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Low ionization lines in high luminosity quasars: The calcium triplet
Abstract
In order to investigate where and how low ionization lines are emitted in
quasars we are studying a new collection of spectra of the CaII triplet at
$\lambda$8498, $\lambda$8542, $\lambda$8662 observed with the Very Large
Telescope (VLT) using the Infrared Spectrometer And Array Camera (ISAAC). Our
sample involves luminous quasars at intermediate redshift for which CaII
observations are almost nonexistent. We fit the CaII triplet and the OI
$\lambda$8446 line using the H$\beta$ profile as a model. We derive constraints
on the line emitting region from the relative strength of the CaII triplet, OI
$\lambda$8446 and H$\beta$.
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ISAAC, the cryogenic infrared spectrometer and array camera saw first light on the VLT on the night of 16/17 November 1998.
Broad emission lines hold fundamental clues about the kinematics and structure of the central regions in AGN. In this article we review the most robust line profile properties and correlations emerging from the best data available. We identify fundamental differences between the profiles of radio-quiet and radio-loud sources as well as differences between the high- and low-ionization lines, especially in the radio-quiet majority of AGN. An Eigenvector 1 correlation space involving FWHM Hbeta, W(FeIIopt)/W(Hbeta), and the soft X-ray spectral index provides optimal discrimination between all principal AGN types (from narrow-line Seyfert 1 to radio galaxies). Both optical and radio continuum luminosities appear to be uncorrelated with the E1 parameters. We identify two populations of radio-quiet AGN: Population A sources (with FWHM(Hbeta) ~ 4000 km s-1 and lack of a soft X-ray excess. There is growing evidence that a fundamental parameter underlying Eigenvector 1 may be the luminosity-to-mass ratio of the active nucleus (L/M), with source orientation playing a concomitant role.
We present high S/N spectra of the Hbeta region in 17 intermediate redshift (0.85= -29 while most of our low redshift sample (n=215) involve sources in the range -19>= MB>= -26. The high redshift sources show E1 parameter values and domain occupation that are similar to our low redshift sample supporting earlier findings that E1 parameters are uncorrelated with source luminosity. Elementary accretion theory can account for a systematic increase of the minimum observed Hbeta profile width with source luminosity. Narrow line Seyfert 1 sources with MB= -28 show FWHM(Hbeta) as much as 2000 km s-1 broader than those with MB= -22. A possible change in the higher redshift/luminosity sources involves systematically weaker [OIII]lambdalambda4959,5007 narrow line emission. Based on observations collected at the European Southern Observatory, Chile. Proposal ref.: ESO 68.B-0364(A). Table \ref{tab:obs} and Figs. \ref{fig:spectra} and \ref{fig:atlas} are only available in electronic form at http://www.edpsciences.org
This paper summarizes observations of Ca II emission from AGN and
discusses their implications for conditions in the emitting gas.
Observations of Ca II K and H, the infrared triplet, and the forbidden
lines near 7300 A are compiled to give a 'standard' set of line ratios
for AGN with relatively strong Fe II emission. A series of
photoionization calculations is presented which examines the conditions
needed to produce the observed emission. Special attention is paid to
the inclusion of heating due to free-free and H(-) absorption processes
which couple the near-infrared to millimeter continuum with the emitting
gas. It is found that, regardless of density or ionization parameters,
thin clouds cannot produce the observed Ca II emission. The
semiforbidden C III 1909 A/C IV 1549 A intensity ratio is not a good
indicator of the ionization parameter for this continuum. Clouds with
large column densities and ionization parameters largely reproduce the
observed carbon, calcium, and hydrogen spectrum.
