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Kinematics of the molecular clouds in the star forming complex M17 is studied using the high-resolution CO-line mapping data at resolution ($20" \sim 0.2$ pc) with the Nobeyama 45-m telescope. The northern molecular cloud of M17, which we call the molecular "lobe", is shown to have an elongated shell structure around a top-covered cylindrical cavity. The lobe is expanding at $\sim 5$ \kms in the minor axis direction, and at $ \sim 3/\cos \ i$ km s$^{-1}$ in the major axis direction, where $i$ is the inclination of the major axis. The kinetic energy of the expanding motion is on the order of $\sim 3\times 10^{49}$ ergs. We show that the lobe is a backyard structure having the common origin to the denser molecular "horn" flowing out from NGC 6618 toward the south, so that the lobe and horn compose a bipolar outflow. Intensity distributions across the lobe and horn show a double-peak profile typical for a cylinder around a cavity. Position-velocity diagrams (PVD) across the lobe and horn exhibit open ring structure with the higher- and/or lower-velocity side(s) being lacking or faded. This particular PVD behavior can be attributed to outflow in a conical cylinder with the flow velocity increasing toward the lobe and horn axes., Comment: Accepted for MNRAS, 10 pages, 13 figures

Filamentary structures identified in far-infrared observations of molecular clouds are typically found to have full-widths at half-maximum $\sim\!0.1$ pc. However, the physical explanation for this phenomenon is currently uncertain. We use hydrodynamic simulations of cylindrically-symmetric converging flows to show that the full-width at half-maximum of the resulting filament's surface density profile, FWHM$_{\Sigma}$, is closely related to the location of the accretion shock, where the inflow meets the boundary of the filament. For inflow Mach Number, ${\cal M}$, between 1 and 5, filament FWHM$_{\Sigma}$s fall in the range $0.03$ pc $\lesssim$ FWHM$_{\Sigma} \lesssim 0.3$ pc, with higher ${\cal M}$ resulting in narrower filaments. A large sample of filaments, seen at different evolutionary stages and with different values of ${\cal M}$, naturally results in a peaked distribution of FWHM$_{\Sigma}$s similar in shape to that obtained from far-infrared observations of molecular clouds. However, unless the converging flows are limited to ${\cal M} \lesssim 3$, the peak of the distribution of FWHM$_{\Sigma}$s is below the observed $\sim 0.1$ pc., Comment: 11 pages, 12 figures. MNRAS accepted

The morphology of gas-rich disc galaxies at redshift ~1-3 is dominated by a few massive clumps. The process of formation or assembly of these clumps and their relation to molecular clouds in contemporary spiral galaxies are still unknown. Using simulations of isolated disc galaxies, we study how the structure of the interstellar medium and the stability regime of the discs change when varying the gas fraction. In all galaxies, the stellar component is the main driver of instabilities. However, the molecular gas plays a non-negligible role in the inter-clumps medium of gas-rich cases, and thus in the assembly of the massive clumps. At scales smaller than a few 100 pc, the Toomre-like disc instabilities are replaced by another regime, specially in the gas-rich galaxies. We find that galaxies at low gas fraction (10%) stand apart from discs with more gas, which all share similar properties on virtually all the aspects we explore. For gas fractions below approximately 20%, the clump-scale regime of instabilities disappears, only leaving the large-scale disc-driven regime. When translating the change of gas fraction to the cosmic evolution of galaxies, this transition marks the end of the clumpy phase of disc galaxies, and allows for the onset of spiral structures, as commonly found in the local Universe., 19 pages, MNRAS accepted

Young stellar clusters across nearly five orders of magnitude in mass appear to follow a power-law mass-radius relationship (MRR), $R_{\star} \propto M_{\star}^{\alpha}$, with $\alpha \approx 0.2 - 0.33$. We develop a simple analytic model for the cluster mass-radius relation. We consider a galaxy disc in hydrostatic equilibrium, which hosts a population of molecular clouds that fragment into clumps undergoing cluster formation and feedback-driven expansion. The model predicts a mass-radius relation of $R_{\star} \propto M_{\star}^{1/2}$ and a dependence on the kpc-scale gas surface density $R_{\star} \propto \Sigma_{\rm g}^{-1/2}$, which results from the formation of more compact clouds (and cluster-forming clumps within) at higher gas surface densities. This environmental dependence implies that the high-pressure environments in which the most massive clusters can form also induce the formation of clusters with the smallest radii, thereby shallowing the observed MRR at high-masses towards the observed $R_{\star} \propto M_{\star}^{1/3}$. At low cluster masses, relaxation-driven expansion induces a similar shallowing of the MRR. We combine our predicted MRR with a simple population synthesis model and apply it to a variety of star-forming environments, finding good agreement. Our model predicts that the high-pressure formation environments of globular clusters at high redshift naturally led to the formation of clusters that are considerably more compact than those in the local Universe, thereby increasing their resilience to tidal shock-driven disruption and contributing to their survival until the present day., Comment: Accepted to MNRAS. Revised model incorporates a new dependence on Toomre Q

The parameters and description of promising objects for observing with the RT-70 millimeter-wave radio telescope under construction on the Suffa plateau (Uzbekistan) are presented. The possible problems of their study using the RT-70 telescope are considered. The necessary time consumptions are estimated. The planned characteristics of the RT-70 are briefly compared with parameters of other large radio telescopes of the millimeter wavelength range.

The Sun’s astrophysical birth environment affected the formation and composition of the Solar System. Primitive meteorites display mass-independent oxygen isotope anomalies that were likely caused by ultraviolet (UV) photochemistry of CO gas-phase molecules, either (i) in the outer solar nebula by light from the young Sun or (ii) in the parent molecular cloud by light from nearby stars. However, measurements of oxygen isotopes alone cannot unambiguously constrain the UV spectrum of the source responsible for the photochemistry. Sulfur, with four stable isotopes, can be used as a more direct probe of the astrophysical environment of mass-independent photochemistry. Here, we report the in situ isotopic analysis of paired oxygen and sulfur isotope systematics in cosmic symplectite (COS), magnetite-pentlandite intergrowths, in the primitive ungrouped carbonaceous chondrite Acfer 094. We show that COS grains contain mass-independent sulfur isotope anomalies (weighted means of Δ33S = +3.84 ± 0.72‰ and Δ36S = −6.05 ± 2.25‰, 2SE) consistent with H2S photochemistry by UV from massive O and B stars close to the Solar System’s parent molecular cloud, and inconsistent with UV from the protosun. The presence of coupled mass-independent sulfur and oxygen (Δ17O = 86 ± 6‰, 2SE) isotope anomalies in COS imply that these anomalies originated in the same astrophysical environment. We propose that this environment is the photodissociation region (PDR) of the Solar System’s parent molecular cloud, where nearby massive stars irradiated the edge of the cloud. We conclude that the Sun’s stellar neighbors, likely O and B stars in a massive-star-forming region, affected the composition of the Solar System’s primordial building blocks.

