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The structure of magnetic fields in galaxies remains poorly constrained, despite the importance of magnetism in the evolution of galaxies. Radio synchrotron and far-infrared (FIR) polarization and polarimetric observations are the best methods to measure galactic scale properties of magnetic fields in galaxies beyond the Milky Way. We use synthetic polarimetric observations of a simulated galaxy to identify and quantify the regions, scales, and interstellar medium (ISM) phases probed at FIR and radio wavelengths. Our studied suite of magnetohydrodynamical cosmological zoom-in simulations features high-resolutions (10 pc full-cell size) and multiple magnetization models. Our synthetic observations have a striking resemblance to those of observed galaxies. We find that the total and polarized radio emission extends to approximately double the altitude above the galactic disk (half-intensity disk thickness of h _I radio ∼ h _PI radio = 0.23 ± 0.03 kpc) relative to the total FIR and polarized emission that are concentrated in the disk midplane ( h _I FIR ∼ h _PI FIR = 0.11 ± 0.01 kpc). Radio emission traces magnetic fields at scales of ≳300 pc, whereas FIR emission probes magnetic fields at the smallest scales of our simulations. These scales are comparable to our spatial resolution and well below the spatial resolution (

Mergers are thought to be a fundamental channel for galaxy growth, perturbing the gas dynamics and the magnetic fields ( B -fields) in the interstellar medium (ISM). However, the mechanisms that amplify and dissipate B -fields during a merger remain unclear. We characterize the morphology of the ordered B -fields in the multiphase ISM of the closest merger of two spiral galaxies, the Antennae galaxies. We compare the inferred B -fields using 154 μ m thermal dust and 11 cm radio synchrotron emission polarimetric observations. We find that the 154 μ m B -fields are more ordered across the Antennae galaxies than the 11 cm B -fields. The turbulent-to-ordered 154 μ m B -field increases at the galaxy cores and star-forming regions. The relic spiral arm has an ordered spiral 154 μ m B -field, while the 11 cm B -field is radial. The 154 μ m B -field may be dominated by turbulent dynamos with high ^12 CO(1–0) velocity dispersion driven by star-forming regions, while the 11 cm B -field is cospatial with high H i velocity dispersion driven by galaxy interaction. This result shows the dissociation between the warm gas mainly disturbed by the merger, and the dense gas still following the dynamics of the relic spiral arm. We find a ∼8.9 kpc scale ordered B -field connecting the two galaxies. The base of the tidal tail is cospatial with the H i and ^12 CO(1–0) emission and has compressed and/or sheared 154 μ m and 11 cm B -fields driven by the merger. We suggest that amplified B -fields, with respect to the rest of the system and other spiral galaxies, may be supporting the gas flow between both galaxies and the tidal tail.

We present the analysis of the magnetic field ( B -field) structure of galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric observations. We use the first data release of the Survey of extragALactic magnetiSm with SOFIA of 14 nearby ( $\lt 20$ Mpc) galaxies with resolved ( $5^{\prime\prime} \mbox{--}18^{\prime\prime} ;$ 90 pc–1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 μ m. We compute the magnetic pitch-angle ( ${{\rm{\Psi }}}_{B}$ ) profiles as a function of the galactocentric radius. We introduce a new magnetic alignment parameter ( ζ ) to estimate the disordered-to-ordered ratio of spiral B -fields. We find FIR and radio wavelengths to not generally trace the same B -field morphology in galaxies. The ${{\rm{\Psi }}}_{B}$ profiles tend to be more ordered across all galactocentric radii in radio ( ${\zeta }_{6\mathrm{cm}}\,=\,0.93\pm 0.03$ ) than in FIR ( ${\zeta }_{154\mu {\rm{m}}}=0.84\pm 0.14$ ). For spiral galaxies, FIR B -fields are 2%–75% more turbulent than the radio B -fields. For starburst galaxies, we find that FIR polarization is a better tracer of the B -fields along the galactic outflows than radio polarization. Our results suggest that the B -fields associated with dense, dusty, turbulent star-forming regions (those traced at FIR) are less ordered than warmer, less dense regions (those traced at radio) of the interstellar medium. The FIR B -fields seem to be more sensitive to the activity of the star-forming regions and molecular clouds within a vertical height of a few hundred parsecs in the disk of spiral galaxies than the radio B -fields.

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)×10 ^13 cm ^−2 , yielding a fractional abundance relative to H _2 of ∼6 × 10 ^−10 , which is about ∼37 and ∼4.8 times less abundant than SO and SO _2 , 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.

