6,080 research outputs found
Environmental changes on Yugorski Peninsula, Kara Sea, Russia, during the last 12,800 radiocarbon years
Propagation of the phase of solar modulation
The phase of the 11 year galactic cosmic ray variation, due to a varying rate of emission of long lived propagating regions of enhanced scattering, travels faster than the scattering regions themselves. The radial speed of the 11 year phase in the quasi-steady, force field approximation is exactly twice the speed of the individual, episodic decreases. A time dependent, numerical solution for 1 GeV protons at 1 and 30 Au gives a phase speed which is 1.85 times the propagation speed of the individual decreases
Respon Masyarakat terhadap Program Jaminan Kesehatan Masyarakat di Puskesmas Mandala Kecamatan Medan Tembung Kota Medan
Publict Response From Health Insurance Programs in Mandala\u27s Health Center District of Medan Tembung Medan City Health is closely related to economic conditions. Economic established by itself will create good health. With economic conditions properly it will affect the health condition. But on the contrary, a bad economy will make it difficult for individual communities improve their health each. Bad economy will lead to the difficulty of the individual to gain access to adequate health because expensive health costs. This resulted in poor people struggling in the same condition. Poverty and disease are related to each other, with the direction of relationships never end unless intervention on one or both sides of any person entitled to receive health care because health is the most important element in human life. To guarantee the right to health of the community, the government, through the Ministry of Health issued a guarantee program for basic human needs as an obligation of the state. Program called the Community Health aims to ensure the health care needs of individuals who deserve it. This is a descriptive study with the population are 7252 and sample totaled 15 people. Sampling conducted by purposive sampling, the sampling intentionally done by selecting the respondent in such a way. Sample or the respondents in this study were participants in Mandala\u27s Health Center Jamkesmas program, and the results of these studies are tabulated into frequency tables further analyzed, and used a Likert scale to measure the variables. Based on the data that has been collected and analyzed can be summarized in average proggram Jamkesmas received a positive response from the participants with a value of 0.76. Consisting of perceptions and attitudes to the value of 0.80 to 0.87 and the value of participation with the value 60. Participants hope Jamkesmas program continued and further enhanced in the ministry
The rich cluster of galaxies ABCG 85. III. Analyzing the ABCG 85/87/89 complex
We present a combined X-ray and optical analysis of the ABCG 85/87/89 complex
of clusters of galaxies, based on the ROSAT PSPC image, optical photometric
catalogues (Slezak et al. 1998), and an optical redshift catalogue (Durret et
al. 1998). From this combined data set, we find striking alignments at all
scales at PA160\deg. At small scales, the cD galaxy in ABCG 85 and the
brightest galaxies in the cluster are aligned along this PA. At a larger scale,
X-ray emission defines a comparable PA south-southeast of ABCG 85 towards ABCG
87, with a patchy X-ray structure very different from the regular shape of the
optical galaxy distribution in ABCG 87. The galaxy velocities in the ABCG 87
region show the existence of subgroups, which all have an X-ray counterpart,
and seem to be falling onto ABCG 85 along a filament almost perpendicular to
the plane of the sky. To the west of ABCG 85, ABCG 89 appears as a significant
galaxy density enhancement, but is barely detected at X-ray wavelengths. The
galaxy velocities reveal that in fact this is not a cluster but two groups with
very different velocities superimposed along the line of sight. These two
groups appear to be located in intersecting sheets on opposite sides of a large
bubble. These data and their interpretation reinforce the cosmological scenario
in which matter, including galaxies, groups and gas, falls onto the cluster
along a filament.Comment: accepted for publication in Astronomy & Astrophysic
The infall of the Virgo elliptical galaxy M60 toward M87 and the gaseous structures produced by Kelvin-Helmholtz instabilities
We present Chandra observations of hot gas structures, characteristic of gas stripping during infall, in the Virgo cluster elliptical galaxy M60 (NGC4649) located 1 Mpc east of M87. 0.5−2 keV Chandra X-ray images show a sharp leading edge in the surface brightness 12.4±0.1 kpc north and west of the galaxy center in the direction of M87 characteristic of a merger cold front due to M60's motion through the Virgo ICM. We measured a temperature of 1.00±0.02 keV for abundance 0.5Z⊙ inside the edge and 1.37+0.35−0.19 keV for abundance 0.1Z⊙ in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio of 6.44+1.04−0.67 between gas inside the edge and in the cluster free stream region. If the edge is a cold front due solely to the infall of M60 in the direction of M87, we find a pressure ratio of 4.7+1.7−1.4 and Mach number 1.7±0.3. For 1.37 keV Virgo gas we find a total infall velocity for M60 of 1030±180 kms−1. We calculate the motion in the plane of the sky to be 1012+183−192 km−1 implying an inclination angle ξ=11±3 degrees. Surface brightness profiles show the presence of a faint diffuse gaseous tail. We identify filamentary, gaseous wing structures caused by the galaxy's motion through the ICM. The structure and dimensions of these wings are consistent with simulations of Kelvin-Helmholtz instabilities as expected if the gas stripping is close to inviscid
