arXiv subjects

A. Lundgren

Publications and source records attributed to A. Lundgren.

At least 19 recordsLinked to original sources

arXiv2025

CONCERTO: forward modeling of interferograms for calibration

The CarbON [CII] line in post-rEionisation and ReionisaTiOn epoch (CONCERTO) instrument is a low-resolution mapping Fourier-transform spectrometer, based on lumped-element kinetic inductance detector (LEKID) technology, operating at 130- 310 GHz. It was installed on the 12-meter APEX telescope in Chile in April 2021 and operated until December 2022. CONCERTO's main science goal is to constrain the [CII] line fluctuations at high redshift. To reach that goal CONCERTO observed 1.4 deg2 in the COSMOS field. To ensure accurate calibration of the data, we have developed a forward model capable of simulating both the spectral response and the corresponding interferograms for each scan of observation in the COSMOS field. We present the modeling approach that enables us to reproduce the expected instrument outputs under controlled input conditions and provides a framework for the different calibration steps, including the absolute brightness calibration of the spectra. We constructed a dedicated analysis pipeline to characterize the raw interferometric data (interferograms) obtained under a broad range of atmospheric conditions at APEX. Using the forward model, we measured the interferogram alignment with the optical path difference (zero path difference, ZPD) and the relative response of each KID (flatfield). Together, these elements enable a robust characterization of the instrument's spectral brightness calibration.

astro-ph.IM↗

arXiv2025

Continuum, CO and Water vapour maps of the Orion Nebula. First millimetre spectral imaging with Concerto

The millimetre spectrum of Galactic regions and galaxies is rich in continuum and molecular lines. This diversity is mostly explored using either broad-band photometry or high-resolution heterodyne spectroscopy. We aim to map the millimetre continuum emission of Galactic regions with an intermediate spectral resolution between broad-band photometry and heterodyne spectroscopy, enabling us to rapidly cover large sky areas with spectroscopy. We report observations of the Orion Nebula with the CONCERTO instrument, which was installed at the APEX telescope focal plane from 2021 to 2023. We find that the spectrum of Orion is dominated by dust emission with an emissivity index ranging between 1.3 and 2.0, along with strong CO(2-1) and H$_2$O lines, which are naturally separated from the continuum due to the CONCERTO spectral capabilities. Many regions also show strong free-free emission at lower frequencies. We demonstrate the spectral capabilities of CONCERTO at intermediate spectral resolution, with a frequency coverage from 130 to 310 GHz. A sensitivity of 200 mK is achieved in one second, for one beam and a 6 GHz frequency width, over an 18 arcmin diameter field of view, which is within a factor of three of the expectations. We show that we can spectrally disentangle the continuum from the CO line emission, but the line is not resolved at a resolution of $\sim 8000\ \mathrm{km s^{-1}}$. The slope of the millimetre continuum is line-free mapped for the first time in Orion.

astro-ph.GA↗

arXiv2024

Central molecular zones in galaxies: 13CO(6-5) and molecular gas conditions in bright nearby galaxies

We summarize all available 13CO and accompanying 12CO measurements of local galaxy centers in transitions of J=5-4 and higher, including new APEX 13CO(6-5) and 12CO(6-5) observations of 11 galaxies. The observed integrated temperature ratios of 12CO(6-5) to 12CO(1-0) range from 0.10 to 0.45. Multi-aperture data indicate that 13CO(6-5) is more centrally concentrated than 12CO(6-5). The emission of 12CO(6-5) and HCO+ but not HCN may be correlated. The new data are essential to constrain the physical properties of the galaxy center molecular gas even in a simple two-phase model approximating the more complex multi-phase structure. In all galaxies, except the Seyfert AGN galaxy NGC 1068, high J emission from the center is dominated by a dense (n = 100 000) and relatively cool (T = 20 to 60 K) high-pressure gas. In contrast, the low-J lines are dominated in most galaxies by low-pressure gas of a moderate density (n = 1000) and more elevated temperature (T = 60 to 150 K). The three exceptions with significant high-pressure gas contributions to the low J emission are all associated with active central star formation.

