2,027 research outputs found
Chandra Observation of the Edge-on Spiral NGC 5775: Probing the Hot Galactic Disk/Halo Connection
We study the edge-on galaxy NGC 5775, utilizing a 58.2 ks {\sl Chandra}
ACIS-S observation together with complementary {\sl HST} ACS, {\sl Spitzer}
IRAC and other multi-wavelength data sets. This edge-on galaxy, with its
disk-wide active star formation, is particularly well-suited for studying the
disk/halo interaction on sub-galactic scales. We detect 27 discrete X-ray
sources within the region of the galaxy, including an ultra-luminous
source with a 0.3-7 keV luminosity of . The
source-removed diffuse X-ray emission shows several prominent extraplanar
features, including a diameter ``shell-like'' feature and a
``blob'' reaching a projected distance of from the galactic
disk. The bulk of the X-ray emission in the halo has a scale height of
1.5 kpc and can be characterized by a two-temperature optically thin
thermal plasma with temperatures of 0.2 and 0.6 keV and a total 0.3-2
keV luminosity of . The high-resolution,
multi-wavelength data reveal the presence of several extraplanar features
around the disk, which appear to be associated with the in-disk star formation.
We suggest that hot gas produced with different levels of mass loading can have
different temperatures, which may explain the characteristic temperatures of
hot gas in the halo. We have obtained a sub-galactic scale X-ray-intensity-star
formation relation, which is consistent with the integrated version in other
star forming galaxies.Comment: 25 pages, 10 figures, 4 tables, accepted for publication in MNRA
Early Time Evolution of High Energy Heavy Ion Collisions
We solve the Yang-Mills equations in the framework of the
McLerran-Venugopalan model for small times tau after a collision of two nuclei.
An analytic expansion around tau=0 leads to explicit results for the field
strength and the energy momentum tensor of the gluon field at early times. We
then discuss constraints for the energy density, pressure and flow of the
plasma phase that emerges after thermalization of the gluon field.Comment: 4 pages, 1 figure; contribution to Quark Matter 2006; submitted to J.
Phys.
Spectroscopic evidence of charge exchange X-ray emission from galaxies
What are the origins of the soft X-ray line emission from non-AGN galaxies?
XMM-Newton RGS spectra of nearby non-AGN galaxies (including starforming ones:
M82, NGC 253, M51, M83, M61, NGC 4631, M94, NGC 2903, and the Antennae
galaxies, as well as the inner bulge of M31) have been analyzed. In particular,
the K{\alpha} triplet of O VII shows that the resonance line is typically
weaker than the forbidden and/or inter-combination lines. This suggests that a
substantial fraction of the emission may not arise directly from optically thin
thermal plasma, as commonly assumed, and may instead originate at its interface
with neutral gas via charge exchange. This latter origin naturally explains the
observed spatial correlation of the emission with various tracers of cool gas
in some of the galaxies. However, alternative scenarios, such as the resonance
scattering by the plasma and the relic photo-ionization by AGNs in the recent
past, cannot be ruled out, at least in some cases, and are being examined. Such
X-ray spectroscopic studies are important to the understanding of the
relationship of the emission to various high-energy feedback processes in
galaxies.Comment: 5 pages, published in Astronomical Notes, for "Charge exchange in the
Universe" workshop, Paris 201
Oxidative Stress, T Cell DNA Methylation, and Lupus
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107387/1/art38427.pd
Synthesis of Stimuli-Responsive Programmable Polymers Through Ring-Opening–Metathesis Cross-Metathesis (ROM-CM)
