2,595 research outputs found
The First CO Map of a Low Surface Brightness Galaxy
Using the Owens Valley Radio Observatory Millimeter-Wavelength Array (OVRO)
we have obtained the first CO map of a low surface brightness (LSB) galaxy. The
studied galaxy, UGC 01922, was chosen for these observations because both of
its previous CO detection with the IRAM 30m telescope and its classification as
a Malin 1 `cousin' - an LSB galaxy with M_HI > 10^10 Msol. The OVRO map
detected approximately 65% of the CO(1-0) flux found earlier with the single
dish measurements, giving a detected gas mass equivalent to M_H2 = 1.1X10^9
Msol. The integrated gas peak lies at the center of the galaxy and coincides
with both the optical and 1.4 GHz continuum emission peaks. The molecular gas
extends well beyond the OVRO beam size (~4'' or 3 kpc), covering ~25% of the
optical bulge. In all, perhaps the most remarkable aspect of this map is its
unexceptional appearance. Given that it took over ten years to successfully
detect molecular gas in any low surface brightness system, it is surprising
that the appearance and distribution of UGC 01922's CO is similar to what would
be expected for a high surface brightness galaxy in the same morphological
class.Comment: 5 pages, including 3 figures and 3 tables. also available online at
http://www.gb.nrao.edu/~koneil. Accepted by ApJ
Mass Density Profiles of LSB Galaxies
We derive the mass density profiles of dark matter halos that are implied by
high spatial resolution rotation curves of low surface brightness galaxies. We
find that at small radii, the mass density distribution is dominated by a
nearly constant density core with a core radius of a few kpc. For rho(r) ~ r^a,
the distribution of inner slopes a is strongly peaked around a = -0.2. This is
significantly shallower than the cuspy a < -1 halos found in CDM simulations.
While the observed distribution of alpha does have a tail towards such extreme
values, the derived value of alpha is found to depend on the spatial resolution
of the rotation curves: a ~ -1 is found only for the least well resolved
galaxies. Even for these galaxies, our data are also consistent with constant
density cores (a = 0) of modest (~ 1 kpc) core radius, which can give the
illusion of steep cusps when insufficiently resolved. Consequently, there is no
clear evidence for a cuspy halo in any of the low surface brightness galaxies
observed.Comment: To be published in ApJ Letters. 6 pages. Uses aastex and
emulateapj5.sty Typo in Eq 1 fixe
До питання про легітимацію влади Рад в період становлення більшовицької диктатури в УСРР
Проаналізувавши документальні джерела, автор статті дійшов висновку, що ради, під прикриттям яких було встановлено диктатуру більшовицької партії в Україні,
мали надати їй легітимного статусу.
Ключові слова: більшовики, переворот, диктатура, ради, влада. легітимація, державність.Проанализировав документальные источники, автор статьи приходит к выводу,
что советы, под прикрытием которых была установлена диктатура большевистской
партии в Украине, были призваны придать ей легитимный статус.
Ключевые слова: большевики, переворот, диктатура, советы, власть, легитимация, государственность.On the basis of the documentary sources, the author of the article proves that the Soviets
under the lee of which the dictatorship of the Bolshevik Party in Ukraine was established
aimed at making it legitimate.
Key words: bolsheviks, coup d'état, dictatorship, soviets, power, legitimization, statehood
Saving energy: bringing down Europe's enery prices
In June 2011 the European Commission proposed a new Directive on Energy Efficiency. Its purpose is to put forward a framework
to deliver the EU’s target of reducing its energy consumption by 20% by 2020. Currently, the EU is only on track to achieve half
of those savings.
Apart from the environmental benefits -notably, reducing greenhouse gas emissions- energy savings have significant economic
benefits for European economies: (1) they reduce the amount of money businesses and consumers need to spend on energy, (2)
they have positive effects on employment and (3) they decrease dependency on fossil fuel imports.
But the actual scale of the benefits is often underestimated. In this paper, we show that energy savings do not only bring direct
cost savings; they also indirectly reduce energy prices. Real cost savings resulting from meeting the 20% savings target are likely
to be considerably higher than figures commonly cited. In other words, consumers would use fewer units of energy, and the price
of the units they do use would be lower than they would otherwise be.
Energy savings can reduce energy prices in the following ways:
1. Decreasing fossil fuel prices: international fossil fuel markets are under pressure because there is little reserve production
capacity. This means prices are very sensitive to changes in energy demand. Because energy savings in Europe and the
spillover effects of this action in other world regions will reduce global demand, we expect significant reductions in future
energy prices.
2. Decreasing electricity prices: cheaper fossil fuel prices will reduce electricity prices (because roughly 50% of the EU’s electricity
is produced from fossil fuels). In addition, a lower demand will impact the fuel mix in electricity production: it will occur more
often that lower-priced fuels determine the marginal costs.This will have an additional reduction effect on electricity prices.
3. Decreasing energy prices in the longer term: meeting the EU’s 20% by 2020 energy saving target is expected to save tens
of billions of Euros per year due to avoided investments in energy infrastructure (power generation and transmission, fuel
import and storage facilities). Since it is usual practice to pass on investment costs to energy consumers, a reduction in these
investments will lead to an additional cost saving.
