P. J. McCarthy

Dynamical, physical, and chemical properties of emission-line nebulae in cooling flows

The results are reported of a program of long-slit spectroscopy, narrow-band imaging, and VLA mapping of the optical emission-line gas and nonthermal radio continuum emission associated with the dominant galaxy in nine galaxy clusters with cooling flows. All the observed emission-line nebulae are very strongly centrally concentrated with typical characteristic radii of 5 kpc or less. If the mass inflow rate varies linearly with radius in cooling flows out to large radii, then the H-alpha surface brightness does not trace the cooling rate. The velocity field of the emission-line gas provides little evidence for organized rotation or shear. This result can be understood if the emission-line filaments condense out of an intracluster medium in which angular momentum has been transported radially outward. Electron densities are measured over spatially resolved regions and are found to by typically a few hundred per cu cm. Spatial variations in the emission-line ratios in the nebulae agree better with shock models than with photoionization models. The various possible mechanisms for heating and ionizing the emission-line nebulae are discussed. 87 refs.

Photometric Redshift and Classification for the XMM-COSMOS Sources

We present photometric redshifts and spectral energy distribution (SED) classifications for a sample of 1542 optically identified sources detected with XMM in the COSMOS field. Our template fitting classifies 46 sources as stars and 464 as nonactive galaxies, while the remaining 1032 require templates with an active galactic nucleus (AGN) contribution. High accuracy in the derived photometric redshifts was accomplished as the result of (1) photometry in up to 30 bands with high-significance detections, (2) a new set of SED templates, including 18 hybrids covering the far-UV to mid-infrared, which have been constructed by the combination of AGNs and nonactive galaxies templates, and (3) multiepoch observations that have been used to correct for variability (most important for type 1 AGNs). The reliability of the photometric redshifts is evaluated using the subsample of 442 sources with measured spectroscopic redshifts. We achieved an accuracy of σΔz/(1+z_(spec)) = 0.014 for i∗_(AB) < 22.5 (σΔz/(1+z_(spec)) ~ 0.015 for i∗_(AB) < 24.5). The high accuracies were accomplished for both type 2 (where the SED is often dominated by the host galaxy) and type 1 AGNs and QSOs out to z = 4.5. The number of outliers is a large improvement over previous photometric redshift estimates for X-ray-selected sources (4.0% and 4.8% outliers for i∗_(AB) < 22.5 and i∗_(AB) < 24.5, respectively). We show that the intermediate band photometry is vital to achieving accurate photometric redshifts for AGNs, whereas the broad SED coverage provided by mid-infrared (Spitzer/IRAC) bands is important to reduce the number of outliers for normal galaxies.

THE COSMOS ACTIVE GALACTIC NUCLEUS SPECTROSCOPIC SURVEY. I. XMM-NEWTON COUNTERPARTS ∗

We present optical spectroscopy for an X-ray and optical flux-limited sample of 677 XMM-Newton selected targets covering the 2 deg^2 Cosmic Evolution Survey field, with a yield of 485 high-confidence redshifts. The majority of the spectra were obtained over three seasons (2005-2007) with the Inamori Magellan Areal Camera and Spectrograph instrument on the Magellan (Baade) telescope. We also include in the sample previously published Sloan Digital Sky Survey spectra and supplemental observations with MMT/Hectospec. We detail the observations and classification analyses. The survey is 90% complete to flux limits of f_(0.5-10 keV) > 8 × 10^(–16) erg cm^(-2) s^(–1) and i^+_(AB) 3 × 10^(42) erg s^(–1)) to z < 1, of both optically obscured and unobscured types. We find statistically significant evidence that the obscured-to-unobscured AGN ratio at z < 1 increases with redshift and decreases with luminosity.We present optical spectroscopy for an X-ray and optical flux-limited sample of 677 XMM-Newton selected targets covering the 2 deg^2 COSMOS field, with a yield of 485 high-confidence redshifts. The majority of the spectra were obtained over three seasons (2005-2007) with the IMACS instrument on the Magellan (Baade) telescope. We also include in the sample previously published Sloan Digital Sky Survey spectra and supplemental observations with MMT/Hectospec. We detail the observations and classification analyses. The survey is 90% complete to flux limits of f_{0.5-10 keV}>8 x 10^-16 erg cm^-2 s^-1 and i_AB+ 3 x 10^42 erg s^-1) to z<1, of both optically obscured and unobscured types. We find statistically significant evidence that the obscured to unobscured AGN ratio at z<1 increases with redshift and decreases with luminosity.