We present a catalog of clouds identified from the ^12 CO (1–0) data of M83, which was observed using the Atacama Large Millimeter/submillimeter Array with a spatial resolution of ∼46 pc and a mass sensitivity of ∼10 ^4 M _⊙ (3 σ ). The almost full-disk coverage and high sensitivity of the data allowed us to sample 5724 molecular clouds with a median mass of ∼1.9 × 10 ^5 M _⊙ , which is comparable to the most frequently sampled mass of giant molecular clouds by surveys in the Milky Way (MW). About 60% of the total CO luminosity in M83's disk arises from clouds more massive than 10 ^6 M _⊙ . Such massive clouds comprise 16% of the total clouds in number and tend to concentrate toward the arm, bar, and center, while smaller clouds are more prevalent in interarm regions. Most >10 ^6 M _⊙ clouds have peak brightness temperatures T _peak above 2 K with the current resolution. Comparing the observed cloud properties with the scaling relations determined by P. M. Solomon et al. ( 1987 , hereafter S87 ), T _peak > 2 K clouds follow the relations, but T _peak < 2 K clouds, which are dominant in number, deviate significantly. Without considering the effect of beam dilution, the deviations would suggest modestly high virial parameters (median α _vir ∼ 2.7) and low surface mass densities (median Σ ∼ 22 M _⊙ pc ^−2 ) for the entire cloud samples, which are similar to values found for the MW clouds by T. S. Rice et al. ( 2016 ) and M.-A Miville-Deschênes et al. ( 2017 ). However, once beam dilution is taken into account, the observed α _vir and Σ for a majority of the clouds (mostly T _peak

We report the first detection of the metal-bearing molecules sodium sulfide and magnesium sulfide and the tentative detection of calcium monoxide in the interstellar medium toward the Galactic center molecular cloud G+0.693-0.027. The derived column densities are (5.0 ± 1.1) × 10 ^10 cm ^−2 , (6.0 ± 0.6) × 10 ^10 cm ^−2 , and (2.0 ± 0.5) × 10 ^10 cm ^−2 , respectively. This translates into fractional abundances with respect to H _2 of (3.7 ± 1.0) × 10 ^−13 , (4.4 ± 0.8) × 10 ^−13 , and (1.5 ± 0.4) × 10 ^−13 , respectively. We have also searched for other Na-, Mg-, and Ca-bearing species toward this source but none of them have been detected and thus we provide upper limits for their abundances. We discuss the possible chemical routes involved in the formation of these molecules containing metals under interstellar conditions. Finally, we compare the ratio between sulfur-bearing and oxygen-bearing molecules with and without metals, finding that metal-bearing sulfur molecules are much more abundant than metal-bearing oxygen ones, in contrast with the general trend found in the ratios between other nonmetal-oxygen- and sulfur-bearing molecules. This further strengthens the idea that sulfur may be a little depleted in G+0.693-0.027 as a result of the low-velocity shocks present in this source sputtering large amounts of material from dust grains.

We report on Atacama Large Millimeter/submillimeter Array observations of polarized dust emission at 1.2 mm from NGC6334I, a source known for its significant flux outbursts. Between five months, our data show no substantial change in total intensity and a modest 8% variation in linear polarization, suggesting a phase of stability or the conclusion of the outburst. The magnetic field, inferred from this polarized emission, displays a predominantly radial pattern from northwest to southeast with intricate disturbances across major cores, hinting at spiral structures. Energy analysis of CS ( J = 5 → 4) emission yields an outflow energy of approximately 3.5 × 10 ^45 erg, aligning with previous interferometric studies. Utilizing the Davis–Chandrasekhar–Fermi method, we determined magnetic field strengths ranging from 1 to 11 mG, averaging at 1.9 mG. This average increases to 4 ± 1 mG when incorporating Zeeman measurements. Comparative analyses using gravitational, thermal, and kinetic energy maps reveal that magnetic energy is significantly weaker, possibly explaining the observed field morphology. We also find that the energy in the outflows and the expanding cometary HII region is also larger than the magnetic energy, suggesting that protostellar feedback may be the dominant driver behind the injection of turbulence in NGC6334I at the scales sampled by our data. The gas in NGC6334I predominantly exhibits supersonic and trans-Alfvenic conditions, transitioning towards a super-Alfvenic regime, underscoring a diminished influence of the magnetic field with increasing gas density. These observations are in agreement with prior polarization studies at 220 GHz, enriching our understanding of the dynamic processes in high-mass star-forming regions.