We present a novel scenario for the growth of dust grains in galaxies at high-redshift ($z\sim 6$). In our model, the mechanical feedback from massive star clusters evolving within high-density pre-enriched media allows to pile-up a large amount of matter into massive supershells. If the gas metallicity ($\geq$ Z$_{\odot}$), number density ($\geq 10^6$ cm$^{-3}$) and dust-to-gas mass ratio ($\sim 1/150 \times Z$) within the supershell are sufficiently large, such supershells may become optically thick to the starlight emerging from their host star clusters and even to radiation from the Cosmic Microwave Background (CMB). Based on semi-analytic models, we argue that this mechanism, occurring in the case of massive ($\geq 10^7$ M$_{\odot}$) molecular clouds hosting $\geq 10^6$ M$_{\odot}$ star clusters, allows a large mass of gas and dust to acquire a temperature below that of the CMB, whereupon dust grain growth may occur with ease. In galaxies with total stellar mass $M_{*}$, grain growth within supershells may increase the dust mass by $\sim 10^6$ M$_{\odot}$ $(M_{*}/10^{8}$ M$_{\odot}$)., Comment: 10 pages, 7 figures, accepted for publication by MNRAS

By performing three-dimensional radiation hydrodynamics simulations, we study the formation of young massive star clusters (YMCs, $M_{*}>10^4~M_{\odot}$) in clouds with the surface density ranging from $\Sigma_{\rm cl} = 80$ to $3200~M_{\odot}\;{\rm pc^{-2}}$. We find that photoionization feedback suppresses star formation significantly in clouds with low surface density. Once the initial surface density exceeds $\sim 100~M_{\odot}\;{\rm pc^{-2}}$ for clouds with $M_{\rm cl}=10^{6}~M_{\odot}$ and $Z= Z_{\odot}$, most of the gas is converted into stars because the photoionization feedback is inefficient in deep gravitational potential. In this case, the star clusters are massive and gravitationally bounded as YMCs. The transition surface density increases as metallicity decreases, and it is $\sim 350~M_{\odot}\;{\rm pc^{-2}}$ for $Z=10^{-2}~Z_{\odot}$. We show that more than 10 percent of star-formation efficiency (SFE) is needed to keep a star cluster gravitationally bounded even after the disruption of a cloud. Also, we develop a semi-analytical model reproducing the SFEs obtained in our simulations. We find that the SFEs are fit with a power-law function with the dependency $\propto \Sigma_{\rm cl}^{1/2}$ for low-surface density and rapidly increases at the transition surface densities. The conditions of the surface density and the metallicity match recent observations of giant molecular clouds forming YMCs in nearby galaxies., Comment: 28 pages, 28 figures, accepted for publication in MNRAS

In the centres of the Milky Way and M83, the global environmental properties thought to control star formation are very similar. However, M83's nuclear star formation rate (SFR), as estimated by synchrotron and H-alpha emission, is an order of magnitude higher than the Milky Way's. To understand the origin of this difference we use ALMA observations of HCN (1-0) and HCO+ (1-0) to trace the dense gas at the size scale of individual molecular clouds (0.54", 12pc) in the inner ~500 pc of M83, and compare this to gas clouds at similar resolution and galactocentric radius in the Milky Way. We find that both the overall gas distribution and the properties of individual clouds are very similar in the two galaxies, and that a common mechanism may be responsible for instigating star formation in both circumnuclear rings. Given the considerable similarity in gas properties, the most likely explanation for the order of magnitude difference in SFR is time variability, with the Central Molecular Zone (CMZ) currently being at a more quiescent phase of its star formation cycle. We show M83's SFR must have been an order of magnitude higher 5-7 Myr ago. M83's `starburst' phase was highly localised, both spatially and temporally, greatly increasing the feedback efficiency and ability to drive galactic-scale outflows. This highly dynamic nature of star formation and feedback cycles in galaxy centres means (i) modeling and interpreting observations must avoid averaging over large spatial areas or timescales, and (ii) understanding the multi-scale processes controlling these cycles requires comparing snapshots of a statistical sample of galaxies in different evolutionary stages., 31 pages, 22 figures, accepted by MNRAS

The origin of the radiation observed in the region of the supernova remnant RX J1713.7−3946, one of the brightest TeV emitters, has been debated since its discovery. The existence of atomic and molecular clouds in this object supports the idea that part of the GeV gamma-ray emission in this region originates from proton–proton collisions. However, the observed column density of protons derived from observations of the gas cannot explain the whole emission. Yet there could be a fraction of protons contained in fainter structures that have not been detected so far. Here we search for faint objects in the line of sight of RX J1713.7−3946 using the principle of light extinction and the European Space Agency’s Gaia mission Data Release 2 astrometric and photometric data. We reveal and locate with precision a number of dust clouds and note that only one appears to be in the vicinity of RX J1713.7−3946. We estimate the embedded mass to be Mdust = (7.0 ± 0.6) × 103 M⊙, which might be big enough to contain the missing protons. Finally, using the fact that the supernova remnant is expected to be located in a dusty environment and that there appears to be only one such structure in the vicinity of RX J1713.7−3946, we set a very precise constraint on the supernova remnant distance, at 1.12 ± 0.01 kpc. A dust cloud in the line of sight towards supernova remnant RX J1713.7−3946—identified using Gaia data —contributes to the GeV gamma-ray emission of the region.

We study the multi-phase medium in the vicinity of the active galactic nucleus Centaurus A (Cen A). Combined high-resolution observations with the ALMA and Chandra observatories indicate that the hot X-ray emitting plasma coexists with the warm and cold media in Cen A. This complex environment is a source of CO lines with great impact for its diagnostics. We present the images from the two above-mentioned instruments covering the nuclear region (diameter of 10'' i.e., ~180 pc), and we study the conditions for plasma thermal equilibrium and possible coexistence of cool clouds embedded within the hot X-ray emitting gas. Further, we demonstrate that the multi-phase medium originates naturally by the thermal instability (TI) arising due to the interaction of the high-energy radiation field from the nucleus with the ambient gas and dust. We demonstrate that cold gas clouds can coexist in the mutual contact with hot plasma, but even colder dusty molecular clouds have to be distanced by several hundred pc from the hot region. Finally, we propose a 3-D model of the appearance of the hot plasma and the CO line-emitting regions consistent with the Chandra image and we derive the integrated emissivity in specific molecular lines observed by ALMA from this model. To reproduce the observed images and the CO line luminosity the dusty shell has to be ~420 pc thick and located at ~1000 pc from the centre., 16 pages, 16 figures, Accepted for publication in MNRAS

With backwards orbit integration we estimate birth locations of young stellar associations and moving groups identified in the solar neighborhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule include are the Argus and Octans associations which formed outside the Sun's Galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a corrugated disk of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the UV stellar velocity distribution for stars in the solar neighborhood. This would be expected if they were born in a spiral arm which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low velocity dispersion disk stars., Comment: The animated movie is available here: http://astro.pas.rochester.edu/~aquillen/figures/movie3D.gif

Secondary positrons produced inside Galactic Molecular Clouds (GMCs) can significantly contribute to the observed positron spectrum on Earth. Multi-wavelength data of GMCs are particularly useful in building this model. A very recent survey implemented the optical/IR dust extinction measurements to trace 567 GMCs within 4 kpc of Earth, residing in the Galactic plane. We use the updated catalog of GMCs reported in recent papers, distributed in the Galactic plane, to find the secondary positrons produced in them in interactions of cosmic rays with molecular hydrogen. Moreover, by analyzing the \textit{Fermi}-LAT data, new GMCs have been discovered near the Galactic plane. We also include some of these GMCs closest to the Earth, where cosmic ray interactions produce secondaries. It has been speculated earlier that cosmic rays may be reaccelerated in some GMCs. We select 7 GMCs out of 567 GMCs recently reported, within 4 kpc of Earth, where reacceleration due to magnetized turbulence is assumed. We include a hardened component of secondary positrons produced from the interaction of reaccelerated CRs in those 7 GMCs. We use publicly available code \texttt{DRAGON} for our simulation setup to study CR propagation in the Galaxy and show that the observed positron spectrum can be well explained in the energy range of 1 to 1000 GeV by our self-consistent model., Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021)

We present models of CO(1-0) emission from Milky Way-mass galaxies at redshift zero in the FIRE-2 cosmological zoom-in simulations. We calculate the molecular abundances by post-processing the simulations with an equilibrium chemistry solver while accounting for the effects of local sources, and determine the emergent CO(1-0) emission using a line radiative transfer code. We find that the results depend strongly on the shielding length assumed, which in our models sets the attenuation of the incident UV radiation field. At the resolution of these simulations, commonly used choices for the shielding length, such as the Jeans length, result in CO abundances that are too high at a given H$_2$ abundance. We find that a model with a distribution of shielding lengths, which has a median shielding length of $\sim 3$ pc in cold gas ($T < 300$ K) for both CO and H$_{2}$, is able to reproduce both the observed CO(1-0) luminosity and inferred CO-to-H$_{2}$ conversion factor at a given star formation rate compared with observations. We suggest that this short shielding length can be thought of as a subgrid model which controls the amount of radiation that penetrates giant molecular clouds., Accepted to MNRAS. 16 pages, 10 figures

