Observed Line Profiles Research Articles

Size and kinematics of the low-ionization broad emission line region from microlensing-induced line profile distortions in gravitationally lensed quasars

Microlensing-induced distortions of broad emission line profiles observed in the spectra of gravitationally lensed quasars can be used to probe the size, geometry, and kinematics of the broad-line region (BLR). To this end, single-epoch Mg ii or Halpha line profile distortions observed in five gravitationally lensed quasars, J1131-1231, J1226-0006, J1355-2257, J1339+1310, and HE0435-1223, have been compared with simulated ones. The simulations are based on three BLR models, a Keplerian disk (KD), an equatorial wind (EW), and a polar wind (PW), with different sizes, inclinations, and emissivities. The models that best reproduce the observed line profile distortions were identified using a Bayesian probabilistic approach. We find that the wide variety of observed line profile distortions can be reproduced with microlensing-induced distortions of line profiles generated by our BLR models. For J1131, J1226, and HE0435, the most likely model for the Mg ii and Halpha BLRs is either KD or EW, depending on the orientation of the magnification map with respect to the BLR axis. This shows that the line profile distortions depend on the position and orientation of the isovelocity parts of the BLR with respect to the caustic network, and not only on their different effective sizes. For the Mg ii BLRs in J1355 and J1339, the EW model is preferred. For all objects, the PW model has a lower probability. As for the high-ionization C iv BLR, we conclude that disk geometries with kinematics dominated by either Keplerian rotation or equatorial outflow best reproduce the microlensing effects on the low-ionization Mg ii and Halpha emission line profiles. The half-light radii of the Mg ii and Halpha BLRs are measured in the range of 3 to 25 light-days. We also confirm that the size of the region emitting the low-ionization lines is larger than the region emitting the high-ionization lines, with a factor of four measured between the sizes of the Mg ii and C iv emitting regions in J1339. Unexpectedly, the microlensing BLR radii of the Mg ii and Halpha BLRs are found to be systematically below the radius-luminosity ($R -L$) relations derived from reverberation mapping, confirming that the intrinsic dispersion of the BLR radii with respect to the $R-L$ relations is large, but also revealing a selection bias that affects microlensing-based BLR size measurements. This bias arises from the fact that, if microlensing-induced line profile distortions are observed in a lensed quasar, the BLR radius should be comparable to the microlensing Einstein radius, which varies only weakly with typical lens and source redshifts.

Intrinsic line profiles for X-ray fluorescent lines in SKIRT

X-ray microcalorimeter instruments are expected to spectrally resolve the intrinsic line shapes of the strongest fluorescent lines. X-ray models should therefore incorporate these intrinsic line profiles to obtain meaningful constraints from observational data. We included the intrinsic line profiles of the strongest fluorescent lines in the X-ray radiative transfer code SKIRT to model the cold-gas structure and kinematics based on high-resolution line observations from XRISM/Resolve and Athena /X-IFU. The intrinsic line profiles of the $ K and $ K lines of Cr, Mn, Fe, Co, Ni, and Cu were implemented based on a multi-Lorentzian parameterisation. Line energies are sampled from these Lorentzian components during the radiative transfer routine. In the optically thin regime, the SKIRT results match the intrinsic line profiles as measured in the laboratory. With a more complex 3D model that also includes kinematics, we find that the intrinsic line profiles are broadened and shifted to an extent that will be detectable with XRISM/Resolve; this model also demonstrates the importance of the intrinsic line shapes for constraining kinematics. We find that observed line profiles directly trace the cold-gas kinematics, without any additional radiative transfer effects. With the advent of the first XRISM/Resolve data, this update to the X-ray radiative transfer framework of SKIRT is timely and provides a unique tool for constraining the velocity structure of cold gas from X-ray microcalorimeter spectra.