We report the first detection in the interstellar medium of N -cyanomethanimine (H _2 CNCN), the stable dimer of HCN of highest energy and the most complex organic molecule identified in space containing the prebiotically relevant NCN backbone. We have identified a plethora of a -type rotational transitions with 3 ≤ J _up ≤ 11 and K _a ≤ 2 that belong to this species toward the Galactic center G+0.693-0.027 molecular cloud, the only interstellar source showing the three cyanomethanimine isomers (including the Z - and E -isomers of C -cyanomethanimine, HNCHCN). We have derived a total column density for H _2 CNCN of (2.9 ± 0.1) × 10 ^12 cm ^−2 , which translates into a total molecular abundance with respect to H _2 of (2.1 ± 0.3) × 10 ^−11 . We have also revisited the previous detection of E - and Z -HNCHCN and found a total C / N -cyanomethanimine abundance ratio of 31.8 ± 1.8 and a Z / E -HNCHCN ratio of 4.5 ± 0.2. While the latter can be explained on the basis of thermodynamic equilibrium, chemical kinetics are more likely responsible for the observed C / N -cyanomethanimine abundance ratio, where the gas-phase reaction between methanimine (CH _2 NH) and the cyanogen radical (CN) arises as the primary formation route.

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) × 10 ^12 cm ^−2 , translating into a fractional abundance relative to H _2 of ∼7 × 10 ^−11 . Conversely, the S-protonated HSCO ^+ isomer remains undetected, and we derive an upper limit to its abundance with respect to H _2 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.

Molecular lines are powerful diagnostics of the physical and chemical properties of the interstellar medium (ISM). These ISM properties, which affect future star formation, are expected to differ in starburst galaxies from those of more quiescent galaxies. We investigate the ISM properties in the central molecular zone of the nearby starburst galaxy NGC 253 using the ultrawide millimeter spectral scan survey from the Atacama Large Millimeter/submillimeter Array Large Program ALCHEMI. We present an atlas of velocity-integrated images at a 1.″6 resolution of 148 unblended transitions from 44 species, including the first extragalactic detection of HCNH ^+ and the first interferometric images of C _3 H ^+ , NO, and HCS ^+ . We conduct a principal component analysis (PCA) on these images to extract correlated chemical species and to identify key groups of diagnostic transitions. To the best of our knowledge, our data set is currently the largest astronomical set of molecular lines to which PCA has been applied. The PCA can categorize transitions coming from different physical components in NGC 253 such as (i) young starburst tracers characterized by high-excitation transitions of HC _3 N and complex organic molecules versus tracers of on-going star formation (radio recombination lines) and high-excitation transitions of CCH and CN tracing photodissociation regions, (ii) tracers of cloud-collision-induced shocks (low-excitation transitions of CH _3 OH, HNCO, HOCO ^+ , and OCS) versus shocks from star formation-induced outflows (high-excitation transitions of SiO), as well as (iii) outflows showing emission from HOC ^+ , CCH, H _3 O ^+ , CO isotopologues, HCN, HCO ^+ , CS, and CN. Our findings show these intensities vary with galactic dynamics, star formation activities, and stellar feedback.

We present a spatially resolved excitation analysis for the central molecular zone (CMZ) of the starburst galaxy NGC 253 using the data from the Atacama Large Millimeter/submillimeter Array Comprehensive High-resolution Extragalactic Molecular Inventory, whereby we explore parameters distinguishing NGC 253 from the quiescent Milky Way’s Galactic center (GC). Non-LTE analyses employing a hierarchical Bayesian framework are applied to Band 3–7 transitions from nine molecular species to delineate the position–position–velocity distributions of column density ( ${N}_{{{\rm{H}}}_{2}}$ ), volume density ( ${n}_{{{\rm{H}}}_{2}}$ ), and temperature ( T _kin ) at 27 pc resolution. Two distinct components are detected: a low-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\sim ({10}^{3.3}\ {\mathrm{cm}}^{-3},85\ {\rm{K}})$ and a high-density component with $({n}_{{{\rm{H}}}_{2}},{T}_{\mathrm{kin}})\,\sim ({10}^{4.4}\ {\mathrm{cm}}^{-3},110\ {\rm{K}})$ , separated at ${n}_{{{\rm{H}}}_{2}}\sim {10}^{3.8}\ {\mathrm{cm}}^{-3}$ . NGC 253 has ∼10 times the high-density gas mass and ∼3 times the dense-gas mass fraction of the GC. These properties are consistent with their HCN/CO ratio but cannot alone explain the factor of ∼30 difference in their star formation efficiencies (SFEs), contradicting the dense-gas mass to star formation rate scaling law. The ${n}_{{{\rm{H}}}_{2}}$ histogram toward NGC 253 exhibits a shallow declining slope up to ${n}_{{{\rm{H}}}_{2}}\sim {10}^{6}\ {\mathrm{cm}}^{-3}$ , while that of the GC steeply drops in ${n}_{{{\rm{H}}}_{2}}\gtrsim {10}^{4.5}\ {\mathrm{cm}}^{-3}$ and vanishes at 10 ^5 cm ^−3 . Their dense-gas mass fraction ratio becomes consistent with their SFEs when the threshold ${n}_{{{\rm{H}}}_{2}}$ for the dense gas is taken at ∼10 ^4.2−4.6 cm ^−3 . The rich abundance of gas above this density range in the NGC 253 CMZ, or its scarcity in the GC, is likely to be the critical difference characterizing the contrasting star formation in the centers of the two galaxies.