astro-ph.GA↗

arXiv2024

CONCERTO at APEX -- On-sky performance in continuum

We present the data-processing algorithms and the performance of CONCERTO (CarbON CII line in post-rEionisation and ReionisaTiOn epoch) in continuum by analysing the data from the commissioning and scientific observations. The beam pattern is characterized by an effective FWHM of 31.9 $\pm$ 0.6" and 34.4 $\pm$ 1.0" for high-frequency (HF) and low-frequency (LF) bands. The main beam is slightly elongated with a mean eccentricity of 0.46. Two error beams of $\sim$65" and $\sim$130" are characterized, enabling the estimate of a main beam efficiency of $\sim$0.52. The field of view is accurately reconstructed and presents coherent distortions between the HF and LF arrays. LEKID parameters were robustly determined for 80% of the read tones. Cross-talks between LEKIDs are the first cause of flagging, followed by an excess of eccentricity for $\sim$10% of the LEKIDs, all located in a given region of the field of view. On the 44 scans of Uranus selected for the absolute photometric calibration, 72.5% and 78.2% of the LEKIDs are selected as valid detectors with a probability >70%. By comparing Uranus measurements with a model, we obtain calibration factors of 19.5$\pm$0.6 [Hz/Jy] and 25.6$\pm$0.9 [Hz/Jy] for HF and LF. The point-source continuum measurement uncertainties are 3.0% and 3.4% for HF and LF bands. The RMS of CONCERTO maps is verified to evolve as proportional to the inverse square root of integration time. The measured NEFDs for HF and LF are 115$\pm$2 mJy/beam$\cdot$s$^{1/2}$ and 95$\pm$1 mJy/beam$\cdot$s$^{1/2}$, obtained using CONCERTO data on the COSMOS field for a mean precipitable water vapour and elevation of 0.81 mm and 55.7 deg. CONCERTO demonstrates unique capabilities in fast dual-band spectral mapping with a $\sim$18.5' instantaneous field-of-view. CONCERTO's performance in continuum is perfectly in line with expectations.

astro-ph.IM↗

arXiv2024

Molecular gas excitation in the circumgalactic medium of MACS1931-26

The evolution of galaxies is largely affected by exchanging material with their close environment, the circumgalactic medium (CGM). In this work, we investigate the CGM and the interstellar medium (ISM) of the bright central galaxy (BCG) of the galaxy cluster, MACS1931-26 at z~0.35. We detected [CI](2-1), CO(1-0), and CO(7-6) emission lines with the APEX 12-m and NRO 45-m telescopes. We complemented these single-dish observations with CO(1-0), CO(3-2), and CO(4-3) ALMA interferometric data and inferred the cold molecular hydrogen physical properties. Using a modified large velocity gradient (LVG) model, we modelled the CO and CI emission of the CGM and BCG to extract the gas thermodynamical properties, including the kinetic temperature, the density, and the virialisation factor. Our study shows that the gas in the BCG is highly excited, comparable to the gas in local ultra luminous infrared galaxies (ULIRGs), while the CGM is likely less excited, colder, less dense, and less bound compared to the ISM of the BCG. The molecular hydrogen mass of the whole system derived using [CI](2-1) is larger than the mass derived from CO(1-0) in literature, showing that part of the gas in this system is CO-poor. Additional spatially resolved CI observations in both transitions, CO(1-0) and [CI](2-1), and the completion of the CO SLED with higher CO transitions are crucial to trace the different phases of the gas in such systems and constrain their properties.

astro-ph.GA↗

arXiv2024

A possible relation between global CO excitation and massive molecular outflows in local ULIRGs

