Mid Infrared Spectra of Radio Galaxies and Quasars

Spitzer Infrared Spectrograph (IRS) observations of 3C radio galaxies and quasars shed new light on the nature of the central engines of AGN. Emission from silicate dust obscuring the central engine can be used to estimate the bolometric luminosity of an AGN. Emission lines from ions such as O IV and Ne V give another indication of the presence or lack of a hidden source of far-UV photons in the nucleus. Radio-loud AGN with relative-to-Eddington luminosity ratios of L/L_Edd < 3E-3 do not appear to have broad optical emission lines, though some do have strong silicate emission. Aromatic emission features from star formation activity are common in low-luminosity radio galaxies. Strong molecular hydrogen pure-rotational emission lines are also seen in some mid-IR weak radio galaxies, caused by either merger shocks or jet shocks in the interstellar medium.Comment: Conference proceedings to appear in "The Central Engine of Active Galactic Nuclei", ed. L. C. Ho and J.-M. Wang (San Francisco: ASP

Joint Trajectories of Spousal Social Support and Depressive Symptoms in Older Age

OBJECTIVE: We describe changes in depressive symptoms and positive and negative social support from the spouse/partner in a representative sample of older people in England. METHOD: Men and women aged 50+ ( N = 7,171) from the English Longitudinal Study of Ageing reported social support and depressive symptoms (Center for Epidemiologic Studies Depression Scale) on up to five occasions between 2002-2003 and 2010-2011. Parallel process latent growth models estimated their bidirectional associations, adjusted for gender, wealth, education, and limiting illness. RESULTS: In age- and gender-adjusted models, positive spousal support decreased and negative support increased over time, especially among women. Greater increases over time in depressive symptoms were seen in those with lower positive support or higher negative support at baseline. More baseline depressive symptoms predicted greater declines in positive support and greater increases in negative support from the spouse. DISCUSSION: Improving older couple's relationship quality may help reduce depressive symptoms

Spectral line profiles changed by dust scattering in heavily obscured young stellar objects

It is known that scattering of radiation by circumstellar dust can strongly change the line profiles in stellar spectra. This hampers the analysis of spectral lines originating in the emitting regions of heavily obscured young stars. To calculate the line profile of the scattered radiation, we suggest to use the approximation of remote scattering particles. This approximation assumes that the scattering dust grains are at a distance from the star that is much larger than the characteristic size of the emitting region. Using this method, we calculated the line profiles of several simple models. They show the H alpha line profiles of Herbig AeBe stars in the presence and absence of motionless or moving dust

An extreme, blueshifted iron line profile in the Narrow Line Seyfert 1 PG 1402+261; an edge-on accretion disk or highly ionized absorption?

We report on a short XMM-Newton observation of the radio-quiet Narrow Line Seyfert 1 PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong excess of counts between 6-9 keV in the rest frame. This feature can be modeled by an unusually strong (equivalent width 2 keV) and very broad (FWHM velocity of 110000 km/s) iron K-shell emission line. The line centroid energy at 7.3 keV appears blue-shifted with respect to the iron Kalpha emission band between 6.4-6.97 keV, while the blue-wing of the line extends to 9 keV in the quasar rest frame. The line profile can be fitted by reflection from the inner accretion disk, but an inclination angle of >60 deg is required to model the extreme blue-wing of the line. Furthermore the extreme strength of the line requires a geometry whereby the hard X-ray emission from PG 1402+261 above 2 keV is dominated by the pure-reflection component from the disk, while little or none of the direct hard power-law is observed. Alternatively the spectrum above 2 keV may instead be explained by an ionized absorber, if the column density is sufficiently high (N_H > 3 x 10^23 cm^-2) and if the matter is ionized enough to produce a deep (tau~1) iron K-shell absorption edge at 9 keV. This absorber could originate in a large column density, high velocity outflow, perhaps similar to those which appear to be observed in several other high accretion rate AGN. Further observations, especially at higher spectral resolution, are required to distinguish between the accretion disk reflection or outflow scenarios.Comment: Accepted for publication in ApJ (18 pages, 5 figures, 1 table

Possible X-ray diagnostic for jet/disk dominance in Type 1 AGN

Using Rossi X-ray Timing Explorer Seyfert 1 and 1.2 data spanning 9 years, we study correlations between X-ray spectral features. The sample consists of 350 time-resolved spectra from 12 Seyfert 1 and 1.2 galaxies. Each spectrum is fitted to a model with an intrinsic powerlaw X-ray spectrum produced close to the central black hole that is reprocessed and absorbed by material around the black hole. To test the robustness of our results, we performed Monte Carlo simulations of the spectral sample. We find a complex relationship between the iron line equivalent width (EW) and the underlying power law index (Gamma). The data reveal a correlation between Gamma and EW which turns over at Gamma <~ 2, but finds a weak anti-correlation for steeper photon indices. We propose that this relationship is driven by dilution of a disk spectrum (which includes the narrow iron line) by a beamed jet component and, hence, could be used as a diagnostic of jet-dominance. In addition, our sample shows a strong correlation between the reflection fraction (R) and Gamma, but we find that it is likely the result of modeling degeneracies. We also see the X-ray Baldwin effect (an anti-correlation between the 2-10 keV X-ray luminosity and EW) for the sample as a whole, but not for the individual galaxies and galaxy types.Comment: Accepted for publication in ApJ, 14 page