Propagation of fast-mode magneto-hydrodynamic (MHD) compression waves is traced in the Galactic Centre. MHD waves produced by the active Galactic nucleus (Sgr A) focus on the molecular clouds such as Sgr B in the central molecular zone, which will trigger star formation, or possibly starburst. MHD waves newly excited by the starburst propagate backward, and focus on the nucleus (Sgr A), where implosive waves compress the nuclear gas to promote fueling the nucleus and may trigger nucleus activity. Echoing focusing of MHD waves between Sgr A (active galactic nucleus: AGN) and Sgr B (starburst) trigger each other at high efficiency by minimal energy requirement. It also solves the problem of angular momentum for AGN fueling, as the focusing waves do not require global gas flow., Accepted for MNRAS, 13 pages, 15 figures

Direct imaging in the infrared at the diffraction limit of large telescopes is a unique probe of the properties of young planetary systems. We survey 55 single class I and class II stars in Taurus in the L' filter using natural and laser guide star adaptive optics and the near-infrared camera (NIRC2) of the Keck II telescope, in order to search for planetary mass companions. We use both reference star differential imaging and kernel phase techniques, achieving typical 5-sigma contrasts of ~6 magnitudes at separations of 0.2" and ~8 magnitudes beyond 0.5". Although we do not detect any new faint companions, we constrain the frequency of wide separation massive planets, such as HR 8799 analogues. We find that, assuming hot-start models and a planet distribution with power-law mass and semi-major axis indices of -0.5 and -1, respectively, less than 20% of our target stars host planets with masses >2 MJ at separations >10 AU., 16 pages, 14 figures, accepted for publication in MNRAS

Supersonic turbulence plays a pivotal role during the formation of molecular clouds and stars in galaxies. However, little is known about how the fraction of compressive and solenoidal modes in the velocity field evolves over time and how it depends on properties of the molecular cloud or the galactic environment. In this work, we carry out magnetohydrodynamical simulations of disc galaxies and study the time evolution of the turbulence driving parameter for an ensemble of clouds. We find that the time-averaged turbulence driving parameter is insensitive to the position of the cloud within the galaxy. The ensemble-averaged driving parameter is found to be rather compressive with $b\sim0.5-0.7$, indicating almost time-independent global star formation properties. However, each individual cloud shows a highly fluctuating driving parameter, which would strongly affect the cloud's star formation rate. We find that the mode of turbulence driving can rapidly change within only a few Myr, both from solenoidal to compressive and vice versa. We attribute these changes to cloud collisions and to tidal interactions with clouds or overdensities in the environment. Last, we find no significant differences in the average driving parameter between hydrodynamic and initially strongly magnetised galaxies. However, the magnetic field tends to reduce the overall fluctuation of the driving parameter. The average driving as well as its uncertainty are seen to be in agreement with recent constraints on the turbulence driving mode for solar neighbourhood clouds., Comment: Accepted for publication by MNRAS. Comments welcome

Understanding the evolution of self-gravitating, isothermal, magnetized gas is crucial for star formation, as these physical processes have been postulated to set the initial mass function (IMF). We present a suite of isothermal magnetohydrodynamic (MHD) simulations using the GIZMO code, that resolve the formation of individual stars in giant molecular clouds (GMCs), spanning a range of Mach numbers found in observed GMCs. As in past works, the mean and median stellar masses are sensitive to numerical resolution, because they are sensitive to low-mass stars that contribute a vanishing fraction of the overall stellar mass. The {\em mass-weighted} median stellar mass $M_\mathrm{50}$ becomes insensitive to resolution once turbulent fragmentation is well-resolved. Without imposing Larson-like scaling laws, our simulations find $M_\mathrm{50} \propto M_\mathrm{0} \mathcal{M}^{-3} \alpha_\mathrm{turb} \mathrm{SFE}^{1/3}$ for GMC mass $M_\mathrm{0}$, sonic Mach number $\mathcal{M}$, virial parameter $\alpha_\mathrm{turb}$, and star formation efficiency $\mathrm{SFE}=M_\mathrm{\star}/M_\mathrm{0}$. This fit agrees well with previous IMF results from the RAMSES, ORION2, and SphNG codes. Although $M_\mathrm{50}$ has no significant dependence on the magnetic field strength at the cloud scale, MHD is necessary to prevent a fragmentation cascade that results in non-convergent stellar masses. For initial conditions and SFE similar to star-forming GMCs in our Galaxy, we predict $M_\mathrm{50}$ to be $>20 M_{\odot}$, an order of magnitude larger than observed ($\sim 2 M_\odot$), together with an excess of brown dwarfs. Moreover, $M_\mathrm{50}$ is sensitive to initial cloud properties and evolves strongly in time within a given cloud, predicting much larger IMF variations than are observationally allowed. We conclude that physics beyond MHD turbulence and gravity are necessary ingredients for the IMF., Comment: Note that this version has erratum at the end (does not affect results) 18 pages, 17 figures

We report the first evidence for high-mass star formation triggered by collisions of molecular clouds in M33. Using the Atacama Large Millimeter/submillimeter Array, we spatially resolved filamentary structures of giant molecular cloud 37 in M33 using $^{12}$CO($J$ = 2-1), $^{13}$CO($J$ = 2-1), and C$^{18}$O($J$ = 2-1) line emission at a spatial resolution of $\sim$2 pc. There are two individual molecular clouds with a systematic velocity difference of $\sim$6 km s$^{-1}$. Three continuum sources representing up to $\sim$10 high-mass stars with the spectral types of B0V-O7.5V are embedded within the densest parts of molecular clouds bright in the C$^{18}$O($J$ = 2-1) line emission. The two molecular clouds show a complementary spatial distribution with a spatial displacement of $\sim$6.2 pc, and show a V-shaped structure in the position-velocity diagram. These observational features traced by CO and its isotopes are consistent with those in high-mass star-forming regions created by cloud-cloud collisions in the Galactic and Magellanic Cloud HII regions. Our new finding in M33 indicates that the cloud-cloud collision is a promising process to trigger high-mass star formation in the Local Group., Comment: 13 pages, 10 figures, 1 table, accepted for publication in PASJ

The purpose of this study is to deal with dust and interstellar molecular and atomic gas owing to obtaining a proportion of cold gas to dust and to understand the characteristics of the molecular gas in extragalactic data selected from the Herschel SPIRE/ FTS archive. The physical properties of a sample of 65 extragalactic spectra characterized by the activity of star formation were discussed in this work. Statistical analyses, using STATISTICA program, were made for the content of cold gas (MHI, MH2), dust mass (Mdust), cold temperature of dust (Td) and luminosities in Far-infrared to CO line radiations, while coefficients of partial correlation within those characteristics were established. The results showed that the molecular hydrogen mass (MH2) is strongly correlated with the HI or the total gas mass corresponding to the Far-infrared emission (LFIR) resulting from dust in the galaxies molecular clouds. The results also indicated that these kinds of galaxies have large molecular mass as well as high star formation efficiency per unit mass.