This review centers on the development and application of Cloudy, a
large-scale code designed to compute the spectrum of gas in
photoionization or collisional balance. Such plasma is far from
equilibrium, and its conditions are set by the balance of a host of
microphysical processes. The development of Cloudy is a three-pronged
effort requiring advances in the underlying atomic data base, the
numerical and computational methods used in the simulation, culminating
in the application to astronomical problems. These three steps are
strongly interwoven. A complete simulation involves many hundreds of
stages of ionization, many thousands of levels, with populations
determined by a vast sea of atomic/molecular processes, many with
accurate cross sections and rate coefficients only now becoming
available. The scope of the calculations and the numerical techniques
they use, can be improved as computers grow ever faster, since previous
calculations were naturally limited by the available hardware. The final
part is the application to observations, driven in part by the
revolution in quality of spectra made possible by advances in
instrumentation. The galactic nebulae represent laboratories for
checking whether the physics of nebulae is complete and for testing
galactic chemical evolution theories, and can validate the analysis
methods to be used on the quasars. Models of ablating molecular clouds,
the likely origin of some gas in quasars, are tested by studies of the
Orion complex. Finally, the quasars themselves present the ultimate
challenge: to deduce the composition of their emitting gas from the
spectrum, determine the dependencies of this spectrum on the shape of
the ionizing continuum, correlating this with observed changes in the
spectral energy distribution, and finally to understand its dependencies
on luminosity (the Baldwin effect). Once the emission line regions of
quasars are understood, we will have a direct probe of the z <= 5
universe. Cloudy is widely used in the astronomical community, with
roughly 50 papers per year employing it. The code is a general
spectroscopic tool whose development has an impact well beyond out
specific studies.
Aims.This paper commences a series devoted to the study of the stellar
content of early-type galaxies. The goal of the series is to set
constraints on the evolutionary status of these objects. Methods:
.In this paper we describe the details of the galaxy sample, the
observations, and the data reduction. Line-strength indices and velocity
dispersions (σ) are measured in 98 early-type galaxies drawn from
different environments, and the relation of the indices with the
velocity dispersion analysed in detail. Results: .The present
sample indicates that some of the index-σ relations depend on
galaxy environment. In particular, the slope of the relation between
Balmer lines and σ is steeper for galaxies in the Virgo cluster,
small groups, and in the field than for galaxies in the Coma cluster. In
several indices there is also a significant offset in the zero point
between the relations defined by the different subsamples. The slopes of
the index-σ relation for the Virgo and low-density environment
galaxies are explained by a variation of both age and metallicity, with
velocity dispersion, as previously noted in other studies. For the
galaxies in the Coma cluster, however, the relation of the indices with
σ only requires a variation of the abundance along the σ
sequence. In agreement with other studies, we find that the models that
better reproduce the slopes are those in which the α elements vary
more than the Fe-peak elements along the σ sequence, while, at a
given σ, older galaxies show an higher α/Fe ratio.
Conclusions: .The results can be explained assuming that galaxies in the
Coma cluster have experienced a truncated star formation and chemical
enrichment history compared to a more continuous time-extended history
for their counterparts in lower density environments.
We are exploring a spectroscopic unification for all types of broad-line emitting AGNs. The four-dimensional Eigenvector 1 (4DE1) parameter space organizes quasar diversity in a sequence primarily governed by Eddington ratio. This paper considers the role of C IV λ1549 measures as 4DE1 diagnostics. We use HST archival spectra for 130 sources with S/N high enough to permit reliable C IV λ1549 broad-component measures. We find a C IV λ1549BC profile blueshift that is strongly concentrated among (largely radio-quiet [RQ]) sources with FWHM(HβBC) 4000 km s-1 (which we call Population A). Narrow-line Seyfert 1 (NLSy1; with FWHM Hβ ≤ 2000 km s-1) sources belong to this population but do not emerge as a distinct class. The systematic blueshift, widely interpreted as arising in a disk wind/outflow, is not observed in broader line AGNs (including most radio-loud [RL] sources), which we call Population B. We find new correlations involving FWHM(C IV λ1549BC), C IV λ1549 line shift, and equivalent width only among Population A sources. Sulentic et al. suggested C IV λ1549 measures enhance an apparent dichotomy between sources with FWHM(HβBC) less and greater than 4000 km s-1, suggesting that it has more significance in the context of broad-line region structure than the more commonly discussed RL versus RQ dichotomy. Black hole masses computed from FWHM C IV λ1549BC for about 80 AGNs indicate that the C IV λ1549 width is a poor virial estimator. Comparison of mass estimates derived from HβBC and C IV λ1549 reveals that the latter show different and nonlinear offsets for Population A and B sources. A significant number of sources also show narrow-line C IV λ1549 emission that must be removed before C IV λ1549BC measures can be made and interpreted effectively. We present a recipe for C IV λ1549 narrow-component extraction.
