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At least 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

EMBEDDED PROTOSTARS IN THE DUST, ICE, AND GAS IN TIME (DIGIT) HERSCHEL KEY PROGRAM: CONTINUUM SEDs, AND AN INVENTORY OF CHARACTERISTIC FAR-INFRARED LINES FROM PACS SPECTROSCOPY

We present 50-210 {mu}m spectral scans of 30 Class 0/I protostellar sources, obtained with Herschel-PACS, and 0.5-1000 {mu}m spectral energy distributions, as part of the Dust, Ice, and Gas in Time Key Program. Some sources exhibit up to 75 H{sub 2}O lines ranging in excitation energy from 100 to 2000 K, 12 transitions of OH, and CO rotational lines ranging from J = 14 {yields} 13 up to J = 40 {yields} 39. [O I] is detected in all but one source in the entire sample; among the sources with detectable [O I] are two very low luminosity objects. The mean 63/145 {mu}m [O I] flux ratio is 17.2 {+-} 9.2. The [O I] 63 {mu}m line correlates with L{sub bol}, but not with the time-averaged outflow rate derived from low-J CO maps. [C II] emission is in general not local to the source. The sample L{sub bol} increased by 1.25 (1.06) and T{sub bol} decreased to 0.96 (0.96) of mean (median) values with the inclusion of the Herschel data. Most CO rotational diagrams are characterized by two optically thin components ( = (0.70 {+-} 1.12) x 10{sup 49} total particles). N{sub CO} correlates strongly with L{sub bol}, but neither T{sub rot} nor N{sub CO}(warm)/N{sub CO}(hot) correlates with L{sub bol}, suggesting that the total excited gas is related to the current source luminosity, but that the excitation is primarily determined by the physics of the interaction (e.g., UV-heating/shocks). Rotational temperatures for H{sub 2}O ( = 194 +/- 85 K) and OH ( = 183 +/- 117 K) are generally lower than for CO, and much of the scatter in the observations about the best fit is attributed to differences in excitation conditions and optical depths among the detected lines.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

REVERBERATION AND PHOTOIONIZATION ESTIMATES OF THE BROAD-LINE REGION RADIUS IN LOW-z QUASARS

Black hole mass estimation in quasars, especially at high redshift, involves the use of single-epoch spectra with signal-to-noise ratio and resolution that permit accurate measurement of the width of a broad line assumed to be a reliable virial estimator. Coupled with an estimate of the radius of the broad-line region (BLR) this yields the black hole mass M{sub BH}. The radius of the BLR may be inferred from an extrapolation of the correlation between source luminosity and reverberation-derived r{sub BLR} measures (the so-called Kaspi relation involving about 60 low-z sources). We are exploring a different method for estimating r{sub BLR} directly from inferred physical conditions in the BLR of each source. We report here on a comparison of r{sub BLR} estimates that come from our method and from reverberation mapping. Our ''photoionization'' method employs diagnostic line intensity ratios in the rest-frame range 1400-2000 A (Al III {lambda}1860/Si III] {lambda}1892, C IV {lambda}1549/Al III {lambda}1860) that enable derivation of the product of density and ionization parameter with the BLR distance derived from the definition of the ionization parameter. We find good agreement between our estimates of the density, ionization parameter, and r{sub BLR} and those from reverberation mapping. We suggest empirical corrections to improve the agreement between individual photoionization-derived r{sub BLR} values and those obtained from reverberation mapping. The results in this paper can be exploited to estimate M{sub BH} for large samples of high-z quasars using an appropriate virial broadening estimator. We show that the width of the UV intermediate emission lines are consistent with the width of H{beta}, thereby providing a reliable virial broadening estimator that can be measured in large samples of high-z quasars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

