136,876 research outputs found
Empirical ugri-UBVRc Transformations for Galaxies
We present empirical color transformations between Sloan Digital Sky Survey
ugri and Johnson-Cousins UBVRc photometry for nearby galaxies (D < 11 Mpc). We
use the Local Volume Legacy (LVL) galaxy sample where there are 90 galaxies
with overlapping observational coverage for these two filter sets. The LVL
galaxy sample consists of normal, non-starbursting galaxies. We also examine
how well the LVL galaxy colors are described by previous transformations
derived from standard calibration stars and model-based galaxy templates. We
find significant galaxy color scatter around most of the previous
transformation relationships. In addition, the previous transformations show
systematic offsets between transformed and observed galaxy colors which are
visible in observed color-color trends. The LVL-based transformations
show no systematic color offsets and reproduce the observed color-color galaxy
trends.Comment: Accepted for publication in MNRAS (9 pages, 6 figures, 4 tables
Extrapolation of Galactic Dust Emission at 100 Microns to CMBR Frequencies Using FIRAS
We present predicted full-sky maps of submillimeter and microwave emission
from the diffuse interstellar dust in the Galaxy. These maps are extrapolated
from the 100 micron emission and 100/240 micron flux ratio maps that Schlegel,
Finkbeiner, & Davis (1998; SFD98) generated from IRAS and COBE/DIRBE data.
Results are presented for a number of physically plausible emissivity models.
We find that no power law emissivity function fits the FIRAS data from 200 -
2100 GHz. In this paper we provide a formalism for a multi-component model for
the dust emission. A two-component model with a mixture of silicate and
carbon-dominated grains (motivated by Pollack et al., 1994}) provides a fit to
an accuracy of about 15% to all the FIRAS data over the entire high-latitude
sky. Small systematic differences are found between the atomic and molecular
phases of the ISM.
Our predictions for the thermal (vibrational) emission from Galactic dust at
\nu < 3000 GHz are available for general use. These full-sky predictions can be
made at the DIRBE resolution of 40' or at the higher resolution of 6.1 arcmin
from the SFD98 DIRBE-corrected IRAS maps.Comment: 48 pages, AAS LaTeX, 6 figures, ApJ (accepted). Data described in the
text, as well as 4 additional figures, are available at
http://astro.berkeley.edu/dus
Pay growth, fairness and job satisfaction : implications for nominal and real wage rigidity
Theories of wage rigidity often rely on a positive relationship between pay changes and utility, arising from concern for fairness or gift exchange. Supportive evidence has emerged from laboratory experiments, but the link has not yet been established with field data. This paper contributes a first step, using representative British data. Workers care about the level and the growth of earnings. Below-median wage increases lead to an insult effect except when similar workers have real wage reductions or frm production is falling. Nominal pay cuts appear insulting even when the firm is doing badly
Near-Infrared Imaging of Early-Type Galaxies IV. The Physical Origins of the Fundamental Plane Scaling Relations
The physical origins of the Fundamental Plane (FP) scaling relations are
investigated for early-type galaxies observed at optical and near-infrared
wavelengths. The slope for the FP is shown to increase systematically with
wavelength from the U-band through the K-band. A distance-independent
construction of the observables is described which provides an accurate
measurement of the change in the FP slope between any pair of bandpasses. The
variation of the FP slope with wavelength is strong evidence of systematic
variations in stellar content along the elliptical galaxy sequence. The
intercept of the diagnostic relationship between log(D_K/D_V) and log(sigma_0)
shows no significant dependence on environment within the uncertainties of the
Galactic extinction corrections, demonstrating the universality of the stellar
populations contributions at the level of Delta(V-K)=0.03 mag to the zero-point
of the global scaling relations.