We present a spectral atlas of the Hβ region for 215 type 1 AGNs (luminous Seyfert 1/radio galaxy nuclei and low-z quasars) up to z ≈ 0.8. Line profiles and measures were derived from the database of intermediate resolution spectra (R 1000) with average continuum level S/N ratio ≈30. Parameters including rest frame equivalent width and FWHM are provided for the Fe IIopt blend at λ4570, Hβ, He II λ4686, and the [O III] λλ4959, 5007 emission lines. We extract clean broad component Hβ profiles and provide wavelength measurements at 0, 1/4, 1/2, 3/4, and 0.9 peak intensity levels in order to permit a quantitative definition of the Hβ broad component for statistical studies. We also discuss sources of uncertainty, selection effects, and biases in our sample. The data are especially important for tests of the eigenvector 1 parameter space occupation and correlation. We show that the I Zw 1 template Fe IIopt spectrum reproduces well the observed Fe IIopt emission for a wide range of line width and strength. A detailed analysis of the data within the eigenvector 1 context is deferred to a companion paper.
We present a 0.8 -5 micron spectral library of 210 cool stars observed at a resolving power of R = lambda / Delta lambda ~ 2000 with the medium-resolution infrared spectrograph, SpeX, at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The stars have well established MK spectral classifications and are mostly restricted to near-solar metallicities. The sample contains the F, G, K, and M spectral types with luminosity classes between I and V, but also includes some AGB, carbon, and S stars. In contrast to some other spectral libraries, the continuum shape of the spectra are measured and preserved in the data reduction process. The spectra are absolutely flux calibrated using Two Micron All Sky Survey (2MASS) photometry. Potential uses of the library include studying the physics of cool stars, classifying and studying embedded young clusters and optically obscured regions of the Galaxy, evolutionary population synthesis to study unresolved stellar populations in optically-obscured regions of galaxies, and synthetic photometry. The library is available in digital form from the IRTF website. Comment: accepted for publication in ApJS
We derive black hole masses for a sample of about 300 AGNs in the redshift range 0 < z < 2.5. We use the same virial velocity measure (FWHM HβBC) for all sources which represents a significant improvement over previous studies. We review methods and caveats for determining AGN black hole masses via the virial assumption for motions in the gas producing low ionization broad emission lines. We derive a corrected FWHM(Hβ BC) measure for the broad component of Hβ that better estimates the virialized line emitting component by comparing our FWHM measures with a sample of reverberated sources with Hβ radial velocity dispersion measures. We also consider the FWHM of the FeIIλ4570 blend as a potential alternative velocity estimator. We find a range of black hole mass between log MBH ∼ 6.0-10.0, where MBH is in solar masses. Estimates using corrected FWHM(Hβ), as well as FWHM(FeII) measures, reduce the number of sources with log MBH > 9.5 and suggest that extremely large MBH values (log MBH ≳ 10) may not be realistic. Derived L/LEdd values show no evidence for a significant population of super-Eddington radiators especially after correction is made for sources with extreme orientation to our line of sight. Sources with FWHM(HβBc) ≲ 4000 km s-1 show systematically higher L/LEdd and lower MBH values than broader lined AGNs (including almost all radio-loud sources).
