Line Survey Research Articles

MALS discovery of a rare H I 21 cm absorber at z ∼ 1.35: Origin of the absorbing gas in powerful active galactic nuclei

We report a new, rare detection of H I 21 cm absorption associated with a quasar (only six quasars are known at 1 < z < 2) toward J2339−5523 at zem = 1.3531, discovered through the MeerKAT Absorption Line Survey (MALS). The absorption profile is broad (∼400 km s−1 ), and the peak is redshifted by ∼200 km s−1 from zem. Interestingly, optical/far-UV spectra of the quasar from the Magellan-MIKE/HST-COS spectrographs do not show any absorption features associated with the 21 cm absorption, despite the coincident presence of the optical quasar and the radio core inferred from a flat-spectrum component with a flux density of ∼65 mJy at high frequencies (> 5 GHz). The simplest explanation would be that no large H I column (N(H I) > 1017 cm−2) is present toward the radio core and the optical active galactic nucleus. Based on the joint optical and radio analysis of a heterogeneous sample of 16 quasars (zmedian = 0.7) and 19 radio galaxies (zmedian = 0.4) with H I 21 cm absorption detection and matched in 1.4 GHz luminosity (L1.4 GHz), a consistent picture emerges according to which quasars primarily trace the gas in the inner circumnuclear disk and cocoon created by the interaction of the jet with interstellar medium. They (i.e., quasars) exhibit a L1.4 GHz – ΔVnull correlation and a frequent mismatch of the radio and optical spectral lines. The radio galaxies show no such correlation and likely trace the gas from the cocoon and the galaxy-wide interstellar medium outside the photoionization cone. The analysis presented here demonstrates the potential of radio spectroscopic observations to reveal the origin of the absorbing gas associated with active galactic nuclei that may be missed in optical observations.

The rotation-tunneling spectrum of 3-hydroxypropenal and confirmation of its detection toward IRAS 16293-2422 B

Context. 3-Hydroxypropenal (HOCHCHCHO) is the lower energy tautomer of malonaldehyde which displays a complex rotation-tunneling spectrum. It was detected somewhat tentatively toward the solar-type protostellar system IRAS 16293-2422 with ALMA in the framework of the Protostellar Interferometric Line Survey (PILS). Several transitions, however, had large residuals, preventing not only their detection, but also the excitation temperature of the species from being determined unambiguously. Aims. We want to extend the existing rotational line list of 3-hydroxypropenal to shed more light on the recent observational results and to facilitate additional radio astronomical searches for this molecule. Methods. We recorded and analyzed the rotation-tunneling spectrum of 3-hydroxypropenal in the frequency regions between 150 and 330 GHz and between 400 and 660 GHz. Transitions were searched for in the PILS observations of IRAS 16293-2422. Local thermodynamic equilibrium (LTE) models were carried out and compared to the observations to constrain the excitation temperature. Additional transitions were searched for in other ALMA archival data of the same source to confirm the presence of 3-hydroxypropenal. Results. More than 7500 different spectral lines, corresponding to more than 11 500 transitions, were assigned in the course of our investigation with quantum numbers 2 ≤ J ≤ 100, Ka ≤ 59, and Kc ≤ 97, resulting in a greatly improved set of spectroscopic parameters. The comparison between the LTE models and the observations yields an excitation temperature of 125 K with a column density N = 1.0 × 1015 cm−2 for this species. We identified seven additional lines of 3-hydroxypropenal that show a good agreement with the model in the ALMA archive data. Conclusions. The calculated rotation-tunneling spectrum of 3-hydroxypropenal has sufficient accuracy for radio astronomical searches. With the solution of the excitation temperature conundrum and the detection of seven more lines, we consider the detection of 3-hydroxypropenal toward IRAS 16293-2422 as secure.

