CO Intensity Research Articles

Environmental monitoring system design based on STM32 platform

This study addresses the current societal demand for environmental monitoring by designing an environmental monitoring system based on the STM32 platform. This system assesses and monitors environmental conditions in real-time by tracking parameters such as CO, PM2.5, temperature, humidity, and light intensity. It holds significant value in preventing air pollution and improving indoor air quality. The system employs four types of sensors: the DHT11 digital temperature and humidity sensor, the BH1750FV light sensor, the GP2Y1010AUOF optical dust sensor, and the MQ-7 CO sensor to collect environmental data, which is then processed by the STM32F103C8T6 controller. This system is characterized by its real-time capabilities, high precision, and low power consumption, making it highly practical and valuable for widespread application. The paper provides a detailed discussion of sensor selection, measurement algorithms, and system design and implementation, offering valuable insights for research and applications in related fields.

Unraveling the Mystery of the Low CO-to-H2 Conversion Factor in Starburst Galaxies: RADEX Modeling of the Antennae

CO emission has been widely used as a tracer of molecular gas mass. However, it is a long-standing issue to accurately constrain the CO-to-H2 conversion factor (α CO) that converts CO luminosity to molecular gas mass, especially in starburst galaxies. We present the first resolved α CO modeling results with multiple Atacama Large Millimeter/submillimeter Array CO and 13CO transition observations at both giant molecular cloud (GMC) scale at 150 pc and kiloparsec scale for one of the closest starburst mergers, the Antennae. By combining our CO modeling results and measurements of 350 GHz dust continuum, we find that most GMCs in the Antennae have α CO values approximately four times smaller than the commonly adopted Milky Way value (4.3). We find that α CO at GMC scales shows a strong dependence on CO intensity, 13CO/CO ratio, and GMC velocity dispersion, which is consistent with various theoretical and simulation predictions. Specifically, we suggest that the 13CO/CO line ratio and the velocity dispersion can be used to infer α CO in starburst regions. By applying our modeled α CO in GMC analyses, we find that GMCs in the Antennae are less gravitationally bound than in normal spiral galaxies, which is more consistent with what is predicted by merger simulations. At kiloparsec scale, we find that our modeled α CO values are smaller than the modeled α CO at GMC scale by 40%, which can be due to inclusion of a diffuse gas component with lower α CO values. We find a similar correlation of α CO and CO intensity at kiloparsec scales to that at GMC scales.

Physical and Chemical Properties of Galactic Molecular Gas toward QSO J1851+0035

Atacama Large Millimeter/submillimeter Array (ALMA) data toward QSO J1851+0035 (l = 33.°498, b = +0.°194) were used to study absorption lines by Galactic molecular gas. We detected 17 species (CO, 13CO, C18O, HCO+, H13CO+, HCO, H2CO, C2H, c-C3H, c-C3H2, CN, HCN, HNC, CS, SO, SiO, and C) and set upper limits to 18 species as reference values for chemical models. About 20 independent velocity components at 4.7–10.9 kpc from the Galactic center were identified. Their column density and excitation temperature estimated from the absorption study, as well as the CO intensity distributions obtained from the FUGIN survey, indicate that the components with τ ≲1 correspond to diffuse clouds or cloud outer edges. Simultaneous multiple-Gaussian fitting of CO J = 1–0 and J = 2–1 absorption lines shows that these are composed of narrow- and broad-line components. The kinetic temperature empirically expected from the high HCN/HNC isomer ratio (≳4) reaches ≳40 K and the corresponding thermal width accounts for the line widths of the narrow-line components. CN-bearing molecules and hydrocarbons have tight and linear correlations within the groups. The CO/HCO+ abundance ratio showed a dispersion as large as 3 orders of magnitude with a smaller ratio in a smaller N(HCO+) (or lower A V) range. Some of the velocity components are detected in single-dish CO emission and ALMA HCO+ absorption but without corresponding ALMA CO absorption. This may be explained by the mixture of clumpy CO emitters not resolved with the ∼1 pc single-dish beam surrounded by extended components with a very low CO/HCO+ abundance ratio (i.e., CO-poor gas).