FIELD LINES TWISTING IN A NOISY CORONA: IMPLICATIONS FOR ENERGY STORAGE AND RELEASE, AND INITIATION OF SOLAR ERUPTIONS

We present simulations modeling closed regions of the solar corona threaded by a strong magnetic field where localized photospheric vortical motions twist the coronal field lines. The linear and nonlinear dynamics are investigated in the reduced magnetohydrodynamic regime in Cartesian geometry. Initially the magnetic field lines get twisted and the system becomes unstable to the internal kink mode, confirming and extending previous results. As typical in this kind of investigations, where initial conditions implement smooth fields and flux-tubes, we have neglected fluctuations and the fields are laminar until the instability sets in. However, previous investigations indicate that fluctuations, excited by photospheric motions and coronal dynamics, are naturally present at all scales in the coronal fields. Thus, in order to understand the effect of a photospheric vortex on a more realistic corona, we continue the simulations after kink instability sets in, when turbulent fluctuations have already developed in the corona. In the nonlinear stage the system never returns to the simple initial state with ordered twisted field lines, and kink instability does not occur again. Nevertheless, field lines get twisted, although in a disordered way, and energy accumulates at large scales through an inverse cascade. This energy can subsequently be released in micro-flares or larger flares, when interaction with neighboring structures occurs or via other mechanisms. The impact on coronal dynamics and coronal mass ejections initiation is discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Densities, temperatures, pressures, and abundances derived from O II recombination lines in H II regions and their implications

Based on high-quality observations of multiplet V1 of O II and the NLTE atomic computations of O II, we study the density and temperature of a sample of H II regions. We find that the signature for oxygen-rich clumps of high density and low temperature is absent in all objects of our sample: one extragalactic and eight Galactic H II regions. The temperatures derived from (1) recombination lines (RLs) of O II, and (2) RLs of H I together with Balmer continua are lower than those derived from forbidden lines, while the densities derived from RLs of O II are similar or smaller than densities derived from forbidden lines. Electron pressures derived from collisionally excited lines are about two times larger than those derived from RLs. These results imply that the proper abundances are those derived from RLs and suggest that other processes in addition to direct photoionization, such as dissipation of turbulent energy in shocks, magnetic reconnection, and shadowed regions, might be responsible for the large abundance discrepancy factor and t {sup 2} values observed in H II regions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

WISE J233237.05–505643.5: A double-peaked, broad-lined active galactic nucleus with a spiral-shaped radio morphology

We present radio continuum mapping, optical imaging, and spectroscopy of the newly discovered double-peaked, broad-lined active galactic nucleus (AGN) WISE J233237.05–505643.5 at redshift z = 0.3447. This source exhibits an FR-I and FR-II hybrid morphology, characterized by a bright core, jet, and Doppler-boosted lobe structures in Australian Telescope Compact Array continuum maps at 1.5, 5.6, and 9 GHz. Unlike most FR-II objects, W2332–5056 is hosted by a disk-like galaxy. The core has a projected 5'' linear radio feature that is perpendicular to the curved primary jet, hinting at unusual and complex activity within the inner 25 kpc. The multi-epoch, optical-near-IR photometric measurements indicate significant variability over a 3-20 yr baseline from the AGN component. Gemini South optical data show unusual double-peaked emission-line features: the centroids of the broad-lined components of Hα and Hβ are blueshifted with respect to the narrow lines and host galaxy by ∼3800 km s{sup –1}. We examine possible cases that involve single or double supermassive black holes in the system and discuss the required future investigations to disentangle the mysterious nature of this system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

The smooth cyclotron line in Her X-1 as seen with nuclear spectroscopic telescope array

Her X-1, one of the brightest and best studied X-ray binaries, shows a cyclotron resonant scattering feature (CRSF) near 37 keV. This makes it an ideal target for a detailed study with the Nuclear Spectroscopic Telescope Array (NuSTAR), taking advantage of its excellent hard X-ray spectral resolution. We observed Her X-1 three times, coordinated with Suzaku, during one of the high flux intervals of its 35 day superorbital period. This paper focuses on the shape and evolution of the hard X-ray spectrum. The broadband spectra can be fitted with a power law with a high-energy cutoff, an iron line, and a CRSF. We find that the CRSF has a very smooth and symmetric shape in all observations and at all pulse phases. We compare the residuals of a line with a Gaussian optical-depth profile to a Lorentzian optical-depth profile and find no significant differences, strongly constraining the very smooth shape of the line. Even though the line energy changes dramatically with pulse phase, we find that its smooth shape does not. Additionally, our data show that the continuum only changes marginally between the three observations. These changes can be explained with varying amounts of Thomson scattering in the hot corona of the accretion disk. The average, luminosity-corrected CRSF energy is lower than in past observations and follows a secular decline. The excellent data quality of NuSTAR provides the best constraint on the CRSF energy to date.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

A molecular line scan in the Hubble deep field north: Constraints on the co luminosity function and the cosmic H{sub 2} density

