1,368 research outputs found
The Dwarf Irregular Galaxy UGC 7636 Exposed: Stripping At Work In The Virgo Cluster
We present the results of optical spectroscopy of a newly discovered H II
region residing in the H I gas cloud located between the dwarf irregular galaxy
UGC 7636 and the giant elliptical galaxy NGC 4472 in the Virgo Cluster. By
comparing UGC 7636 with dwarf irregular galaxies in the field, we show that the
H I cloud must have originated from UGC 7636 because (1) the oxygen abundance
of the cloud agrees with that expected for a galaxy with the blue luminosity of
UGC 7636, and (2) M_{H I}/L_B for UGC 7636 becomes consistent with the measured
oxygen abundance of the cloud if the H I mass of the cloud is added back into
UGC 7636. It is likely that tides from NGC 4472 first loosened the H I gas,
after which ram-pressure stripping removed the gas from UGC 7636.Comment: 12 pages, 2 eps figures (AASTeX 5.0); accepted for publication in ApJ
Letter
Dense Cloud Ablation and Ram Pressure Stripping of the Virgo Spiral NGC 4402
We present optical, HI and radio continuum observations of the highly
inclined Virgo Cluster Sc galaxy NGC 4402, which show evidence for ram-pressure
stripping and dense cloud ablation. VLA HI and radio continuum maps show a
truncated gas disk and emission to the northwest of the main disk emission. In
particular, the radio continuum emission is asymmetrically extended to the
north and skewed to the west. The Halpha image shows numerous HII complexes
along the southern edge of the gas disk, possibly indicating star formation
triggered by the ICM pressure. BVR images at 0.5" resolution obtained with the
WIYN Tip-Tilt Imager show a remarkable dust lane morphology: at half the
optical radius, the dust lane of the galaxy curves up and out of the disk,
matching the HI morphology. Large dust plumes extend upward for ~1.5 kpc from
luminous young star clusters at the SE edge of the truncated gas disk. These
star clusters are very blue, indicating very little dust reddening, which
suggests dust blown away by an ICM wind at the leading edge of the interaction.
To the south of the main ridge of interstellar material, where the galaxy is
relatively clean of gas and dust, we have discovered 1 kpc long linear dust
filaments with a position angle that matches the extraplanar radio continuum
tail; we interpret this angle as the projected ICM wind direction. One of the
observed dust filaments has an HII region at its head. We interpret these dust
filaments as large, dense clouds which were initially left behind as the
low-density ISM is stripped, but are then ablated by the ICM wind. These
results provide striking new evidence on the fate of molecular clouds in
stripped cluster galaxies.Comment: 17 pages, 4 figures, accepted for publication in AJ. See
ftp://ftp.astro.yale.edu/pub/hugh/papers/crowl_n4402.ps.gz for a version with
high-resolution figure
Aid for trade and the political economy of trade liberalization
The Aid for Trade (AfT) initiative has gained much popularity since its launch at the World Trade Organization's Ministerial Conference in 2005, and there are ongoing discussions on its effectiveness and potential to improve the integration of developing countries into the world economy. This paper contributes to the debate by analyzing AfT in a political economy context. We find that the delivery of AfT is a precondition for trade reform in developing countries, as well as for trade liberalization and trade-enhancing rule-making in regional and international forums. Accordingly, AfT may be a catalyst of trade reforms domestically and internationally. --Aid for Trade,Trade Liberalization,Trade Policy,Trade Reform
Acoustical modes of arbitrary volumes using NASTRAN transient heat transfer RF9
An equivalence between temperature and pressure, heat conduction and stiffness and heat capacity and mass is defined, enabling acoustical modal analysis of arbitrary three dimensional volumes. The transient heat transfer analysis rigid format in NASTRAN, RF9, has been altered providing the acoustical analysis capability. Examples and ALTERs are included
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