Correlated radio and optical asymmetries in powerful radio sources

The spatial distributions of thermal emission-line gas and nonthermal radio-emitting plasma in powerful radio galaxies are examined. At high redshifts and luminosities, the thermal gas is distributed very asymmetrically with respect to the galaxy nucleus. The one-sidedness of the emission line regions is clear evidence of an intrinsically asymmetric property of powerful radio sources. The radio sources are more asymmetric in their lobe spacings at high redshifts, but not at a highly significant level

The Environment of Lyman- alpha Absorbers in the Sight Line toward 3C 273

We present new ground-based data following up on the Hubble Space Telescope discovery of low-redshift Lya absorption in the sight line to the quasar 3C 273. Our goal is to investigate the relationship between the low column density absorbers and higher column density objects such as galaxies or H II regions. Narrow-band filter observations with a coronagraph show that there are no H II regions or other strong Hα line- emitting gas within a 12 kpc radius of the line of sight to the quasar, at the velocities of three of the absorbers. Broad-band imaging in Gunn r shows that there are no dwarf galaxies at Virgo distances with absolute magnitude above M B ≃-13.5 and within a radius of 40 kpc from the line of sight to the quasar

Evidence for large-scale winds from starburst galaxies. I - The nature of the ionized gas in M82 and NGC 253

The results of long-slit spectroscopy and narrow-band imaging of M82 and NGC 253, the two nearest examples of FIR luminous galaxies believed to be undergoing intense bursts of star formation, are presented. The profile of the gas pressure in the emission-line filaments in M82 is derived and found to be in good agreement with the model of Chevalier and Clegg (1985) of a supernovae-driven wind from a starburst nucleus. Lower quality data from NGC 253 support the same interpretation. Analysis of the emission-line ratios suggests that the line-emitting gas may be heated by low-velocity shocks, although photoionization from dilute UV radiation from unusually hot stars in the central starburst may also be important. 56 references.

OBSERVATIONAL LIMITS ON TYPE 1 ACTIVE GALACTIC NUCLEUS ACCRETION RATE IN COSMOS

We present black hole masses and accretion rates for 182 Type 1 active galactic nuclei (AGNs) in COSMOS. We estimate masses using the scaling relations for the broad H??, Mg?II, and C?IV emission lines in the redshift ranges 0.16 < z < 0.88, 1 < z < 2.4, and 2.7 < z < 4.9. We estimate the accretion rate using an Eddington ratio LI /L Edd estimated from optical and X-ray data. We find that very few Type 1 AGNs accrete below LI /L Edd ~ 0.01, despite simulations of synthetic spectra which show that the survey is sensitive to such Type 1 AGNs. At lower accretion rates the broad-line region may become obscured, diluted, or nonexistent. We find evidence that Type 1 AGNs at higher accretion rates have higher optical luminosities, as more of their emission comes from the cool (optical) accretion disk with respect to shorter wavelengths. We measure a larger range in accretion rate than previous works, suggesting that COSMOS is more efficient at finding low accretion rate Type 1 AGNs. However, the measured range in accretion rate is still comparable to the intrinsic scatter from the scaling relations, suggesting that Type 1 AGNs accrete at a narrow range of Eddington ratio, with LI /L Edd ~ 0.1.

Extended Ly-alpha emission associated with 3C 294

Optical, IR, and radio observations of the powerful radio source 3C 294, which is surrounded by a large cloud of ionized gas, are presented. The galaxy is faint in the rest-frame UV, yet has a near-IR luminosity that is typical of radio galaxies at redshifts of order two. In contrast to the large extent of the ionized gas, the K-band image is quite compact. The emission-line cloud is closely aligned with the radio source axis and has an ionization state indicative of ionization by a nonstellar source. The velocity field of the gas has both large ordered motions and large turbulent components. The total mass required to keep the gas bound to the system is comparable to present-day massive galaxies and their halos. The velocity fields of the high-ionization lines are systematically different from Ly-alpha in a manner that is not easily understood. 88 refs.

Interaction of energetic particles with large and small scale instabilities

Beyond a certain heating power, measured and predicted distributions of NBI driven currents deviate from each other, in a form that can be explained by the assumption of a modest diffusion of fast particles. Direct numerical simulation of fast test particles in a given field of electrostatic turbulence indicates that for reasonable parameters fast and thermal particle diffusion indeed are similar. High quality plasma edge plasma profiles on ASDEX Upgrade, used in the linear, gyrokinetic, global stability code LIGKA give excellent agreement with the eigenfunction measured by a newly extended reflectometry system for ICRH-excited TAE-modes. They support the hypothesis of TAE-frequency crossing of the continuum in the edge region as explanation of the high TAE-damping rates measured on JET.A new fast ion loss detector with 1MHz time resolution allows frequency and phase resolved correlation between low frequency magnetic perturbation, giving, together with modelling of the particle orbits, new insights into the mechanism of fast particle losses during NBI and ICRH due to helical perturbations.

Poloidal polarimeter for current density measurements in ITER

One of the systems envisaged for measuring the current density profile in the ITER is a 118 μm poloidal polarimeter system. The proposed system has two independent views: one fan of chords observes the plasma via an equatorial port and a second fan views down from an upper port. This article will present the status of the on-going work and will address issues as sensitivity and accuracy, refraction, Gaussian beam ray-tracing, alignment, and calibration as well as some specific design details.