We present simulations of a 500 pc$^2$ region, containing gas of mass 4 $\times$ 10$^6$ M$_\odot$, extracted from an entire spiral galaxy simulation, scaled up in resolution, including photoionising feedback from stars of mass > 18 M$_\odot$. Our region is evolved for 10 Myr and shows clustered star formation along the arm generating $\approx$ 5000 cluster sink particles $\approx$ 5% of which contain at least one of the $\approx$ 4000 stars of mass > 18 M$_\odot$. Photoionisation has a noticeable effect on the gas in the region, producing ionised cavities and leading to dense features at the edge of the HII regions. Compared to the no-feedback case, photoionisation produces a larger total mass of clouds and clumps, with around twice as many such objects, which are individually smaller and more broken up. After this we see a rapid decrease in the total mass in clouds and the number of clouds. Unlike studies of isolated clouds, our simulations follow the long range effects of ionisation, with some already-dense gas becoming compressed from multiple sides by neighbouring HII regions. This causes star formation that is both accelerated and partially displaced throughout the spiral arm with up to 30% of our cluster sink particle mass forming at distances > 5 pc from sites of sink formation in the absence of feedback. At later times, the star formation rate decreases to below that of the no-feedback case., 22 pages, 20 figures, accepted for publication in MNRAS

Protostars and young stars are strongly spatially "clustered" or "correlated" within their natal giant molecular clouds (GMCs). We demonstrate that such clustering leads to the conclusion that the incident bolometric radiative flux upon a random young star/disc is enhanced (relative to volume-averaged fluxes) by a factor which increases with the total stellar mass of the complex. Because the Galactic cloud mass function is top-heavy, the typical star in our Galaxy experienced a much stronger radiative environment than those forming in well-observed nearby (but relatively small) clouds, exceeding fluxes in the Orion Nebular Cluster by factors of $\gtrsim$30. Heating of the circumstellar disc around a median young star is dominated by this external radiation beyond $\sim 50\,$AU. And if discs are not well-shielded by ambient dust, external UV irradiation can dominate over the host star down to sub-AU scales. Another consequence of stellar clustering is an extremely broad Galaxy-wide distribution of incident flux (spanning $>10$ decades), with half the Galactic star formation in a substantial "tail" towards even more intense background radiation. We also show that the strength of external irradiation is amplified super-linearly in high-density environments such as the Galactic centre, starbursts, or high-redshift galaxies., MNRAS Letters in press

With the spatial resolution of the Atacama Large Millimetre Array (ALMA), dusty galaxies in the distant Universe typically appear as single, compact blobs of dust emission, with a median half-light radius, $\approx$ 1 kpc. Occasionally, strong gravitational lensing by foreground galaxies or galaxy clusters has probed spatial scales 1-2 orders of magnitude smaller, often revealing late-stage mergers, sometimes with tantalising hints of sub-structure. One lensed galaxy in particular, the Cosmic Eyelash at $z=$ 2.3, has been cited extensively as an example of where the interstellar medium exhibits obvious, pronounced clumps, on a spatial scale of $\approx$ 100 pc. Seven orders of magnitude more luminous than giant molecular clouds in the local Universe, these features are presented as circumstantial evidence that the blue clumps observed in many $z\sim$ 2-3 galaxies are important sites of ongoing star formation, with significant masses of gas and stars. Here, we present data from ALMA which reveal that the dust continuum of the Cosmic Eyelash is in fact smooth and can be reproduced using two S\'ersic profiles with effective radii, 1.2 and 4.4 kpc, with no evidence of significant star-forming clumps down to a spatial scale of $\approx$ 80 pc and a star-formation rate of $, Comment: 5 pages; 3 figures; in press as a Letter to MNRAS

We use the hydrodynamical simulation of our inner Galaxy presented in Armillotta et al. (2019) to study the gas distribution and kinematics within the CMZ. We use a resolution high enough to capture the gas emitting in dense molecular tracers such as NH3 and HCN, and simulate a time window of 50 Myr, long enough to capture phases during which the CMZ experiences both quiescent and intense star formation. We then post-process the simulated CMZ to calculate its spatially-dependent chemical and thermal state, producing synthetic emission data cubes and maps of both HI and the molecular gas tracers CO, NH3 and HCN. We show that, as viewed from Earth, gas in the CMZ is distributed mainly in two parallel and elongated features extending from positive longitudes and velocities to negative longitudes and velocities. The molecular gas emission within these two streams is not uniform, and it is mostly associated to the region where gas flowing towards the Galactic Center through the dust lanes collides with gas orbiting within the ring. Our simulated data cubes reproduce a number of features found in the observed CMZ. However, some discrepancies emerge when we use our results to interpret the position of individual molecular clouds. Finally, we show that, when the CMZ is near a period of intense star formation, the ring is mostly fragmented as a consequence of supernova feedback, and the bulk of the emission comes from star-forming molecular clouds. This correlation between morphology and star formation rate should be detectable in observations of extragalactic CMZs., 19 pages, 11 figures, accepted for publication in MNRAS

Feedback from supernovae is often invoked as an important process in limiting star formation, removing gas from galaxies and hence as a determining process in galaxy formation. Here we report on numerical simulations investigating the interaction between supernova explosions and the natal molecular cloud. We also consider the cases with and without previous feedback from the high-mass star in the form of ionising radiation and stellar winds. The supernova is able to find weak points in the cloud and create channels through which it can escape, leaving much of the well shielded cloud largely unaffected. This effect is increased when the channels are pre-existing due to the effects of previous stellar feedback. The expanding supernova deposits its energy in the gas that is in these exposed channels, and hence sweeps up less mass when feedback has already occurred, resulting in faster outflows with less radiative losses. The full impact of the supernova explosion is then able to impact the larger scale of the galaxy in which it abides. We conclude that supernova explosions only have moderate effects on their dense natal environments but that with pre-existing feedback, the energetic effects of the supernova are able to escape and affect the wider scale medium of the galaxy., 12 pages, 10 figures, MNRAS in press

We study the dust evolution in galaxies by implementing a detailed dust prescription in the SAGE semi-analytical model for galaxy formation. The new model, called Dusty SAGE, follows the condensation of dust in the ejecta of type II supernovae and asymptotic giant branch (AGB) stars, grain growth in the dense molecular clouds, destruction by supernovae shocks, and the removal of dust from the ISM by star formation, reheating, inflows and outflows. Our model successfully reproduces the observed dust mass function at redshift z = 0 and the observed scaling relations for dust across a wide range of redshifts. We find that the dust mass content in the present Universe is mainly produced via grain growth in the interstellar medium (ISM). By contrast, in the early Universe, the primary production mechanism for dust is the condensation in stellar ejecta. The shift of the significant production channel for dust characterises the scaling relations of dust-to-gas (DTG) and dust-to-metal (DTM) ratios. In galaxies where the grain growth dominates, we find positive correlations for DTG and DTM ratios with both metallicity and stellar mass. On the other hand, in galaxies where dust is produced primarily via condensation, we find negative or no correlation for DTM and DTG ratios with either metallicity or stellar mass. In agreement with observation showing that the circumgalactic medium (CGM) contains more dust than the ISM, our model also shows the same trend for z < 4. Our semi-analytic model is publicly available at https: //github.com/dptriani/dusty-sage., 19 pages, 14 figures, accepted for publication in MNRAS

In order to understand the formation of massive OB stars, we report a multi-wavelength observational study of a giant molecular cloud hosting the S147/S153 complex (size ~90 pc X 50 pc). The selected complex is located in the Perseus arm, and contains at least five HII regions (S147, S148, S149, S152, and S153) powered by massive OB stars having dynamical ages of ~0.2 - 0.6 Myr. The Canadian Galactic Plane Survey 12CO line data (beam size ~100".4) trace the complex in a velocity range of [-59, -43] km/s, and also reveal the presence of two molecular cloud components around -54 and -49 km/s in the direction of the complex. Signatures of the interaction/collision between these extended cloud components are investigated through their spatial and velocity connections. These outcomes suggest the collision of these molecular cloud components about 1.6 Myr ago. Based on the observed overlapping zones of the two clouds, the collision axis appears to be parallel to the line-of-sight. Deep near-infrared photometric analysis of point-like sources shows the distribution of infrared-excess sources in the direction of the overlapping zones of the molecular cloud components, where all the HII regions are also spatially located. All elements put together, the birth of massive OB stars and embedded infrared-excess sources seems to be triggered by two colliding molecular clouds in the selected site. High resolution observations of dense gas tracer will be required to further confirm the proposed scenario., 22 pages, 8 figures, Accepted for publication in The Publications of the Astronomical Society of Japan (PASJ)