Stimuli-responsive polymers can change their physical and/or chemical properties in response to external stimuli. These polymers have found great success in a number of important areas including molecular gels and biomedical engineering, as well as success in applications such as targeted drug delivery and biosensors. We have been working toward the development of programmable polymers that remember the response after a stimulus is withdrawn. To this end, we set out to synthesize specific functional monomers. While different types of reactions could potentially result in the desired target monomer, we studied the ring-opening metathesis–cross-metathesis reaction (ROM-CM). Previous work of ours synthesized monomer 1a, a cis-norbornene-2,3-dicarboxylic imide precursor to functional monomer 2a. We report herein the attempts to prepare the target monomers 2a and 3 via alternative ROM-CM routes that varied in starting materials, solvent systems, reaction temperatures, and catalyst amounts. We discovered that methanol based solvent systems resulted in a higher production of oligomers and other side products. In addition, one promising route using the new maleic acid starting material in place of ethyl acrylate was found to effectively undergo the ROM-CM reaction with monomer 1b. This reaction appeared to produce the desired product 2b which is currently being converted to the diester monomer 3 for further characterization. Future efforts will involve further examination of the ROM-CM reaction of maleic acid and other olefins with the norbornene-dicarboxylic imide precursor, dilute conditions in norbornene reactions, and alternative synthetic routes
An XMM-Newton Observation of the Massive Edge-on Sb Galaxy NGC 2613
We present an XMM-Newton observation of the massive edge-on Sb galaxy NGC
2613. We discover that this galaxy contains a deeply embedded active nucleus
with a 0.3-10 keV luminosity of 3.3x10^40 erg/s and a line-of-sight absorption
column of 1.2x10^23 cm^-2. Within the 25 mag/arcsec^2 optical B-band isophote
of the galaxy, we detect an additional 4 sources with an accumulated luminosity
of 4.3x10^39 erg/s. The bulk of the unresolved X-ray emission spatially follows
the near-infrared (NIR) K-band surface brightness distribution; the luminosity
ratio L_X/L_K ~ 8x10^-4 is consistent with that inferred from galactic discrete
sources. This X-ray-NIR association and the compatibility of the X-ray spectral
fit with the expected spectrum of a population of discrete sources suggest that
low-mass X-ray binaries (LMXBs) are the most likely emitters of the unresolved
emission in the disk region. The remaining unresolved emission is primarily due
to extraplanar hot gas. The luminosity of this gas is at least a factor of 10
less than that predicted by recent simulations of intergalactic gas accretion
by such a massive galaxy with a circular rotation speed V_c ~ 304 km/s^2 (Toft
et al. 2002). Instead, we find that the extraplanar hot gas most likely
represents discrete extensions away from the disk, including two
``bubble-like'' features on either side of the nucleus. These extensions appear
to correlate with radio continuum emission and, energetically, can be easily
explained by outflows from the galactic disk.Comment: 17 pages, accepted by MNRA
The Origin and Kinematics of Cold Gas in Galactic Winds: Insight from Numerical Simulations
We study the origin of Na I absorbing gas in ultraluminous infrared galaxies
motivated by the recent observations by Martin of extremely superthermal
linewidths in this cool gas. We model the effects of repeated supernova
explosions driving supershells in the central regions of molecular disks with
M_d=10^10 M_\sun, using cylindrically symmetric gas dynamical simulations run
with ZEUS-3D. The shocked swept-up shells quickly cool and fragment by
Rayleigh-Taylor instability as they accelerate out of the dense, stratified
disks. The numerical resolution of the cooling and compression at the shock
fronts determines the peak shell density, and so the speed of Rayleigh-Taylor
fragmentation. We identify cooled shells and shell fragments as Na I absorbing
gas and study its kinematics. We find that simulations with a numerical
resolution of \le 0.2 pc produce multiple Rayleigh-Taylor fragmented shells in
a given line of sight. We suggest that the observed wide Na I absorption lines,
= 320 \pm 120 km s^-1 are produced by these multiple fragmented shells
traveling at different velocities. We also suggest that some shell fragments
can be accelerated above the observed average terminal velocity of 750 km s^-1
by the same energy-driven wind with an instantaneous starburst of \sim 10^9
M_\sun. The bulk of mass is traveling with the observed average shell velocity
330 \pm 100 km s^-1. Our results show that an energy-driven bubble causing
Rayleigh-Taylor instabilities can explain the kinematics of cool gas seen in
the Na I observations without invoking additional physics relying primarily on
momentum conservation, such as entrainment of gas by Kelvin-Helmholtz
