Removing Cool Cores and Central Metallicity Peaks in Galaxy Clusters with Powerful AGN Outbursts

Recent X-ray observations of galaxy clusters suggest that cluster populations are bimodally distributed according to central gas entropy and are separated into two distinct classes: cool core (CC) and non-cool core (NCC) clusters. While it is widely accepted that AGN feedback plays a key role in offsetting radiative losses and maintaining many clusters in the CC state, the origin of NCC clusters is much less clear. At the same time, a handful of extremely powerful AGN outbursts have recently been detected in clusters, with a total energy ~10^{61}-10^{62} erg. Using two dimensional hydrodynamic simulations, we show that if a large fraction of this energy is deposited near the centers of CC clusters, which is likely common due to dense cores, these AGN outbursts can completely remove CCs, transforming them to NCC clusters. Our model also has interesting implications for cluster abundance profiles, which usually show a central peak in CC systems. Our calculations indicate that during the CC to NCC transformation, AGN outbursts efficiently mix metals in cluster central regions, and may even remove central abundance peaks if they are not broad enough. For CC clusters with broad central abundance peaks, AGN outbursts decrease peak abundances, but can not effectively destroy the peaks. Our model may simultaneously explain the contradictory (possibly bimodal) results of abundance profiles in NCC clusters, some of which are nearly flat, while others have strong central peaks similar to those in CC clusters. A statistical analysis of the sizes of central abundance peaks and their redshift evolution may shed interesting insights on the origin of both types of NCC clusters and the evolution history of thermodynamics and AGN activity in clusters.Comment: Slightly revised version, accepted for publication in ApJ. 12 pages, 11 figure

Neutrinos and Big-Bang Nucleosynthesis

Observations of clusters and super clusters of galaxies have indicated that the Universe is more dominated by baryons than ever estimated in the homogeneous cosmological model for primordial nucleosynthesis. Recent detections of possibly low deuterium abundance in Lyman-$\alpha$ clouds along the line of sight to high red-shift quasars have raised another potential difficulty that \he4 is overproduced in any cosmological models which satisfy the low deuterium abundance constraint. We show that the inhomogeneous cosmological model with degenerate electron-neutrino can resolve these two difficulties.Comment: 7 pages, latex, 3 figures. To appear in Nucl. Phys. A62

Serendipitous XMM-Newton discovery of a cluster of galaxies at z=0.28

We report the discovery of a galaxy cluster serendipitously detected as an extended X-ray source in an offset observation of the group NGC 5044. The cluster redshift, z=0.281, determined from the optical spectrum of the brightest cluster galaxy, agrees with that inferred from the X-ray spectrum using the Fe K alpha complex of the hot ICM (z=0.27 +/- 0.01). Based on the 50 ks XMM observation, we find that within a radius of 383 kpc the cluster has an unabsorbed X-ray flux, f_X (0.5-2 keV) = 3.34 (+0.08, -0.13) x 10^{-13} erg/cm^2/s, a bolometric X-ray luminosity, L_X = 2.21 (+0.34, -0.19) x 10^{44} erg/s, kT = 3.57 +/- 0.12 keV, and metallicity, 0.60 +/- 0.09 solar. The cluster obeys the scaling relations for L_X and T observed at intermediate redshift. The mass derived from an isothermal NFW model fit is, M_vir = 3.89 +/- 0.35 x 10^{14} solar masses, with a concentration parameter, c = 6.7 +/- 0.4, consistent with the range of values expected in the concordance cosmological model for relaxed clusters. The optical properties suggest this could be a ``fossil cluster''.Comment: 5 pages, 4 colour figures, accepted for publication in Ap

Cooling flow bulk motion corrections to the Sunyaev Zel'dovich effect

We study the influence of converging cooling flow bulk motions on the Sunyaev-Zel'dovich (SZ) effect. To that purpose we derive a modified Kompaneets equation which takes into account the contribution of the accelerated electron media of the cooling flow inside the cluster frame. The additional term is different from the usual kinematic SZ-effect, which depends linearly on the velocity, whereas the contribution described here is quadratic in the macroscopic electron fluid velocity, as measured in the cluster frame. For clusters with a large cooling flow mass deposition rate and/or a small central electron density, it turns out that this effect becomes relevant.Comment: accepted for publication in New Astronom

Nerve growth factor receptor TrkA, a new receptor in insulin signaling pathway in PC12 cells

Background: TrkA is a transmembrane receptor tyrosine kinase for nerve growth factor. Results: TrkA forms a molecular complex with insulin receptor and IRS-1 to induce Akt and Erk5 phosphorylation. Conclusion: The NGF-TrkA receptor influences insulin signaling. Significance: The TrkA receptor is involved in insulin signaling, and NGF may regulate neuronal glucose uptake as neurons are insulin-insensitive. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc

Where Do Cooling Flows Cool?

