and > 10^8 M_solar for NGC 1068 within the central
25 pc.Comment: 14 pages, Ap.J. letter, accepte
Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
We study the low-contrast Fe II emission blends in the ultraviolet
(1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC
5548 and show that these features vary in flux and that these variations are
correlated with those of the optical continuum. The amplitude of variability of
the optical Fe II emission is 50% - 75% that of Hbeta and the ultraviolet Fe II
emission varies with an even larger amplitude than Hbeta. However, accurate
measurement of the flux in these blends proves to be very difficult even using
excellent Fe II templates to fit the spectra. We are able to constrain only
weakly the optical Fe II emission-line response timescale to a value less than
several weeks; this upper limit exceeds all the reliably measured emission-line
lags in this source so it is not particularly meaningful. Nevertheless, the
fact that the optical Fe II and continuum flux variations are correlated
indicates that line fluorescence in a photoionized plasma, rather than
collisional excitation, is responsible for the Fe II emission. The iron
emission templates are available upon request.Comment: 34 pages including 12 figures and 2 tables. Accepted for publication
by ApJ (tentatively in vol. 626 June 10, 2005
The host galaxy of GRB010222: The strongest damped Lyman-alpha system known
Analysis of the absorption lines in the afterglow spectrum of the gamma-ray
burst GRB010222 indicates that its host galaxy (at a redshift of z=1.476) is
the strongest damped Lyman-alpha (DLA) system known, having a very low
metallicity and modest dust content. This conclusion is based on the detection
of the red wing of Lyman-alpha plus a comparison of the equivalent widths of
ultraviolet Mg I, Mg II, and Fe II lines with those in other DLAs. The column
density of H I, deduced from a fit to the wing of Lyman-alpha, is (5 +/- 2)
10^22 cm^-2. The ratio of the column densities of Zn and Cr lines suggests that
the dust content in our line of sight through the galaxy is low. This could be
due to either dust destruction by the ultraviolet emission of the afterglow or
to an initial dust composition different to that of the diffuse interstellar
material, or a combination of both.Comment: Submitted to MNRAS 12 page
The First VLT FORS1 spectra of Lyman-break candidates in the HDF-S and AXAF Deep Field
We report on low-resolution multi-object spectroscopy of 30 faint targets (R
\~ 24-25) in the HDF-S and AXAF deep field obtained with the VLT Focal
Reducer/low dispersion Spectrograph (FORS1). Eight high-redshift galaxies with
2.75< z < 4 have been identified. The spectroscopic redshifts are in good
agreement with the photometric ones with a dispersion at z<2
and at z>2. The inferred star formation rates of the
individual objects are moderate, ranging from a few to a few tens solar masses
per year. Five out of the eight high-z objects do not show prominent emission
lines. One object has a spectrum typical of an AGN. In the AXAF field two
relatively close pairs of galaxies have been identified, with separations of
8.7 and 3.1 proper Mpc and mean redshifts of 3.11 and 3.93, respectively.Comment: 5 pages Latex, with 2 PostScript figures. Astronomy and Astrophysics,
in pres
An absorption event in the X-ray lightcurve of NGC 3227
We have monitored the Seyfert galaxy NGC 3227 with the Rossi X-ray Timing
Explorer (RXTE) since January 1999. During late 2000 and early 2001 we observed
an unusual hardening of the 2-10 keV X-ray spectrum which lasted several
months. The spectral hardening was not accompanied by any correlated variation
in flux above 8 keV. We therefore interpret the spectral change as transient
absorption by a gas cloud of column density 2.6 10^23 cm^-2 crossing the line
of sight to the X-ray source. A spectrum obtained by XMM-Newton during an early
phase of the hard-spectrum event confirms the obscuration model and shows that
the absorbing cloud is only weakly ionised. The XMM-Newton spectrum also shows
that ~10% of the X-ray flux is not obscured, but this unabsorbed component is
not significantly variable and may be scattered radiation from a large-scale
scattering medium. Applying the spectral constraints on cloud ionisation
parameter and assuming that the cloud follows a Keplerian orbit, we constrain
the location of the cloud to be R~10-100 light-days from the central X-ray
source, and its density to be n_H~10^8cm^-3, implying that we have witnessed
the eclipse of the X-ray source by a broad line region cloud.Comment: 5 pages, 6 figures, accepted for publication in MNRAS letter
Luminosity Evolution of Early-type Galaxies to z=0.83: Constraints on Formation Epoch and Omega
We present deep spectroscopy with the Keck telescope of eight galaxies in the
luminous X-ray cluster MS1054-03 at z=0.83. The data are combined with imaging
observations from the Hubble Space Telescope (HST). The spectroscopic data are
used to measure the internal kinematics of the galaxies, and the HST data to
measure their structural parameters. Six galaxies have early-type spectra, and
two have "E+A" spectra. The galaxies with early-type spectra define a tight
Fundamental Plane (FP) relation. The evolution of the mass-to-light ratio is
derived from the FP. The M/L ratio evolves as \Delta log M/L_B \propto -0.40 z
(Omega_m=0.3, Omega_Lambda=0). The observed evolution of the M/L ratio provides
