435,172 research outputs found
Evidence for a Non-Expanding Universe: Surface Brightness Data From HUDF
Surface brightness data can distinguish between a Friedman-Robertson-Walker
expanding universe and a non-expanding universe. For surface brightness
measured in AB magnitudes per angular area, all FRW models, regardless of
cosmological parameters, predict that surface brightness declines with redshift
as (z+1)^-3, while any non-expanding model predicts that surface brightness is
constant with distance and thus with z. High-z UV surface brightness data for
galaxies from the Hubble Ultra Deep Field and low-z data from GALEX are used to
test the predictions of these two models up to z=6. A preliminary analysis
presented here of samples observed at the same at-galaxy wavelengths in the UV
shows that surface brightness is constant, mu=kz^0.026+-0.15, consistent with
the non-expanding model. This relationship holds if distance is linearly
proportional to z at all redshifts, but seems insensitive to the particular
choice of d-z relationship. Attempts to reconcile the data with FRW predictions
by assuming that high-z galaxies have intrinsically higher surface brightness
than low-z galaxies appear to face insurmountable problems. The intrinsic FUV
surface brightness required by the FRW models for high-z galaxies exceeds the
maximum FUV surface brightness of any low-z galaxy by as much as a factor of
40. Dust absorption appears to make such extremely high intrinsic FUV surface
brightness physically impossible. If confirmed by further analysis, the
impossibility of such high-surface-brightness galaxies would rule out all FRW
expanding universe (big bang) models.Comment: 16 pages, 9 figures, to be published in the Proceedings of the First
Crisis in Cosmology Conference, AIP proceedings series typos correcte
The influence of galaxy surface brightness on the mass-metallicity relation
We study the effect of surface brightness on the mass-metallicity relation
using nearby galaxies whose gas content and metallicity profiles are available.
Previous studies using fiber spectra indicated that lower surface brightness
galaxies have systematically lower metallicity for their stellar mass, but the
results were uncertain because of aperture effect. With stellar masses and
surface brightnesses measured at WISE W1 and W2 bands, we re-investigate the
surface brightness dependence with spatially-resolved metallicity profiles and
find the similar result. We further demonstrate that the systematical
difference cannot be explained by the gas content of galaxies. For two galaxies
with similar stellar and gas masses, the one with lower surface brightness
tends to have lower metallicity. Using chemical evolution models, we
investigate the inflow and outflow properties of galaxies of different masses
and surface brightnesses. We find that, on average, high mass galaxies have
lower inflow and outflow rates relative to star formation rate. On the other
hand, lower surface brightness galaxies experience stronger inflow than higher
surface brightness galaxies of similar mass. The surface brightness effect is
more significant for low mass galaxies. We discuss implications on the
different inflow properties between low and high surface brightness galaxies,
including star formation efficiency, environment and mass assembly history
The Effects of Washing between Hydrogen Peroxide Bleaching Stages on Brightness Reversion of a Spruce High-Yield Pulp
The final brightness of a bleached high-yield pulp paper product is a very important factor in determining the quality of the pulp and the product. If the brightness of this product tends to revert in time, then the quality of the product could be viewed lesser than before. Brightness reversion of high-yield pulps is the one flaw which is keeping the high-yield pulp market from really expanding in the paper industry.
High-yield pulps show economical and environmental advantages with their use in the high quality printing and copy papers market. Much research has been done to find ways to reduce and control brightness reversion, however, no concrete methodology of solving the problem has been derived. The following study takes a spruce CTMP pulp from Canada and sets up an experiment to try and show whether or not washing between hydrogen peroxide bleaching stages can help reduce and control brightness reversion. Two bleaching concentration levels of 2% and 4%, with and without washing, are used as part of the bleaching sequence. The data defining the conclusions of this study are before and after ageing brightness values taken from brightness pads made by the bleached CTMP pulp.
This study, based on the data obtained, concludes that a washing stage implemented into the two-stage bleaching sequence was not effective in reducing brightness reversion. The trend in the reduction of brightness reversion shows no significant reduction taking place. It is concluded that the chromophoric structure in the pulp, which aid in causing brightness reversion, are not water soluble and can not be easily washed out of the bleached CTMP pulp. Suggestions for future studies would be to use hot water washing stages and a more industry-based ageing technique
Keck/LRIS Spectroscopic Confirmation of Coma Cluster Dwarf Galaxy Membership Assignments
Keck/LRIS multi-object spectroscopy has been carried out on 140 of some of
the lowest and highest surface brightness faint (19 < R < 22) dwarf galaxy
candidates in the core region of the Coma Cluster. These spectra are used to
measure redshifts and establish membership for these faint dwarf populations.
The primary goal of the low surface brightness sample is to test our ability to
use morphological and surface brightness criteria to distinguish between Coma
Cluster members and background galaxies using high resolution HST/ACS images.
Candidates were rated as expected members, uncertain, or expected background.
From 93 spectra, 51 dwarf galaxy members and 20 background galaxies are
identified. Our morphological membership estimation success rate is ~100% for
objects expected to be members and better than ~90% for galaxies expected to be
in the background. We confirm that low surface brightness is a very good
indicator of cluster membership. High surface brightness galaxies are almost
always background with confusion arising only from the cases of the rare
compact elliptical galaxies. The more problematic cases occur at intermediate
surface brightness. Many of these galaxies are given uncertain membership
ratings, and these were found to be members about half of the time. Including
color information will improve membership determination but will fail for some
of the same objects that are already mis-identified when using only surface
brightness and morphology criteria. Compact elliptical galaxies with B-V colors
~0.2 magnitudes redward of the red sequence in particular require spectroscopic
follow-up. In a sample of 47 high surface brightness, UCD candidates, 19
objects have redshifts which place them in the Coma Cluster. Redshift
measurements are presented and the use of indirect means for establishing
cluster membership is discussed.Comment: Accepted for publication in ApJ, 25 pages, 15 figure
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