Gas phase Elemental abundances in Molecular cloudS (GEMS)

Context. We explore the chemistry of the most abundant C-, O-, S-, and N-bearing species in molecular clouds, in the context of the IRAM 30 m Large Programme Gas phase Elemental abundances in Molecular Clouds (GEMS). Thus far, we have studied the impact of the variations in the temperature, density, cosmic-ray ionisation rate, and incident UV field in a set of abundant molecular species. In addition, the observed molecular abundances might be affected by turbulence which needs to be accounted for in order to have a more accurate description of the chemistry of interstellar filaments. Aims. In this work, we aim to assess the limitations introduced in the observational works when a uniform density is assumed along the line of sight for fitting the observations, developing a very simple numerical model of a turbulent box. We searched for any observational imprints that might provide useful information on the turbulent state of the cloud based on kinematical or chemical tracers. Methods. We performed a magnetohydrodynamical (MHD) simulation in order to reproduce the turbulent steady state of a turbulent box with properties typical of a molecular filament before collapse. We post-processed the results of the MHD simulation with a chemical code to predict molecular abundances, and then post-processed this cube with a radiative transfer code to create synthetic emission maps for a series of rotational transitions observed during the GEMS project. Results. From the kinematical point of view, we find that the relative alignment between the observer and the mean magnetic field direction affect the observed line profiles, obtaining larger line widths for the case when the line of sight is perpendicular to the magnetic field. These differences might be detectable even after convolution with the IRAM 30 m efficiency for a nearby molecular cloud. From the chemical point of view, we find that turbulence produces variations for the predicted abundances, but they are more or less critical depending on the chosen transition and the chemical age. When compared to real observations, the results from the turbulent simulation provides a better fit than when assuming a uniform gas distribution along the line of sight. Conclusions. In the view of our results, we conclude that taking into account turbulence when fitting observations might significantly improve the agreement with model predictions. This is especially important for sulfur bearing species which are very sensitive to the variations of density produced by turbulence at early times (0.1 Myr). The abundance of CO is also quite sensitive to turbulence when considering the evolution beyond a few 0.1 Myr.

An Expanding Accretion Disk and a Warm Disk Wind as Seen in the Spectral Evolution of HBC 722

We present a comprehensive analysis of the post-outburst evolution of the FU Ori object HBC 722 in optical/near-infrared (NIR) photometry and spectroscopy. Using a modified viscous accretion disk model, we fit the outburst epoch spectral energy distribution to determine the physical parameters of the disk, including Ṁacc=10−4.0M⊙ yr−1, R inner = 3.65 R ⊙, i = 79°, and a maximum disk temperature of Tmax=5700 K. We then use a decade of optical/NIR spectra to demonstrate a changing accretion rate drives the visible-range photometric variation, while the NIR shows the outer radius of the active accretion disk expands outward as the outburst progresses. We also identify the major components of the disk system: a plane-parallel disk atmosphere in Keplerian rotation and a two-part warm disk wind that is collimated near the star and wide-angle at larger radii. The wind is traced by classic wind lines, and appears as a narrow, low-velocity, deep absorption component in several atomic lines spanning the visible spectrum and in the CO 2.29 μm band. We compare the wind lines to those computed from wind models for other FU Ori systems and rapidly accreting young stellar disks and find a 4000–6000 K wind can explain the observed line profiles. Fitting the progenitor spectrum, we find M * = 0.2 M ⊙ and Ṁprogenitor=7.8×10−8M⊙yr−1 . Finally, we discuss HBC 722 relative to V960 Mon, another FU Ori object we have previously studied in detail.