a combined constraint on the formation redshift of the stars, the IMF, and
cosmological parameters. For a Salpeter IMF (x=2.35) we find that z_form>2.8
and Omega_m<0.86 with 95% confidence. The constraint on the formation redshift
is weaker if Omega_Lambda>0: z_form>1.7 if Omega_m=0.3 and Omega_Lambda=0.7. At
present the limiting factor in constraining z_form and Omega from the observed
luminosity evolution of early-type galaxies is the poor understanding of the
IMF. We find that if Omega_m=1 the IMF must be significantly steeper than the
Salpeter IMF (x>2.6).Comment: To be published in ApJ Letters, Volume 504, September 1, 1998. 5
pages, 4 figure
The Nature of Star Formation in Lensed Galaxies at High Redshift
We present near-infrared photometry of all available gravitationally lensed âarcsâ with spectroscopic redshifts. By combining this photometry with optical data, we find that the bulk of the systems with z ~ 1 are intrinsically blue across the rest-frame spectral region 2000 Ă
to 1 ÎŒm. Using a combination of optical and optical-infrared colours, we demonstrate that these systems cannot be blue by virtue of a secondary burst of star formation superimposed on an evolved population, but we are unable to distinguish directly between major star formation events in a generic young galaxy and an extended era of constant star formation typical of late-type spirals. Using various arguments, we conclude that our arcs represent modest gravitational magnification of typical field galaxies. Consequently, if the star formation seen is representative of that in field galaxies at z â„ 1, the absence of high-redshift galaxies in current deep spectroscopic surveys to bJâ24bJâ24 supports the hypothesis that the bulk of the star formation in normal galaxies occurred over an extended era up to the epoch corresponding to z ~ 1
An Optical/Near-Infrared Study of Radio-Loud Quasar Environments II. Imaging Results
We use optical and near-IR imaging to examine the properties of the
significant excess population of K>=19 galaxies found in the fields of 31 z=1-2
radio-loud quasars by Hall, Green & Cohen (1998). The excess occurs on two
spatial scales: a component at <40'' from the quasars significant compared to
the galaxy surface density at >40'' in the same fields, and a component roughly
uniform to ~100'' significant compared to the galaxy surface density seen in
random-field surveys in the literature. The r-K color distributions of the
excess galaxy populations are indistinguishable and are significantly redder
than the color distribution of the field population.
The excess galaxies are consistent with being predominantly early-type
galaxies at the quasar redshifts, and there is no evidence that they are
associated with intervening MgII absorption systems. The average excess within
0.5 Mpc (~65'') of the quasars corresponds to Abell richness class ~0 compared
to the galaxy surface density at >0.5 Mpc from the quasars, and to Abell
richness class ~1.5 compared to that from the literature.
We discuss the spectral energy distributions (SEDs) of galaxies in fields
with data in several passbands. Most candidate quasar-associated galaxies are
consistent with being 2-3 Gyr old early-types at the quasar redshifts of z~1.5.
However, some objects have SEDs consistent with being 4-5 Gyr old at z~1.5, and
a number of others are consistent with ~2 Gyr old but dust-reddened galaxies at
the quasar redshifts. These potentially different galaxy types suggest there
may be considerable dispersion in the properties of early-type cluster galaxies
at z~1.5. There is also a population of galaxies whose SEDs are best modelled
by background galaxies at z>2.5.Comment: Accepted to ApJ; 54 pages including 30 figures; 2 color GIF files
available separately; also available from
http://www.astro.utoronto.ca/~hall/thesis.htm
The Deficit of Distant Galaxy Clusters in the RIXOS X-ray Survey
Clusters of galaxies are the largest gravitationally bound systems and
therefore provide an important way of studying the formation and evolution of
the large scale structure of the Universe. Cluster evolution can be inferred
from observations of the X-ray emission of the gas in distant clusters, but
interpreting these data is not straightforward. In a simplified view, clusters
grow from perturbations in the matter distribution: their intracluster gas is
compressed and shock-heated by the gravitational collapse. The resulting
X-ray emission is determined by the hydrostatic equilibrium of the gas in the
changing gravitational potential. However, if processes such as radiative
cooling or pre-collapse heating of the gas are important, then the X-ray
evolution will be strongly influenced by the thermal history of the gas. Here
we present the first results from a faint flux-limited sample of X-ray selected
clusters compiled as part of the ROSAT International X-ray and Optical Survey
(RIXOS). Very few distant clusters have been identified. Most importantly,
their redshift distribution appears to be inconsistent with simple models based
on the evolution of the gravitational potential. Our results suggest that
radiative cooling or non-gravitational heating of the intracluster gas must
play an important role in the evolution of clusters.Comment: uuencoded compressed postscript. The preprint is also available at
http://www.ast.cam.ac.uk/preprint/PrePrint.htm
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