We present direct constraints on the CO luminosity function at high redshift and the resulting cosmic evolution of the molecular gas density, ρ{sub H{sub 2}}(z), based on a blind molecular line scan in the Hubble Deep Field North (HDF-N) using the IRAM Plateau de Bure Interferometer. Our line scan of the entire 3 mm window (79-115 GHz) covers a cosmic volume of ∼7000 Mpc{sup 3}, and redshift ranges z < 0.45, 1.01 < z < 1.89 and z > 2. We use the rich multiwavelength and spectroscopic database of the HDF-N to derive some of the best constraints on CO luminosities in high redshift galaxies to date. We combine the blind CO detections in our molecular line scan (presented in a companion paper) with stacked CO limits from galaxies with available spectroscopic redshifts (slit or mask spectroscopy from Keck and grism spectroscopy from the Hubble Space Telescope) to give first blind constraints on high-z CO luminosity functions and the cosmic evolution of the H{sub 2} mass density ρ{sub H{sub 2}}(z) out to redshifts z ∼ 3. A comparison to empirical predictions of ρ{sub H{sub 2}}(z) shows that the securely detected sources in our molecular line scan already provide significant contributions to the predicted ρ{sub H{sub 2}}(z) in the redshift bins (z) ∼ 1.5 and (z) ∼ 2.7. Accounting for galaxies with CO luminosities that are not probed by our observations results in cosmic molecular gas densities ρ{sub H{sub 2}}(z) that are higher than current predictions. We note, however, that the current uncertainties (in particular the luminosity limits, number of detections, as well as cosmic volume probed) are significant, a situation that is about to change with the emerging ALMA observatory.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Determining inclinations of active galactic nuclei via their narrow-line region kinematics. II. Correlation with observed properties

Active galactic nuclei (AGNs) are axisymmetric systems to first order; their observed properties are likely strong functions of inclination with respect to our line of sight, yet the specific inclinations of all but a few AGNs are generally unknown. By determining the inclinations and geometries of nearby Seyfert galaxies using the kinematics of their narrow-line regions (NLRs) and comparing them with observed properties, we find strong correlations between inclination and total hydrogen column density, infrared color, and Hβ FWHM. These correlations provide evidence that the orientation of AGNs with respect to our line of sight affects how we perceive them beyond the Seyfert 1/2 dichotomy. They can also be used to constrain three-dimensional models of AGN components such as the broad-line region and torus. Additionally, we find weak correlations between AGN luminosity and several modeled NLR parameters, which suggests that the NLR geometry and kinematics are dependent to some degree on the AGN's radiation field.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Star formation rates from [C II] 158 μm and mid-infrared emission lines for starbursts and active galactic nuclei

A summary is presented for 130 galaxies observed with the Herschel Photodetector Array Camera and Spectrometer instrument to measure fluxes for the [C II] 158 μm emission line. Sources cover a wide range of active galactic nucleus to starburst classifications, as derived from polycyclic aromatic hydrocarbon strength measured with the Spitzer Infrared Spectrograph. Redshifts from [C II] and line to continuum strengths (equivalent width (EW) of [C II]) are given for the full sample, which includes 18 new [C II] flux measures. Calibration of L([C II)]) as a star formation rate (SFR) indicator is determined by comparing [C II] luminosities with mid-infrared [Ne II] and [Ne III] emission line luminosities; this gives the same result as determining SFR using bolometric luminosities of reradiating dust from starbursts: log SFR = log L([C II)]) – 7.0, for SFR in M{sub ☉} yr{sup –1} and L([C II]) in L{sub ☉}. We conclude that L([C II]) can be used to measure SFR in any source to a precision of ∼50%, even if total source luminosities are dominated by an active galactic nucleus (AGN) component. The line to continuum ratio at 158 μm, EW([C II]), is not significantly greater for starbursts (median EW([C II]) = 1.0 μm) compared to composites and AGNs (median EW([C II]) = 0.7 μm), showing that the far-infrared continuum at 158 μm scales with [C II] regardless of classification. This indicates that the continuum at 158 μm also arises primarily from the starburst component within any source, giving log SFR = log νL{sub ν}(158 μm) – 42.8 for SFR in M{sub ☉} yr{sup –1} and νL{sub ν}(158 μm) in erg s{sup –1}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Star formation relations and CO spectral line energy distributions across the J-ladder and redshift