Abundances of neutron-capture elements in selected solar-type stars

The primary objective of this study is to accurately determine the abundances of Cu, Sr, Y, Zr, Ba, La, and Ce in selected solar-type stars. This will allow us to establish observational abundance--metallicity and abundance--age relations and to explore the reasons for the excess of Ba compared to other $s$-elements in younger solar-type stars. The chosen $s$-process elements are critical diagnostics for understanding the chemical evolution of our Galaxy. We analysed HARPS spectra with a high resolution ($R$ = 115\,000) and high signal-to-noise ratio (close to 100) of main-sequence solar-type FGK stars with metallicities from $-0.15$ to +0.35 dex and ages from 2 to 14 Gyr using one-dimensional (1D) local thermodynamic equilibrium (LTE) synthesis and MARCS atmospheric models. In the procedure of fitting synthetic to observed line profiles, the free parameters included abundance and microturbulent and macroturbulent velocity. The macroturbulent velocity can substantially compensate for non-local thermodynamic equilibrium (NLTE) effects in the line core. The resulting elemental abundance X/H increases with metallicity and age for solar-type stars. The ratio of the abundances of $s$-process elements s/Fe increases with decreasing metallicity and age, while the Cu/Fe ratio increases with both metallicity and age. These observed trends agree well with published observational data and with predictions from Galactic chemical evolution (GCE) models. A small Ba/Fe enhancement of 0.08 ± 0.08 dex has been detected in seven younger stars with an average age of $2.8 0.6$ Gyr. Compared to the abundances of other $s$-process elements Ba/Fe is 0.07 and 0.08 dex higher than La and Ce on average, respectively. Furthermore, we find that the Ba/Fe ratio increases with increasing chromospheric activity. The average Ba/Fe for the three most active stars is $0.15 0.10$ dex higher than that of the other stars. Chromospheric activity, characterised by stronger magnetic fields found in active regions such as pores, spots, plages, and networks, can significantly alter the physical conditions in the formation layers of the Ba lines. Our primary conclusion is that to account for the observed excess of Ba/Fe abundance in younger stars, it is essential to use more complex atmospheric models that incorporate magnetic structures.

Size and kinematics of the C IV broad emission line region from microlensing-induced line profile distortions in two gravitationally lensed quasars

Microlensing of the broad emission line region (BLR) in gravitationally lensed quasars produces line profile distortions that can be used to probe the BLR size, geometry, and kinematics. Based on single-epoch spectroscopic data, we analyzed the C IV line profile distortions due to microlensing in two quasars, SDSS J133907.13+131039.6 (J1339) and SDSS J113803.73+031457.7 (J1138), complementing previous studies of microlensing in the quasars Q2237+0305 and J1004+4112. J1339 shows a strong, asymmetric line profile deformation, while J1138 shows a more modest, symmetric deformation, confirming the rich diversity of microlensing-induced spectral line deformations. To probe the C IV BLR, we compared the observed line profile deformations to simulated ones. The simulations are based on three simple BLR models, a Keplerian disk (KD), an equatorial wind (EW), and a polar wind (PW), of various sizes, inclinations, and emissivities. These models were convolved with microlensing magnification maps specific to the microlensed quasar images, which produced a large number of distorted line profiles. The models that best reproduce the observed line profile deformations were then identified using a Bayesian probabilistic approach. We find that the line profile deformations can be reproduced with the simple BLR models under consideration, with no need for more complex geometries or kinematics. The models with disk geometries (KD and EW) are preferred, while the PW model is definitely less likely. In J1339, the EW model is favored, while the KD model is preferred in Q2237+0305, suggesting that various kinematical models can dominate the C IV BLR. For J1339, we find the C IV BLR half-light radii to be r1/2 = 5.1−2.9+4.6 light-days and r1/2 = 6.7−3.8+6.0 light-days from spectra obtained in 2014 and 2017, respectively. They do agree within uncertainties. For J1138, the amplitude of microlensing is smaller and more dependent on the macro-magnification factor. From spectra obtained in 2005 (single epoch), we find r1/2 = 4.9−2.7+4.9 light-days and r1/2 = 12−8+13 light-days for two extreme values of the macro-magnification factor. Combining these new measurements with those previously obtained for the quasars Q2237+0305 and J1004+4112, we show that the BLR radii estimated from microlensing do follow the C IV radius–luminosity relation obtained from reverberation mapping, although the microlensing radii seem to be systematically smaller, which could indicate either a selection bias or a real offset.

A Monte Carlo Simulation on Resonant Scattering of X-Ray Line Emission in Supernova Remnants