Local ULIRGs host ubiquitous molecular outflows, including the most massive and powerful ever detected. These sources have also exceptionally excited global, galaxy-integrated CO ladders. A connection between outflows and molecular gas excitation has however never been established, since previous multi-J CO surveys were limited in spectral resolution and sensitivity and so could only probe the global molecular gas conditions. We address this question using new, ground-based, sensitive heterodyne spectroscopy of multiple CO rotational lines (up to CO(7-6)) in a sample of 17 local ULIRGs. We used the APEX telescope to survey the CO($J_{up}\geq4$) lines at a high signal-to-noise ratio, and complemented these data with CO($J_{up}\leq3$) observations presented in Montoya Arroyave et al. (2023). We detected 74 (out of 75) CO lines, with up to six transitions per source. Some CO SLEDs peak at $J_{up}\sim3,4$, which we classify as 'lower excitation', while others plateau or keep increasing up to the highest-J CO transition probed, and we classify these as 'higher excitation'. Our analysis includes the results of CO SLED fits performed with a single large velocity gradient component, but our main focus is the investigation of possible links between global CO excitation and the presence of broad and/or high-velocity CO spectral components that can contain outflowing gas. We discovered an increasing trend of line width as a function of $J_{up}$ of the CO transition, which is significant at the $4\sigma$ level and appears to be driven by the eight sources classified as 'higher excitation'. For such ULIRGs we found that the CO ladders are more excited for spectral components characterised by higher velocities and/or velocity dispersion. We favour an interpretation whereby the highly excited CO-emitting gas in ULIRGs resides in galactic-scale massive molecular outflows.

astro-ph.GA↗

arXiv2023

The Quasar Feedback Survey: characterising CO excitation in quasar host galaxies

We present a comprehensive study of the molecular gas properties of 17 Type 2 quasars at $z <$ 0.2 from the Quasar Feedback Survey (L$_{[OIII]}$ > $10^{42.1}$ $\rm ergs^{-1}$), selected by their high [OIII] luminosities and displaying a large diversity of radio jet properties, but dominated by LIRG-like galaxies. With these data, we are able to investigate the impact of AGN and AGN feedback mechanisms on the global molecular interstellar medium. Using APEX and ALMA ACA observations, we measure the total molecular gas content using the CO(1-0) emission and homogeneously sample the CO spectral line energy distributions (SLEDs), observing CO transitions (J$_{up}$ = 1, 2, 3, 6, 7). We observe high $r_{21}$ ratios (r$_{21}$ = L'$_{CO(2-1)}$/L'$_{CO(1-0)}$) with a median $r_{21}$ = 1.06, similar to local (U)LIRGs (with $r_{21}$ $\sim$ 1) and higher than normal star-forming galaxies (with r$_{21}$ $\sim$ 0.65). Despite the high $r_{21}$ values, for the 7 targets with the required data we find low excitation in CO(6-5) & CO(7-6) ($r_{61}$ and $r_{62}$ < 0.6 in all but one target), unlike high redshift quasars in the literature, which are far more luminous and show higher line ratios. The ionised gas traced by [OIII] exhibit systematically higher velocities than the molecular gas traced by CO. We conclude that any effects of quasar feedback (e.g. via outflows and radio jets) do not have a significant instantaneous impact on the global molecular gas content and excitation and we suggest that it only occurs on more localised scales.

astro-ph.GA↗

arXiv2023

Bright beacons? ALMA non-detection of a supposedly bright [OI] 63-um line in a redshift-6 dusty galaxy

We report a non-detection of the [OI] 63-um emission line from the z = 6.03 galaxy G09.83808 using ALMA Band 9 observations, refuting the previously claimed detection with APEX by (Rybak et al. 2020); the new upper limit on the [OI] 63-um flux is almost 20-times lower. [OI] 63-um line could be a powerful tracer of neutral gas in the Epoch of Reionisation: yet our null result shows that detecting [OI] 63-um from z$\geq$6 galaxies is more challenging than previously hypothesised.

astro-ph.GA↗

arXiv2023

A sensitive APEX and ALMA CO(1-0), CO(2-1), CO(3-2), and [CI](1-0) spectral survey of 40 local (U)LIRGs