Low energy cosmic-rays (CRs) are responsible for gas heating and ionization of interstellar clouds, which in turn introduces coupling to Galactic magnetic fields. So far the CR ionization rate (CRIR) has been estimated using indirect methods, such as its effect on the abundances of various rare molecular species. Here we show that the CRIR may be constrained from line emission of H$_2$ rovibrational transitions, excited by CRs. We derive the required conditions for CRs to dominate line excitation, and show that CR-excited lines may be detected with the Very Large Telescope (VLT) over 8 hours integration. Our method, if successfully applied to a variety of clouds at different Galactic locations will provide improved constraints on the spectrum of low energy CRs and their origins., Comment: Accepted for publication in Nature Communications Physics. (editorial style changes following Nature publishing requirements, and some typo corrections)

We present a large, homogeneous catalogue of molecular clouds within 4 kpc from the Sun at low Galactic latitudes ($|b|$ $, Comment: 11 pages, 7 figures, 2 tables, MNRAS in press

A review is given of low-energy cosmic rays (1 MeV-10 GeV), which play an important role in the physics and chemistry of interstellar medium of our Galaxy. According to the generally accepted theory of star formation, cosmic rays penetrate into molecular clouds and ionize the dense gaseous medium of star formation centers besides due to a process of ambipolar diffusion they establish a star formation time scale of about 100-1000 thousand years. The source of cosmic rays in the Galaxy are supernovae remnants where diffusion acceleration at the shock front accelerates particles up to energies of 1015 eV. Being the main source of ionization in the inner regions of molecular clouds, cosmic rays play a fundamental role in the global chemistry of clouds, triggering the entire chain of ion-molecular reactions that make it possible to obtain basic molecules. The review also noted the importance of cosmic rays in atmospheric chemistry: playing a significant role in the formation of nitric oxide, especially with an increase in the flux, they cause a decrease in the concentration of ozone in the atmosphere with all climatic consequences.

Context and Background: The product of the electromagnetic (EM) wave’s power P times its period τ, i.e. Pτ, is the amount of energy conserved in EM wave’s absorption in matter. Whether Pτ is the amount of energy conserved in the emission of EM waves from matter is not assessed. Motivation: In this research, we perform a computational study to explore the ability of Pτ to represent the amount of energy conserved in EM wave’s emission from matter. Hypothesis: Since the magnitude of the power P of emitted EM waves computed through Larmor’s formula for a rotating dipole is excessively small, we alternatively hypothesize that Pτ and the law of conservation of energy can lead to a realistic estimation of P. Methods: We estimate the power PAME of the anomalous microwave emission (AME), a well-characterized radiation generated in the interstellar medium (ISM) by spinning dust grains, and one possible source of contamination of the cosmic microwave background (CMB). For our estimation of PAME, we assume the AME to be generated in a molecular cloud mostly populated by spinning silicate nanoparticles (SSNs) or polycyclic aromatic hydrocarbon (PAH) spinning dust grains. Indeed, SSNs and PAHs are listed among the most probable sources of AME, and their characteristics are well-known. We discriminate between realistic and non-realistic values of PAME based upon the magnitude of two parameters that depend on PAME: the significant distance z, and the time of photon production T. The parameter z is the space interval from the spinning dust grain within which the spinning dust grain’s electric field is effective. Results: Using the information available for AME, SSNs and PAHs, we estimate the power PAME using both Larmor’s formula and Pτ. We compare and comment the results obtained for z and T. Conclusions: Our study highlights the effectiveness of Pτ over Larmor’s formula in providing a realistic value of PAME. This finding might have consequences in quantum technology of single photon detection and production.

Planck Collaboration: et al., Observations of the submillimetre emission from Galactic dust, in both total intensity I and polarization, have received tremendous interest thanks to the Planck full-sky maps. In this paper we make use of such full-sky maps of dust polarized emission produced from the third public release of Planck data. As the basis for expanding on astrophysical studies of the polarized thermal emission from Galactic dust, we present full-sky maps of the dust polarization fraction p, polarization angle ψ, and dispersion function of polarization angles 𝒮. The joint distribution (one-point statistics) of p and NH confirms that the mean and maximum polarization fractions decrease with increasing NH. The uncertainty on the maximum observed polarization fraction, pmax = 22.0−1.4+3.5% at 353 GHz and 80′ resolution, is dominated by the uncertainty on the Galactic emission zero level in total intensity, in particular towards diffuse lines of sight at high Galactic latitudes. Furthermore, the inverse behaviour between p and 𝒮 found earlier is seen to be present at high latitudes. This follows the 𝒮 ∝ p−1 relationship expected from models of the polarized sky (including numerical simulations of magnetohydrodynamical turbulence) that include effects from only the topology of the turbulent magnetic field, but otherwise have uniform alignment and dust properties. Thus, the statistical properties of p, ψ, and 𝒮 for the most part reflect the structure of the Galactic magnetic field. Nevertheless, we search for potential signatures of varying grain alignment and dust properties. First, we analyse the product map 𝒮 × p, looking for residual trends. While the polarization fraction p decreases by a factor of 3−4 between NH = 1020 cm−2 and NH = 2 × 1022 cm−2, out of the Galactic plane, this product 𝒮 × p only decreases by about 25%. Because 𝒮 is independent of the grain alignment efficiency, this demonstrates that the systematic decrease in p with NH is determined mostly by the magnetic-field structure and not by a drop in grain alignment. This systematic trend is observed both in the diffuse interstellar medium (ISM) and in molecular clouds of the Gould Belt. Second, we look for a dependence of polarization properties on the dust temperature, as we would expect from the radiative alignment torque (RAT) theory. We find no systematic trend of 𝒮 × p with the dust temperature Td, whether in the diffuse ISM or in the molecular clouds of the Gould Belt. In the diffuse ISM, lines of sight with high polarization fraction p and low polarization angle dispersion 𝒮 tend, on the contrary, to have colder dust than lines of sight with low p and high 𝒮. We also compare the Planck thermal dust polarization with starlight polarization data in the visible at high Galactic latitudes. The agreement in polarization angles is remarkable, and is consistent with what we expect from the noise and the observed dispersion of polarization angles in the visible on the scale of the Planck beam. The two polarization emission-to-extinction ratios, RP/p and RS/V, which primarily characterize dust optical properties, have only a weak dependence on the column density, and converge towards the values previously determined for translucent lines of sight. We also determine an upper limit for the polarization fraction in extinction, pV/E(B − V), of 13% at high Galactic latitude, compatible with the polarization fraction p ≈ 20% observed at 353 GHz. Taken together, these results provide strong constraints for models of Galactic dust in diffuse gas., The research leading to these results has received funding from the European Research Council under the European Union’s Horizon 2020 Research & Innovation Framework Programme/ERC grant agreement ERC-2016-ADG-742719. This research has received funding from the Agence Nationale de la Recherche (ANR-17-CE31-0022). The Planck Collaboration acknowledges the support of ESA; CNES, and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MINECO, JA, and RES (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); ERC and PRACE (EU).