NEATH − III. A molecular line survey of a simulated star-forming cloud

ABSTRACT We present synthetic line observations of a simulated molecular cloud, utilizing a self-consistent treatment of the dynamics and time-dependent chemical evolution. We investigate line emission from the three most common CO isotopologues (12CO, 13CO, C18O) and six supposed tracers of dense gas (NH3, HCN, N2H+, HCO+, CS, HNC). Our simulation produces a range of line intensities consistent with that observed in real molecular clouds. The HCN-to-CO intensity ratio is relatively invariant with column density, making HCN (and chemically similar species such as CS) a poor tracer of high-density material in the cloud. The ratio of N2H+ to HCN or CO, on the other hand, is highly selective of regions with densities above $10^{22} \, {\rm cm}^{-2}$, and the N2H+ line is a very good tracer of the dynamics of high volume density ($\gt 10^4 \, {\rm cm}^{-3}$) material. Focusing on cores formed within the simulated cloud, we find good agreement with the line intensities of an observational sample of prestellar cores, including reproducing observed CS line intensities with an undepleted elemental abundance of sulphur. However, agreement between cores formed in the simulation, and models of isolated cores which have otherwise-comparable properties, is poor. The formation from and interaction with the large-scale environment has a significant impact on the line emission properties of the cores, making isolated models unsuitable for interpreting observational data.

QUIJOTE discovery of the cation radicals HC5N+ and HC7N+

We present the discovery with the QUIJOTE line survey of the cations HC5N+ and HC7N+ in the direction of TMC-1. Seven lines with half-integer quantum numbers from J = 25/2–23/2 to 37/2–35/2 have been assigned to HC5N+ and eight lines from J = 55/2–53/2 to 71/2–69/2 to HC7N+. Both species have inverted 2Π ground electronic states with very good estimates for their B0 and ASO constants based on optical observations. The lines with the lowest J of HC5N+ exhibit multiple components due to the hyperfine structure introduced by the H and N nuclei. However, these different components collapse for the higher J. No hyperfine structure is found for any of the lines of HC7N+. The derived effective rotational and distortion constants for HC5N+ are Beff = 1336.662 ± 0.001 MHz and Deff = 27.4 ± 2.6 Hz, while for HC7N+ they are Beff = 567.85036 ± 0.00037 MHz and Deff = 4.01 ± 0.19 Hz. From the observed intensities, we derived Trot = 5.5 ± 0.5 K and N = (9.9 ± 1.0) × 1010 cm−2 for HC5N+, while we obtained Trot = 8.5 ± 0.5 K and N = (2.3 ± 0.2) × 1010 cm−2 for HC7N+. The HC5N/HC5N+, C5N/HC5N+, C5N−/HC5N+, HC7N/HC7N+, HC5N+/HC7N+, and C7N−/HC7N+ abundance ratios are 670 ± 80, 4.8 ± 0.8, 1.2 ± 0.2, 1000 ± 150, 4.2 ± 0.5, and 2.2 ± 0.2, respectively. We have run chemical modelling calculations to investigate the formation and destruction of these new cations. We find that these species are mainly formed through the reactions of H2 and the cations C5N+ and C7N+, and by the reactions of H+ with HC5N and HC7N, while they are mostly destroyed through a reaction with H2 and a dissociative recombination with electrons. Based on the underestimation of the abundances of HC5N+ and HC7N+ by the chemical model by a factor ∼20, we suggest that the rate coefficients currently assumed for the reactions of these cations with H2 could be too high by the same factor, something that will be worth investigating.

CN and CCH derivatives of ethylene and ethane: Confirmation of the detection of CH3CH2CCH in TMC-1