We present a high sensitivity spectral line survey of CO(1-0), CO(2-1), CO(3-2) and [CI](1-0) in 40 local (ultra) luminous infrared galaxies ((U)LIRGs), all with previous Herschel OH119 $μ$m observations. We use single-dish observations (PI and archival) conducted with APEX, complemented with ALMA and ACA data. We study the total emission and pay special attention to the extended low-surface brightness components. We find a tight correlation between low-J CO and [CI] line luminosities suggesting their emission arise from similar regions, at least when averaged over galactic scales. We estimate a median CO-to-H$_2$ conversion factor of $1.7\pm 0.5$ M$_{\odot}$ (K km s$^{-1}$ pc$^2)^{-1}$ for ULIRGs, using [CI] as an independent tracer. We derive median galaxy-integrated CO line ratios ($r_{21}$, $r_{31}$ and $r_{32}$), as well as $r_{CICO}$, significantly higher than normal star forming galaxies, confirming the exceptional molecular gas properties of ULIRGs. We find that $r_{21}$ and $r_{32}$ are poor tracers of CO excitation in ULIRGs, while $r_{31}$ shows a positive trend with $L_{IR}$ and SFR, and a negative trend with the H$_2$ gas depletion timescales ($τ_{dep}$). When studying CO line ratios as a function of gas kinematics, we find a positive relation between $r_{21}$ and $σ_v$, which can be explained by CO opacity effects. We find that the linewidths of [CI] lines are ~10% narrower than CO lines, which may suggest that the low optical depth of [CI] can challenge its detection in diffuse, low-surface brightness outflows, and so its use as a tracer of CO-dark H$_2$ gas in these components. Finally, we find that higher $L_{AGN}$ are associated to longer $τ_{dep}$, consistent with the hypothesis that AGN feedback may reduce the efficiency of star formation.

astro-ph.GA↗

arXiv2021

The Issues of Mismodelling Gravitational-Wave Data for Parameter Estimation

Bayesian inference is used to extract unknown parameters from gravitational wave signals. Detector noise is typically modelled as stationary, although data from the LIGO and Virgo detectors is not stationary. We demonstrate that the posterior of estimated waveform parameters is no longer valid under the assumption of stationarity. We show that while the posterior is unbiased, the errors will be under- or overestimated compared to the true posterior. A formalism was developed to measure the effect of the mismodelling, and found the effect of any form of non-stationarity has an effect on the results, but are not significant in certain circumstances. We demonstrate the effect of short-duration Gaussian noise bursts and persistent oscillatory modulation of the noise on binary-black-hole-like signals. In the case of short signals, non-stationarity in the data does not have a large effect on the parameter estimation, but the errors from non-stationary data containing signals lasting tens of seconds or longer will be several times worse than if the noise was stationary. Accounting for this limiting factor in parameter sensitivity could be very important for achieving accurate astronomical results, including an estimation of the Hubble parameter. This methodology for handling the non-stationarity will also be invaluable for analysis of waveforms that last minutes or longer, such as those we expect to see with the Einstein Telescope.

astro-ph.IM↗

arXiv2021

CONCERTO at APEX: installation and technical commissioning

We describe the deployment and first tests on Sky of CONCERTO, a large field-of-view (18.6arc-min) spectral-imaging instrument. The instrument operates in the range 130-310GHz from the APEX 12-meters telescope located at 5100m a.s.l. on the Chajnantor plateau. Spectra with R=1-300 are obtained using a fast (2.5Hz mechanical frequency) Fourier Transform Spectrometer (FTS), coupled to a continuous dilution cryostat with a base temperature of 60mK. Two 2152-pixels arrays of Lumped Element Kinetic Inductance Detectors (LEKID) are installed in the cryostat that also contains the cold optics and the front-end electronics. CONCERTO, installed in April 2021, generates more than 20k spectra per second during observations. We describe the final development phases, the installation and the first results obtained on Sky.

astro-ph.IM↗

arXiv2020

Dynamic Normalization for Compact Binary Coalescence Searches in Non-Stationary Noise

The output of gravitational-wave interferometers, such as LIGO and Virgo, can be highly non-stationary. Broadband detector noise can affect the detector sensitivity on the order of tens of seconds. Gravitational-wave transient searches, such as those for colliding black holes, estimate this noise in order to identify gravitational-wave events. During times of non-stationarity we see a higher rate of false events being reported. To accurately separate signal from noise, it is imperative to incorporate the changing detector state into gravitational-wave searches. We develop a new statistic which estimates the variation of the interferometric detector noise. We use this statistic to re-rank candidate events identified during LIGO-Virgo's second observing run by the PyCBC search pipeline. This results in a 5% improvement in the sensitivity volume for low mass binaries, particularly binary neutron stars mergers.

