122 research outputs found
Limits on the Peculiar Velocities of Two Distant Clusters Using the Kinematic Sunyaev-Zel'dovich Effect
We report millimeter-wavelength observations of the Sunyaev-Zel'dovich (S-Z)
effect in two distant galaxy clusters. A relativistically correct analysis of
the S-Z data is combined with the results of X-ray observations to determine
the radial peculiar velocities v_r of the clusters. We observed Abell 2163
(z=.201) in three mm-wavelength bands centered at 2.1, 1.4, and 1.1 mm. We
report a significant detection of the thermal component of the S-Z effect seen
as both a decrement in the brightness of the CMB at 2.1 mm, and as an increment
at 1.1 mm. Including uncertainties due to the calibration of the instrument,
distribution and temperature of the IC gas, and astrophysical confusion, a
simultaneous fit to the data in all three bands gives v_r=+490 +1370/-880 km/s
at 68% confidence. We observed Abell 1689 (z=.181) in the 2.1 and 1.4 mm bands.
Including the same detailed accounting of uncertainty, a simultaneous fit to
the data in both bands gives v_r=+170 +815/-630 km/s. The limits on the
peculiar velocities of A2163 and A1689 correspond to deviations from the
uniform Hubble flow of <= 2-3%.Comment: 21 pages, 13 postscript figures, LaTeX(aaspptwo.sty), ApJ(in press
Looking for the S-Z Effect towards Distant ROSAT Clusters of Galaxies
We report on observations of the Sunyaev-Zeldovich effect towards X-ray ROSAT
clusters taken with a double channel (1.2 and 2 mm) photometer installed at the
focus of the 15m SEST antenna in Chile. This paper describes the first results
obtained for the high-z clusters S1077, A2744 and S295. Marginal detections
were found for A2744 and at 1 mm for S1077. We discuss these data in terms of
contamination of sources along the line of sight and give a constraint on the
amplitude of the kinematic effect.Comment: 17 pg Latex file (using aasms4.sty) gzip'd tar'd uuencoded file
including 1 ps figure, ApJ Letter in pres
Disparate Impact of Butyroyloxymethyl Diethylphosphate (AN-7), a Histone Deacetylase Inhibitor, and Doxorubicin in Mice Bearing a Mammary Tumor
The histone deacetylase inhibitor (HDACI) butyroyloxymethyl diethylphosphate (AN-7) synergizes the cytotoxic effect of doxorubicin (Dox) and anti-HER2 on mammary carcinoma cells while protecting normal cells against their insults. This study investigated the concomitant changes occurring in heart tissue and tumors of mice bearing a subcutaneous 4T1 mammary tumor following treatment with AN-7, Dox, or their combination. Dox or AN-7 alone led to inhibition of both tumor growth and lung metastases, whereas their combination significantly increased their anticancer efficacy and attenuated Dox- toxicity. Molecular analysis revealed that treatment with Dox, AN-7, and to a greater degree, AN-7 together with Dox increased tumor levels of ÎłH2AX, the marker for DNA double-strand breaks and decreased the expression of Rad51, a protein needed for DNA repair. These events culminated in increased apoptosis, manifested by the appearance of cytochrome-c in the cytosol. In the myocardium, Dox-induced cardiomyopathy was associated with an increase in ÎłH2AX expression and a reduction in Rad51 and MRE11 expression and increased apoptosis. The addition of AN-7 to the Dox treatment protected the heart from Dox insults as was manifested by a decrease in ÎłH2AX levels, an increase in Rad51 and MRE11 expression, and a diminution of cytochrome-c release. Tumor fibrosis was high in untreated mice but diminished in Dox- and AN-7-treated mice and was almost abrogated in AN-7+Dox-treated mice. By contrast, in the myocardium, Dox alone induced a dramatic increase in fibrosis, and AN7+Dox attenuated it. The high expression levels of c-Kit, Ki-67, c-Myc, lo-FGF, and VEGF in 4T1 tumors were significantly reduced by Dox or AN-7 and further attenuated by AN-7+Dox. In the myocardium, Dox suppressed these markers, whereas AN-7+Dox restored their expression. In conclusion, the combination of AN-7 and Dox results in two beneficial effects, improved anticancer efficacy and cardioprotection
Cosmic Ray Protons and Magnetic Fields in Clusters of Galaxies and their Cosmological Consequences
The masses of clusters of galaxies estimated by gravitational lensing exceed
