1,391 research outputs found
A Test for Large-Scale Systematic Errors in Maps of Galactic Reddening
Accurate maps of Galactic reddening are important for a number of
applications, such as mapping the peculiar velocity field in the nearby
Universe. Of particular concern are systematic errors which vary slowly as a
function of position on the sky, as these would induce spurious bulk flow. We
have compared the reddenings of Burstein & Heiles (BH) and those of Schlegel,
Finkbeiner & Davis (SFD) to independent estimates of the reddening, for
Galactic latitudes |b| > 10. Our primary source of Galactic reddening estimates
comes from comparing the difference between the observed B-V colors of
early-type galaxies, and the predicted B-V color determined from the B-V--Mg_2
relation. We have fitted a dipole to the residuals in order to look for
large-scale systematic deviations. There is marginal evidence for a dipolar
residual in the comparison between the SFD maps and the observed early-type
galaxy reddenings. If this is due to an error in the SFD maps, then it can be
corrected with a small (13%) multiplicative dipole term. We argue, however,
that this difference is more likely to be due to a small (0.01 mag.) systematic
error in the measured B-V colors of the early-type galaxies. This
interpretation is supported by a smaller, independent data set (globular
cluster and RR Lyrae stars), which yields a result inconsistent with the
early-type galaxy residual dipole. BH reddenings are found to have no
significant systematic residuals, apart from the known problem in the region
230 < l < 310, -20 < b < 20.Comment: 8 pages, PASP, in press (Jan 1999
Cosmological Parameters from the Comparison of the 2MASS Gravity Field with Peculiar Velocity Surveys
We compare the peculiar velocity field within 65 Mpc predicted from
2MASS photometry and public redshift data to three independent peculiar
velocity surveys based on type Ia supernovae, surface brightness fluctuations
in ellipticals, and Tully-Fisher distances to spirals. The three peculiar
velocity samples are each in good agreement with the predicted velocities and
produce consistent results for \beta_{K}=\Omega\sbr{m}^{0.6}/b_{K}. Taken
together the best fit . We explore the effects of
morphology on the determination of by splitting the 2MASS sample into
E+S0 and S+Irr density fields and find both samples are equally good tracers of
the underlying dark matter distribution, but that early-types are more
clustered by a relative factor b\sbr{E}/b\sbr{S} \sim 1.6. The density
fluctuations of 2MASS galaxies in Mpc spheres in the local volume is
found to be \sigma\sbr{8,K} = 0.9. From this result and our value of
, we find \sigma_8 (\Omega\sbr{m}/0.3)^{0.6} = 0.91\pm0.12. This
is in excellent agreement with results from the IRAS redshift surveys, as well
as other cosmological probes. Combining the 2MASS and IRAS peculiar velocity
results yields \sigma_8 (\Omega\sbr{m}^/0.3)^{0.6} = 0.85\pm0.05.Comment: 11 pages, ApJ accepte
Ages and metallicities of faint red galaxies in the Shapley Supercluster
We present results on the stellar populations of 232 quiescent galaxies in
the Shapley Supercluster, based on spectroscopy from the AAOmega spectrograph
at the AAT. The key characteristic of this survey is its coverage of many
low-luminosity objects (sigma ~ 50 km/s), with high signal-to-noise (~45 per
Angstrom). Balmer-line age estimates are recovered with ~25% precision even for
the faintest sample members. We summarize the observations and absorption line
data, and present correlations of derived ages and metallicities with mass and
luminosity. We highlight the strong correlation between age and alpha-element
abundance ratio, and the anti-correlation of age and metallicity at fixed mass,
which is shown to extend into the low-luminosity regime.Comment: Four pages, three figures; To appear in Proceedings of IAU Symp. 245
"Formation and Evolution of Galaxy Bulges", (Oxford, July 16-20 2007), Eds.
Martin Bureau, Lia Athanassoula, and Beatriz Barbu
LIVESTOCK FUTURES MARKETS AND RATIONAL PRICE FORMATION: EVIDENCE FOR LIVE CATTLE AND LIVE HOGS
The efficiency of livestock futures markets continues to receive attention, particularly with regard to their forward pricing or forecasting ability. The purpose of this paper is to present a more general theory that encompasses the forward pricing concept. It is argued that futures contract prices for competitively produced nonstorable commodities, such as live cattle and live hogs, follow a rational formation process. Futures contract prices reflect expected market conditions when contracts are sufficiently close to the delivery month that the supply of the underlying commodity cannot be changed. However, prior to the period when future supplies are relatively fixed, futures contract prices should adjust to reflect the competitive equilibrium, where output price equals average costs of production. Presented evidence suggests that live cattle and live hog futures markets support the rational price formation hypothesis: prices for distant contracts reflect average costs of feeding. Implications for risk management strategies are considered.Demand and Price Analysis, Livestock Production/Industries,
Are Recent Peculiar Velocity Surveys Consistent?
We compare the bulk flow of the SMAC sample to the predictions of popular
cosmological models and to other recent large-scale peculiar velocity surveys.
Both analyses account for aliasing of small-scale power due to the sparse and
non-uniform sampling of the surveys. We conclude that the SMAC bulk flow is in
marginal conflict with flat COBE-normalized Lambda-CDM models which fit the
cluster abundance constraint. However, power spectra which are steeper
shortward of the peak are consistent with all of the above constraints. When
recent large-scale peculiar velocity surveys are compared, we conclude that all
measured bulk flows (with the possible exception of that of Lauer & Postman)
are consistent with each other given the errors, provided the latter allow for
`cosmic covariance'. A rough estimate of the mean bulk flow of all surveys
(except Lauer & Postman) is ~400 km/s towards l=270, b=0.Comment: 8 pages, 3 figures. To appear in Proceedings of the Cosmic Flows
Workshop, Victoria, B. C., Canada, July 1999, eds. S. Courteau, M. Strauss,
and J. Willic
Galaxy-Galaxy Lensing in the Hubble Deep Field: The Halo Tully-Fisher Relation at Intermediate Redshift
A tangential distortion of background source galaxies around foreground lens
galaxies in the Hubble Deep Field is detected at the 99.3% confidence level. An
important element of our analysis is the use of photometric redshifts to
determine distances of lens and source galaxies and rest-frame B-band
luminosities of the lens galaxies. The lens galaxy halos obey a Tully-Fisher
relation between halo circular velocity and luminosity; the typical lens
galaxy, at a redshift z = 0.6, has a circular velocity of 210 +/-40 km/s at M_B
= -18.5, if q_0 = 0.5. Control tests, in which lens and source positions and
source ellipticities are randomized, confirm the significance level of the
detection quoted above. Furthermore, a marginal signal is also detected from an
independent, fainter sample of source galaxies without photometric redshifts.
Potential systematic effects, such as contamination by aligned satellite
galaxies, the distortion of source shapes by the light of the foreground
galaxies, PSF anisotropies, and contributions from mass distributed on the
scale of galaxy groups are shown to be negligible. A comparison of our result
with the local Tully-Fisher relation indicates that intermediate-redshift
galaxies are fainter than local spirals by 1.0 +/- 0.6 B mag at a fixed
circular velocity. This is consistent with some spectroscopic studies of the
rotation curves of intermediate-redshift galaxies. This result suggests that
the strong increase in the global luminosity density with redshift is dominated
by evolution in the galaxy number density.Comment: Revised version with minor changes. 13 pages, 7 figures, LaTeX2e,
uses emulateapj and multicol styles (included). Accepted by Ap
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