MOJAVE: Monitoring of Jets in AGN with VLBA Experiments. IV. The Parent Luminosity Function of Radio-Loud Blazars

(Abridged) We use a complete sample of active galactic nuclei (AGN) selected on the basis of relativistically beamed 15 GHz radio flux density to derive the parent radio luminosity function (RLF) of bright radio-selected blazar cores. We use a maximum likelihood method to fit a beamed RLF to the observed data and thereby recover the parameters of the intrinsic (unbeamed) RLF. We analyze two subsamples of the MOJAVE sample: the first contains only objects of known FR II class, with a total of 103 sources, and the second subsample adds 24 objects of uncertain FR class for a total of 127 sources. Both subsamples exclude four known FR I radio galaxies and two gigahertz-peaked spectrum sources. We obtain good fits to both subsamples using a single power law intrinsic RLF with pure density evolution function. We find that a previously reported break in the observed MOJAVE RLF actually arises from using incomplete bins (because of the luminosity cutoff) across a steep and strongly evolving RLF, and does not reflect a break in the intrinsic RLF. The derived space density of the parent population of the FR II sources from the MOJAVE sample (with L>1.3e25 W/Hz) is approximately 1600/Gpc^3.Comment: 31 pages, 7 figures and 2 tables. Accepted for publication in ApJ. Changes: classification of sources based on radio morphology instead of optical classes; added the parameters of the RLF of the FR II sources; added more explanations; added a table listing the sample sources; added 2 extra figures related to the observed break in the RLF; updated reference

VLBI Imaging of Water Maser Emission from the Nuclear Torus of NGC 1068

We have made the first VLBI synthesis images of the H2O maser emission associated with the central engine of the Seyfert galaxy NGC 1068. Emission extends about +/-300 km/s from the systemic velocity. Images with submilliarcsecond angular resolution show that the red-shifted emission lies along an arc to the northwest of the systemic emission. (The blue-shifted emission has not yet been imaged with VLBI.) Based on the maser velocities and the relative orientation of the known radio jet, we propose that the maser emission arises on the surface of a nearly edge-on torus, where physical conditions are conducive to maser action. The visible part of the torus is axially thick, with comparable height and radius. The velocity field indicates sub-Keplerian differential rotation around a central mass of about 1e7 Msun that lies within a cylindrical radius of about 0.65 pc. The estimated luminosity of the central engine is about 0.5 of the Eddington limit. There is no detectable compact radio continuum emission near the proposed center of the torus (T_B< 5e6 K on size scales of about 0.1 pc), so that the observed flat-spectrum core cannot be direct self-absorbed synchrotron radiation.Comment: 12 pages, 4 figures. To appear in ApJ Part 2. Also available at http://www.physics.ucsb.edu/~vlbiweb

The Polarized Spectrum of Apm 08279+5255

We report the discovery of significant linear polarization (p > 1%) in the hyperluminous z=3.87 BALQSO APM~08279+5255. The polarization spectrum is complex, with properties similar to those of other, lower redshift but more highly polarized BALQSOs. The resonance emission lines are unpolarized while the absorption troughs show polarization similar to or higher than the continuum. In particular, an apparent increase of polarization in the trough covering 1000-1030 angstroms (rest) supports the interpretation of this feature as a broad absorption component associated with OVI/Ly_beta local to the QSO, as opposed to an intervening damped Ly_alpha absorption system. The elevated polarization in some of the absorption features implies that we view the scattered (polarized) spectrum through a sightline with less absorbing material than the direct spectrum. Therefore, the complex structure of the polarization spectrum in this brilliant lensed BALQSO suggests that it will be an important laboratory for studying the structure of QSOs at high redshift.Comment: 8 pages, 1 figure. Accepted for publication in The Astrophysical Journal Letter

RHESSI Observations of the Solar Flare Iron-line Feature at 6.7 keV

Analysis of RHESSI 3--10 keV spectra for 27 solar flares is reported. This energy range includes thermal free--free and free--bound continuum and two line features, at 6.7keV and 8keV, principally due to highly ionized iron (Fe). We used the continuum and the flux in the so-called Fe-line feature at 6.7keV to derive the electron temperature T_e, the emission measure, and the Fe-line equivalent width as functions of time in each flare. The Fe/H abundance ratio in each flare is derived from the Fe-line equivalent width as a function of T_e. To minimize instrumental problems with high count rates and effects associated with multi-temperature and nonthermal spectral components, spectra are presented mostly during the flare decay phase, when the emission measure and temperature were smoothly varying. We found flare Fe/H abundance ratios that are consistent with the coronal abundance of Fe (i.e. 4 times the photospheric abundance) to within 20% for at least 17 of the 27 flares; for 7 flares, the Fe/H abundance ratio is possibly higher by up to a factor of 2. We find evidence that the Fe XXV ion fractions are less than the theoretically predicted values by up to 60% at T_e=25 MK appear to be displaced from the most recent theoretical values by between 1 and 3 MK.Comment: To be published, Ap

The Nuclear Reddening Curve for Active Galactic Nuclei and the Shape of the Infra-Red to X-Ray Spectral Energy Distribution