Resonant scattering (RS) of X-ray line emission in supernova remnants (SNRs) may modify the observed line profiles and fluxes and has a potential impact on estimating the physical properties of the hot gas and hence on understanding the SNR physics, but has not been theoretically modeled ever. Here we present our Monte Carlo simulation of the RS effect on X-ray resonant-line emission, typified by the O vii Heα r line, from SNRs. We employ the physical conditions characterized by the Sedov–Taylor solution and some basic parameters similar to those in Cygnus Loop. We show that the impact of the RS effect is most significant near the edge of the remnant. The line profiles are predicted to be asymmetric because of different temperatures and photon production efficiencies of the expanding gas at different radii. We also predict the surface brightness of the line emission would decrease in the outer projected region but is slightly enhanced in the inner. The G-ratio of the O vii Heα triplet can be effectively elevated by RS in the outer region. We show that the RS effect of the O vii Heα r line in the southwestern boundary region of Cygnus Loop is nonnegligible. The observed O vii G-ratio of ∼1.8 of the region could be achieved with RS taken into account for properly elevated O abundance from the previous estimates. Additional simulation performed for the SNRs in ejecta-dominated phases like Cas A shows that RS in the shocked ejecta may have some apparent effects on the observational properties of oxygen-resonant lines.

The diversity of spectral shapes of hydrogen Lyman lines and Mg II lines in a quiescent prominence

Context. Broad sets of spectroscopic observations comprising multiple lines represent an excellent opportunity for diagnostics of the properties of the prominence plasma and the dynamics of their fine structures. However, they also bring significant challenges when they are compared with synthetic spectra provided by radiative transfer modeling. Aims. In this work, we provide a statistical spectroscopic analysis of a unique dataset of coordinated prominence observations in the Lyman lines (Lyα to Lyδ) and the Mg II k and h lines. The observed data were obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrograph on board of the Solar and Heliospheric Observatory (SoHO) satellite and the Interface Region Imaging Spectrograph (IRIS) on 22 October 2013. Only a few similar coordinated datasets of Lyman and Mg II k and h observations have ever been obtained in prominences and we present here the first analysis using these two sets of spectral lines. Moreover, for the first time, we assess the influence of noise on the statistical properties of the studied profile characteristics. Methods. We focus on the following profile characteristics: the shape of the observed line profiles based on the number of distinct peaks, the integrated line intensity, the center-to-peak ratio describing the depth of the reversal of two-peaked profiles, and the asymmetry of these peaks. Results. We show that the presence of noise has a negligible effect on the integrated intensity of all observed lines, but it significantly affects the classification of spectral profiles using the number of distinct peaks, the reversal depth, and also the peak asymmetry. We also demonstrate that by taking the influence of noise into account, we can assess which profile characteristics in which spectral lines are suitable for diagnostics of different properties of the observed prominence. For example, we show that the subordinate peaks (peaks below error bars) in the Lyman line profiles are mostly caused by noise, which means that only the dominant peaks should be used for statistical analyses or comparisons with synthetic spectra. On the other hand, in the Mg II k and h profiles, the key role in the distinction between the multi-peaked profiles with low peaks and the profiles with deep reversals is played by the dynamics of multiple fine structures located along a line of sight. The complex, multi-peaked profiles are observed in places where multiple fine structures with different line-of-sight velocities are crossing the line of sight, while the profiles with deep reversals likely correspond to instances when we observe single fine structures or more fine structures but with similar line-of-sight velocities. Conclusions. This study allows us to conclude that if we are interested in the diagnostics of the dynamics of prominence fine structures, the best approach is to use a combination of profile asymmetry in the Lyman lines together with the complex profiles of Mg II k and h lines. On the other hand, if we want to diagnose the temperature and pressure properties of individual prominence fine structures, we need to focus on the deeply reversed Mg II k and h lines in combination with the Lyman lines and to analyze the depth of the central reversal and the integrated intensities.

Exomoon Phase Curves: Toroidal Exosphere Simulations of Exo‐Ios Orbiting 8 Exoplanets in Alkali Spectroscopy

