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 PA$\simeq$160\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

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

Borrowing from Millennials to Pay Boomers: Can Tax Policy Create Sustainable Intergenerational Equity?

At the outset, Part I of the Article provides an overview of sustainable intergenerational justice and tax policy. Part II then provides an overview of the U.S. tax system, deficits, and public debt. Part III then considers how taxes can influence the level of resources that are available to future generations, and Part IV considers how taxes can influence the mix of resources that are available to future generations

Making the Internal Revenue Service Work

This is an Article about how to redesign the federal tax system so that the Internal Revenue Service (IRS) can administer it more effectively given that Congress is only willing to let the IRS have around 82,000 employees and a $12 billion budget. As the IRS Oversight Board and the National Taxpayer Advocate have frequently emphasized, the United States underinvests in the IRS. Underinvesting means that taxpayer services are suffering and that tax enforcement has been significantly weakened. With budget deficits for “as far as the eye can see” and the recent IRS troubles with tax-exempt political organizations, the prospects for increased funding for the IRS are remote. In this Article, we consider a variety of approaches that would make it easier for the IRS to raise and collect revenue, and we offer a number of recommendations for legislative and administrative changes. For example, we recommend simplifying the tax system, enhancing third-party reporting, and streamlining the tax-filing and dispute-resolution procedures. In short, this Article discusses how the tax system should be designed so that it can work with a modestly-funded tax administrator. Part II of this Article provides an overview of the federal tax system, and Part III of this Article provides an overview of tax administration. Part IV of this Article discusses the key problems with current tax administration. Finally, Part V of this Article offers a number of recommendations for change, including some that would require legislation and some that could be achieved administratively

Stormy weather in 3C 196.1: nuclear outbursts and merger events shape the environment of the hybrid radio galaxy 3C 196.1

We present a multi-wavelength analysis based on archival radio, optical and X-ray data of the complex radio source 3C 196.1, whose host is the brightest cluster galaxy of a $z=0.198$ cluster. HST data show H$\alpha$+[N II] emission aligned with the jet 8.4 GHz radio emission. An H$\alpha$+[N II] filament coincides with the brightest X-ray emission, the northern hotspot. Analysis of the X-ray and radio images reveals cavities located at galactic- and cluster- scales. The galactic-scale cavity is almost devoid of 8.4 GHz radio emission and the south-western H$\alpha$+[N II] emission is bounded (in projection) by this cavity. The outer cavity is co-spatial with the peak of 147 MHz radio emission, and hence we interpret this depression in X-ray surface brightness as being caused by a buoyantly rising bubble originating from an AGN outburst $\sim$280 Myrs ago. A \textit{Chandra} snapshot observation allowed us to constrain the physical parameters of the cluster, which has a cool core with a low central temperature $\sim$2.8 keV, low central entropy index $\sim$13 keV cm$^2$ and a short cooling time of $\sim$500 Myr, which is $<0.05$ of the age of the Universe at this redshift. By fitting jumps in the X-ray density we found Mach numbers between 1.4 and 1.6, consistent with a shock origin. We also found compelling evidence of a past merger, indicated by a morphology reminiscent of gas sloshing in the X-ray residual image. Finally, we computed the pressures, enthalpies $E_{cav}$ and jet powers $P_{jet}$ associated with the cavities: $E_{cav}\sim7\times10^{58}$ erg, $P_{jet}\sim1.9\times10^{44}$ erg s$^{-1}$ for the inner cavity and $E_{cav}\sim3\times10^{60}$ erg, $P_{jet}\sim3.4\times10^{44}$ erg s$^{-1}$ for the outer cavity.Comment: 14 pages, 4 figures, ApJ accepte

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 $\sim$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 $\sim$0.29 keV (the temperature of the ambient ISM) to $\sim$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