in many cases the mass estimates based on hydrostatic equilibrium. This may
suggest the existence of nonthermal pressure. We ask if radio galaxies can heat
and support the cluster gas with injected cosmic ray protons and magnetic field
densities, which are permitted by Faraday rotation and gamma ray observations
of clusters of galaxies. We conclude that they are powerful enough to do this
within a cluster radius of roughly 1 Mpc. If present, nonthermal pressures
could lead to a revised estimate of the ratio of baryonic mass to total mass,
and the apparent baryonic overdensity in clusters would disappear. In
consequence, , the clumping part of the cosmological density
, would be larger than .Comment: Accepted by ApJ, 16 pages, LaTeX, 2 figures, epsfig.sty, aaspp4.st
Weak reaction freeze-out constraints on primordial magnetic fields
We explore constraints on the strength of the primordial magnetic field based
upon the weak reaction freeze-out in the early universe. We find that limits on
the strength of the magnetic field found in other works are recovered simply by
examining the temperature at which the rate of weak reactions drops below the
rate of universal expansion ( H). The temperature for which the
ratio at freeze-out leads to acceptable helium production implies limits
on the magnetic field. This simplifies the application of magnetic fields to
other cosmological variants of the standard big-bang. As an illustration we
also consider effects of neutrino degeneracy on the allowed limits to the
primordial magnetic field.Comment: Submitted to Phys. Rev. D., 6 pages, 2 figure
Tsunamis in Galaxy Clusters: Heating of Cool Cores by Acoustic Waves
Using an analytical model and numerical simulations, we show that acoustic
waves generated by turbulent motion in intracluster medium effectively heat the
central region of a so-called ``cooling flow'' cluster. We assume that the
turbulence is generated by substructure motion in a cluster or cluster mergers.
Our analytical model can reproduce observed density and temperature profiles of
a few clusters. We also show that waves can transfer more energy from the outer
region of a cluster than thermal conduction alone. Numerical simulations
generally support the results of the analytical study.Comment: 18 pages, accepted for publication in Ap
From 10 Kelvin to 10 TeraKelvin: Insights on the Interaction Between Cosmic Rays and Gas in Starbursts
Recent work has both illuminated and mystified our attempts to understand
cosmic rays (CRs) in starburst galaxies. I discuss my new research exploring
how CRs interact with the ISM in starbursts. Molecular clouds provide targets
for CR protons to produce pionic gamma rays and ionization, but those same
losses may shield the cloud interiors. In the densest molecular clouds, gamma
rays and Al-26 decay can provide ionization, at rates up to those in Milky Way
molecular clouds. I then consider the free-free absorption of low frequency
radio emission from starbursts, which I argue arises from many small, discrete
H II regions rather than from a "uniform slab" of ionized gas, whereas
synchrotron emission arises outside them. Finally, noting that the hot
superwind gas phase fills most of the volume of starbursts, I suggest that it
has turbulent-driven magnetic fields powered by supernovae, and that this phase
is where most synchrotron emission arises. I show how such a scenario could
explain the far-infrared radio correlation, in context of my previous work. A
big issue is that radio and gamma-ray observations imply CRs also must interact
with dense gas. Understanding how this happens requires a more advanced
understanding of turbulence and CR propagation.Comment: Conference proceedings for "Cosmic-ray induced phenomenology in
star-forming environments: Proceedings of the 2nd Session of the Sant Cugat
Forum of Astrophysics" (April 16-19, 2012). 16 pages, 5 figure
Measurement of the Hubble Constant from X-ray and 2.1 mm Observations of Abell 2163
We report 2.1 mm observations of the Sunyaev-Zel'dovich (S-Z) effect; these
observations confirm our previous detection of a decrement in the Cosmic
Microwave Background intensity towards the cluster Abell 2163. The S-Z data are
analyzed using the relativistically correct expression for the Comptonization.