We report the first detection in the interstellar medium (ISM) of a C _2 H _5 O _2 N isomer: syn -glycolamide (NH _2 C(O)CH _2 OH). The exquisite sensitivity at sub-mK levels of an ultradeep spectral survey carried out with the Yebes 40 m and IRAM 30 m telescopes toward the G+0.693–0.027 molecular cloud has allowed us to unambiguously identify multiple transitions of this species. We derived a column density of (7.4 ± 0.7) × 10 ^12 cm ^−2 , which implies a molecular abundance with respect to H _2 of 5.5 × 10 ^−11 . The other C _2 H _5 O _2 N isomers, including the higher-energy anti conformer of glycolamide and two conformers of glycine, were not detected. The upper limit derived for the abundance of glycine indicates that this amino acid is surely less abundant than its isomer glycolamide in the ISM. The abundances of the C _2 H _5 O _2 N isomers cannot be explained in terms of thermodynamic equilibrium; thus, chemical kinetics need to be invoked. While the low abundance of glycine might not be surprising, based on the relative low abundances of acids in the ISM compared to other compounds (e.g., alcohols, aldehydes, or amines), several chemical pathways can favor the formation of its isomer glycolamide. It can be formed through radical–radical reactions on the surface of dust grains. The abundances of these radicals can be significantly boosted in an environment affected by a strong ultraviolet field induced by cosmic rays, such as that expected in G+0.693–0.027. Therefore, as shown by several recent molecular detections toward this molecular cloud, it stands out as the best target to discover new species with carbon, oxygen, and nitrogen with increasing chemical complexity.

In compact and dense star-forming clouds a global star cluster wind could be suppressed. In this case stellar feedback is unable to expel the leftover gas from the cluster. Young massive stars remain embedded in a dense residual gas and stir it by moving in the gravitational well of the system. Here we present a self-consistent model for the molecular gas distribution in such young, enshrouded stellar clusters. It is assumed that the cloud collapse terminates and the star formation ceases when a balance between the turbulent pressure and gravity and between the turbulent energy dissipation and regeneration rates is established. These conditions result in an equation that determines the residual gas density distribution that, in turn, allows one to determine the other characteristics of the leftover gas and the star formation efficiency. It is shown that our model predictions are in good agreement with several observationally determined properties of cloud D1 in the nearby dwarf spheroidal galaxy NGC 5253 and its embedded cluster.

A quarter century after the detection of the last interstellar carboxylic acid, acetic acid (CH _3 COOH), we report the discovery of a new one, the cis-trans form of carbonic acid (HOCOOH), toward the Galactic center molecular cloud G+0.693–0.027. HOCOOH stands as the first interstellar molecule containing three oxygen atoms and the third carboxylic acid detected so far in the interstellar medium. Albeit the limited available laboratory measurements (up to 65 GHz), we have also directly identified several pairs of unblended lines in the astronomical data (between 75 and 120 GHz), which allowed us to slightly improve the set of spectroscopic constants. We derive a column density for cis-trans HOCOOH of N = (6.4 ± 0.4) × 10 ^12 cm ^−2 , which yields an abundance with respect to molecular H _2 of 4.7 × 10 ^−11 . Meanwhile, the extremely low dipole moment (about 15 times lower) of the lower-energy conformer, cis-cis HOCOOH, precludes its detection. We obtain an upper limit to its abundance with respect to H _2 of ≤1.2 × 10 ^−9 , which suggests that cis-cis HOCOOH might be fairly abundant in interstellar space, although it is nearly undetectable by radio astronomical observations. We derive a cis-cis / cis-trans ratio of ≤25, consistent with the smaller energy difference between both conformers compared with the relative stability of trans- and cis -formic acid. Finally, we compare the abundance of these acids in different astronomical environments, further suggesting a relationship between the chemical content found in the interstellar medium and the chemical composition of the minor bodies of the solar system, which could be inherited during the star formation process.