A Chandra Study of the Lobe/ISM Interactions Around the Inner Radio Lobes of Centaurus A: Constraints on the Temperature Structure and Transport Processes
We present results from deeper {\em Chandra} observations of the southwest
radio lobe of Centaurus A, first described by Kraft et al. (2003). We find that
the sharp X-ray surface brightness discontinuity extends around 75% of
the periphery of the radio lobe, and detect significant temperature jumps in
the brightest regions of this discontinuity nearest to the nucleus. This
demonstrates that this discontinuity is indeed a strong shock which is the
result of an overpressure which has built up in the entire lobe over time.
Additionally, we demonstrate that if the mean free path for ions to transfer
energy and momentum to the electrons behind the shock is as large as the
Spitzer value, the electron and proton temperatures will not have equilibrated
along the SW boundary of the radio lobe where the shock is strongest. Thus the
proton temperature of the shocked gas could be considerably larger than the
observed electron temperature, and the total energy of the outburst
correspondingly larger as well. We investigate this using a simple
one-dimensional shock model for a two-fluid (proton/electron) plasma. We find
that for the thermodynamic parameters of the Cen A shock the electron
temperature rises rapidly from 0.29 keV (the temperature of the ambient
ISM) to 3.5 keV at which point heating from the protons is balanced by
adiabatic losses. The proton and electron temperatures do not equilibrate in a
timescale less than the age of the lobe. We note that the measured electron
temperature of similar features in other nearby powerful radio galaxies in poor
environments may considerably underestimate the strength and velocity of the
shock.Comment: 29 pages, 9 figures, 2 tables - accepted for publication in the
Astrophysical Journa
Stellar Metallicities and SNIa Rates in the Early-type Galaxy NGC5846 from ROSAT and ASCA Observations
In this paper we analyze the diffuse X-ray coronae surrounding the elliptical
galaxy NGC5846, combining measurements from two observatories, ROSAT and ASCA.
We map the gas temperature distribution and find a central cool region within
an approximately isothermal gas halo extending to a radius of about 50 kpc, and
evidence for a temperature decrease at larger radii. With a radially falling
temperature profile, the total mass converges to 9.6+/-1.0 10^12 Msun at ~230
kpc radius. Using the spectroscopic measurements, we also derive radial
distributions for the heavy elements silicon and iron and find that the
abundances of both decrease with galaxy radius. The mass ratio of Si to Fe lies
between the theoretical predictions for element production in SN Ia and SN II,
suggesting an important role for SN Ia, as well as SN II, for gas enrichment in
ellipticals. Using the SN Ia yield of Si, we set an upper limit of 0.012 SNU
for the SN Ia rate at radii >50 kpc, which is independent of possible
uncertainties in the iron L-shell modeling. We compare our observations with
the theoretical predictions for the chemical evolution of ellipticals, taken
from Matteucci & Gibson (1995). We conclude that the metal content in stars, if
explained by the star formation duration, requires a significant decline in the
duration of star formation with galaxy radius, ranging from ~1 Gyr at the
center to ~0.01 Gyr at 100 kpc radius. Alternatively, the decline in
metallicity with galaxy radius may be caused by a similar drop with radius in
the efficiency of star formation. Based on the Si and Fe measurements presented
in this paper, we conclude that the latter scenario is preferred, unless a
dependence of the SN Ia rate on stellar metallicity is invoked. (Abridged).Comment: 11 pages, figures&tables included, emulapj.sty, accepted for Ap
Chandra Observations of Gas Stripping in the Elliptical Galaxy NGC 4552 in the Virgo Cluster
We use a 54.4 ks Chandra observation to study ram-pressure stripping in
NGC4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the
0.5-2 keV band show a sharp leading edge in the surface brightness 3.1 kpc
north of the galaxy center, a cool (kT =0.51^{+0.09}_{-0.06} keV) tail with
mean density n_e ~5.4 +/- 1.7 x 10^{-3} cm^{-3} extending ~10 kpc to the south
of the galaxy, and two 3-4 kpc horns of emission extending southward away from
the leading edge. These are all features characteristic of supersonic
ram-pressure stripping of galaxy gas, due to NGC4552's motion through the
surrounding Virgo ICM. Fitting the surface brightness profile and spectra
across the leading edge, we find the galaxy gas inside the edge is cooler (kT =
0.43^{+0.03}_{-0.02} keV) and denser (n_e ~ 0.010 cm^{-3}) than the surrounding
Virgo ICM (kT = 2.2^{+0.7}_{-0.4} keV and n_e = 3.0 +/- 0.3 x 10^{-4} cm^{-3}).