[Abridged] We present new VLT ISAAC spectra for 30 quasars, which we combine with previous data to yield a sample of 53 intermediate redshift (z ~ 0.9 - 3.0) sources. The sample is used to explore properties of prominent lines in the Hbeta spectral region of these very luminous quasars. We find two major trends: (1) a systematic increase of minimum FWHM Hbeta with luminosity (discussed in a previous paper). This lower FWHM envelope is best fit assuming that the narrowest sources radiate near the Eddington limit, show line emission from a virialized cloud distribution, and obey a well defined broad line region size vs. luminosity relation. (2) A systematic decrease of equivalent width of [OIII] (from W ~ 15 to ~ 1 A) with increasing source bolometric luminosity (from log L ~ 43 to log L ~ 49). Further identified trends required discrimination between so-called Population A and B sources. We generate median composite spectra in six luminosity bins Pop. A sources show reasonably symmetric Lorentzian Hbeta profiles at all luminosities while Pop. B sources require two component fits involving an unshifted broad and a redshifted very broad component. Very broad Hbeta increases in strength with increasing L while the broad component remains constant resulting in an apparent "Baldwin effect" with equivalent width decreasing from W ~ 80 to ~ 20 A over our sample luminosity range. The roughly constant equivalent width shown by the Hbeta very broad component implies production in optically-thick, photoionized gas. The onset of the redshifted very broad component appears to be a critical change that occurs near the Pop. A-B boundary at FWHM Hbeta ~ 4000 km/s which we relate to a critical Eddington ratio (~ 0.2 +/- 0.1). Comment: Accepted for publication in Astronomy and Astrophysics
[LaTeX removed] Recent work has shown that it is possible to systematize quasar spectral diversity in a parameter space called ``Eigenvector 1'' (E1). We present median AGN spectra for fixed regions of the E1 (optical) parameter space (FWHM(H-beta) vs. equivalent width ratio RFE=W(FeII4570)/W(H-beta). Comparison of the median spectra for different regions show considerable differences. We suggest that an E1-driven approach to median/average spectra emphasizes significant differences between AGN, and offers more insights into AGN physics and dynamics than a single population median/average derived from a large and heterogeneous sample of sources. We find that the H-beta broad component line profile changes in shape along the E1 sequence both in average centroid shift and asymmetry. While objects with FWHM(H-beta)< 4000 km/s are well fitted by a Lorentz function, AGN with FWHM(H-beta)> 4000 km/s are well fitted if two broad line components are used: a broad (the "classical" broad line component) and a very broad/redshifted component. Comment: 1 table + 3 figures, accepted for publication in ApJL
[Latex markup removed] We recently discussed an Eigenvector 1 (E1) parameter space that provides optimal discrimination between the principal classes of broad-line Active Galactic Nuclei (AGN). In this paper we begin a search for the most important physical parameters that are likely to govern correlations and data point distribution in E1 space. We focus on the principal optical parameter plane involving the width of the H-beta broad component and the equivalent width ratio between the FeII blend at 4570 A and H-beta broad component. We show that the observed correlation for radio-quiet sources can be accounted for if it is primarily driven by the ratio of AGN luminosity to black hole mass (L/M proportional to Eddington ratio) convolved with source orientation. L/M apparently drives the radio-quiet correlation only for FWHM(H-beta) < 4000 km/s which includes Narrow Line Seyfert 1 (NLSy1) galaxies and can be said to define an AGN ``main sequence.'' Source orientation plays an increasingly important role as FWHM(H-beta) increases. We also argue that AGN lying outside the radio-quiet ``main sequence,'' and specifically those with optical FeII much stronger than expected for a given FWHM(H-beta), may all be Broad Absorption Line QSOs. Comment: 4 figures, 1 table, accepted for publication in the Astrophysical Journal
We identify a correlation space involving optical and UV emission line
parameters as well as the soft X-ray spectral index that provides optimal
discrimination between all principal classes of active galactic nuclei. Most of
the sources in our three high quality data samples show a strong
intercorrelation with narrow line Seyfert 1 (NLSy1) galaxies and steep spectrum
radio galaxies occupying opposite extrema in the space. NLSy1 sources show a
clear continuity with broader line sources indicating that they are not a
disjoint class of AGN as is sometimes suggested. We interpret the principal
intercorrelation in the parameter space as being driven by AGN luminosity to
black hole mass ratio (L/M prop. to the Eddington ratio). Source orientation no
doubt also plays an important role but it is not yet clear whether FWHM H beta
or CIV 1549 line shift is the better indicator. We tentatively identify two RQ
populations: an almost pure RQ population A with FWHM<=4000 and population B
which occupies the same parameter domain as the flat spectrum RL sources. A
possible interpretation sees Pop. A/NLSy1 as lower mass/high accretion rate
sources and Pop. B/RL sources the opposite.