We present FIR [50-300 μm]–CO luminosity relations (i.e., log L{sub FIR}=αlog L{sub CO}{sup ′}+β) for the full CO rotational ladder from J = 1-0 up to J = 13-12 for a sample of 62 local (z ≤ 0.1) (Ultra) Luminous Infrared Galaxies (LIRGs; L {sub IR[8-1000} {sub μm]} > 10{sup 11} L {sub ☉}) using data from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts (z > 1) by including 35 submillimeter selected dusty star forming galaxies from the literature with robust CO observations, and sufficiently well-sampled FIR/submillimeter spectral energy distributions (SEDs), so that accurate FIR luminosities can be determined. The addition of luminous starbursts at high redshifts enlarge the range of the FIR–CO luminosity relations toward the high-IR-luminosity end, while also significantly increasing the small amount of mid-J/high-J CO line data (J = 5-4 and higher) that was available prior to Herschel. This new data set (both in terms of IR luminosity and J-ladder) reveals linear FIR–CO luminosity relations (i.e., α ≅ 1) for J = 1-0 up to J = 5-4, with a nearly constant normalization (β ∼ 2). In the simplest physical scenario, this is expected from the (also) linear FIR–(molecular line) relations recently found for the dense gas tracer lines (HCN and CS), as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However, from J = 6-5 and up to the J = 13-12 transition, we find an increasingly sublinear slope and higher normalization constant with increasing J. We argue that these are caused by a warm (∼100 K) and dense (>10{sup 4} cm{sup –3}) gas component whose thermal state is unlikely to be maintained by star-formation-powered far-UV radiation fields (and thus is no longer directly tied to the star formation rate). We suggest that mechanical heating (e.g., supernova-driven turbulence and shocks), and not cosmic rays, is the more likely source of energy for this component. The global CO spectral line energy distributions, which remain highly excited from J = 6-5 up to J = 13-12, are found to be a generic feature of the (U)LIRGs in our sample, and further support the presence of this gas component.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Strong nebular line ratios in the spectra of z ∼ 2-3 star forming galaxies: first results from KBSS-MOSFIRE

We present initial results of a deep near-IR spectroscopic survey covering the 15 fields of the Keck Baryonic Structure Survey using the recently commissioned MOSFIRE spectrometer on the Keck 1 telescope. We focus on a sample of 251 galaxies with redshifts 2.0 < z < 2.6, star formation rates (SFRs) 2 ≲ SFR ≲ 200 M {sub ☉} yr{sup –1}, and stellar masses 8.6 < log (M {sub *}/M {sub ☉}) < 11.4, with high-quality spectra in both H- and K-band atmospheric windows. We show unambiguously that the locus of z ∼ 2.3 galaxies in the 'BPT' nebular diagnostic diagram exhibits an almost entirely disjointed, yet similarly tight, relationship between the line ratios [N II] λ6585/Hα and [O III]/Hβ as compared to local galaxies. Using photoionization models, we argue that the offset of the z ∼ 2.3 BPT locus relative to that at z ∼ 0 is caused by a combination of harder stellar ionizing radiation field, higher ionization parameter, and higher N/O at a given O/H compared to most local galaxies, and that the position of a galaxy along the z ∼ 2.3 star-forming BPT locus is surprisingly insensitive to gas-phase oxygen abundance. The observed nebular emission line ratios are most easily reproduced by models in which the net stellar ionizing radiation field resembles a blackbody with effective temperature T {sub eff} = 50, 000-60, 000 K, the gas-phase oxygen abundances lie in the range 0.2 < Z/Z {sub ☉} < 1.0, and the ratio of gas-phase N/O is close to the solar value. We critically assess the applicability at high redshift of commonly used strong line indices for estimating gas-phase metallicity, and consider the implications of the small intrinsic scatter of the empirical relationship between excitation-sensitive line indices and M {sub *} (i.e., the 'mass-metallicity' relation) at z ≅ 2.3.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