The resulting pressure ratio between the free-streaming ICM and cluster gas at
the stagnation point is ~7.6^{+3.4}_{-2.0} for galaxy gas metallicities of
0.5^{+0.5}_{-0.3} Zsolar, which suggests that NGC4552 is moving supersonically
through the cluster with a velocity v ~ 1680^{+390}_{-220} km/s (Mach
2.2^{+0.5}_{-0.3}) at an angle xi ~ 35 +/- 7 degrees towards us with respect to
the plane of the sky.Comment: 31 pages, 12 figures, ApJ, in press; paper split into 2 parts, Paper
I(sec 1-3) here, added figs and discussion to conform to published version;
Paper II (sec. 4) in astro-ph/060440
Chandra Observations of NGC 4438: An Environmentally Damaged Galaxy in the Virgo Cluster
We present results from a 25 ksec CHANDRA ACIS-S observation of galaxies
NGC4438 and NGC4435 in the Virgo Cluster. X-ray emission in NGC4438 is observed
in a ~700 pc nuclear region, a 2.3 kpc spherical bulge, and a network of
filaments extending 4-10 kpc to the W and SW of the galaxy. The X-ray emission
in all 3 regions is highly correlated to similar features observed in Halpha.
Spectra of the filaments and bulge are well represented by a 0.4 keV MEKAL
model with combined 0.3-2 keV intrinsic luminosity of 1.24x10^{40}erg/s,
electron densities ~ 0.02-0.04 cm^{-3}, cooling times of 400-700 Myr and X-ray
gas mass <~ 3.7x10^8 Msolar. In the nuclear region of NGC4438 X-ray emission is
seen from the nucleus and from two outflow bubbles extending 360(730) pc to the
NW(SE) of the nucleus. The spectrum of the NW outflow bubble plus nucleus is
well fitted by an absorbed (n_H=1.9x10^{21} cm^{-2}) 0.58 keV MEKAL plasma
model plus a heavily absorbed (n_H = 2.9 x10^{22} cm^{-2}) Gamma = 2, power law
component. The electron density, cooling time, and X-ray gas mass in the NW
outflow are ~0.5 cm^{-3}, 30 Myr and 3.5x10^6 Msolar. Weak X-ray emission is
observed in the central region of NGC4435 with the peak of the hard emission
coincident with the galaxy's optical center; while the peak of the soft X-ray
emission is displaced 316 pc to the NE. The spectrum of NGC 4435 is well fitted
by a non-thermal power law plus a thermal component from 0.2-0.3 keV diffuse
ISM gas. We argue that the X-ray properties of gas outside the nuclear region
in NGC4438 and in NGC4435 favor a high velocity, off-center collision between
these galaxies ~ 100 Myr ago; while the nuclear X-ray emitting outflow gas in
NGC4438 has been heated only recently (within ~ 1-2 Myr) by shocks (v_s ~ 600
kms^{-1}) possibly powered by a central AGN.Comment: 40 pages, 7 figures; minor changes to conform to published version,
improved spectral fits to NGC 4435, improved figures 3,5; new figures 6b,
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