We present a study of CH3CH2CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN in TMC-1 using the QUIJOTE line survey. We confirm the presence of CH3CH2CCH in TMC-1, which was previously reported as tentative by our group. From a detailed study of the ethynyl and cyanide derivatives of CH2CH2 and CH3CH3 in TMC-1, we found that the CH2CHCCH/CH2CHCN and CH3CH2CCH/CH3CH2CN abundance ratios are 1.5±0.1 and 4.8±0.5, respectively. The derived CH2CHCCH/CH3CH2CCH abundance ratio is 15.3±0.8, and that of CH2CHCN over CH3CH2CN is 48±5. All the single substituted isotopologs of vinyl cyanide have been detected, and we found that the first and second carbon substitutions in CH2CHCN provide a 12C/13C ratio in line with that found for other three-carbon bearing species such as HCCNC and HNCCC. However, the third 13C isotopolog, CH2CH13CN, presents an increase in its abundance similar to that found for HCCCN. Finally, we observed eight b-type transitions of CH2CHCN, and we find that their intensity cannot be fitted adopting the dipole moment µb derived previously. These transitions involve the same rotational levels as those of the a-type transitions. From their intensity, we obtain µb = 0.80±0.03 D, which is found to be in between earlier values derived in the laboratory using intensity measurements or the Stark effect. Our chemical model indicates that the abundances of CH3CH2 CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN observed in TMC-1 can be explained in terms of gas-phase reactions.

Laboratory and astronomical discovery of cyanothioketene, NCCHCS, in the cold starless core TMC-1

We present the detection of cyanothioketene, NCCHCS, in the laboratory and toward TMC-1. This transient species was produced through a discharge of a gas mixture of CH2CHCN and CS2 using argon as carrier gas, and its rotational spectrum between 9 and 40 GHz was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer. A total of 21 rotational transitions were detected in the laboratory, all of them exhibiting hyperfine structure induced by the spin of the N nucleus. The spectrum for NCCHCS was predicted in the domain of our line surveys using the derived rotational and distortion constants. The detection in the cold starless core TMC-1 was based on the QUIJOTE1 line survey performed with the Yebes 40 m radio telescope. Twenty-three lines were detected with Ka = 0, 1, and 2 and Ju = 9 up to 14. The derived column density is (1.2 ± 0.1)×1011 cm−2 for a rotational temperature of 8.5 ± 1.0 K. The abundance ratio of thioketene and its cyano derivative, H2CCS/NCCHCS, is 6.5 ± 1.3. Although ketene is more abundant than thioketene by ∼15 times, its cyano derivative NCCHCO surprisingly is not detected with a 3σ upper level to the column density of 3.0 × 1010 cm−2, which results in an abundance ratio H2CCO/NCCHCO > 430. Hence, the chemistry of CN derivatives seems to be more favored for S-bearing than for O-bearing molecules. We carried out chemical modeling calculations and found that the gas-phase neutral-neutral reactions CCN + H2CS and CN + H2CCS could be a source of NCCHCS in TMC-1.

PRODIGE – planet-forming disks in Taurus with NOEMA

Context. The physics and chemistry of planet-forming disks are far from being fully understood. To make further progress, both broad line surveys and observations of individual tracers in a statistically significant number of disks are required. Aims. Our aim is to perform a line survey of eight planet-forming Class II disks in Taurus with the IRAM NOrthern Extended Millimeter Array (NOEMA), as a part of the MPG-IRAM Observatory Program PRODIGE (PROtostars and DIsks: Global Evolution; PIs: P. Caselli and Th. Henning). Methods. Compact and extended disks around T Tauri stars CI, CY, DG, DL, DM, DN, IQ Tau, and UZ Tau E are observed in ~80 lines from > 20 C-, O,- N-, and S-bearing species. The observations in four spectral settings at 210–280 GHz with a 1σ rms sensitivity of ~8–12 mJy beam−1 at a 0.9″ and 0.3 km s−1 resolution will be completed in 2024. The uv visibilities are fitted with the DiskFit model to obtain key stellar and disk properties. Results. In this first paper, the combined 12CO, 13CO, and C18O J = 2–1 data are presented. We find that the CO fluxes and disk masses inferred from dust continuum tentatively correlate with the CO emission sizes. We constrained dynamical stellar masses, geometries, temperatures, the CO column densities, and gas masses for each disk. The best-fit temperatures at 100 au are ~ 17–37 K, and decrease radially with the power-law exponent q ~ 0.05–0.76. The inferred CO column densities decrease radially with the power-law exponent p ~ 0.2–3.1. The gas masses estimated from 13CO (2–1) are ~0.001–0.2 M⊙. Conclusions. Using NOEMA, we confirm the presence of temperature gradients in our disk sample. The best-fit CO column densities point to severe CO freeze-out in these disks. The DL Tau disk is an outlier, and has either stronger CO depletion or lower gas mass than the rest of the sample. The CO isotopologue ratios are roughly consistent with the observed values in disks and the low-mass star-forming regions. The high 13CO/C18O ratio of ~23 in DM Tau could be indicative of strong selective photodissociation of C18O in this disk.