We explore to what extent simple algebraic models can be used to describe H II regions when winds, radiation pressure, gravity and photon breakout are included. We a) develop algebraic models to describe the expansion of photoionised H II regions under the influence of gravity and accretion in power-law density fields with $\rho \propto r^{-w}$, b) determine when terms describing winds, radiation pressure, gravity and photon breakout become significant enough to affect the dynamics of the H II region where $w=2$, and c) solve these expressions for a set of physically-motivated conditions. We find that photoionisation feedback from massive stars is the principal mode of feedback on molecular cloud scales, driving accelerating outflows from molecular clouds in cases where the peaked density structure around young massive stars is considered at radii between $\sim$0.1 and 10-100 pc. Under a large range of conditions the effect of winds and radiation on the dynamics of H II regions is around 10% of the contribution from photoionisation. The effect of winds and radiation pressure are most important at high densities, either close to the star or in very dense clouds such as those in the Central Molecular Zone of the Milky Way. Out to $\sim$0.1 pc they are the principal drivers of the H II region. Lower metallicities make the relative effect of photoionisation even stronger as the ionised gas temperature is higher., Comment: 20 pages, 13 figures, accepted by MNRAS

This paper aims to provide new insights on the origin of the TeV source VER J1907+062 through new high-quality radio observations. We used the Karl G. Jansky Very Large Array (VLA) to observe the whole extension of VER J1907+062 at 1.5 GHz with a mosaicking technique and the PSR J1907+0602 in a single pointing at 6 GHz. These data were used together with $^{12}$CO and atomic hydrogen observations obtained from public surveys to investigate the interstellar medium in the direction of VER J1907+062. The new radio observations do not show any evidence of a pulsar wind nebula (PWN) driven by the pulsars present in the field and no radio counterpart to the proposed X-ray PWN powered by PSR J1907+0602 is seen in the new VLA image at 6 GHz down to a noise level of 10 $\mu$Jy/beam. Molecular clouds were discovered over the eastern, southern, and western borders of the radio shell of G40.5$-$0.5, suggesting an association with this supernova remnant. We explored several scenarios for the origin of VER J1907+062. We propose as the most probable scenario one in which the TeV emission is produced by two separated gamma-ray sources located at different distances: one of leptonic origin and associated with a PWN powered by PSR J1907+0602 at $\sim 3.2$ kpc and another of hadronic origin and produced by the interaction between G40.5$-$0.5 and the surrounding molecular gas at $\sim 8.7$ kpc., Comment: Accepted for publicacion in MNRAS. Preprint version

We introduce a new suite of simulations, "The Cloud Factory", which self-consistently forms molecular cloud complexes at high enough resolution to resolve internal substructure (up to 0.25 Msol in mass) all while including galactic-scale forces. We use a version of the Arepo code modified to include a detailed treatment of the physics of the cold molecular ISM, and an analytical galactic gravitational potential for computational efficiency. The simulations have nested levels of resolution, with the lowest layer tied to tracer particles injected into individual cloud complexes. These tracer refinement regions are embedded in the larger simulation so continue to experience forces from outside the cloud. This allows the simulations to act as a laboratory for testing the effect of galactic environment on star formation. Here we introduce our method and investigate the effect of galactic environment on filamentary clouds. We find that cloud complexes formed after a clustered burst of feedback, have shorter lengths and are less likely to fragment compared to quiescent clouds (e.g. the Musca filament) or those dominated by the galactic potential (e.g. Nessie). Spiral arms and differential rotation preferentially align filaments, but strong feedback randomises them. Long filaments formed within the cloud complexes are necessarily coherent with low internal velocity gradients, which has implications for the formation of filamentary star-clusters. Cloud complexes formed in regions dominated by supernova feedback have fewer star-forming cores, and these are more widely distributed. These differences show galactic-scale forces can have a significant impact on star formation within molecular clouds., 20 pages, 15 figures, submitted to MNRAS

The morphology of the Milky Way is still a matter of debate. In order to shed light on uncertainties surrounding the structure of the Galaxy, in this paper, we study the imprint of spiral arms on the distribution and properties of its molecular gas. To do so, we take full advantage of the SEDIGISM survey that observed a large area of the inner Galaxy in the $^{13}$CO(2-1) line at an angular resolution of 28". We analyse the influences of the spiral arms by considering the features of the molecular gas emission as a whole across the longitude-velocity map built from the full survey. Additionally, we examine the properties of the molecular clouds in the spiral arms compared to the properties of their counterparts in the inter-arm regions. Through flux and luminosity probability distribution functions, we find that the molecular gas emission associated with the spiral arms does not differ significantly from the emission between the arms. On average, spiral arms show masses per unit length of $\sim10^5-10^6$ M$_{\odot} $kpc$^{-1}$. This is similar to values inferred from data sets in which emission distributions were segmented into molecular clouds. By examining the cloud distribution across the Galactic plane, we infer that the molecular mass in the spiral arms is a factor of 1.5 higher than that of the inter-arm medium, similar to what is found for other spiral galaxies in the local Universe. We observe that only the distributions of cloud mass surface densities and aspect ratio in the spiral arms show significant differences compared to those of the inter-arm medium; other observed differences appear instead to be driven by a distance bias. By comparing our results with simulations and observations of nearby galaxies, we conclude that the measured quantities would classify the Milky Way as a flocculent spiral galaxy, rather than as a grand-design one., Comment: Accepted for publication in A&A. 38 pages (17 of Appendices), 26 figures, 7 tables. The updated SEDIGISM cloud catalogue, containing spiral arm association information, will be available as part of the SEDIGISM database ( https://sedigism.mpifr-bonn.mpg.de/index.html )

The aim of this study is to investigate the evolution of the dust-to-gas ratio in the self-similar collapse of a filamentary molecular cloud. For this purpose, we use single fluid dusty-gas model in our study, which describes a single fluid moving with the barycentric velocity of the mixture instead of two-fluid method. The self-similar technique is used to consider the problem in two phases of the collapse, i.e. isothermal and polytropic collapse phases. Regarding the analytical methods, we obtain a semi-analytical solution for the dust-to-gas ratio as a function of the barycentric velocity at large radii of the filament. Furthermore, the polytropic collapse is solved numerically at large radii of a collapsing filamentary cloud. The results show that the profile of dust-to-gas ratio is very different for the isothermal and polytropic cases. This issue suggests that thermodynamic processes during the collapse have the most significant effect on the evolution of the dust-to-gas ratio. It was also proved that the intrinsic density and the grain size play important roles on the values of the dust-to-gas ratio during the self-similar collapse. Finally, the results address some outstanding issues about the dust distribution during the gravitational collapse (either the isothermal and adiabatic collapse) which has not received much attention before.

Over the past decade, studies of dust in the Andromeda galaxy (M31) have shown radial variations in the dust emissivity index ($\beta$). Understanding the astrophysical reasons behind these radial variations may give clues about the chemical composition of dust grains, their physical structure, and the evolution of dust. We use $^{12}$CO(J=1-0) observations taken by the Combined Array for Research in Millimeter Astronomy (CARMA) and dust maps derived from \textit{Herschel} images, both with an angular resolution of 8" and spatial resolution of 30 pc, to study variations in $\beta$ across an area of $\approx$ 18.6 kpc$^2$ in M31. We extract sources, which we identify as molecular clouds, by applying the astrodendro algorithm to the $^{12}$CO and dust maps, which as a byproduct allows us to compare continuum emission from dust and CO emission as alternative ways of finding molecular clouds. We then use these catalogues to investigate whether there is evidence that $\beta$ is different inside and outside molecular clouds. Our results confirm the radial variations of $\beta$ seen in previous studies. However, we find little difference between the average $\beta$ inside molecular clouds compared to outside molecular clouds, in disagreement with models which predict an increase of $\beta$ in dense environments. Finally, we find some clouds traced by dust with very little CO which may be either clouds dominated by atomic gas or clouds of molecular gas that contain little CO., Comment: 14 pages, 11 figures, accepted for publication in MNRAS