We present Atacama Large Millimeter/submillimeter Array (ALMA) imaging of molecular gas across the full star-forming disk of the barred spiral galaxy M83 in CO( J = 1–0). We jointly deconvolve the data from ALMA’s 12 m, 7 m, and Total Power arrays using the MIRIAD package. The data have a mass sensitivity and resolution of 10 ^4 M _⊙ (3 σ ) and 40 pc—sufficient to detect and resolve a typical molecular cloud in the Milky Way with a mass and diameter of 4 × 10 ^5 M _⊙ and 40 pc, respectively. The full disk coverage shows that the characteristics of molecular gas change radially from the center to outer disk, with the locally measured brightness temperature, velocity dispersion, and integrated intensity (surface density) decreasing outward. The molecular gas distribution shows coherent large-scale structures in the inner part, including the central concentration, offset ridges along the bar, and prominent molecular spiral arms. However, while the arms are still present in the outer disk, they appear less spatially coherent, and even flocculent. Massive filamentary gas concentrations are abundant even in the interarm regions. Building up these structures in the interarm regions would require a very long time (≳100 Myr). Instead, they must have formed within stellar spiral arms and been released into the interarm regions. For such structures to survive through the dynamical processes, the lifetimes of these structures and their constituent molecules and molecular clouds must be long (≳100 Myr). These interarm structures host little or no star formation traced by H α . The new map also shows extended CO emission, which likely represents an ensemble of unresolved molecular clouds.

The radio galaxy NGC 1052 casts absorption features of sulfur-bearing molecules, H _2 S, SO, SO _2 , and CS toward the radio continuum emission from the core and jets. Using the Atacama Large Millimeter/submillimeter Array, we have measured the equivalent widths of SO absorption features in multiple transitions and determined the temperatures of 344 ± 43 K and 26 ± 4 K in submillimeter and millimeter wavelengths, respectively. Since submillimeter and millimeter continuum represents the core and jets, the high and low temperatures of the absorbers imply a warm environment in the molecular torus and cooler downstream flows. The high temperature in the torus is consistent with the presence of 22 GHz H _2 O maser emission, vibrationally excited HCN and HCO ^+ absorption lines, and sulfur-bearing molecules in the gas phase released from dust. The origin of the sulfur-bearing gas is ascribed to the evaporation of the icy dust component through a jet–torus interaction. Shock heating is the sole plausible mechanism to maintain such a high temperature of gas and dust in the torus. The implication of the jet–torus interaction also supports the collimation of the sub-relativistic jets by the gas pressure of the torus.

Mergers of galaxies are an important mode for galaxy evolution because they serve as an efficient trigger of powerful starbursts. However, observational studies of molecular gas properties during their early stages are scarce. We present interferometric CO(2–1) maps of two luminous infrared galaxies, NGC 3110 and NGC 232, obtained with the Submillimeter Array with ∼1 kpc resolution. While NGC 3110 is a spiral galaxy interacting with a minor (14:1 stellar mass) companion, NGC 232 is interacting with a similarly sized object. We find that such interactions in these galaxies have likely induced enhancements in the molecular gas content and central concentrations, partly at the expense of atomic gas. The obtained molecular gas surface densities in their circumnuclear regions are Σmol ≳ 102.5M⊙ pc−2, higher than in noninteracting objects by an order of magnitude. Gas depletion times of 0.5–1 Gyr are found for the different regions, lying in between noninteracting disk galaxies and the starburst sequence. In the case of NGC 3110, the spiral arms show on average 0.5 dex shorter depletion times than in the circumnuclear regions if we assume a similar H2–CO conversion factor. We show that even in the early stages of the interaction with a minor companion, a starburst is formed along the circumnuclear region and spiral arms, where a large population of SSCs is found (∼350), and at the same time a large central gas concentration is building up that might be the fuel for an active galactic nucleus. The main morphological properties of the NGC 3110 system are reproduced by our numerical simulations and allow us to estimate that the current epoch of the interaction is at ∼150 Myr after closest approach. [ABSTRACT FROM AUTHOR]