astro-ph.IM↗

arXiv2017

Physical conditions of the molecular gas in metal-poor galaxies

Studying the molecular component of the interstellar medium in metal-poor galaxies has been challenging because of the faintness of carbon monoxide emission, the most common proxy of H2. Here we present new detections of molecular gas at low metallicities, and assess the physical conditions in the gas through various CO transitions for 8 galaxies. For one, NGC 1140 (Z/Zsun ~ 0.3), two detections of 13CO isotopologues and atomic carbon, [CI](1-0), and an upper limit for HCN(1-0) are also reported. After correcting to a common beam size, we compared 12CO(2-1)/12CO(1-0) (R21) and 12CO(3-2)/12CO(1-0) (R31) line ratios of our sample with galaxies from the literature and find that only NGC 1140 shows extreme values (R21 ~ R31 ~ 2). Fitting physical models to the 12CO and 13CO emission in NGC 1140 suggests that the molecular gas is cool (kinetic temperature Tkin<=20 K), dense (H2 volume density nH2 >= $10^6$ cm$^{-3}$), with moderate CO column density (NCO ~ $10^{16}$ cm$^{-2}$) and low filling factor. Surprisingly, the [12CO]/[13CO] abundance ratio in NGC 1140 is very low (~ 8-20), lower even than the value of 24 found in the Galactic Center. The young age of the starburst in NGC 1140 precludes 13C enrichment from evolved intermediate-mass stars; instead we attribute the low ratio to charge-exchange reactions and fractionation, because of the enhanced efficiency of these processes in cool gas at moderate column densities. Fitting physical models to 12CO and [CI](1-0) emission in NGC 1140 gives an unusually low [12CO]/[12C] abundance ratio, suggesting that in this galaxy atomic carbon is at least 10 times more abundant than 12CO.

astro-ph.GA↗

arXiv2016

GRB 110715A: The peculiar multiwavelength evolution of the first afterglow detected by ALMA

We present the extensive follow-up campaign on the afterglow of GRB 110715A at 17 different wavelengths, from X-ray to radio bands, starting 81 seconds after the burst and extending up to 74 days later. We performed for the first time a GRB afterglow observation with the ALMA observatory. We find that the afterglow of GRB 110715A is very bright at optical and radio wavelengths. We use optical and near infrared spectroscopy to provide further information about the progenitor's environment and its host galaxy. The spectrum shows weak absorption features at a redshift z = 0.8225, which reveal a host galaxy environment with low ionization, column density and dynamical activity. Late deep imaging shows a very faint galaxy, consistent with the spectroscopic results. The broadband afterglow emission is modelled with synchrotron radiation using a numerical algorithm and we determine the best fit parameters using Bayesian inference in order to constrain the physical parameters of the jet and the medium in which the relativistic shock propagates. We fitted our data with a variety of models, including different density profiles and energy injections. Although the general behaviour can be roughly described by these models, none of them are able to fully explain all data points simultaneously. GRB 110715A shows the complexity of reproducing extensive multi-wavelength broadband afterglow observations, and the need of good sampling in wavelength and time and more complex models to accurately constrain the physics of GRB afterglows.

astro-ph.HE↗

arXiv2015

Magnetic and gaseous spiral arms in M83

Isotropic and anisotropic wavelet transforms are used to decompose the images of the spiral galaxy M83 in various tracers to quantify structures in a range of scales from 0.2 to 10 kpc. We used radio polarization observations at λ6 cm and 13 cm obtained with the VLA, Effelsberg and ATCA telescopes and APEX sub-mm observations at 870 μm, which are first published here, together with maps of the emission of warm dust, ionized gas, molecular gas, and atomic gas. The spatial power spectra are similar for the tracers of dust, gas, and total magnetic field, while the spectra of the ordered magnetic field are significantly different. The wavelet cross-correlation between all material tracers and total magnetic field is high, while the structures of the ordered magnetic field are poorly correlated with those of other tracers. -- The magnetic field configuration in M83 contains pronounced magnetic arms. Some of them are displaced from the corresponding material arms, while others overlap with the material arms. The magnetic field vectors at λ6 cm are aligned with the outer material arms, while significant deviations occur in the inner arms and in the bar region, possibly due to non-axisymmetric gas flows. Outside the bar region, the typical pitch angles of the material and magnetic spiral arms are very close to each other at about 10°. The typical pitch angle of the magnetic field vectors is about 20° larger than that of the material spiral arms. One of the main magnetic arms in M83 is displaced from the gaseous arms, while the other main arm overlaps a gaseous arm. We propose that a regular spiral magnetic field generated by a mean-field dynamo is compressed in material arms and partly aligned with them. The interaction of galactic dynamo action with a transient spiral pattern is a promising mechanism for producing such complicated spiral patterns as in M83.