We present extinction curves derived from the broad emission lines and continua of large samples of both radio-loud and radio-quiet AGNs. The curves are significantly flatter in the UV than are curves for the local ISM. The reddening curves for the radio-quiet LBQS quasars are slightly steeper than those of the radio-loud quasars in the UV, probably because of additional reddening by dust further out in the host galaxies of the former. The UV extinction curves for the radio-loud AGNs are very flat. This is explicable with slight modifications to standard MRN dust models: there is a relative lack of small grains in the nuclear dust. Our continuum and broad-emission line reddening curves agree in both shape and amplitude, confirming that the continuum shape is indeed profoundly affected by reddening for all but the bluest AGNs. With correction by our generic extinction curve, all of the radio-loud AGNs have continuous optical-UV spectra consistent with a single shape. We show that radio-quiet AGNs have very similar intrinsic UV to optical shape over orders of magnitude in luminosity. We also argue that radio-loud and radio-quiet AGNs probably share the same underlying continuum shape and that most of the systematic differences between their observed continuum shapes are due to higher nuclear reddening in radio-selected AGNs, and additional reddening from dust further out in the host galaxies in radio-quiet AGNs. Our conclusions have important implications for the modelling of quasar continua and the analysis of quasar demographics.Comment: 41 pages, including 6 figures and 3 tables. To appear in ApJ vol. 614, October 20 issue. Some slight wording changes. Some additional references added. Small changes in the model fit in section 6.2, to the analytical fit in the Appendix, and to the tabulated reddening curve in the Appendi

Identifying Compact Symmetric Objects in the Southern Sky

We present results of multifrequency polarimetric VLBA observations of 20 compact radio sources. The observations represent the northern and southern extensions of a large survey undertaken to identify Compact Symmetric Objects (CSOs) Observed in the Northern Sky (COINS). CSOs are young radio galaxies whose jet axes lie close to the plane of the sky, and whose appearance is therefore not dominated by relativistic beaming effects. The small linear sizes of CSOs make them valuable for studies of both the evolution of radio galaxies and testing unified schemes for active galactic nuclei (AGN). In this paper we report on observations made of 20 new CSO candidates discovered in the northern and southern extremities of the VLBA Calibrator Survey. We identify 4 new CSOs, and discard 12 core-jet sources. The remaining 4 sources remain candidates pending further investigation. We present continuum images at 5 GHz and 15 GHz and, where relevant, images of the polarized flux density and spectral index distributions for the 8 new CSOs and CSO candidates.Comment: accepted to Ap

Oxidative potential associated with urban aerosol deposited into the respiratory system and relevant elemental and ionic fraction contributions

Size-segregated aerosol measurements were carried out at an urban and at an industrial site. Soluble and insoluble fractions of elements and inorganic ions were determined. Oxidative potential (OP) was assessed on the soluble fraction of Particulate Matter (PM) by ascorbic acid (AA), dichlorofluorescein (DCFH) and dithiothreitol (DTT) assays. Size resolved elemental, ion and OP doses in the head (H), tracheobronchial (TB) and alveolar (Al) regions were estimated using the Multiple-Path Particle Dosimetry (MPPD) model. The total aerosol respiratory doses due to brake and soil resuspension emissions were higher at the urban than at the industrial site. On the contrary, the doses of anthropic combustion tracers were generally higher at the industrial site. In general, the insoluble fraction was more abundantly distributed in the coarse than in the fine mode and vice versa for the soluble fraction. Consequently, for the latter, the percent of the total respiratory dose deposited in TB and Al regions increased. Oxidative potential assay (OPAA) doses were distributed in the coarse region; therefore, their major contribution was in the H region. The contribution in the TB and Al regions increased for OPDTT and OPDCFH

Beyond the Nuclear Family: Children’s Social Networks and Depressive Symptomology

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156181/2/cdev13307.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156181/1/cdev13307_am.pd

An Extraordinary Scattered Broad Emission Line in a Type 2 QSO

An infrared-selected, narrow-line QSO has been found to exhibit an extraordinarily broad Halpha emission line in polarized light. Both the extreme width (35,000 km/sec full-width at zero intensity) and 3,000 km/sec redshift of the line centroid with respect to the systemic velocity suggest emission in a deep gravitational potential. An extremely red polarized continuum and partial scattering of the narrow lines at a position angle common to the broad-line emission imply extensive obscuration, with few unimpeded lines of sight to the nucleus.Comment: 4 pages, 1 figure, to appear in the Astrophysical Journal Letter

The Phoenix galaxy: UGC4203 re-birth from its ashes?

We report on a dramatic transition between a Compton-thick, reflection-dominated state and a Compton-thin state in the Seyfert 2 galaxy UGC4203, discovered by comparing a recent (May 2001) XMM-Newton observation with ASCA observations performed about six years earlier. This transition can be explained either as a change in the column density of the absorber, maybe due to moving clouds in a clumpy torus, or as the revival of a transient active nucleus, which was in a phase of very low activity when observed by ASCA. If the latter explanation is correct, spectral transitions of this kind provide observational support to the idea that Compton-thick and Compton-thin regions coexist in the same source, the former likely to be identified with the "torus", the latter with dust lanes on much larger scales.Comment: 6 Latex pages, 5 figures, To appear in Astronomy & Astrophysic