On the basis of the evidence examined in this report, we estimate that the indirect impact on energy prices will be of the same
order as the direct impact of the energy savings. Put simply, for every €1 of energy cost saving, an additional €1 could be saved
due to lower energy prices
First Detection of CO in a Low Surface Brightness Galaxy
We report on the first attempts at searching for CO in red low surface
brightness galaxies, and the first detection of molecular gas in a low surface
brightness (mu_B(0)_{obs} > 23 mag arcsec^{-2}) galaxy. Using the IRAM 30m
telescope, CO(1-0) and CO(2-1) lines were searched for in four galaxies --
P06-1, P05-5, C05-3, & C04-2. In three of the galaxies no CO was detected, to
T_{MB} ~ 1.8mK (at the 3 sigma level). In the fourth galaxy, P06-1, both lines
were detected. Comparing our findings with previous studies shows P06-1 to have
a molecular-to-atomic mass ratio considerably lower than is predicted using
theoretical models based on high surface brightness galaxy studies. This
indicates the N(H_2)/(int{T(CO)dv}) conversion factor for low surface
brightness galaxies may currently be consistently underestimated by a factor of
3 - 20.Comment: 8 pages, 2 figures, accepted by the ApJ
Star Formation and Tidal Encounters with the Low Surface Brightness Galaxy UGC 12695 and Companions
We present VLA H I observations of the low surface brightness galaxy UGC
12695 and its two companions, UGC 12687 and a newly discovered dwarf galaxy
2333+1234. UGC 12695 shows solid body rotation but has a very lopsided
morphology of the H I disk, with the majority of the H I lying in the southern
arm of the galaxy. The H I column density distribution of this very blue, LSB
galaxy coincides in detail with its light distribution. Comparing the H I
column density of UGC 12695 with the empirical (but not well understood) value
of Sigma_c = 10E21 atoms/cm^2 found in, i.e., Skillman's 1986 paper shows the
star formation to be a local affair, occurring only in those regions where the
column density is above this star formation threshold. The low surface
brightness nature of this galaxy could thus be attributed to an insufficient
gas surface density, inhibiting star formation on a more global scale.
Significantly, though, the Toomre criterion places a much lower critical
density on the galaxy (+/-10E20 atoms/cm^2), which is shown by the galaxy's low
SFR to not be applicable.
Within a projected distance of 300kpc/30kms of UGC 12695 lie two companion
galaxies - UGC 12687, a high surface brightness barred spiral galaxy, and
2333+1234, a dwarf galaxy discovered during this investigation. The close
proximity of the three galaxies, combined with UGC 12695's extremely blue color
and regions of localized starburst and UGC 12687's UV excess bring to mind
mutually induced star formation through tidal activity.Comment: 14 pages, 8 figures (2 color), To be published in A.J., May 2000
Further Discoveries of 12CO in Low Surface Brightness Galaxies
Using the IRAM 30m telescope we have obtained seven new, deep CO J(1-0) and
J(2-1) observations of low surface brightness (LSB) galaxies. Five of the
galaxies have no CO detected to extremely low limits (0.1-0.4 K km/s at
J(1-0)), while two of the galaxies, UGC 01922 and UGC 12289, have clear
detections in both line transitions. When these observations are combined with
all previous CO observations taken of LSB systems, we compile a total of 34
observations, in which only 3 galaxies have had detections of their molecular
gas. Comparing the LSB galaxies with and without CO detections to a sample of
high surface brightness (HSB) galaxies with CO observations indicates that it
is primarily the low density of baryonic matter within LSB galaxies which is
causing their low CO fluxes. Finally, we note that one of the massive LSB
galaxies studied in this project, UGC 06968 (a Malin-1 `cousin'), has upper
limits placed on both M_H2 and M_H2/M_HI which are 10-20 times lower than the
lowest values found for any galaxy (LSB or HSB) with similar global properties.
This may be due to an extremely low temperature and metallicity within UGC
06968, or simply due to the CO distribution within the galaxy being too diffuse
to be detected by the IRAM beam.Comment: 18 pages, 8 figures, 4 tables. Accepted by Ap
Integrable hierarchy underlying topological Landau-Ginzburg models of D-type
A universal integrable hierarchy underlying topological Landau-Ginzburg
models of D-tye is presented. Like the dispersionless Toda hierarchy, the new
hierarchy has two distinct (``positive" and ``negative") set of flows. Special
solutions corresponding to topological Landau-Ginzburg models of D-type are
characterized by a Riemann-Hilbert problem, which can be converted into a
generalized hodograph transformation. This construction gives an embedding of
the finite dimensional small phase space of these models into the full space of
flows of this hierarchy. One of flat coordinates in the small phase space turns
out to be identical to the first ``negative" time variable of the hierarchy,
whereas the others belong to the ``positive" flows.Comment: 14 pages, Kyoto University KUCP-0061/9
On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy
As part of a continuing survey of nearby galaxies, we have mapped the neutral
gas content of the low surface brightness, Magellanic-type galaxy NGC 3109 ---
and its environment, including the Antlia dwarf galaxy --- at unprecedented
velocity resolution and brightness sensitivity. The HI mass of NGC 3109 is
measured to be (3.8 +/- 0.5) x 10^8 Msun. A substantial warp in the disk of NGC
3109 is detected in the HI emission image in the form of an extended low
surface brightness feature. We report a positive detection in HI of the nearby
Antlia dwarf galaxy, and measure its total neutral gas mass to be (6.8 +/- 1.4)
x 10^5 Msun. We show the warp in NGC 3109 to lie at exactly the same radial
velocity as the gas in the Antlia dwarf galaxy and speculate that Antlia
disturbed the disk of NGC 3109 during a mild encounter ~1 Gyr in the past. HI
data for a further eight galaxies detected in the background are presented.Comment: Accepted for publication in A
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