Although only about 5 percent of the total baryonic mass in luminous elliptical galaxies is in the form of cooled interstellar gas, it is concentrated within the optical effective radius r_e where it influences the local dynamical mass. The mass of cooled gas must be spatially distributed since it greatly exceeds the masses of central black holes. We explore here the proposition that a population of low mass, optically dark stars is created from the cooled gas. We consider a wide variety of radial distributions for the interstellar cooling, but only a few are consistent with observed X-ray surface brightness profiles. In a region of concentrated interstellar cooling, the X-ray emission can exceed that observed, suggesting the presence of additional support by magnetic stresses or non-thermal pressure. In general we find that the mass of cooled gas contributes significantly to stellar dynamical mass to light ratios which vary with galactic radius. If the stars formed from cooled interstellar gas are optically luminous, their influence on the the mass to light ratio would be reduced. The mass of cooled gas inside r_e is sensitive to the rate that old stars lose mass, which is nearly independent of the initial mass function of the old stellar population.Comment: 18 pages with 6 figures; accepted by Astrophysical Journa

Higher Education Exchange: 2006

This annual publication serves as a forum for new ideas and dialogue between scholars and the larger public. Essays explore ways that students, administrators, and faculty can initiate and sustain an ongoing conversation about the public life they share.The Higher Education Exchange is founded on a thought articulated by Thomas Jefferson in 1820: "I know no safe depository of the ultimate powers of the society but the people themselves; and if we think them not enlightened enough to exercise their control with a wholesome discretion, the remedy is not to take it from them, but to inform their discretion by education."In the tradition of Jefferson, the Higher Education Exchange agrees that a central goal of higher education is to help make democracy possible by preparing citizens for public life. The Higher Education Exchange is part of a movement to strengthen higher education's democratic mission and foster a more democratic culture throughout American society.Working in this tradition, the Higher Education Exchange publishes interviews, case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies

Removal and mixing of the coronal gas from satellites in galaxy groups: cooling the intragoup gas

The existence of an extended hot gaseous corona surrounding clusters, groups and massive galaxies is well established by observational evidence and predicted by current theories of galaxy formation. When a small galaxy collides with a larger one, their coronae are the first to interact, producing disturbances that remove gas from the smaller system and settle it into the corona of the larger one. For a Milky-Way-size galaxy merging into a low-mass group, ram pressure stripping and the Kelvin-Helmholtz instability are the most relevant of these disturbances. We argue that the turbulence generated by the latter mixes the material of both coronae in the wake of the orbiting satellite creating a "warm phase" mixture with a cooling time a factor of several shorter than that of the ambient intragroup gas. We reach this conclusion using analytic estimates, as well as adiabatic and dissipative high resolution numerical simulations of a spherical corona subject to the ablation process of a constant velocity wind with uniform density and temperature. Although this is a preliminary analysis, our results are promising and we speculate that the mixture could potentially trigger in situ star formation and/or be accreted into the central galaxy as a cold gas flow resulting in a new mode of star formation in galaxy groups and clusters.Comment: 15 pages, 5 figures, accepted for publication in MNRA

Development and Testing of Program Evaluation Instruments for the iCook 4-H Curriculum

Objective: To develop and test the validity of program outcome evaluation instruments for cooking, eating, and playing together for obesity prevention during iCook 4-H. Design: Instrument development for both youth and adults through pre-post testing of items newly constructed and compiled to address key curriculum constructs. Testing occurred throughout program intervention and dissemination to determine dimensionality, internal consistency and test-retest reliability, and validity. Setting: A 5-state out-of-school program in cooperative extension and other community sites. Participants: Youths aged 9−10 years; adults were main food preparers; the first phase involved 214 dyads and the second phase, 74 dyads. Main Outcome Measure(s): Youth measures were cooking skills, culinary self-efficacy, physical activity, and openness to new foods. Adult measures were cooking together, physical activity, and eating together. Analysis: Exploratory factor analysis to determine initial scale structure and confirmatory factor analysis to confirm factor structures. Longitudinal invariance tests to see whether the factor structure held over time. Test-retest reliability was determined by Pearson r and internal consistency was determined by coefficient V and Cronbach a. Validity testing was determined by Pearson r correlations. Results: Youth cooking skills, openness to new foods, and adult eating together and cooking together showed strong evidence for dimensionality, reliability, and validity. Youth physical activity and adult physical activity measures showed strong evidence for dimensionality and validity but not reliability. The youth culinary selfefficacy measure showed strong evidence for reliability and validity but weaker evidence for dimensionality. Conclusions and Implications: Program outcome evaluation instruments for youths and adults were developed and tested to accompany the iCook 4-H curriculum. Program leaders, stakeholders, and administrators may monitor outcomes within and across programs and generate consistent reporting

Development and Testing of Program Evaluation Instruments for the iCook 4-H Curriculum

Objective To develop and test the validity of program outcome evaluation instruments for cooking, eating, and playing together for obesity prevention during iCook 4-H. Design Instrument development for both youth and adults through pre-post testing of items newly constructed and compiled to address key curriculum constructs. Testing occurred throughout program intervention and dissemination to determine dimensionality, internal consistency and test-retest reliability, and validity. Setting A 5-state out-of-school program in cooperative extension and other community sites. Participants Youths aged 9–10 years; adults were main food preparers; the first phase involved 214 dyads and the second phase, 74 dyads. Main Outcome Measure(s) Youth measures were cooking skills, culinary self-efficacy, physical activity, and openness to new foods. Adult measures were cooking together, physical activity, and eating together. Analysis Exploratory factor analysis to determine initial scale structure and confirmatory factor analysis to confirm factor structures. Longitudinal invariance tests to see whether the factor structure held over time. Test-retest reliability was determined by Pearson r and internal consistency was determined by coefficient Ω and Cronbach α. Validity testing was determined by Pearson rcorrelations. Results Youth cooking skills, openness to new foods, and adult eating together and cooking together showed strong evidence for dimensionality, reliability, and validity. Youth physical activity and adult physical activity measures showed strong evidence for dimensionality and validity but not reliability. The youth culinary self-efficacy measure showed strong evidence for reliability and validity but weaker evidence for dimensionality. Conclusions and Implications Program outcome evaluation instruments for youths and adults were developed and tested to accompany the iCook 4-Hcurriculum. Program leaders, stakeholders, and administrators may monitor outcomes within and across programs and generate consistent reporting