2,513 research outputs found
Dust in Hot Plasma of Nearby Dusty Elliptical Galaxies Observed with the Spitzer Space Telescope
We report on mid- and far-IR Spitzer observations of 7 nearby dusty
elliptical galaxies by using the Multiband Imaging Photometer (MIPS) and
Infrared Spectrograph (IRS). Our sample galaxies are known to contain an
excessive amount of interstellar dust against sputtering destruction in hot
plasma filling the interstellar space of elliptical galaxies. In order to study
the origin and the properties of the excess dust in the hot plasma, we selected
galaxies with a wide range of X-ray luminosities but similar optical luminos
ities for our Spitzer Guest Observers (GO1) program. The 7 galaxies are
detected at the MIPS 24 um, 70 um, and 160 um bands; the far- to mid-IR flux
ratios of relatively X-ray-bright elliptical galaxies are lower than those of
X-ray-faint galaxies. From the IRS spectra, polycyclic aromatic hydrocarbon
(PAH) emission features are detected significantly from 5 of the 7 galaxies; t
he emission intensities are weaker as the X-ray luminosity of the galaxy is
larger. We have found a correlation between the far- to mid-IR flux ratio and
the equivalent width of the PAH emission feature. We have obtained apparent
spatial correspondence between mid-IR and X-ray distributions in the outer
regions for the three X-ray-brightest galaxies in our sample. Possible
interpretations for our observational results are discussed.Comment: 25 pages, 7 figures, accepted for publication in Publications of the
Astronomical Society of Japa
Systematic Errors in the Hubble Constant Measurement from the Sunyaev-Zel'dovich effect
The Hubble constant estimated from the combined analysis of the
Sunyaev-Zel'dovich effect and X-ray observations of galaxy clusters is
systematically lower than those from other methods by 10-15 percent. We examine
the origin of the systematic underestimate using an analytic model of the
intracluster medium (ICM), and compare the prediction with idealistic triaxial
models and with clusters extracted from cosmological hydrodynamical
simulations. We identify three important sources for the systematic errors;
density and temperature inhomogeneities in the ICM, departures from
isothermality, and asphericity. In particular, the combination of the first two
leads to the systematic underestimate of the ICM spectroscopic temperature
relative to its emission-weighed one. We find that these three systematics well
reproduce both the observed bias and the intrinsic dispersions of the Hubble
constant estimated from the Sunyaev-Zel'dovich effect.Comment: 26 pages, 7 figures, accepted for publication in ApJ, Minor change
Physiological Correlates of Choice‐Induced Dissonance: An Exploration of HPA‐Axis Responses
Choice can produce a negatively arousing cognitive conflict (called dissonance), which is thought to motivate the chooser to spread their preferences for the relevant options (called Spreading of Alternatives, or SA). The current work aimed to determine the relationship between HPA‐axis activity and both choice‐induced dissonance and its reduction (i.e. SA) among individuals with varying cultural backgrounds. European–Americans and Asians made a choice between two equally attractive CDs either in the presence of a cue indicative of social eyes (i.e. public‐choice condition) or in the absence thereof (i.e. private‐choice condition). As predicted, European–Americans and Asians showed a reliable SA primarily in the private and public choice conditions, respectively. Importantly, a sharp decline of salivary cortisol was observed over the span of 30 min, and, moreover, this decline was reliably predicted by the magnitude of SA regardless of either culture or the choice being private vs. public. These results suggest that although choice‐induced dissonance is too weak to elicit an HPA‐axis stress response, SA is associated with variability in the decline of salivary cortisol during the laboratory task. Copyright © 2015 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113729/1/bdm1845.pd
DIOS: the Diffuse Intergalactic Oxygen Surveyor
We present our proposal for a small X-ray mission DIOS (Diffuse Intergalactic
Oxygen Surveyor), consisting of a 4-stage X-ray telescope and an array of TES
microcalorimeters, cooled with mechanical coolers, with a total weight of about
400 kg. The mission will perform survey observations of warm-hot intergalactic
medium using OVII and OVIII emission lines, with the energy coverage up to 1.5
keV. The wide field of view of about 50' diameter, superior energy resolution
close to 2 eV FWHM, and very low background will together enable us a wide
range of science for diffuse X-ray sources. We briefly describe the design of
the satellite, performance of the subsystems and the expected results.Comment: 9 pages, 11 figures, a proceedings of SPIE "Astronomical Telescopes
and Instrumentation" 200
Observing H2 Emission in Forming Galaxies
We study the H2 cooling emission of forming galaxies, and discuss their
observability using the future infrared facility SAFIR. Forming galaxies with
mass >10^11 Msun emit most of their gravitational energy liberated by
contraction in molecular hydrogen line radiation, although a large part of
thermal energy at virialization is radiated away by the H Ly alpha emission.
For more massive objects, the degree of heating due to dissipation of kinetic
energy is so great that the temperature does not drop below 10^4 K and the
gravitational energy is emitted mainly by the Ly alpha emission. Therefore, the
total H2 luminosity attains the peak value of about 10^42 ergs/s for forming
galaxies whose total mass 10^11 Msun. If these sources are situated at redshift
z=8, they can be detected by rotational lines of 0-0S(3) at 9.7 micron and
0-0S(1) at 17 micron by SAFIR. An efficient way to find such H2 emitters is to
look at the Ly alpha emitters, since the brightest H2 emitters are also
luminous in the Ly alpha emission.Comment: 20 pages, 7 figures, ApJ accepte
Imaging Simulations of the Sunyaev-Zel'dovich Effect for ALMA
We present imaging simulations of the Sunyaev-Zel'dovich effect of galaxy
clusters for the Atacama Large Millimeter/submillimeter Array (ALMA) including
the Atacama Compact Array (ACA). In its most compact configuration at 90GHz,
ALMA will resolve the intracluster medium with an effective angular resolution
of 5 arcsec. It will provide a unique probe of shock fronts and relativistic
electrons produced during cluster mergers at high redshifts, that are hard to
spatially resolve by current and near-future X-ray detectors. Quality of image
reconstruction is poor with the 12m array alone but improved significantly by
adding ACA; expected sensitivity of the 12m array based on the thermal noise is
not valid for the Sunyaev-Zel'dovich effect mapping unless accompanied by an
ACA observation of at least equal duration. The observations above 100 GHz will
become excessively time-consuming owing to the narrower beam size and the
higher system temperature. On the other hand, significant improvement of the
observing efficiency is expected once Band 1 is implemented in the future.Comment: 16 pages, 12 figures. Accepted for publication in PASJ. Note added in
proof is include
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