AbstractToroidal atmospheres and exospheres characterized at exoplanets may be fueled by volcanically active exomoons, often referred to as exo‐Ios. We study the neutral outgassing and volatile evolution of a close‐orbiting, evaporating satellite at eight candidate exoplanet‐exomoon systems WASP‐49,‐96,‐69,‐17 b, XO‐2N b, HAT‐P‐1 b, HD‐189733 b, and HD‐209458 b by developing a 3‐D test‐particle Monte Carlo simulation, Simulating the Evolution of Ring Particles Emergent from Natural Satellites. The module is coupled to dishoom, approximating the minimum mass‐flux needed to reproduce observations of alkali line profiles identified in dozens of transmission spectra. We focus on sputtered neutral sodium, limited by photoionization and radiative effects. By considering Earth‐, Io‐, and Enceladus‐like masses, we systematically simulate the imprint of a non‐hydrostatic medium (characteristic of volcanic exospheres) in density and velocity space using a novel Delaunay tesselation field estimator algorithm. Our results demonstrate how exomoons can considerably modulate gas density observations probed near exoplanet transit, depending on the orbital phase of the putative satellite at the time of observation. The density evolution, therefore, manifests on orbital timescales as “exomoon phase curves” from shadow to occultation. We find two regimes of density evolution, characteristic of a: (a) localized cloud and (b) an azimuthally symmetric exoring/torus, degenerate with an exoplanet atmosphere, ranging from ∼109.5±0.5 cm−2 to ∼1015±0.25 cm−2 at our leading candidate WASP‐69b I. In certain orbital architectures, the smallest evaporating satellite mass surprisingly generates the brightest sodium signal, fueling optimism for discovering photometrically indiscernible rocky exomoons. We suggest long baseline monitoring of alkali and SO2 systems in spectroscopy to search for the temporal and spatial variability predicted here.

Two-horn quiescent prominence observed in Hα and Mg II h&k lines with THEMIS and IRIS

Context. Prominences are large magnetic structures in the corona filled by cool plasma with fast evolving fine structure. Aims. We aim to better understand the plasma conditions in the fine structure of a quiescent prominence including two transient horns observed at the bottom of the cavity using the high resolution Interface Region Imaging Spectrograph (IRIS) and the MulTi-Raies (MTR) spectrograph of the Télescope Heliographique pour l’Etude du Magnétisme et des Instabilités Solaires (THEMIS) in the Canary Islands. Methods. We analysed the spectra obtained in Hα by THEMIS and Mg II by IRIS and compare them with a grid of 23 940 1D radiative transfer models which include a prominence-to-corona transition region (PCTR). The full observed profiles of Mg II in each pixel are fitted completely by synthesised profiles with ×RMS (Cross RMS; an improved version of the rolling root mean square (rRMS) method). When the RMS is below a certain threshold value, we recover the plasma conditions from the parameters of the model best fitting the observed line profile. This criterion is met in two regions (the horns and edge of the prominence) where the line profiles can generally be described as single peaked. Results. The 1D models suggest that two different kinds of model atmospheres correspond to these two regions. The region at the edge is found to be fitted mainly with isothermal and isobaric models, while the other area (the horns) is seen to be fitted with models with a PCTR that have optical thicknesses of less than 5. In the prominence edge, the theoretical relationship between the integrated intensities in Hα and Mg II is verified and corresponds to low emission measure values. In these regions the electron density is around 1010 cm−3, while it is one order of magnitude less in the horn regions around 109 cm−3. Conclusions. In the horns, we find some profiles are best fitted with models with high mean temperatures. This suggests that the hot PCTR found in the horns could be interpreted as prominence plasma in condensation phase at the bottom of the coronal cavity.

Incorporation of realistic intrinsic profiles for the Fe Kα and Fe Kβ emission lines in X-ray reprocessor models

ABSTRACT The Fe Kα fluorescent emission line from neutral matter is widely used as a diagnostic tool in X-ray spectroscopy for many astrophysical X-ray sources. The line properties can potentially be used to constrain the geometry, column density, and kinematics of the material in which the line is formed. The intrinsic width and the shape of the intrinsic line profile has been neglected thus far, because it is much smaller than the instrumental broadening in all space-based X-ray detectors before Hitomi. However, the instrumental broadening of X-ray microcalorimeters is comparable to the intrinsic line width. We have performed new calculations based on Monte Carlo simulations of the MYTORUS X-ray reprocessor spectral-fitting model that utilize parametrizations of historical high-precision laboratory measurements of the intrinsic profiles of the Fe Kα and Fe Kβ lines. A publicly available table is provided that can seamlessly replace the existing Fe Kα and Fe Kβ line spectrum in the MYTORUS model. The new table can also be used in a standalone mode (without the MYTORUS model) in order to derive empirical velocity widths, if the line-emitting matter is Compton thin. Neglecting to account for the intrinsic profiles of the Fe Kα and Fe Kβ lines can result in a significant overestimate of the velocity broadening, if the true velocity broadening is less than ${\sim} 2000 \ \rm km \ s^{-1}$. Residual artefacts may also appear in observed line profiles in data with a high signal-to-noise ratio.