High mass proto-stars create Ultra-Compact Hii regions (UCHII) at the stage of evolution when most of the accretion is finished but the star is still heavily embedded in molecular material. The morphologies of UCHII regions reflect the interactions of stellar winds, stellar motions, and density structure in the molecular cloud; they are complex and it has been very difficult to interpret them. We here present data obtained with TEXES on the NASA IRTF of the [NeII] emission line in the proto-cluster of young OB stars in W33 Main. The data cube has a spatial resolution of ~ 1.4 arcsec and true velocity resolution ~ 5 km/s; with A ~ 0.02Av it is relatively unaffected by extinction. We have run 3D hydrodynamic and line profile simulations, using PLUTO and RADMC-3D, of the gas structures created by multiple windy stars moving relative to each other through the ambient cloud. By iterative comparison of the data cube and the simulations, we arrive at models that reproduce the different morphology and kinematic structure of each UCHII region in W33 Main. The results indicate that each sub-source probably holds multiple exciting stars, permitting an improved view of the stellar population, and finds the stellar trajectories, which may determine the dynamical development of the proto-cluster., 20 pages, 12 figures, Accepted by MNRAS 18 October 2021

We present arcminute-resolution intensity and polarization maps of the Galactic center made with the Atacama Cosmology Telescope (ACT). The maps cover a 32 deg$^2$ field at 98, 150, and 224 GHz with $\vert l\vert\le4^\circ$, $\vert b\vert\le2^\circ$. We combine these data with Planck observations at similar frequencies to create coadded maps with increased sensitivity at large angular scales. With the coadded maps, we are able to resolve many known features of the Central Molecular Zone (CMZ) in both total intensity and polarization. We map the orientation of the plane-of-sky component of the Galactic magnetic field inferred from the polarization angle in the CMZ, finding significant changes in morphology in the three frequency bands as the underlying dominant emission mechanism changes from synchrotron to dust emission. Selected Galactic center sources, including Sgr A*, the Brick molecular cloud (G0.253+0.016), the Mouse pulsar wind nebula (G359.23-0.82), and the Tornado supernova remnant candidate (G357.7-0.1), are examined in detail. These data illustrate the potential for leveraging ground-based Cosmic Microwave Background polarization experiments for Galactic science., 26 pages, 14 figures, accepted for publication in ApJ

The spiral structure in the Solar neighborhood is an important issue in astronomy. In the past few years, there is significant progress in observation. The distances for a large number of good spiral tracers, i.e. giant molecular clouds, high-mass star-formation region masers, HII regions, O-type stars and young open clusters, have been accurately estimated, making it possible to depict the detailed properties of nearby spiral arms. In this work, we first give an overview about the research status for the Galaxy's spiral structure based on different types of tracers. Then the objects with distance uncertainties better than 15\% and $, Comment: 23 pages, 4 figures, published in Frontiers in Astronomy and Space Sciences as a REVIEW article

A major question in the field of star formation is how molecular clouds form out of the diffuse Interstellar Medium (ISM). Recent advances in 3D dust mapping are revolutionizing our view of the structure of the ISM. Using the highest-resolution 3D dust map to date, we explore the structure of a nearby star-forming region, which includes the well-known Perseus and Taurus molecular clouds. We reveal an extended near-spherical shell, 156 pc in diameter, hereafter the "Per-Tau Shell", in which the Perseus and Taurus clouds are embedded. We also find a large ring structure at the location of Taurus, hereafter, the "Tau Ring". We discuss a formation scenario for the Per-Tau Shell, in which previous stellar and supernova (SN) feedback events formed a large expanding shell, where the swept-up ISM has condensed to form both the shell and the Perseus and Taurus molecular clouds within it. We present auxiliary observations of HI, H$\alpha$, $^{26}$Al, and X-rays that further support this scenario, and estimate Per-Tau Shell's age to be $\approx 6-22$ Myrs. The Per-Tau shell offers the first three-dimensional observational view of a phenomenon long-hypothesized theoretically, molecular cloud formation and star formation triggered by previous stellar and SN feedback., Comment: ApJ Letters, accepted. Main text: 8 pages, 4 figures. An Interactive + Augmented Reality Figure at https://faun.rc.fas.harvard.edu/czucker/Paper_Figures/sbialy/pertau_superbubble.html

Recently the MAGIC telescope observed three TeV gamma-ray extended sources in the galactic plane in the neighborhood of radio SNR G24.7+0.6. Among them, the PWN HESS J1837-069 was detected earlier by the HESS observatory during its first galactic plane survey. The other two sources, MAGIC J1835-069 and MAGIC J1837-073 are detected for the first time at such high energies. Here we shall show that the observed gamma-rays from the SNR G24.7+0.6 and the HESS J1837-069 can be explained in terms of hadronic interactions of the PWN/SNR accelerated cosmic rays with the ambient matter. We shall further demonstrate that the observed gamma-rays from the MAGIC J1837$-$073 can be interpreted through hadronic interactions of runaway cosmic-rays from PWN HESS J1837-069 with the molecular cloud at the location of MAGIC J1837-073. No such association has been found between MAGIC J1835$-$069 and SNR G24.7+0.6 or PWN HESS J1837$-$069. We have examined the maximum energy attainable by cosmic-ray particles in the SNR G24.7+0.6/ PWN HESS J1837-069 and the possibility of their detection with future gamma-ray telescopes. The study of TeV neutrino emissions from the stated sources suggests that the HESS J1837$-$069 should be detected by IceCube Gen-2 neutrino telescope in a few years of observation., 9 pages, 6 figures

Molecular clouds are complex magnetized structures, with variations over a broad range of length scales. Ionization in dense, shielded clumps and cores of molecular clouds is thought to be caused by charged cosmic rays (CRs). These CRs can also contribute to heating the gas deep within molecular clouds, and their effect can be substantial in environments where CRs are abundant. CRs propagate predominantly by diffusion in media with disordered magnetic fields. The complex magnetic structures in molecular clouds therefore determine the propagation and spatial distribution of CRs within them, and hence regulate their local ionization and heating patterns. Optical and near-infrared (NIR) polarization of starlight through molecular clouds is often used to trace magnetic fields. The coefficients of CR diffusion in magnetized molecular cloud complexes can be inferred from the observed fluctuations in these optical/NIR starlight polarisations. Here, we present calculations of the expected CR heating patterns in the star-forming filaments of IC 5146, determined from optical/NIR observations. Our calculations show that local conditions give rise to substantial variation in CR propagation. This affects the local CR heating power. Such effects are expected to be severe in star-forming galaxies rich in CRs. The molecular clouds in these galaxies could evolve differently to those in galaxies where CRs are less abundant., Comment: Presented at the 37th International Cosmic Ray Conference (ICRC 2021). 8 pages, 2 figures, 1 table

Cosmic Ray (CR) interactions with the dense gas inside Giant Molecular Clouds (GMCs) produce neutral pions, which in turn decay into gamma rays. Thus, the gamma ray emission from GMCs is a direct tracer of the cosmic ray density and the matter density inside the clouds. Detection of enhanced TeV emission from GMCs, i.e., an emission significantly larger than what is expected from the average Galactic cosmic rays illuminating the cloud, can imply a variation in the local cosmic ray density, due to, for example, the presence of a recent accelerator in proximity to the cloud. Such gamma-ray observations can be crucial in probing the cosmic ray distribution across our Galaxy, but are complicated to perform with present generation Imaging Atmospheric Cherenkov Telescopes (IACTs). These studies require differentiating between the strong cosmic-ray induced background, the large scale diffuse emission, and the emission from the clouds, which is difficult to the small field of view of present generation IACTs. In this contribution, we use H.E.S.S. data collected over 16 years to search for TeV emission from GMCs in the inner molecular galacto-centric ring of our Galaxy. We implement a 3D FoV likelihood technique, and simultaneously model the hadronic background, the galactic diffuse emission and the emission expected from known VHE sources to probe for excess TeV gamma ray emission from GMCs., PoS: Proceedings of Science, 395, ISSN:1824-8039, Proceedings of 37th International Cosmic Ray Conference

