Diffuse Non-thermal X-ray Emission: Evidence for Cosmic-ray Acceleration at the Shock Front in IC1262

We report the first localization of diffuse, non-thermal, X-ray emission from a nearby galaxy cluster. Using Chandra data, we have isolated a diffuse non-thermal X-ray component with a photon index, Gamma_ X = 2.21 +0.14 -0.15 and a flux of 9.5 +1.1 -2.5 x 10^-5 photons cm^-2 s^-1 keV^-1 at 1 keV, that extends from ~1'.5 to ~2'.5 to the south of the X-ray flux peak. Comparison to simulations implies that the diffuse non-thermal emission is produced by primary electrons, accelerated at shocks to relativistic velocities. Using these results and the flux and hardness maps produced with data from the Chandra Advanced CCD Imaging Spectrometer, we conclude that a smaller subclump coming from the north merged with IC1262. The offset of the cD galaxy from the X-ray peak and large peculiar velocity indicate that the subclump's impact parameter was to the west and on the near side of IC1262.Comment: 5 pages, 4 figures, 2 tables. Accepted by ApJ

Studying the Nature of Dark Energy with Galaxy Clusters

We report on the status of our effort to constrain the nature of dark energy through the evolution of the cluster mass function. Chandra temperature profiles for 31 clusters from a local cluster sample are shown. The X-ray appearance of the proto supermassive binary black hole at the center of the cluster Abell 400 is described. Preliminary weak lensing results obtained with Megacam@MMT for a redshift z=0.5 cluster from a distant cluster sample are given.Comment: 5 pages, to appear in: Aschenbach, B., Burwitz, V., Hasinger, G., Leibundgut, B. (eds.), Relativistic Astrophysics and Cosmology - Einstein's Legacy. ESO Astrophysics Symposia, Springer Verlag, Berlin, German

Orbital Targeting Using Reduced Eccentric Anomaly Low-Thrust Coefficients

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90625/1/AIAA-51336-469.pd

Equivalent Average Trajectory Dynamics Using the Reduced Low-Thrust Coefficients

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83639/1/AIAA-2010-7829-955.pd

A Soft X-ray Component in the Abell 754 Cluster

We have analyzed the Chandra, BeppoSax, and ROSAT observations of Abell 754 and report evidence of a soft, diffuse X-ray component. The emission is peaked in the cluster center and is detected out to 8' from the X-ray center. Fitting a thermal model to the combined BeppoSax and PSPC spectra show excess emission below 1 keV in the PSPC and above 100 keV in the BeppoSax PDS. The source 26W20 is in the field of view of the PDS. The addition of a powerlaw with the spectral parameters measured by Silverman et al. (1998) for 26W20 successfully models the hard component in the PDS. The remaining excess soft emission can be modeled by either a low temperature, 0.75 - 1.03 keV component, or by a powerlaw with a steep spectral index, 2.3. Addition of a second thermal component model provides a much better fit to the data than does the addition of a non-thermal component. The Chandra temperature map does not show any region cooler than 6.9 keV within the region where the cool component was detected. Simulations of the emission from embedded groups were performed and compared with the Chandra temperature map which show groups are a plausible source of ~1 keV emission. The cool component is centrally peaked in the cluster and the gas density and temperature are relatively high arguing against the WHIM as the source of the X-ray emission. X-ray emission from elliptical galaxies is not high enough to provide the total cool component luminosity, 7.0x10^43 ergs s^-1. The peak of the cool component is located between the low frequency radio halos arguing against a non-thermal interpretation for the emission. We conclude that emission from embedded groups is the most likely origin of the cool component in Abell 754.Comment: Submitted to Ap

Seeking the Local Convergence Depth. V. Tully-Fisher Peculiar Velocities for 52 Abell Clusters