Impacts of Bar-driven Shear and Shocks on Star Formation

Bars drive gas inflow. As the gas flows inward, shocks and shear occur along the bar dust lanes. Such shocks and shear can affect the star formation (SF) and change the gas properties. For four barred galaxies, we present Hα velocity gradient maps that highlight bar-driven shocks and shear using data from the PHANGS-MUSE and PHANGS-ALMA surveys, which allow us to study bar kinematics in unprecedented detail. Velocity gradients are enhanced along the bar dust lanes, where shocks and shear are shown to occur in numerical simulations. Velocity gradient maps also efficiently pick up H ii regions that are expanding or moving relative to the surroundings. We put pseudo-slits on the regions where velocity gradients are enhanced and find that Hα and CO velocities jump up to ∼170 km s−1, even after removing the effects of circular motions due to the galaxy rotation. Enhanced velocity gradients either coincide with the peak of CO intensity along the bar dust lanes or are slightly offset from CO intensity peaks, depending on the objects. Using the Baldwin–Philips–Terlevich BPT diagnostic, we identify the source of ionization on each spaxel and find that SF is inhibited in the high-velocity gradient regions of the bar, and the majority of those regions are classified as a low-ionization nuclear emission-line region (LINER) or composite. This implies that SF is inhibited where bar-driven shear and shocks are strong. Our results are consistent with the results from the numerical simulations that show SF is inhibited in the bar where the shear force is strong.

CO emission survey of asymptotic giant branch stars with ultraviolet excesses

Context. The transition from the spherically symmetric envelopes around asymptotic giant branch (AGB) stars to the asymmetric morphologies observed in planetary nebulae is still not well understood, and the shaping mechanisms are a subject of debate. Even though binarity is widely accepted as a promising option, it is limited by the complication of identifying binary AGB stars observationally. Recently, the presence of ultraviolet excesses in AGB stars has been suggested as a potential indicator of binarity. Aims. Our main goals are to characterise the properties of the circumstellar envelopes (CSEs) around candidate AGB binary stars, specifically those selected based on their UV excess emission, and to compare these properties with those derived from previous CO-based studies of AGB stars. Methods. We observed the 12CO (J=1–0) and 12CO (J=2–1) millimetre-wavelength emission in a sample of 29 AGB binary candidates with the IRAM-30 m antenna. We measured the systemic velocities and the terminal expansion velocities from their line profiles. Population diagrams were used to interpret the results, enabling the estimation of excitation temperatures (Tex), mass-loss rates (Ṁ), and the characteristic sizes of the envelope layers where the CO millimetre emission originates (Rs). We explored different trends between the envelope parameters deduced, multiwavelength flux measurements, and other properties of our sample, and compared them with those previously derived from larger samples of AGB stars found in the literature. Results. We detected 12CO emission in 15 sources, of which 5 are first detections. We found relatively low expansion velocities (3 km s−1 ≲ Vexp ≲ 20 km s−1) in our sample. We derived the average excitation temperature and column density of the CO-emitting layers, which we used to estimate self-consistently the average mass-loss rate (10−8 M⊙ yr−1 ≲ Ṁ ≲ 10−5 M⊙ yr−1) and the CO pho-todissociation radius (5 × 1015 cm ≲ RCO ≲ 2 × 1017 cm) of our targets. We find a correlation between CO intensity and IRAS 60 µm fluxes, revealing a CO-to-IRAS 60 µm ratio lower than for AGB stars and closer to that found for pre-planetary nebulae (pPNe). An anti-correlation is observed between 12CO (and IRAS 60 µm) and the near-ultraviolet (NUV), but no such correlation is observed with the far-ultraviolet (FUV). It is also worth noting that there is no correlation between bolometric luminosity and NUV or FUV. Conclusions. For the first time we have studied the mass-loss properties of UV-excess AGB binary candidates and estimated their main CSE parameters. Our sample of uvAGB stars shows similarities with the broader category of AGB stars, except for a distinct CO-to-IRAS 60 µm trend suggesting enhanced CO photodissociation. Our findings, based on single-dish low-J CO line emission observations, support the dust-driven wind scenario and indicate that alternative mass-loss mechanisms are not necessary (in principle) to explain the ~200–2000 yr old mass-loss ejecta in uvAGBs. The different relationships between 12CO and IRAS 60 µm, with NUV and FUV are consistent with an intrinsic origin of NUV emission, but potential dominance of an extrinsic process (e.g. presence of a binary companion) in FUV emission.

Magnetically Aligned Striations in the L914 Filamentary Cloud

We present CO(J = 1–0) multiline observations toward the L914 dark cloud in the vicinity of the Cygnus X region, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. The CO observations reveal in the L914 cloud a long filament with an angular length of ∼3.°6, corresponding to approximately 50 pc at the measured distance of ∼ 760 pc. Furthermore, a group of hair-like striations are discovered in two subregions of the L914 cloud, which are connected with the dense ridge of the filament. These striations display quasiperiodic characteristics in both the CO intensity images and position–velocity diagrams. Two of the striations also show increasing velocity gradients and dispersions toward the dense ridge, which could be fitted by accretion flows under gravity. Based on the Planck 353 GHz dust polarization data, we find that the striations are well aligned with the magnetic fields. Moreover, both the striations and magnetic fields are perpendicular to the dense ridge, constructing a bimodal configuration. Using the classic method, we estimate the strength of the magnetic field and further evaluate the relative importance of gravity, turbulence, and the magnetic field, finding that the L914 cloud is strongly magnetized. Our results suggest that magnetic fields play an important role in the formation of filamentary structures by channeling the material along the striations toward the dense ridge. The comparison between the observations and simulations suggests that striations could be a product of the magnetohydrodynamic process.