Galactic cosmic-rays (GCRs) are thought to be accelerated in strong shocks induced by massive star winds and supernova explosions sweeping across the interstellar medium. But the phase of the interstellar medium from which the CRs are extracted has remained elusive until now. Here, we study in detail the GCR source composition deduced from recent measurements by the AMS-02, Voyager 1 and SuperTIGER experiments to obtain information on the composition, ionisation state and dust content of the GCR source reservoirs. We show that the volatile elements of the CR material are mainly accelerated from a plasma of temperature higher than $\sim 2$ MK, which is typical of the hot medium found in galactic superbubbles energised by the activity of massive star winds and supernova explosions. Another GCR component, which is responsible for the overabundance of $^{22}$Ne, most likely arises from acceleration of massive star winds in their termination shocks. From the CR-related $\gamma$-ray luminosity of the Milky Way, we estimate that the ion acceleration efficiency in both supernova shocks and wind termination shocks is of the order of $10^{-5}$. The GCR source composition also shows evidence for a preferential acceleration of refractory elements contained in interstellar dust. We suggest that the GCR refractories are also produced in superbubbles, from shock acceleration and subsequent sputtering of dust grains continuously incorporated into the hot plasma through thermal evaporation of embedded molecular clouds. Our model explains well the measured abundances of all primary and mostly primary CRs from H to Zr, including the overabundance of $^{22}$Ne., Comment: 24 pages, 18 figures, submitted to MNRAS. Version 2: as accepted for publication

We observed the G305 star forming complex in the $J=3\text{-}2$ lines of $^{12}$CO and $^{13}$CO to investigate how molecular gas surrounding the central stellar clusters is being impacted by feedback. The APEX telescope's LAsMA multi-beam receiver was used to observe the region. Excitation temperatures and column density maps were produced. Combining our data with data from the SEDIGISM survey resulted in a $^{13}$CO $J=3\text{-}2/2\text{-}1$ excitation map. To verify whether feedback from stellar clusters is responsible for exciting the gas, the distribution of CO excitation was compared with that of 8$\,\mu\rm{m}$ emission imaged with Spitzer, which is dominated by UV-excited emission from PAHs. Line centroid velocities, as well as stacked line profiles were examined to investigate the effect of feedback on the gas dynamics. Line profiles along radially outward directions demonstrate that the excitation temperature and $^{13}$CO $J=3\text{-}2/2\text{-}1$ ratio increase steeply by factors of $\sim\,2-3$ at the edge of the denser gas traced by $^{13}$CO that faces the hot stars at the center of the complex and steadily decreases away from it. Column density also increases at the leading edge, but does not always decrease steadily outward. Regions with higher 8$\,\mu\rm{m}$ flux have higher median excitation temperatures, column densities and $^{13}$CO $J=3\text{-}2/2\text{-}1$ ratio. The centroid velocity probability distribution function of the region shows exponential wings, indicative of turbulence driven by strong stellar winds. Stacked spectra in regions with stronger feedback have higher skewness and narrower peaks with pronounced wings compared to regions with weaker feedback. Feedback from the stellar cluster in G305 has demonstrable effects on the excitation as well as on the dynamics of the giant molecular cloud., Comment: 18 pages, 17 figures, to be published in A&A

We aim to characterize a diverse selection of dense, potentially star-forming cores, clumps, and clouds within the Milky Way in terms of their dust emission and SF activity. We studied 53 fields that have been observed in the JCMT SCUBA-2 continuum survey SCOPE and have been mapped with Herschel. We estimated dust properties by fitting Herschel observations with modified blackbody functions, studied the relationship between dust temperature and dust opacity spectral index $\beta$, and estimated column densities. We extracted clumps from the SCUBA-2 850 $\mu$m maps with the FellWalker algorithm and examined their masses and sizes. Clumps are associated with young stellar objects found in several catalogs. We estimated the gravitational stability of the clumps with virial analysis. The clumps are categorized as unbound starless, prestellar, or protostellar. We find 529 dense clumps, typically with high column densities from (0.3-4.8)$\times 10^{22}$ cm$^{-2}$, with a mean of (1.5$\pm$0.04)$\times10^{22}$ cm$^{-2}$, low temperatures ($T\sim $10-20 K), and estimated submillimeter $\beta$ =1.7$\pm$0.1. We detect a slight increase in opacity spectral index toward millimeter wavelengths. Masses of the sources range from 0.04 $M_\odot$ to 4259 $M_\odot$. Mass, linear size, and temperature are correlated with distance. Furthermore, the estimated gravitational stability is dependent on distance, and more distant clumps appear more virially bound. Finally, we present a catalog of properties of the clumps.Our sources present a large array of SF regions, from high-latitude, nearby diffuse clouds to large SF complexes near the Galactic center. Analysis of these regions will continue with the addition of molecular line data, which will allow us to study the densest regions of the clumps in more detail., Comment: 60 pages (article 18 pages), 73 figures To be published in A&A

30 Doradus C is a superbubble which emits the brightest nonthermal X- and TeV gamma-rays in the Local Group. In order to explore detailed connection between the high energy radiation and the interstellar medium, we have carried out new CO and HI observations using the Atacama Large Millimeter$/$Submillimeter Array (ALMA), Atacama Submillimeter Telescope Experiment, and the Australia Telescope Compact Array with resolutions of up to 3 pc. The ALMA data of $^{12}$CO($J$ = 1-0) emission revealed 23 molecular clouds with the typical diameters of $\sim$6-12 pc and masses of $\sim$600-10000 $M_{\odot}$. The comparison with the X-rays of $XMM$-$Newton$ at $\sim$3 pc resolution shows that X-rays are enhanced toward these clouds. The CO data were combined with the HI to estimate the total interstellar protons. Comparison of the interstellar proton column density and the X-rays revealed that the X-rays are enhanced with the total proton. These are most likely due to the shock-cloud interaction modeled by the magnetohydrodynamical simulations (Inoue et al. 2012, ApJ, 744, 71). Further, we note a trend that the X-ray photon index varies with distance from the center of the high-mass star cluster, suggesting that the cosmic-ray electrons are accelerated by one or multiple supernovae in the cluster. Based on these results we discuss the role of the interstellar medium in cosmic-ray particle acceleration., 20 pages, 14 figures, 3 tables, accepted for publication in The Astrophysical Journal

We present high spatial resolution (12pc) Atacama Large Millimeter/sub-millimeter Array CO(J=3-2) observations of the nearby lenticular galaxy NGC4429. We identify 217 giant molecular clouds within the 450pc radius molecular gas disc. The clouds generally have smaller sizes and masses but higher surface densities and observed linewidths than those of Milky Way disc clouds. An unusually steep size - line width relation and large cloud internal velocity gradients (0.05 - 0.91 km s^-1 pc^-1) and observed Virial parameters (alpha_obs,vir = 4.0) are found, that appear due to internal rotation driven by the background galactic gravitational potential. Removing this rotation, an internal Virial equilibrium appears to be established between the self-gravitational (Usg) and turbulent kinetic (Eturb) energies of each cloud, i.e. alpha_sg,vir=Usg/Eturb = 1.3. However, to properly account for both self and external gravity (shear and tidal forces), we formulate a modified Virial theorem and define an effective Virial parameter alpha_eff,vir = alpha_sg,vir + Usg/Eext (and associated effective velocity dispersion). The NGC4429 clouds then appear to be in a critical state in which the self-gravitational energy and the contribution of external gravity to the cloud's energy budget (Eext) are approximately equal, i.e. Eext/Usg~1. As such, alpha_eff,vir = 2.2 and most clouds are not virialised but remain marginally gravitationally bound. We show this is consistent with the clouds having sizes similar to their tidal radii and being generally radially elongated. External gravity is thus as important as self-gravity to regulate the clouds of NGC4429., Comment: Accepted by MNRAS