We have investigated the spectro-photometric properties of the Asymptotic Giant Branch (AGB) stars and their contribution to the integrated infrared emission in simple stellar populations (SSP). Adopting analytical relations describing the evolution of these stars in the HR diagram and empirical relations for the mass-loss rate and the wind terminal velocity, we were able to model the effects of the dusty envelope around these stars, with a minimal number of parameters. We computed isochrones at different age and initial metal content. We compare our models with existing infrared colors of M giants and Mira stars and with IRAS PSC data. Contrary to previous models, in the new isochrones the mass-loss rate, which establishes the duration of the AGB phase, also determines the spectral properties of the stars. The contribution of these stars to the integrated light of the population is thus obtained in a consistent way. We find that the emission in the mid infrared is about one order of magnitude larger when dust is taken into account in an intermediate age population, irrespective of the particular mixture adopted. The dependence of the integrated colors on the metallicity and age is discussed, with particular emphasis on the problem of age-metallicity degeneracy. We show that, contrary to the case of optical or near infrared colors, the adoption of a suitable pass-band in the mid infrared allows a fair separation of the two effects. We suggest intermediate redshift elliptical galaxies as possible targets of this method of solving the age-metallicity dilemma. The new SSP models constitute a first step in a more extended study aimed at modelling the spectral properties of the galaxies from the ultraviolet to the far infrared.
We present line-strength gradients for 22 spectral indices measured in a sample of 82 early-type galaxies in different environments,including the high-density core of the Coma cluster, the Virgo cluster,poor groups,and field galaxies. We derive age and metallicity gradients, and compare the mean values with the predictions of different galaxy formation models. We explore the behaviour of individual chemical species by deriving the metallicity gradient with different indicators.We find that the strength of the metallicity gradient inferred from stellar population models depends on the specific Lick index employed. In particular, metallicity gradients obtained with CN2 and C4668 combined with Hb are steeper than when measured using Ca4227 or Fe4383. The correlation of the metallicity gradients with other parameters also depends on the specific index employed. If the metallicity gradient is obtained using CN2 and Mgb then it correlates with the central age of the galaxies. On the contrary, if Fe4383 or Ca4227 are used, the metallicity gradient correlates with the velocity dispersion gradient.This may suggests that several mechanism have helped to set the age and metallicity gradients in early-type galaxies. While we do not find any correlation between the metallicity gradient and the central velocity dispersion for galaxies in low-density environments, we find a marginal correlation between the metallicity gradient and the mass for galaxies in the centre of the Coma cluster. We also find a trend for which galaxies in denser environments show a steeper metallicity gradient than galaxies in less dense environments.We interpret these results in light of the different models to explain the differences between galaxies as a function of environment. Comment: Accepted for publication in A&A
This is the second paper of a series devoted to study the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. We use a new set of models which include an improved stellar library (MILES) to derive simple stellar population (SSP)-equivalent parameters in a sample of 98 early-type galaxies. The sample contains galaxies in the field, poor groups, and galaxies in the Virgo and Coma clusters.We find that low-density environment galaxies span a larger range in SSP age and metallicity than their counterparts in high density environments, with a tendency for lower sigma galaxies to be younger. Early-type galaxies in low-density environments appear on average ~1.5 Gyr younger and more metal rich than their counterparts in high density environments. The sample of low-density environment galaxies shows an age metallicity relation in which younger galaxies are found to be more metal rich, but only when metallicity is measured with a Fe-sensitive index. Conversely, there is no age-metallicity relation when the metallicity is measured with a Mg sensitive index. The mass-metallicity relation is only appreciable for the low-density environment galaxies when the metallicity is measured with a Mg-sensitive index and not when the metallicity is measured with other indicators. On the contrary, this relation exists for the high-density environment galaxies independently of the indicator used to measure the metallicity. This suggests a dependence of the mass-metallicity relation on the environment of the galaxies. Our data favour a scenario in which galaxies in low density environments have suffered a more extended star formation history than the galaxies in the Coma cluster, which appear to host more homogenous stellar populations. Comment: 19 pages, accepted for publication in A&A