Limitations in Tunnel Portal Design: An Evaluation Using Numerical Models and Line Surveys

In this study, engineering geology and geotechnical design studies of a highway tunnel project, located on the route of Zonguldak-Amasra-Kurucasile, was expressed. Owing to the low overburden thickness the subjected slope tunnel, especially the right tube in accordance with the project kilometer incremental direction, will be exposed to asymmetrical load after commence of the excavation. Besides, thicknesses between right tube right wall and the slope face in this section has decreased up to 6 m level. Moreover, as the tunnel is passing under the 1st grade archeological protection area, some of the site investigation studies, such as geotechnical drilling and site laboratory works could not have been performed. Thus, this study is explaining the determination of excavation support system of slope tunnel by using engineering geology studies and numerical models. As the tunnel site is located under the 1st grade archeological protection area, any of the required geotechnical site investigation drilling studies and corresponding site testing was not performed on the tunnel axis. Instead of this, line surveys, local sampling, and internationally accepted rock mass classification studies (RMR, Q, GSI) were performed on the rock mass outcrops, which are positioned against to the Black Sea. At the conclusion of these studies, rock mass engineering properties were determined through the utilization of empirical equations that incorporate data derived from site investigation studies and laboratory test results as input.

Discovery of Thionylimide, HNSO, in Space: The first N-, S-, and O-bearing Interstellar Molecule

We present the first detection in space of thionylimide (HNSO) toward the Galactic center molecular cloud G + 0.693-0.027, thanks to the superb sensitivity of an ultradeep molecular line survey carried out with the Yebes 40 m and IRAM 30 m telescopes. This molecule is the first species detected in the interstellar medium containing, simultaneously, N, S, and O. We have identified numerous K a = 0, 1, and 2 transitions belonging to HNSO covering from J up = 2 to J up =10, including several completely unblended features. We derive a molecular column density of N = (8 ± 1)×1013 cm−2, yielding a fractional abundance relative to H2 of ∼6 × 10−10, which is about ∼37 and ∼4.8 times less abundant than SO and SO2, respectively. Although there are still many unknowns in the interstellar chemistry of NSO-bearing molecules, we propose that HNSO is likely formed through the reaction of the NSO radical and atomic H on the surface of icy grains, with alternative routes also deserving exploration. Finally, HNSO appears as a promising link between N, S, and O interstellar chemistry, and its discovery paves the route to the detection of a new family of molecules in space.

Interstellar Detection of O-protonated Carbonyl Sulfide, HOCS+

We present the first detection in space of O-protonated carbonyl sulfide (HOCS+), in the midst of an ultradeep molecular line survey toward the G+0.693-0.027 molecular cloud. From the observation of all K a = 0 transitions ranging from J lo = 2 to J lo = 13 of HOCS+ covered by our survey, we derive a column density of N = (9 ± 2) × 1012 cm−2, translating into a fractional abundance relative to H2 of ∼7 × 10−11. Conversely, the S-protonated HSCO+ isomer remains undetected, and we derive an upper limit to its abundance with respect to H2 of ≤3 × 10−11, a factor of ≥2.3 less abundant than HOCS+. We obtain an HOCS+/OCS ratio of ∼2.5 × 10−3, in good agreement with the prediction of astrochemical models. These models show that one of the main chemical routes to the interstellar formation of HOCS+ is likely the protonation of OCS, which appears to be more efficient at the oxygen end. Also, we find that high values of cosmic-ray ionization rates (10−15–10−14 s−1) are needed to reproduce the observed abundance of HOCS+. In addition, we compare the O/S ratio across different interstellar environments. G+0.693-0.027 appears as the source with the lowest O/S ratio. We find an HOCO+/HOCS+ ratio of ∼31, in accordance with other O/S molecular pairs detected toward this region and also close to the O/S solar value (∼37). This fact indicates that S is not significantly depleted within this cloud due to the action of large-scale shocks, unlike in other sources where S-bearing species remain trapped on icy dust grains.