We have obtained I band Tully-Fisher (TF) measurements for 522 late-type galaxies in the fields of 52 rich Abell clusters distributed throughout the sky between 50 and 200\h Mpc. Here we estimate corrections to the data for various forms of observational bias, most notably Malmquist and cluster population incompleteness bias. The bias-corrected data are applied to the construction of an I band TF template, resulting in a relation with a dispersion of 0.38 magnitudes and a kinematical zero-point accurate to 0.02 magnitudes. This represents the most accurate TF template relation currently available. Individual cluster TF relations are referred to the average template relation to compute cluster peculiar motions. The line-of-sight dispersion in the peculiar motions is 341+/-93 km/s, in general agreement with that found for the cluster sample of Giovanelli and coworkers.Comment: 31 pages, 14 figures, uses AAS LaTeX; to appear in the Astronomical Journa

A BeppoSAX Observation of the IC1262 Galaxy Cluster

We present an analysis of BeppoSAX observations of the IC1262 galaxy cluster and report the first temperature and abundance measurements, along with preliminary indications of diffuse, nonthermal emission. By fitting a 6' (~360 h_50^-1 kpc) region with a single Mewe-Kaastra-Liedahl model with photoelectric absorption, we find a temperature of 2.1 - 2.3 keV, and abundance of 0.45 - 0.77 (both 90% confidence). We find the addition of a power-law component provides a statistically significant improvement (F-test = 90%) to the fit. The addition of a second thermal component also improves the fit but we argue that it is physically implausible. The power-law component has a photon index (Gamma_X) of 0.4 - 2.8 and a nonthermal flux of (4.1 - 56.7) x 10-5 photons cm^-2 s^-1 over the 1.5 - 10.5 keV range in the Medium Energy Concentrator spectrometer detector. An unidentified X-ray source found in the ROSAT High Resolution Imager observation (~0'.9 from the center of the cluster) is a possible explanation for the nonthermal flux; however, additional evidence of diffuse, nonthermal emission comes from the NRAO VLA Sky Survey and the Westerbork Northern Sky Survey radio measurements, in which excess diffuse, radio flux is observed after point-source subtraction. The radio excess can be fitted to a simple power law with a spectral index of ~1.8, which is consistent with the nonthermal X-ray emission spectral index. The steep spectrum is typical of diffuse emission and the size of the radio source implies that it is larger than the cD galaxy and not due to a discreet source

Fatty acid 16:4(n-3) stimulates a GPR120-induced signaling cascade in splenic macrophages to promote chemotherapy resistance

Although chemotherapy is designed to eradicate tumor cells, it also has significant effects on normal tissues. The platinum-induced fatty acid 16:4(n-3) (hexadeca-4,7,10,13-tetraenoic acid) induces systemic resistance to a broad range of DNA-damaging chemotherapeutics. We show that 16:4(n-3) exerts its effect by activating splenic F4/80+/CD11blow macrophages, which results in production of chemoprotective lysophosphatidylcholines (LPCs). Pharmacologic studies, together with analysis of expression patterns, identified GPR120 on F4/80+/CD11blow macrophages as the relevant receptor for 16:4(n-3). Studies that used splenocytes from GPR120-deficient mice have confirmed this conclusion. Activation of the 16:4(n-3)-GPR120 axis led to enhanced cPLA2 activity in these splenic macrophages and secretion of the resistance-inducing lipid mediator, lysophosphatidylcholine(24:1). These studies identify a novel and unexpected function for GPR120 and suggest that antagonists of this receptor might be effective agents to limit development of chemotherapy resistance.—Houthuijzen, J. M., Oosterom, I., Hudson, B. D., Hirasawa, A., Daenen, L. G. M., McLean, C. M., Hansen, S. V. F., van Jaarsveld, M. T. M., Peeper, D. S., Jafari Sadatmand, S., Roodhart, J. M. L., van de Lest, C. H. A., Ulven, T., Ishihara, K., Milligan, G., Voest, E. E. Fatty acid 16:4(n-3) stimulates a GPR120-induced signaling cascade in splenic macrophages to promote chemotherapy resistance