Several other constraints on the properties of early-type galaxies --- the
slope of the Mg_2-sigma_0 relation, the effects of stellar populations
gradients, and deviations of early-type galaxies from a dynamically homologous
family --- are included to construct an empirical, self-consistent model which
provides a complete picture of the underlying physical properties which are
varying along the early-type galaxy sequence. This empirical approach
demonstrates that there are significant systematic variations in both age and
metallicity along the elliptical galaxy sequence, and that a small, but
systematic, breaking of dynamical homology (or a similar, wavelength
independent effect) is required. Predictions for the evolution of the slope of
the FP with redshift are described. [abriged]Comment: to appear in The Astronomical Journal; 40 pages, including 10
Postscript figures and 3 tables; uses AAS LaTeX style file
Beyond trial-by-trial adaptation : a quantification of the time scale of cognitive control
The idea that adaptation to stimulus or response conflict can operate over different time scales takes a prominent position in various theories and models of cognitive control. The mechanisms underlying temporal variations in control are nevertheless poorly understood, which is partly due to a lack of appropriate empirical measures. Inspired by reinforcement learning models, we developed a method to quantify the time scale of control behaviorally, by computing trial-by-trial effects that go beyond the preceding trial. Briefly, we extended the congruency sequence effect from 1 trial to multiple trials into the past and quantified the influence of previous trials on current-trial performance as a function of trial distance. The rate at which this influence changes across trials was taken as a measure of the time scale of control. We applied the method to a flanker task with different conflict frequencies and volatility. Results showed that the time scale of control was smaller in rare-conflict and volatile contexts, compared to frequent-conflict and neutral contexts. This is in agreement with theories differentiating transient from sustained control. The method offers new opportunities to reveal temporal differences in control modes and can easily be applied to various empirical paradigms. (PsycINFO Database Recordstatus: publishe
The First Comparison Between Swarm-C Accelerometer-Derived Thermospheric Densities and Physical and Empirical Model Estimates
The first systematic comparison between Swarm-C accelerometer-derived
thermospheric density and both empirical and physics-based model results using
multiple model performance metrics is presented. This comparison is performed
at the satellite's high temporal 10-s resolution, which provides a meaningful
evaluation of the models' fidelity for orbit prediction and other space weather
forecasting applications. The comparison against the physical model is
influenced by the specification of the lower atmospheric forcing, the
high-latitude ionospheric plasma convection, and solar activity. Some insights
into the model response to thermosphere-driving mechanisms are obtained through
a machine learning exercise. The results of this analysis show that the
short-timescale variations observed by Swarm-C during periods of high solar and
geomagnetic activity were better captured by the physics-based model than the
empirical models. It is concluded that Swarm-C data agree well with the
climatologies inherent within the models and are, therefore, a useful data set
for further model validation and scientific research.Comment: https://goo.gl/n4QvU
MIUSCAT: extended MILES spectral coverage. I. Stellar populations synthesis models
We extend the spectral range of our stellar population synthesis models based
on the MILES and CaT empirical stellar spectral libraries. For this purpose we
combine these two libraries with the Indo-U.S. to construct composite stellar
spectra to feed our models. The spectral energy distributions (SEDs) computed
with these models and the originally published models are combined to construct
composite SEDs for single-age, single-metallicity stellar populations (SSPs)
covering the range 3465 - 9469\AA at moderately high, and uniform, resolution
(FWHM=2.51\AA). The colours derived from these SSP SEDs provide good fits to
Galactic globular cluster data. We find that the colours involving redder
filters are very sensitive to the IMF, as well as a number of features and
molecular bands throughout the spectra. To illustrate the potential use of
these models we focus on the NaI doublet at 8200 \AA and with the aid of the
newly synthesized SSP model SEDs we define a new IMF-sensitive index that is
based on this feature, which overcomes various limitations from previous index
definitions for low velocity dispersion stellar systems. We propose an
index-index diagram based on this feature and the neighboring CaII triplet at
8600 \AA, to constrain the IMF if the age and [Na/Fe] abundance are known.
Finally we also show a survey-oriented spectrophotometric application which
evidences the accurate flux calibration of these models for carrying out
reliable spectral fitting techniques. These models are available through our
user-friendly website.Comment: 16 pages, 17 figures, 2 tables; MNRAS in press. Model predictions
available at our website: http://miles.iac.e
Comparing Single-Epoch Virial Black Hole Mass Estimators for Luminous Quasars
Single-epoch virial black hole (BH) mass estimators utilizing broad emission
lines have been routinely applied to high-redshift quasars to estimate their BH
masses. Depending on the redshift, different line estimators (Halpha, Hbeta,
MgII, CIV) are often used with optical/near-infrared spectroscopy. Here we use
a homogeneous sample of 60 intermediate-redshift (z~1.5-2.2) SDSS quasars with
optical and near-infrared spectra covering CIV through Halpha to investigate
the consistency between different line estimators. We critically compare
restframe UV line estimators (CIV, CIII], and MgII) with optical estimators
(Hbeta and Halpha) in terms of correlations between line widths and between
continuum/line luminosities, for the high-luminosity regime (L_5100>10^45.4
erg/s) probed by our sample. The continuum luminosities of L_1350 and L_3000,
and the broad line luminosities are well correlated with L_5100. We found that
the MgII FWHM correlates well with the FWHMs of the Balmer lines, and that the
MgII line estimator can be calibrated to yield consistent virial mass estimates
with those based on the Hbeta/Halpha estimators, thus extending earlier results
on less luminous objects. The CIV FWHM is poorly correlated with the Balmer
line FWHMs, and the scatter between the CIV and Hbeta FWHMs consists of an
irreducible part (~0.12 dex), and a part that correlates with the blueshift of
the CIV centroid relative to that of Hbeta. The CIII] FWHM is found to
correlate with the CIV FWHM, and hence is also poorly correlated with the Hbeta
FWHM. While the CIV and CIII] lines can be calibrated to yield consistent
virial mass estimates as Hbeta on average, the scatter is substantially larger
than MgII, and the usage of CIV/CIII] FWHM in the mass estimators does not
improve the agreement with the Hbeta estimator. (Abridged)Comment: 17 emulateapj pages; submitted to Ap
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