A λ 3 mm Line Survey toward the Circumstellar Envelope of the Carbon-rich AGB Star IRC+10216 (CW Leo)

We present an unbiased λ 3 mm spectral line survey (between 84.5 and 115.8 GHz), conducted by the Purple Mountain Observatory 13.7 m radio telescope, together with updated modeling results, toward the carbon-rich asymptotic giant branch star IRC+10216 (CW Leo). A total of 75 spectral lines (96 transitions) are detected, and identified to arise from 19 molecules: C2H, l-C3H, C4H, CN, C3N, HC3N, HC5N, HCN, HNC, CH3CN, MgNC, CO, c-C3H2, SiC2, SiO, SiS, CS, C2S, C3S, and their isotopologues. Among them, one molecular emission line (H13CCCN J = 13–12) is discovered in IRC+10216 for the first time. The excitation temperature, column density, and fractional abundance of the detected species are deduced by assuming they are in local thermodynamic equilibrium. In addition, the isotopic ratios of [12C]/[13C], [32S]/[34S], [28Si]/[29Si], and [12C34S]/[13C32S] are obtained and found to be consistent with previous studies. Finally, we summarize all of the 106 species detected in IRC+10216 to date with their observed and modeled column densities for the convenience of future studies.

A deep search for large complex organic species toward IRAS16293-2422 B at 3 mm with ALMA

Complex organic molecules (COMs) have been detected ubiquitously in protostellar systems. However, at shorter wavelengths ($ sim 0.8$\,mm), it is generally more difficult to detect larger molecules than at longer wavelengths sim 3$\,mm) because of the increase in millimeter dust opacity, line confusion, and unfavorable partition function. We aim to search for large molecules (more than eight atoms) in the Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 spectrum of IRAS 16293-2422 B. In particular, the goal is to quantify the usability of ALMA Band 3 for molecular line surveys in comparison to similar studies at shorter wavelengths. We used deep ALMA Band 3 observations of IRAS 16293-2422 B to search for more than 70 molecules and identified as many lines as possible in the spectrum. The spectral settings were set to specifically target three-carbon species such as i- and n-propanol and glycerol, the next step after glycolaldehyde and ethylene glycol in the hydrogenation of CO. We then derived the column densities and excitation temperatures of the detected species and compared the ratios with respect to methanol between Band 3 ($ sim 3$\,mm) and Band 7 sim 1$\,mm, Protostellar Interferometric Line Survey) observations of this source to examine the effect of the dust optical depth. We identified lines of 31 molecules including many oxygen-bearing COMs such as CH$_3$OH, CH$_2$OHCHO, CH$_3$CH$_2$OH, and c-C$_2$H$_4$O and a few nitrogen- and sulfur-bearing ones such as HOCH$_2$CN and CH$_3$SH. The largest detected molecules are gGg-(CH$_2$OH)$_2$ and CH$_3$COCH$_3$. We did not detect glycerol or i- and n-propanol, but we do provide upper limits for them which are in line with previous laboratory and observational studies. The line density in Band 3 is only $ sim 2.5$ times lower in frequency space than in Band 7. From the detected lines in Band 3 at a $ level sim 25-30<!PCT!>$ of them could not be identified indicating the need for more laboratory data of rotational spectra. We find similar column densities and column density ratios of COMs (within a factor $ sim 2$) between Band 3 and Band 7. The effect of the dust optical depth for IRAS 16293-2422 B at an off-source location on column densities and column density ratios is minimal. Moreover, for warm protostars, long wavelength spectra ($ sim 3$\,mm) are not only crowded and complex, but they also take significantly longer integration times than shorter wavelength observations sim 0.8$\,mm) to reach the same sensitivity limit. The 3\,mm search has not yet resulted in the detection of larger and more complex molecules in warm sources. A full deep ALMA Band $2-3$ (i.e. sim 3-4$\,mm wavelengths) survey is needed to assess whether low frequency data have the potential to reveal more complex molecules in warm sources.