Resolved Measurements of the CO-to-H2 Conversion Factor in 37 Nearby Galaxies

We measure the CO-to-H2 conversion factor (α CO) in 37 galaxies at 2 kpc resolution, using the dust surface density inferred from far-infrared emission as a tracer of the gas surface density and assuming a constant dust-to-metal ratio. In total, we have ∼790 and ∼610 independent measurements of α CO for CO (2–1) and (1–0), respectively. The mean values for α CO (2–1) and α CO (1–0) are 9.3−5.4+4.6 and 4.2−2.0+1.9M⊙pc−2(Kkms−1)−1 , respectively. The CO-intensity-weighted mean is 5.69 for α CO (2–1) and 3.33 for α CO (1–0). We examine how α CO scales with several physical quantities, e.g., the star formation rate (SFR), stellar mass, and dust-mass-weighted average interstellar radiation field strength ( U¯ ). Among them, U¯ , ΣSFR, and the integrated CO intensity (W CO) have the strongest anticorrelation with spatially resolved α CO. We provide linear regression results to α CO for all quantities tested. At galaxy-integrated scales, we observe significant correlations between α CO and W CO, metallicity, U¯ , and ΣSFR. We also find that α CO in each galaxy decreases with the stellar mass surface density (Σ⋆) in high-surface-density regions (Σ⋆ ≥ 100 M ⊙ pc−2), following the power-law relations αCO(2–1)∝Σ⋆−0.5 and αCO(1–0)∝Σ⋆−0.2 . The power-law index is insensitive to the assumed dust-to-metal ratio. We interpret the decrease in α CO with increasing Σ⋆ as a result of higher velocity dispersion compared to isolated, self-gravitating clouds due to the additional gravitational force from stellar sources, which leads to the reduction in α CO. The decrease in α CO at high Σ⋆ is important for accurately assessing molecular gas content and star formation efficiency in the centers of galaxies, which bridge “Milky Way–like” to “starburst-like” conversion factors.

Study on the thermal effect of coal oxidation under different stresses

The utilization of coal resources has been improved by using the method of narrow coal pillar mining, but this leads to a stress concentration in the coal pillars, which causes differences in the oxidation of coal pillars. To study the effect of stress on the oxidation and spontaneous combustion of coal samples, programmed heating-gas chromatography coupling experiments were carried out on coal samples under different stresses, analyzing the effect rule of stress on the gas derivatives of coal samples in the process of heating and oxidation. Furthermore, the mechanism of stress influence on thermal effect parameters is explored on the basis of that analysis. The results show that the rate of oxygen consumption, CO, CO2 concentration and heat release intensity of coal samples show a changing trend, initially increasing and then decreasing with increasing stress, and these values within coal are at the maximum when the stress is 9 MPa; and with increasing stress, the activation energy shows a “V” type change and reaches the minimum of 26.89 kJ/mol at 6 MPa, which indicates that low stress promotes coal spontaneous combustion (CSC), while high stress inhibits CSC. The thermal conduction coefficient of coal samples shows a negative correlation with temperature at the low-temperature stage, while the thermal conductivity of coal samples shows a positive correlation with temperature at the high-temperature stage, and the thermal conduction coefficient of coal samples reaches a minimum at temperatures of 70 °C and 0 MPa of stress. The porosity within coal decreases, and the thermal conductivity coefficient within coal increases with increasing stress because the increase in stress makes the macromolecules within coal disassemble into small molecules, the structure becomes more compact, and the thermal conductivity increases. The study provides an important theoretical basis for better understanding the effect mechanism of stress on CSC.

C ii] Spectral Mapping of the Galactic Wind and Starbursting Disk of M82 with SOFIA

M82 is an archetypal starburst galaxy in the local Universe. The central burst of star formation, thought to be triggered by M82's interaction with other members in the M81 group, is driving a multiphase galaxy-scale wind away from the plane of the disk that has been studied across the electromagnetic spectrum. Here, we present new velocity-resolved observations of the [C ii] 158 μm line in the central disk and the southern outflow of M82 using the upGREAT instrument on board SOFIA. We also report the first detections of velocity-resolved (ΔV = 10 km s−1) [C ii] emission in the outflow of M82 at projected distances of ≈1–2 kpc south of the galaxy center. We compare the [C ii] line profiles to observations of CO and H i and find that likely the majority (>55%) of the [C ii] emission in the outflow is associated with the neutral atomic medium. We find that the fraction of [C ii] actually outflowing from M82 is small compared to the bulk gas outside the midplane (which may be in a halo or tidal streamers), which has important implications for observations of [C ii] outflows at higher redshift. Finally, by comparing the observed ratio of the [C ii] and CO intensities to models of photodissociation regions, we estimate that the far-ultraviolet (FUV) radiation field in the disk is ∼103.5 G 0, in agreement with previous estimates. In the outflow, however, the FUV radiation field is 2–3 orders of magnitudes lower, which may explain the high fraction of [C ii] arising from the neutral medium in the wind.