A method to deconvolve stellar profiles

Context. Currently, one of the standard procedures used to determine stellar and wind parameters of massive stars involves to comparing the observed spectral lines with a grid of synthetic lines. These synthetic lines are calculated using non-local thermodynamic equilibrium radiative transfer codes. In this standard procedure, after estimating the stellar-projected rotational speed (v sin i), all synthetic models need to be convolved using this value in order to perform the comparison with the observed line and estimate the stellar parameters. Aims. In this work, we propose a methodology to deconvolve the observed line profile to one from a non-rotating star. Thus, to perform a comparison, we will not need to convolve all the synthetic profiles, saving significant time and resources. Methods. The proposed deconvolution method is based on transforming this inverse problem into an optimization of a direct problem. We propose using a Gaussian sum approximation (GSA) to obtain the line profile without the broadening effect due to stellar rotation. After selecting the most adequate model to derive the fundamental GSA parameters, we convolved it with the known v sin i in order to obtain the profile considering the v sin i. Finally, we compared this approximated line profile directly with the observed spectrum. Results. The performance of the proposed method is analyzed using synthetic and observed lines. The results show that the proposed deconvolution method yields accurate non-rotating profiles. Conclusions. The proposed approach utilizing GSA is an accurate method to deconvolve spectral lines.

TALIF at H− ion sources for the determination of the density and EDF of atomic hydrogen

The production of H− ions in negative ion sources relevant for particle accelerator facilities and neutral beam injection systems is based predominantly on the surface conversion of H atoms at a low work function surface covered with caesium (the plasma grid (PG)). Therefore, the H atom density n H and energy distribution function (EDF) close to the PG determine the amount of surface produced H− ions. As a direct method for the density and EDF determination, two-photon absorption laser induced fluorescence (TALIF) on H atoms was implemented at the ion source of the teststand BATMAN Upgrade (BUG) being the first time that this was accomplished at an H− ion source. Several challenges had to be overcome concerning the application of the diagnostic at the complex facility and the evaluation of the fluorescence signals against a bright H background. The observed line profiles suggest a Maxwellian EDF with an H atom temperature of K. The presence of highly energetic H atoms (measured by optical emission spectroscopy, (OES)) could not be resolved by the TALIF system due to the insufficient signal-to-noise ratio. Atomic densities were measured for H2 and D2 plasmas for varying ion source parameters at BUG resulting in values between m−3 and m−3 for hydrogen. For the operation with deuterium, higher atomic densities are observed for similar ion source parameters which agree well with the previous results obtained with OES.

Spiral arms in broad-line regions of active galactic nuclei

There is growing evidence that broad-line regions (BLRs) in active galactic nuclei (AGNs) have regular substructures, such as spiral arms. This is supported by the fact that the radii of BLRs measured by reverberation mapping (RM) observations are generally consistent with the self-gravitating regions of accretion disks. We showed in Paper I that the spiral arms excited by the gravitational instabilities in these regions may exist in some disk-like BLRs. Here, in the second paper of the series, we investigate the loosely wound spiral arms excited by gravitational instabilities in disk-like BLRs and present their observational characteristics. We solve the governing integro-differential equation by a matrix scheme. The emission-line profiles, velocity-delay maps, and velocity-resolved lags of the BLR spiral arms are calculated. We find that the spiral arms can explain some of the phenomena seen in observations: (1) different asymmetries in the emission-line profiles in the mean and rms spectra; (2) complex subfeatures (incomplete ellipse) in some velocity-delay maps, for example that of NGC 5548; and (3) the short timescales of the asymmetry changes in emission-line profiles (rms spectra). These features are attractive for modeling the observed line profiles and the properties of reverberation, and for revealing the details of the BLR geometry and kinematics.