An ALMA Molecular Inventory of Warm Herbig Ae Disks. I. Molecular Rings, Asymmetries, and Complexity in the HD 100546 Disk

Observations of disks with the Atacama Large Millimeter/submillimeter Array (ALMA) allow us to map the chemical makeup of nearby protoplanetary disks with unprecedented spatial resolution and sensitivity. The typical outer Class II disk observed with ALMA is one with an elevated C/O ratio and a lack of oxygen-bearing complex organic molecules, but there are now some interesting exceptions: three transition disks around Herbig Ae stars all show oxygen-rich gas traced via the unique detections of the molecules SO and CH3OH. We present the first results of an ALMA line survey at ≈337–357 GHz of such disks and focus this paper on the first Herbig Ae disk to exhibit this chemical signature—HD 100546. In these data, we detect 19 different molecules including NO, SO2, and CH3OCHO (methyl formate). We also make the first tentative detections of H213CO and 34SO in protoplanetary disks. Multiple molecular species are detected in rings, which are, surprisingly, all peaking just beyond the underlying millimeter continuum ring at ≈200 au. This result demonstrates a clear connection between the large dust distribution and the chemistry in this flat disk. We discuss the physical and/or chemical origin of these substructures in relation to ongoing planet formation in the HD 100546 disk. We also investigate how similar and/or different this molecular makeup of this disk is to other chemically well-characterized Herbig Ae disks. The line-rich data we present motivate the need for more ALMA line surveys to probe the observable chemistry in Herbig Ae systems, which offer unique insight into the composition of disks ices, including complex organic molecules.

Diversity, Encounter Rate and Detection of Non-Volant Nocturnal Mammals on Two Malaysian Islands.

Nocturnal mammals constitute a crucial component of tropical faunal diversity, but not much is known about the effects of anthropogenic disturbance on the habitat use and detectability of these species. We investigated which habitat and environmental variables impact the detectability of non-volant nocturnal arboreal mammals across varying habitat types at two tropical islands with different levels of anthropogenic development in Malaysia. We conducted night transect line and point count surveys following pre-existing paths in Penang Island and Langkawi Island between 2019 and 2020. We used a head torch with red filter and a thermal imaging device (FLIR) to enhance animal detection success. We calculated the encounter rates (individual km-1) for each species as a proxy for abundance. Overall, we detected 17 species, but did not find higher species diversity in intact forested environments compared to disturbed areas. Encounter rates of the most observed species were influenced by 'time after sunset' on the highly developed island of Penang, whereas on the rural island of Langkawi, detection was higher in sites with better canopy connectivity. Different species of non-volant nocturnal arboreal mammals use their respective habitats differently and thus, are differently impacted by varying levels of anthropogenic activities. Our results provided baseline data on the diversity, encounter rate, and detectability of these highly elusive species, which can also help to further improve methodologies for the detection of nocturnal wildlife.

Effect of a Structured Integrated Obstetric Triage Model (SIOTEL) on Patient Waiting time in Maternity Units in Kiambu County – A Quasi Experimental Study