MAGNETIC FIELD LINE RANDOM WALK IN ISOTROPIC TURBULENCE WITH ZERO MEAN FIELD

In astrophysical plasmas, magnetic field lines often guide the motions of thermal and non-thermal particles. The field line random walk (FLRW) is typically considered to depend on the Kubo number R = (b/B {sub 0})(ℓ{sub ∥}/ℓ ) for rms magnetic fluctuation b, large-scale mean field B {sub 0}, and parallel and perpendicular coherence scales ℓ{sub ∥} and ℓ , respectively. Here we examine the FLRW when R → ∞ by taking B {sub 0} → 0 for finite b{sub z} (fluctuation component along B {sub 0}), which differs from the well-studied route with b{sub z} = 0 or b{sub z} << B {sub 0} as the turbulence becomes quasi-two-dimensional (quasi-2D). Fluctuations with B {sub 0} = 0 are typically isotropic, which serves as a reasonable model of interstellar turbulence. We use a non-perturbative analytic framework based on Corrsin's hypothesis to determine closed-form solutions for the asymptotic field line diffusion coefficient for three versions of the theory, which are directly related to the k {sup –1} or k {sup –2} moment of the power spectrum. We test these theories by performing computer simulations of the FLRW, obtaining the ratio of diffusion coefficients for two different parameterizations of a field line. Comparing this with theoretical ratios, the random ballistic decorrelation version of the theory agrees well with the simulations. All results exhibit an analog to Bohm diffusion. In the quasi-2D limit, previous works have shown that Corrsin-based theories deviate substantially from simulation results, but here we find that as B {sub 0} → 0, they remain in reasonable agreement. We conclude that their applicability is limited not by large R, but rather by quasi-two-dimensionality.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

CONTINUUM INTENSITY AND [O i] SPECTRAL LINE PROFILES IN SOLAR 3D PHOTOSPHERIC MODELS: THE EFFECT OF MAGNETIC FIELDS

The importance of magnetic fields in three-dimensional (3D) magnetoconvection models of the Sun’s photosphere is investigated in terms of their influence on the continuum intensity at different viewing inclination angles and on the intensity profile of two [O i] spectral lines. We use the RH numerical radiative transfer code to perform a posteriori spectral synthesis on the same time series of magnetoconvection models used in our publications on the effect of magnetic fields on abundance determination. We obtain a good match of the synthetic disk-center continuum intensity to the absolute continuum values from the Fourier Transform Spectrometer (FTS) observational spectrum; the match of the center-to-limb variation synthetic data to observations is also good, thanks, in part, to the 3D radiation transfer capabilities of the RH code. The different levels of magnetic flux in the numerical time series do not modify the quality of the match. Concerning the targeted [O i] spectral lines, we find, instead, that magnetic fields lead to nonnegligible changes in the synthetic spectrum, with larger average magnetic flux causing both of the lines to become noticeably weaker. The photospheric oxygen abundance that one would derive if instead using nonmagnetic numerical models would thus be lower by a few to several centidex. The inclusion of magnetic fields is confirmed to be important for improving the current modeling of the Sun, here in particular in terms of spectral line formation and of deriving consistent chemical abundances. These results may shed further light on the still controversial issue regarding the precise value of the solar oxygen abundance.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Weak emission-line quasars in the context of a modified Baldwin effect

We investigate the relationship between the rest-frame equivalent width (EW) of the C iv λ1549 broad-emission line, monochromatic luminosity at rest-frame 5100 Å, and the Hβ-based Eddington ratio in a sample of 99 ordinary quasars across the widest possible ranges of redshift (0<z<3.5) and bolometric luminosity (10{sup 44}≲L≲10{sup 48} erg s{sup −1}). We find that EW(C iv) is primarily anti-correlated with the Eddington ratio, a relation we refer to as a modified Baldwin effect (MBE), an extension of the result previously obtained for quasars at z<0.5. Based on the MBE, weak emission line quasars (WLQs), typically showing EW(C iv)≲10 Å, are expected to have extremely high Eddington ratios. By selecting all WLQs with archival Hβ and C iv spectroscopic data, nine sources in total, we find that their Hβ-based Eddington ratios are typical of ordinary quasars with similar redshifts and luminosities. Four of these WLQs can be accommodated by the MBE, but the other five deviate significantly from this relation, at the ≳3σ level, by exhibiting C iv lines much weaker than predicted from their Hβ-based Eddington ratios. Assuming the supermassive black hole masses in all quasars can be determined reliably using the single-epoch Hβ-method, our results indicate that EW(C iv) cannot depend solely on the Eddington ratio. We briefly discuss a strategy for further investigation into the roles that basic physical properties play in controlling the relative strengths of broad-emission lines in quasars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Predictions for the reverberating spectral line from a newly formed black hole accretion disk: Case of tidal disruption flares