Radiation Pressure Supported Starburst Disks and AGN Fueling

We consider the structure of marginally Toomre-stable starburst disks under the assumption that radiation pressure on dust grains provides the dominant vertical support against gravity. This is particularly appropriate when the disk is optically thick to its own IR radiation, as in the central regions of ULIRGs. Because the disk radiates at its Eddington limit, the Schmidt-law for star formation changes in the optically-thick limit, with the star formation rate per unit area scaling as Sigma_g/kappa, where Sigma_g is the gas surface density and kappa is the mean opacity. We show that optically thick starburst disks have a characteristic flux and dust effective temperature of F ~ 10^{13} L_sun/kpc^2 and T_eff ~ 90K, respectively. We compare our predictions with observations and find good agreement. We extend our model from many-hundred parsec scales to sub-parsec scales and address the problem of fueling AGN. We assume that angular momentum transport proceeds via global torques rather than a local viscosity. We account for the radial depletion of gas due to star formation and find a strong bifurcation between two classes of disk models: (1) solutions with a starburst on large scales that consumes all of the gas with little fueling of a central AGN and (2) models with an outer large-scale starburst accompanied by a more compact starburst on 1-10 pc scales and a bright central AGN. The luminosity of the latter models is in many cases dominated by the AGN. We show that the vertical thickness of the starburst disk on pc scales can approach h ~ r, perhaps accounting for the nuclear obscuration in some Type 2 AGN. We also argue that the disk of young stars in the Galactic Center may be the remnant of such a compact nuclear starburst.Comment: 26 pages, 9 figures, emulateapj, accepted to ApJ, minor changes, discussion tightened, references adde

The Spitzer View of FR I Radio Galaxies: On the Origin of the Nuclear Mid-Infrared Continuum

We present Spitzer mid-infrared (MIR) spectra of 25 FR I radio galaxies and investigate the nature of their MIR continuum emission. MIR spectra of star-forming galaxies and quiescent elliptical galaxies are used to identify host galaxy contributions while radio/optical core data are used to isolate the nuclear nonthermal emission. Out of the 15 sources with detected optical compact cores, four sources are dominated by emission related to the host galaxy. Another four sources show signs of warm, nuclear dust emission: 3C15, 3C84, 3C270, and NGC 6251. It is likely that these warm dust sources result from hidden active galactic nuclei of optical spectral type 1. The MIR spectra of seven sources are dominated by synchrotron emission, with no significant component of nuclear dust emission. In parabolic spectral energy distribution fits of the nonthermal cores FR Is tend to have lower peak frequencies and stronger curvature than blazars. This is roughly consistent with the common picture in which the core emission in FR Is is less strongly beamed than in blazars

Dust Emission from Active Galactic Nuclei

Unified schemes of active galactic nuclei (AGN) require an obscuring dusty torus around the central source, giving rise to Seyfert 1 line spectrum for pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the observed IR is in broad agreement with this scheme, the behavior of the 10 micron silicate feature and the width of the far-IR emission peak remained serious problems in all previous modeling efforts. We show that these problems find a natural explanation if the dust is contained in about 5-10 clouds along radial rays through the torus. The spectral energy distributions (SED) of both type 1 and type 2 sources are properly reproduced from different viewpoints of the same object if the visual optical depth of each cloud is larger than about 60 and the clouds' mean free path increases roughly in proportion to radial distance.Comment: 11 pages, submitted to ApJ Letter

The Transverse Proximity Effect: A Probe to the Environment, Anisotropy, and Megayear Variability of QSOs

The transverse proximity effect is the expected decrease in the strength of the Lya forest absorption in a QSO spectrum when another QSO lying close to the line of sight enhances the photoionization rate above that due to the average cosmic ionizing background. We select three QSOs from the Early Data Release of the Sloan Digital Sky Survey that have nearby foreground QSOs, with proper line of sight tangential separations of 0.50, 0.82, and 1.10 h^{-1} Mpc. We estimate that the ionizing flux from the foreground QSO should increase the photoionization rate by a factor (94, 13, 13) in these three cases, which would be clearly detectable in the first QSO and marginally so in the other two. We do not detect the transverse proximity effect. Three possible explanations are provided: an increase of the gas density in the vicinity of QSOs, time variability, and anisotropy of the QSO emission. We find that the increase of gas density near QSOs can be important if they are located in the most massive halos present at high redshift, but is not enough to fully explain the absence of the transverse proximity effect. Anisotropy requires an unrealistically small opening angle of the QSO emission. Variability demands that the luminosity of the QSO with the largest predicted effect was much lower 10^6 years ago, whereas the transverse proximity effect observed in the HeII Lya absorption in QSO 0302-003 by Jakobsen et al. (2003) implies a lifetime longer than 10^7 years. A combination of all three effects may better explain the lack of Lya absorption reduction. A larger sample of QSO pairs may be used to diagnose the environment, anisotropy and lifetime distribution of QSOs.Comment: 27 pages, 13 figures, accepted by 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