We present the optical to near-infrared (IR) spectrum of the galaxy TSPS
J1329-0957, a red and bright member of the class of extremely red objects
(EROs) at z = 1.26. This galaxy was found in the course of the Tokyo-Stromlo
Photometry Survey (TSPS) which we are conducting in the southern sky. The
spectroscopic observations were carried out with the Gemini Multi-Object
Spectrograph (GMOS) and the Gemini Near Infra-Red Spectrograph (GNIRS) mounted
on the Gemini-South telescope. The wide wavelength coverage of 0.6 - 2.3 um
provides useful clues as to the nature of EROs while most published spectra are
limited to a narrower spectral range which is dictated by the need for
efficient redshift determination in a large survey. We compare our spectrum
with several optical composite spectra obtained in recent large surveys, and
with stellar population synthesis models. The effectiveness of using near-IR
broad-band data, instead of the spectral data, in deriving the galaxy
properties are also investigated. We find that TSPS J1329-0957 formed when the
universe was 2 - 3 Gyr old, and subsequently evolved passively to become one of
the most massive galaxies found in the z = 1 - 2 universe. Its early type and
estimated stellar mass of M* = 10^{11.5} Msun clearly point to this galaxy
being a direct ancestor of the brightest elliptical and spheroidal galaxies in
the local universe.
We present a 0.8-5 μm spectral library of 210 cool stars observed at a resolving power of R ≡ λ/Δλ ∼ 2000 with the medium-resolution infrared spectrograph, SpeX, at the 3.0 m NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. The stars have well-established MK spectral classifications and are mostly restricted to near-solar metallicities. The sample not only contains the F, G, K, and M spectral types with luminosity classes between I and V, but also includes some AGB, carbon, and S stars. In contrast to some other spectral libraries, the continuum shape of the spectra is measured and preserved in the data reduction process. The spectra are absolutely flux calibrated using the Two Micron All Sky Survey photometry. Potential uses of the library include studying the physics of cool stars, classifying and studying embedded young clusters and optically obscured regions of the Galaxy, evolutionary population synthesis to study unresolved stellar populations in optically obscured regions of galaxies and synthetic photometry. The library is available in digital form from the IRTF Web site. © 2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
Our current knowledge of active nuclei is reviewed. The importance of observational data taken over a wide range of frequencies, from radio and infrared through optical and ultraviolet to x-rays and y-rays, is emphasized. Important overall principles include the continuity from quasars and QSOs through Seyfert and radio galaxies to low-luminosity LINE-, the importance of considering roughly cylindrically symmetric (rather than spherically symmetric) structures, and that the various regions generally have different axes and planes of symmetry, and are often warped.
Fast work stations make the fitting of complex, multi-parameter models
to UV and optical spectral data practical for the average user. I will
describe an interactive tool called specfit that runs in the IRAF
environment which can fit data spanning a large in wavelength from a
variety of instruments using a -minimization technique. Data can be
input either as IRAF images or as ASCII files containing triplet entries
of wavelength, flux, and errors. A variety of functional forms can be
used to describe the continuum, emission lines and absorption lines,
including user-defined functions that are input as ASCII files. The user
has a choice of either a simplex algorithm or a Levenburg-Marquadt
procedure for minimizing . specfit can run either interactively, in
which case the user can modify parameters and display various
representations of the data and the current fit, or as a background
task.