Towards an automatic approach to modelling the circumgalactic medium: new tools for mock making and fitting of metal profiles in large surveys

Abstract We present two new tools for studying and modelling metal absorption lines in the circumgalactic medium. The first tool, dubbed ‘NMF Profile Maker’ (NMF–PM), uses a non-negative matrix factorization (NMF) method and provides a robust means to generate large libraries of realistic metal absorption profiles. The method is trained and tested on 650 unsaturated metal absorbers in the redshift interval z = 0.9–4.2 with column densities in the range of 11.2 ≤ log (N/cm−2) ≤ 16.3, obtained from high-resolution (R > 4000) and high-signal-to-noise ratio (S/N ≥ 10) quasar spectroscopy. To avoid spurious features, we train on infinite S/N Voigt models of the observed line profiles derived using the code ‘Monte-Carlo Absorption Line Fitter’ (MC–ALF), a novel automatic Bayesian fitting code that is the second tool we present in this work. MC–ALF is a Monte-Carlo code based on nested sampling that, without the need for any prior guess or human intervention, can decompose metal lines into individual Voigt components. Both MC–ALF and NMF–PM are made publicly available to allow the community to produce large libraries of synthetic metal profiles and to reconstruct Voigt models of absorption lines in an automatic fashion. Both tools contribute to the scientific effort of simulating and analysing metal absorbers in very large spectroscopic surveys of quasars like the ongoing Dark Energy Spectroscopic Instrument, the 4-m Multi-Object Spectroscopic Telescope, and the WHT Enhanced Area Velocity Explorer surveys.

The Spectral Line Evolution in a Semi-infinite Atmosphere with Local Time-dependent Energy Sources

The time-dependent problem of spectral line formation in a one-dimensional semi-infinite scattering and absorbing atmosphere containing a local energy source radiating equally in both directions is considered. The energy release is assumed to be non-stationary and to be either δ(t)-shaped or of the unit jump form given by the Heaviside H(t) function. The main attention is paid to the temporal dependence of the observed line profiles on the depth of energy eruption in the atmosphere. The role of scattering in the continuous spectrum is emphasized.

Being KLEVER at cosmic noon: Ionized gas outflows are inconspicuous in low-mass star-forming galaxies but prominent in massive AGN hosts

ABSTRACTWe investigate the presence of ionized gas outflows in a sample of 141 main-sequence star-forming galaxies at 1.2 < z < 2.6 from the KLEVER (KMOS Lensed Emission Lines and VElocity Review) survey. Our sample covers an exceptionally wide range of stellar masses, 8.1 < log (M⋆/M⊙) < 11.3, pushing outflow studies into the dwarf regime thanks to gravitationally lensed objects. We stack optical rest-frame emission lines (H β, [O iii], H α, and [N ii]) in different mass bins and seek for tracers of gas outflows by using a novel, physically motivated method that improves over the widely used, simplistic double Gaussian fitting. We compare the observed emission lines with the expectations from a rotating disc (disc + bulge for the most massive galaxies) model, whereby significant deviations are interpreted as a signature of outflows. We find clear evidence for outflows in the most massive, log (M⋆/M⊙) > 10.8, AGN-dominated galaxies, suggesting that AGNs may be the primary drivers of these gas flows. Surprisingly, at log (M⋆/M⊙) ≤ 9.6, the observed line profiles are fully consistent with a rotating disc model, indicating that ionized gas outflows in dwarf galaxies might play a negligible role even during the peak of cosmic star-formation activity. Finally, we find that the observed mass loading factor scales with stellar mass as expected from the TNG50 cosmological simulation, but the ionized gas mass accounts for less than 2 ${{\ \rm per\ cent}}$ of the predicted value. This suggests that either the bulk of the outflowing mass is in other gaseous phases or the current feedback models implemented in cosmological simulations need to be revised.