We begin by assuming the intracluster (IC) gas to be isothermal at the emission
weighted average temperature determined by a combined analysis of the ASCA and
GINGA X-ray satellite observations. Combining the X-ray and S-Z measurements,
we determine the Hubble constant to be H_0(q_0=0.5)= 60 +40/-23 km/s/Mpc, where
the uncertainty is dominated by the systematic difference in the ASCA and GINGA
determined IC gas temperatures. ASCA observations suggest the presence of a
significant thermal gradient in the IC gas. We determine as a function of
the assumed IC gas thermal structure. Using the ASCA determined thermal
structure and keeping the emission weighted average temperature the same as in
the isothermal case, we find H_0(q_0=0.5)= 78 +54/-28 km/s/Mpc. Including
additional uncertainties due to cluster asphericity, peculiar velocity, IC gas
clumping, and astrophysical confusion, we find H_0(q_0=0.5)= 78 +60/-40
km/s/Mpc.Comment: 24 pages, 10 postscript figures, LaTeX(aaspptwo.sty), ApJ(in press
Dark Matter Annihilation around Intermediate Mass Black Holes: an update
The formation and evolution of Black Holes inevitably affects the
distribution of dark and baryonic matter in the neighborhood of the Black Hole.
These effects may be particularly relevant around Supermassive and Intermediate
Mass Black Holes (IMBHs), the formation of which can lead to large Dark Matter
overdensities, called {\em spikes} and {\em mini-spikes} respectively. Despite
being larger and more dense, spikes evolve at the very centers of galactic
halos, in regions where numerous dynamical effects tend to destroy them.
Mini-spikes may be more likely to survive, and they have been proposed as
worthwhile targets for indirect Dark Matter searches. We review here the
formation scenarios and the prospects for detection of mini-spikes, and we
present new estimates for the abundances of mini-spikes to illustrate the
sensitivity of such predictions to cosmological parameters and uncertainties
regarding the astrophysics of Black Hole formation at high redshift. We also
connect the IMBHs scenario to the recent measurements of cosmic-ray electron
and positron spectra by the PAMELA, ATIC, H.E.S.S., and Fermi collaborations.Comment: 12 pages, 7 figures. Invited contribution to NJP Focus Issue on "Dark
Matter and Particle Physics
Rotation Measures of Radio Sources in Hot Galaxy Clusters
The goal of this work is to investigate the Faraday rotation measure (RM) of
radio galaxies in hot galaxy clusters in order to establish a possible
connection between the magnetic field strength and the gas temperature of the
intracluster medium. We performed Very Large Array observations at 3.6 cm and 6
cm of two radio galaxies located in A401 and Ophiuchus, a radio galaxy in
A2142, and a radio galaxy located in the background of A2065. All these galaxy
clusters are characterized by high temperatures. We obtained detailed RM images
at an angular resolution of 3'' for most of the observed radio galaxies. The RM
images are patchy and reveal fine substructures of a few kpc in size. Under the
assumption that the radio galaxies themselves have no effect on the measured
RMs, these structures indicate that the intracluster magnetic fields fluctuate
down to such small scales. These new data are compared with RM information
present in the literature for cooler galaxy clusters. For a fixed projected
distance from the cluster center, clusters with higher temperature show a
higher dispersion of the RM distributions (sigmaRM), mostly because of the
higher gas density in these clusters. Although the previously known relation
between the clusters X-ray surface brightness (Sx) at the radio galaxy location
and sigmaRM is confirmed, a possible connection between the sigmaRM-Sx relation
and the cluster temperature, if present, is very weak. Therefore, in view of
the current data, it is impossible to establish a strict link between the
magnetic field strength and the gas temperature of the intracluster medium.Comment: Accepted by Astronomy and Astrophysics, 26 pages, 19 figure
- âŠ