Tidal disruption events (TDEs) can be perfect probes of dormant supermassive black holes in normal galaxies. During the rising phase, the accretion luminosity can increase by orders of magnitude in several weeks, and the emergent ionizing radiation illuminates the fresh accretion flow. In this paper, we simulated the evolution of the expected spectral line profile of iron due to such a flare by using a ray-tracing code with effects of general relativity taken into account. We found that the time-dependent profile changes significantly with black hole spin, inclination angle with respect to the black hole equatorial plane, and the expansion velocity of the ionization front. At low values of spin, a “loop” feature appears in the line profile versus time plot when the inclination is no less than 30° and the expansion velocity v{sub exp} is no less than half the speed of light, owing to a shadow in the emission of the truncated disk. In the light curve two peaks occur depending on the inclination angle. At large v{sub exp}, a shallow “nose” feature may develop ahead of the loop; its duration depends on the expansion velocity and the inclination angle. We explore the entire interval of black hole spin parameter ranging from extreme prograde to extreme retrograde rotation, −1<a<1. In the prograde case, a low-energy tail appears to be more pronounced in the evolving centroid energy of the line. Our results demonstrate the importance of searching for X-ray spectral lines in the early phase of TDE flares in order to constrain black hole mass and spin, as well as properties of the innermost accretion flow.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

FAINT CO LINE WINGS IN FOUR STAR-FORMING (ULTRA)LUMINOUS INFRARED GALAXIES

We report the results of a search for large velocity width, low-intensity line wings—a commonly used signature of molecular outflows—in four low redshift (ultra)luminous infrared galaxies that appear to be dominated by star formation. The targets were drawn from a sample of fourteen targets presented in Chung et al., who showed the stacked CO spectrum of the sample to exhibit 1000 km s{sup −1}-wide line wings. We obtained sensitive, wide bandwidth imaging of our targets using the IRAM Plateau de Bure Interferometer. We detect each target at very high significance but do not find the claimed line wings in these four targets. Instead, we constrain the flux in the line wings to be only a few percent. Casting our results as mass outflow rates following Cicone et al. we show them to be consistent with a picture in which very high mass loading factors preferentially occur in systems with high active galactic nucleus contributions to their bolometric luminosity. We identify one of our targets, IRAS 05083 (VII Zw 31), as a candidate molecular outflow.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

POLARIZED LINE FORMATION IN MOVING ATMOSPHERES WITH PARTIAL FREQUENCY REDISTRIBUTION AND A WEAK MAGNETIC FIELD

The dynamical state of the solar and stellar atmospheres depends on the macroscopic velocity fields prevailing within them. The presence of such velocity fields in the line formation regions strongly affects the polarized radiation field emerging from these atmospheres. Thus it becomes necessary to solve the radiative transfer equation for polarized lines in moving atmospheres. Solutions based on the “observer’s frame method” are computationally expensive to obtain, especially when partial frequency redistribution (PRD) in line scattering and large-amplitude velocity fields are taken into account. In this paper we present an efficient alternative method of solution, namely, the comoving frame technique, to solve the polarized PRD line formation problems in the presence of velocity fields. We consider one-dimensional planar isothermal atmospheres with vertical velocity fields. We present a study of the effect of velocity fields on the emergent linear polarization profiles formed in optically thick moving atmospheres. We show that the comoving frame method is far superior when compared to the observer’s frame method in terms of the computational speed and memory requirements.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Microlensing constraints on broad absorption and emission line flows in the quasar H1413+117

We present new integral field spectroscopy of the gravitationally lensed broad absorption line (BAL) quasar H1413+117, covering the ultraviolet restframe spectral range. We observe strong microlensing signatures in lensed image D, and we use this microlensing to simultaneously constrain both the broad emission and broad absorption line gas. The wavelength independence of image D magnifications across the broad emission lines (BELs) indicates a lower limit on the broad emission line region (BELR) size equal to the Einstein radius (ER) of the system: ≳11 (〈M〉/M{sub ⊙}){sup 0.5} lt-day for a lens redshift of 1.4 and ≳15 (〈M〉/M{sub ⊙}){sup 0.5} lt-day for z{sub L} = 0.94. Lensing simulations verify that the observed wavelength independence is very unlikely for BELRs with significant velocity stratification at size scales below an ER. We perform spectral decomposition to derive the intrinsic BEL and continuum spectrum, subject to BAL absorption. We reconstruct the intrinsic BAL absorption profile, whose features allow us to constrain outflow kinematics in the context of a disk-wind model. We find a very sharp, blueshifted onset of absorption of 1500 km s{sup −1} in both C iv and N v, which may correspond to an inner edge of a disk-wind’s radial outflow. The lower ionization Si iv and Al iii have higher-velocity absorption onsets, consistent with a decreasing ionization parameter with radius in an accelerating outflow. There is evidence of strong absorption in the BEL component, which indicates a high covering factor for absorption over two orders of magnitude in outflow radius.

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