HCN and HCO+ in Planetary Nebulae: The Next Level

Abstract Observations of HCN and HCO+ have been carried out toward 13 planetary nebulae (PNe) using the facilities of the Arizona Radio Observatory (ARO). These nebulae represent a wide range of morphologies and ages (∼2000–28,000 yr). For both molecules, the J = 1 → 0 transitions at 88–89 GHz and the J = 3 → 2 lines at 265–267 GHz were measured, together with CO lines (J = 1 → 0, 2 → 1, and 3 → 2, depending on the source), using the ARO 12 m and Submillimeter Telescopes. HCN and HCO+ were detected with at least one transition in 10 nebulae: He 2-459, Hu 1-1, K3-52, K3-65, M1-8, M1-40, M1-59, M2-53, M4-17, and NGC 6445. HCO+ was additionally identified via two transitions in Na 2. Some observed line profiles were complex, with multiple velocity components tracing varied outflows. From radiative transfer modeling, column densities were established for HCN and HCO+: N tot(HCN) = 0.005–1.1 × 1014 and N tot(HCO+) = 0.008–9.5 × 1013 cm−2. Gas densities of n(H2) ∼ 105–107 cm−3 were also determined for all PNe. Fractional abundances with respect to H2, calculated using CO as a proxy, are f(HCN) ∼ 0.2–1.5 × 10−7 and f(HCO+) ∼ 0.3–5.1 × 10−8. The abundances of HCN and HCO+ did not significantly vary with nebular age to 28,000 yr. Combined with previous observations, at least 30 PNe contain HCN and/or HCO+, indicating that polyatomic molecules are common constituents of these objects. The data strongly support a scenario where dense ejecta from PNe seed the interstellar medium with molecular material.

ArH+ and H2O+ absorption towards luminous galaxies

Context. Along several sight lines within the Milky Way ArH+ has been ubiquitously detected with only one detection in extragalactic environments, namely along two sight lines in the redshift z = 0.89 absorber towards the lensed blazar PKS 1830-211. Being formed in predominantly atomic gas by reactions between Ar+, which were initially ionised by cosmic rays and molecular hydrogen, ArH+ has been shown to be an excellent tracer of atomic gas as well as the impinging cosmic-ray ionisation rates. Aims. In this work, we attempt to extend the observations of ArH+ in extragalactic sources to examine its use as a tracer of the atomic interstellar medium (ISM) in these galaxies. Methods. We report the detection of ArH+ towards two luminous nearby galaxies, NGC 253 and NGC 4945, and the non-detection towards Arp 220 observed using the SEPIA660 receiver on the APEX 12 m telescope. In addition, the two sidebands of this receiver allowed us to observe the NKaKc = 11,0 − 10,1 transitions of another atomic gas tracer p-H2O+ at 607.227 GHz with the ArH+ line, simultaneously. We modelled the optically thin spectra of both species and compared their observed line profiles with that of other well-known atomic gas tracers such as OH+ and o-H2O+ and diffuse and dense molecular gas tracers HF and CO, respectively. Results. Assuming that the observed absorption from the ArH+, OH+, and H2O+ molecules are affected by the same flux of cosmic rays, we investigate the properties of the different cloud layers. Based on a steady-state analysis of the chemistry of these three species and using statistical equilibrium calculations, we estimate the molecular fraction traced by ArH+ to be ∼​10−3 and find that ArH+ resides in gas volumes with low electron densities. We further study the ortho-to-para ratio of H2O+ and find that the derived ratios do not significantly deviate from the equilibrium value of three with spin temperatures greater than 15 and 24 K.

Radiative transfer modeling of the observed line profiles in G31.41+0.31

An inverse P-Cygni profile of H13CO+ (1-0) in G31.41+0.31 was recently observed, which indicates the presence of an infalling gas envelope. Also, an outflow tracer, SiO, was observed. Here, exclusive radiative transfer modelings have been implemented to generate synthetic spectra of some key species (H13 CO+, HCN, SiO, NH3, CH3 CN, CH3OH, CH3SH, and CH3NCO) and extract the physical features to infer the excitation conditions of the surroundings where they observed. The gas envelope is assumed to be accreting in a spherically symmetric system towards the central hot core region. Our principal intention was to reproduce the observed line profiles toward G31.41+0.31 and extract various physical parameters. The LTE calculation with CASSIS and non-LTE analysis with the RATRAN radiative transfer codes are considered for the modeling purpose. The best-fitted line parameters are derived, which represents the prevailing physical condition of the gas envelope. Our results suggest that an infalling gas could explain the observed line profiles of all the species mentioned above except SiO. An additional outflow component is required to confer the SiO line profile. Additionally, an astrochemical model is implemented to explain the observed abundancests various species in this source.