Emission in the Ca II infrared triplet lines has been detected in at
least nine, and probably 14, active galactic nuclei, out of a total of
40 surveyed. The Ca II line strengths are roughly correlated with the
strength of optical Fe II emission and appear over a wide range of
luminosity, BLR linewidth, and forbidden O III/H-beta ratio. Calcium
emission is thus a general property of AGN that have extremely dense and
neutral gas near the active nucleus. The Ca II linewidth is correlated
with that of the 8446 A O I line, indicating that the Ca(+) zone is
intimately associated with the broad-line region. An exception is Mrk
231, in which the Ca II linewidths are significantly narrower than that
of the O I line; kinematically distinct region, perhaps in the form of a
disk, is indicated. The level of ionization in the zone that gives rise
to the optically thick calcium lines is very low, with neutral carbon
providing the shielding for the Ca(+) ions from the incident ultraviolet
continuum. If these ultradense zones are heated by a nonradiative
mechanism, as advocated by Collin-Souffrin, Joly, and others, and if
such heating occurs in the accretion disk, then the kinematical
information conveyed by the Ca II lines indicates that in general the
BLR lies close to the disk plane.
CLOUDY is a large-scale spectral synthesis code designed to simulate
fully physical conditions within an astronomical plasma and then predict
the emitted spectrum. Here we describe version 90 (C90) of the code,
paying particular attention to changes in the atomic database and
numerical methods that have affected predictions since the last publicly
available version, C84. The computational methods and uncertainties are
outlined together with the direction future development will take. The
code is freely available and is widely used in the analysis and
interpretation of emission-line spectra. Web access to the Fortran
source for CLOUDY, its documentation Hazy, and an independent electronic
form of the atomic database is also described.
The conditions of formation of the Ca II lines in AGN are investigated
and the variations of line intensities with physical parameters are
discussed. Ionization equilibrium of Ca(+) is dominated by
photoionization by L-alpha photons. Computed intensities of the IR Ca II
triplet are in good agreement with observations if the emitting gas has
a low temperature, a high density, and a high column density. The
stronger the Ca II intensity, the lower the temperature and the higher
the column density. These physical conditions are those of the optical
Fe II lines emission region. Results derived from the models confirm the
correlation found between the Ca II triplet and optical Fe II lines
observed in a sample of AGN.
We present a full-sky 100 μm map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 μm data, we have constructed a map of the dust temperature so that the 100 μm map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of H2 in molecular clouds. In contrast, high-velocity H I clouds are deficient in dust emission, as expected.
We present the updated version of the code used to compute stellar
evolutionary tracks in Padova. It is the result of a thorough revision of the
major input physics, together with the inclusion of the pre-main sequence
phase, not present in our previous releases of stellar models. Another
innovative aspect is the possibility of promptly generating accurate opacity
tables fully consistent with any selected initial chemical composition, by
coupling the OPAL opacity data at high temperatures to the molecular opacities
computed with our AESOPUS code (Marigo & Aringer 2009). In this work we present
extended sets of stellar evolutionary models for various initial chemical
compositions, while other sets with different metallicities and/or different
distributions of heavy elements are being computed. For the present release of
models we adopt the solar distribution of heavy elements from the recent
revision by Caffau et al. (2011), corresponding to a Sun's metallicity
Z=0.0152. From all computed sets of stellar tracks, we also derive isochrones
in several photometric systems. The aim is to provide the community with the
basic tools to model star clusters and galaxies by means of population
synthesis techniques.