instabilities, ram pressure driving of cold clouds by a hot wind, or radiation
pressure acting on dust. (abridged)Comment: 65 pages, 22 figures, accepted by Astrophys. J. Changes during
refereeing focused on context and comparison to observation
Effects of Aloe vera on dressing percentage and haemato-biochemidal parameters of broiler chickens
Aim: To evaluate the effects of Aloe vera on dressing percentage and hemato-biochemical parameters of broiler chickens.Materials and Methods: A total of 90 chicks were used in this study. They were randomly allocated into 3 treatment groups.Fresh Aloe vera leaf juice (ALJ) was prepared and administered to the test group T3 at the rate of 20 g/Lin drinking water daily.This study was carried out for 42 days. Dressing percentage and hemato-biochemical parameters were recorded at the end ofexperiment.Results: Group that was given Aloe vera (T3) showed numerically higher dressing percentage as compared to control group(T1) and drug control group (T2). It also showed significantly (P<0.05) higher value of Hb concentration, PCV percentage,total leukocyte count (TLC), blood plasma glucose concentration, and serum calcium level as compared to control and drugcontrol groups. No significant (P>0.05) differences were observed in other parameters among all the treatment groups.Conclusion: Aloe vera has potential to be a growth promoter in broiler chicks and its growth promoting effects are comparableto that of antibiotic growth promoter (AGP)
Ferromagnetic redshift of the optical gap in GdN
We report measurements of the optical gap in a GdN film at temperatures from
300 to 6K, covering both the paramagnetic and ferromagnetic phases. The gap is
1.31eV in the paramagnetic phase and red-shifts to 0.9eV in the spin-split
bands below the Curie temperature. The paramagnetic gap is larger than was
suggested by very early experiments, and has permitted us to refine a
(LSDA+U)-computed band structure. The band structure was computed in the full
translation symmetry of the ferromagnetic ground state, assigning the
paramagnetic-state gap as the average of the majority- and minority-spin gaps
in the ferromagnetic state. That procedure has been further tested by a band
structure in a 32-atom supercell with randomly-oriented spins. After fitting
only the paramagnetic gap the refined band structure then reproduces our
measured gaps in both phases by direct transitions at the X point.Comment: 5 pages, 4 figure
Type-Ia Supernova-driven Galactic Bulge Wind
Stellar feedback in galactic bulges plays an essential role in shaping the
evolution of galaxies. To quantify this role and facilitate comparisons with
X-ray observations, we conduct 3D hydrodynamical simulations with the adaptive
mesh refinement code, FLASH, to investigate the physical properties of hot gas
inside a galactic bulge, similar to that of our Galaxy or M31. We assume that
the dynamical and thermal properties of the hot gas are dominated by mechanical
energy input from SNe, primarily Type Ia, and mass injection from evolved stars
as well as iron enrichment from SNe. We study the bulge-wide outflow as well as
the SN heating on scales down to ~4 pc. An embedding scheme that is devised to
plant individual SNR seeds, allows to examine, for the first time, the effect
of sporadic SNe on the density, temperature, and iron ejecta distribution of
the hot gas as well as the resultant X-ray morphology and spectrum. We find
that the SNe produce a bulge wind with highly filamentary density structures
and patchy ejecta. Compared with a 1D spherical wind model, the non-uniformity
of simulated gas density, temperature, and metallicity substantially alters the
spectral shape and increases the diffuse X-ray luminosity. The differential
emission measure as a function of temperature of the simulated gas exhibits a
log-normal distribution, with a peak value much lower than that of the
corresponding 1D model. The bulk of the X-ray emission comes from the
relatively low temperature and low abundance gas shells associated with SN
blastwaves. SN ejecta are not well mixed with the ambient medium, at least in
the bulge region. These results, at least partly, account for the apparent lack
of evidence for iron enrichment in the soft X-ray-emitting gas in galactic
bulges and intermediate-mass elliptical galaxies.[...]Comment: 37 pages, 19 figures, submitted to MNRAS; comments are welcom
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