Background: Perinatal mortality and morbidity remains high in Kenya over the years, and this has been attributed to the Three Delays, the third focusing on access to care once the client is in the health facility. Structured frameworks for obstetric triage have been shown to improve perinatal outcomes across the globe. In Kenya, anecdotal evidence suggests that there is no formal framework for conducting obstetric triage in public facilities. This study sought to assess the effect of a Structured Integrated Obstetric Triage Model (SIOTEL) on patient waiting time in maternity units of Kiambu Referral Hospitals.
 Methods: A quasi experimental design was applied in the study. The intervention facility was Kiambu County Referral Hospital and control facility was Thika Level 5 Hospital. Study population included files of patients admitted in the labour wards. The intervention (SIOTEL) was a 3-scale modified Obstetric Triage Acuity Scale, a client assessment tool that was used to conduct obstetric triage. A baseline survey was conducted followed by development, validation and implementation of the tool, then an end line survey conducted to assess effect of the model on waiting time. Quantitative data was analyzed using STATA and presented in tables and graphs. T-statistic was used to test for significance of mean waiting time in the two facilities.
 Results: A total of 455 files were reviewed, 231 at baseline and 224 at endline survey. The mean client waiting time at baseline was 113.19 and 124.91 minutes in the intervention and control facilities respectively. At endline, the mean waiting time was 57.46 minutes in the intervention facility and 112.92 minutes in the control facility. Findings thus revealed a significant effect of the SIOTEL on client waiting time in the intervention facility (t-3.77;p value 0.00) compared to the control facility (t-0.78; p value 0.44)
 Conclusions and recommendations: The study concludes that implementation of structured models for obstetric triage contributes to reduction in client waiting time, and recommendations are made to adopt such models for triage in public facilities in Kenya

The First Ka-band (26.1–35 GHz) Blind Line Survey toward Orion KL

We conducted a Ka-band (26.1–35 GHz) line survey toward Orion KL using the TianMa 65 m Radio Telescope (TMRT). It is the first blind line survey in the Ka band and achieves a sensitivity at the mK level (1–3 mK at a spectral resolution of ∼1 km s−1). In total, 592 Gaussian features are extracted. Among them, 257 radio recombination lines (RRLs) are identified. The maximum Δn of RRLs of H, He, and C are 20, 15, and 5, respectively. Through stacking, we have detected the β lines of ion RRLs (RRLs of C+ with the possible contribution of other ions like O+) for the first time, and a tentative signal of the γ lines of ion RRLs can also be seen on the stacked spectrum. Besides this, 318 other line features were assigned to 37 molecular species, and 10 of these species were not detected in the Q-band survey of TMRT. The vibrationally excited states of nine species were also detected. The emission of most species can be modeled under LTE. A number of transitions of E-CH3OH (J 2 − J 1) display maser effects, which are confirmed by our modeling, and besides the bumping peak at J ∼ 6, there is another peak at J ∼ 13. Methylcyanoacetylene (CH3C3N) is detected in Orion KL for the first time. This work emphasizes that the Ka band, which was long ignored for spectral line surveys, is very useful for surveying RRLs and molecular lines simultaneously.

Doubly substituted isotopologues of HCCCN in TMC-1: Detection of D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N

We report the first detection in space of a complete sample of nine doubly substituted isotopologues of HCCCN towards the cyanopolyyne peak of TMC-1 using observations of the QUIJOTE1 line survey taken with the Yebes 40 m telescope. We detected D13CCCN, DC13CCN, DCC13CN, DCCC15N, H13C13CCN, H13CC13CN, HC13C13CN, HCC13C15N, and HC13CC15N through their J = 4 − 3 and J = 5 − 4 lines in the 7 mm window. In addition, we present an extensive analysis of the emission of HCCCN and its singly substituted isotopologues through a large velocity gradient model of the lines detected at 7 mm and 3 mm using the Yebes 40 m and the IRAM 30 m telescopes, respectively. The derived column densities for all the isotopologues are consistent in the two spectral bands for an H2 volume density of 1 × 104 cm−3 and a kinetic temperature of 10 K. Whereas we observed a 13C fractionation for HCC13CN and other double isotopologues with a 13C atom adjacent to the nitrogen atom, we derived similar C/13C abundance ratios for the three 13C substituted species of DCCCN. This suggests additional chemical discrimination for deuterated isotopologues of HCCCN. Finally, we present the spatial distribution of the J = 4 − 3 and J = 5 − 4 lines from the singly substituted species observed with the Yebes 40 m telescope. The emission peak of the spatial distribution of DCCCN appears to be displaced by ∼40″ with respect to that of HCCCN and the 13C and 15N isotopologues. In addition to a different formation route for the deuterated species, we could also expect that this differentiation owing to the deuterium fractionation is more efficient at low temperatures, and therefore, that deuterated species trace a colder region of the cloud.