In active galactic nucleus spectra, a series of Fe II multiplets form a pseudo-continuum that extends from the ultraviolet to the near-infrared (NIR). This emission is believed to originate in the broad-line region, and it has been known for a long time that pure photoionization fails to reproduce it in the most extreme cases, as does the collisional excitation alone. The most recent models by Sigut & Pradhan include details of the Fe II ion microphysics and cover a wide range in the ionization parameter log U
ion = (– 3.0 → –1.3) and density log n
H = (9.6 → 12.6). With the aid of such models and a spectral synthesis approach, we studied for the first time in detail the NIR emission of I Zw 1. The main goals were to confirm the role played by Lyα fluorescence mechanisms in the production of the Fe II spectrum and to construct the first semi-empirical NIR Fe II template that best represents this emission, consequently allowing its clean subtraction in other sources. A good overall match between the observed Fe II+Mg II features with those predicted by the best-fitted model was obtained, corroborating the Lyα fluorescence as a key process to understand the Fe II spectrum. The best model was fine-tuned by applying a deconvolution method to the observed Fe II+Mg II spectrum. This derived semi-empirical template was then fitted to the spectrum of Ark 564, showing that it nicely reproduced its observed Fe II+Mg II emission. Our work extends the current set of available Fe II templates into the NIR region.
[Abridged] We compute the virial mass of the central black hole (M) and the luminosity-to-mass (L/M) ratio of ~ 300 low-z quasars and luminous Seyfert 1 nuclei. We analyze: (1) whether radio-quiet and radio-loud objects show systematic differences in terms of M and L/M; (2) the influence of M and L/M on the shape of the H-beta broad component line profile; (3) the significance of the so-called "blue outliers" i.e., sources showing a significant blueshift of the [OIII] 4959, 5007 lines with respect to the narrow component of H-beta which is used as an estimator of the quasar reference frame. We show that M and L/M distributions for RQ and RL sources are likely different for samples matched in luminosity and redshift. Line profile comparisons for median spectra computed over narrow ranges of M and L/M indicate that a Lorentz function provides a better fit for higher L/M sources and a double Gaussian for lower L/M values. A second (redshifted) Gaussian component at low L/M appears as a red asymmetry frequently observed in radio-loud and radio-quiet sources with broader (FWHM > 4000 km/s) H-beta broad component profiles. This component becomes stronger in larger mass and lower L/M sources. No specific influence of radio loudness on the H-beta broad component profile is detected, although equivalent widths of H-beta broad component and especially of [OIII] 4959,5007 are larger for radio-loud sources. We identify five more "blue outlier" sources. Since these sources are, on average, one magnitude brighter than other AGNs with similar mass, they are accreting at an Eddington ratio that is 2-3 times higher. We hint at evolutionary effects that explain some of these results and reinforce the "Eigenvector 1" correlations. Comment: Accepted for publication in MNRAS
We present results of the near-infrared (IR) spectroscopy of six quasars whose redshifts range from 0.158 to 1.084. Combined with the satellite ultraviolet data, the relative line strengths of OI 1304, OI 8446, OI 11287, and the near-IR CaII triplet are given. In addition, the corresponding OI line strengths measured in normal Seyfert 1s and narrow-line Seyfert 1s are collected from the literature. These lines are thought to emerge from the same gas as do the FeII lines, so they are good tracers of the FeII emission region within a broad emission line region (BELR) in active galactic nuclei (AGNs). In order to reveal the physical condition within the relevant emission region, we performed photoionized model calculations and compared them to the observations. It suggests that a rather dense gas with density nH ~ 10^(11.5) cm-3 is present at an outer portion of the BELR, illuminated by the ionizing radiation corresponding to an ionization parameter U ~ 10^(-2.5) and is primarily responsible for the observed OI, CaII, and FeII lines, based on the resemblance of their profiles. The three OI lines are proven to be formed through Ly beta fluorescence and collisional excitation. We also show that the lambda1304 bump typically observed in AGN spectra consists of the comparable contributions of OI and SiII multiplets, and we discuss the origin of such a strong SiII emission. The results are interpreted in the context of the locally optimally emitting cloud (LOC) scenario to find the plausible gas distribution within the BELR as a function of distance from the central source and density.
Stellar populations of early-type galaxies in different environments
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