astro-ph.GA↗

arXiv2015

A semianalytic Fisher matrix for precessing binaries with a single significant spin

Gravitational waves from a binary with a single dynamically significant spin, notably including precessing black hole-neutron star (BH-NS) binaries, let us constrain that binary's properties: the two masses and the dominant black hole spin. Based on a straightforward fourier transform of $h(t)$ enabled by the corotating frame, we show the Fisher matrix for precessing binaries can be well-approximated by an extremely simple semianalytic approximation. This approximation can be easily understood as a weighted average of independent information channels, each associated with one gravitational wave harmonic. Generalizing previous studies of nonprecessing binaries to include critical symmetry-breaking precession effects required to understand plausible astrophysical sources, our ansatz can be applied to address how well gravitational wave measurements can address a wide range of astrophysical and fundamental questions. Our approach provides a simple method to assess what parameters gravitational wave detectors can measure, how well, and why.

gr-qc↗

arXiv2015

Molecular depletion times and the CO-to-H2 conversion factor in metal-poor galaxies

Tracing molecular hydrogen content with carbon monoxide in low-metallicity galaxies has been exceedingly difficult. Here we present a new effort, with IRAM 30-m observations of 12CO(1-0) of a sample of 8 dwarf galaxies having oxygen abundances ranging from 12+logO/H=7.7 to 8.4. CO emission is detected in all galaxies, including the most metal-poor galaxy of our sample (0.1 Zsun); to our knowledge this is the largest number of 12CO(1-0) detections ever reported for galaxies with 12+logO/H<=8 (0.2 Zsun) outside the Local Group. We calculate stellar masses (Mstar) and star-formation rates (SFRs), and analyze our results by combining our observations with galaxy samples from the literature. Extending previous results for a correlation of the molecular gas depletion time, tau(dep), with Mstar and specific SFR (sSFR), we find a variation in tau(dep) of a factor of 200 or more (from <50 Myr to 10 Gyr) over a spread of 1000 in sSFR and Mstar. We exploit the variation of tau(dep) to constrain the CO-to-H2 mass conversion factor alpha(CO) at low metallicity, and assuming a power-law variation find alpha(CO) \propto (Z/Zsun)^1.9, similar to results based on dust continuum measurements compared with gas mass. By including HI measurements, we show that the fraction of total gas mass relative to the baryonic mass is higher in galaxies that are metal poor, of low mass, and of high sSFR. Finally, comparisons of the data with star-formation models of the molecular gas phases suggest that, at metallicities Z/Zsun<=0.2, there are some discrepancies with model predictions.

astro-ph.GA↗

arXiv2014

Multi-molecule ALMA observations towards the Seyfert 1 galaxy NGC 1097

The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory to explore the molecular chemistry in the presence and surroundings of an active galactic nucleus. Exploring the distribution of different molecular species allows us to understand the physical processes affecting the ISM both in the AGN vicinity as well as in the outer star forming molecular ring. We carried out 3 mm ALMA observations of HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO as well as the 13C isotopologues. All species were imaged over the central 2 kpc (~30") of the galaxy at a resolution of ~2.2"x1.5 (150 pc x 100 pc). HCO+ and CS appear to be slightly enhanced in the star forming ring. CCH, showing the largest variations across NGC 1097, is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS differences observed between AGN dominated and starburst galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally we claim the lower HCN/CS to be a combination of a small under-abundance of CS in AGNs together with excitation effects, where a high dense gas component (~10^6 cm^-3) may be more prominent in SB galaxies. However the most promising are the differences found among the dense gas tracers which, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well shielded gas in the disk, surrounding the dense material moderately exposed to X-ray radiation traced by HC3N. Finally SiO might be the innermost molecule in the disk structure.

astro-ph.GA↗