Study of the HCCNC and HNCCC isotopologs in TMC-1

We present the detection of the three 13C isotopologs of HCCNC and HNCCC toward TMC-1 using the QUIJOTE line survey. In addition, the D species has also been detected for these two isomers of HCCCN, whereas the 15N isotopolog was only detected for HCCNC. Using high-J lines of HCCNC and HNCCC, we were able to derive very precise rotational temperatures, column densities, and subsequently the isotopic abundance ratios. We found that 12C/13C is ∼90 for the three possible substitutions in both isomers. These results are slightly different from what has been found for the most abundant isomer HCCCN, for which abundances of 105, 95, and 66 were found for each one of the three possible positions of 13C. The H/D abundance ratio was found to be 31 ± 4 for HCCNC and of 53 ± 6 for HNCCC. The latter is similar to the H/D abundance ratio derived for HCCCN (∼59). The 14N/15N isotopic abundance ratio in HCCNC is 243 ± 24.

The MeerKAT Absorption Line Survey (MALS) Data Release. I. Stokes I Image Catalogs at 1–1.4 GHz

The MeerKAT Absorption Line Survey (MALS) has observed 391 telescope pointings at the L band (900–1670 MHz) at δ ≲ +20°. We present radio continuum images and a catalog of 495,325 (240,321) radio sources detected at a signal-to-noise ratio (S/N) > 5 over an area of 2289 deg2 (1132 deg2) at 1006 MHz (1381 MHz). Every MALS pointing contains a central bright radio source (S 1 GHz ≳ 0.2 Jy). The median spatial resolution is 12″ (8″). The median rms noise away from the pointing center is 25 μJy beam−1 (22 μJy beam−1) and is within ∼15% of the achievable theoretical sensitivity. The flux density scale ratio and astrometric accuracy deduced from multiply observed sources in MALS are <1% (8% scatter) and 1″, respectively. Through comparisons with NVSS and FIRST at 1.4 GHz, we establish the catalog’s accuracy in the flux density scale and astrometry to be better than 6% (15% scatter) and 0.″8, respectively. The median flux density offset is higher (9%) for an alternate beam model based on holographic measurements. The MALS radio source counts at 1.4 GHz are in agreement with literature. We estimate spectral indices (α) of a subset of 125,621 sources (S/N > 8), confirm the flattening of spectral indices with decreasing flux density, and identify 140 ultra-steep-spectrum (α < −1.3) sources as prospective high-z radio galaxies (z > 2). We have identified 1308 variable and 122 transient radio sources comprising primarily active galactic nuclei that demonstrate long-term (26 yr) variability in their observed flux densities. The MALS catalogs and images are publicly available at https://mals.iucaa.in.

Discovery of thiofulminic acid with the QUIJOTE line survey: A study of the isomers of HNCS and HNCO in TMC-1

We present the first detection of HCNS (thiofulminic acid) in space with the QUIJOTE line survey in the direction of TMC-1. We performed a complete study of the isomers of CHNS and CHNO, including NCO and NCS. The derived column densities for HCNS, HNCS, and HSCN are (9.0 ± 0.5) × 109, (3.2 ± 0.1) × 1011, and (8.3 ± 0.4) × 1011 cm−2, respectively. The HNCS/HSCN abundance ratio is 0.38. The abundance ratios HNCO/HNCS, HCNO/HCNS, HOCN/HSCN, and NCO/NCS are 34 ± 4, 8.3 ± 0.7, 0.18 ± 0.03, and 0.78 ± 0.07, respectively. These ratios cannot be correctly reproduced by our gas-phase chemical models, which suggests that formation paths for these species are missing, and/or that the adopted dissociative recombination rates for their protonated precursors have to be revised. The isotopologues H15NCO, DNCO, HN13CO, DCNO, H34SCN, and DSCN have also been detected with the ultrasensitive QUIJOTE line survey.