Characterizing the line emission from molecular clouds

Aims. We aim to characterize and compare the molecular-line emission of three clouds whose star-formation rates span one order of magnitude: California, Perseus, and Orion A. Methods. We used stratified random sampling to select positions representing the different column density regimes of each cloud and observed them with the IRAM 30 m telescope. We covered the 3 mm wavelength band and focused our analysis on CO, HCN, CS, HCO+, HNC, and N2H+. Results. We find that the line intensities depend most strongly on the H2 column density, with which they are tightly correlated. A secondary effect, especially visible in Orion A, is a dependence of the line intensities on the gas temperature. We explored a method that corrects for temperature variations and show that, when it is applied, the emission from the three clouds behaves very similarly. CO intensities vary weakly with column density, while the intensity of traditional dense-gas tracers such as HCN, CS, and HCO+ varies almost linearly with column density. N2H+ differs from all other species in that it traces only cold dense gas. The intensity of the rare HCN and CS isotopologs reveals additional temperature-dependent abundance variations. Overall, the clouds have similar chemical compositions that, as the depth increases, are sequentially dominated by photodissociation, gas-phase reactions, molecular freeze-out, and stellar feedback in the densest parts of Orion A. Our observations also allowed us to calculate line luminosities for each cloud, and a comparison with literature values shows good agreement. We used our HCN(1–0) data to explore the behavior of the HCN conversion factor, finding that it is dominated by the emission from the outermost cloud layers. It also depends strongly on the gas kinetic temperature. Finally, we show that the HCN/CO ratio provides a gas volume density estimate, and that its correlation with the column density resembles that found in extragalactic observations.

Hydrodynamic simulations of the disc of gas around supermassive black holes (HDGAS) – I. Molecular gas dynamics

ABSTRACT We present hydrodynamic simulations of the interstellar medium (ISM) within the circumnuclear disc (CND) of a typical active galactic nucleus (AGN)-dominated galaxy influenced by mechanical feedback from an AGN. The simulations are coupled with the CHIMES non-equilibrium chemistry network to treat the radiative-cooling and AGN-heating. A focus is placed on the central 100 pc scale where AGN outflows are coupled to the ISM and constrained by observational Seyfert-2 galaxies. AGN-feedback models are implemented with different wind-velocity and mass-loading factors. We post-process the simulation snapshots with a radiative-transfer code to obtain the molecular emission lines. We find that the inclusion of an AGN promotes the formation of CO in clumpy and dense regions surrounding supermassive black holes (SMBHs). The CO(1-0) intensity maps (<6 Myr) in the CND seem to match well with observations of NGC 1068 with a best match for a model with 5000 km s−1 wind-velocity and a high mass-loading factor. We attempt to discern between competing explanations for the apparent counter-rotating gas disc in the NGC 1068 through an analysis of kinematic maps of the CO line emission. We suggest that mechanical AGN-feedback could explain the alignment-stability of position-angle across the different CND radii around the SMBH through momentum and energy loading of the wind. It is the wind-velocity that drives the disc out of alignment on a 100 pc scale for a long period of time. The position–velocity diagrams are in broad agreement with the predicted Keplerian rotation-curve in the model without AGN, but the AGN models exhibit a larger degree of scatter, in better agreement with NGC 1068 observations.

Potassium hydroxide surface modification for low temperature Cu/SiO2 hybrid bonding

This paper reports a novel plasma-free surface modification approach for low temperature Cu/SiO2 hybrid bonding. A 1-M KOH solution was employed, which acts as a hydroxyl group supply and further modifies the surface of SiO2 dielectric layer by the Si–OH transformation. Such a KOH solution makes the Cu surface more hydrophilic without increasing its surface roughness. We found that the contact angles significantly decreased after dipping into 0.5–3 M of KOH. A contact angle below 5° was achieved with > 1 M KOH. The X-ray photoelectron spectroscopy (XPS) results showed an increase in Si–OH (7.8% to 40.6%) and decreases in Si–O–Si (64% to 55%), Si–O and CO (28.2% to 4.4%) intensities after KOH wet treatment. Furthermore, the KOH treatment almost does not etch nor roughen the Cu surfaces. Therefore, the bonding temperature could be lowered to 200 °C while keeping high bonding strength and reliability performance. A low specific contact resistance of 5 × 10−8 Ω.cm2 was obtained. Results obtained by scanning electron microscope (SEM) and transmission electron microscope (TEM) show the excellent bonding quality of both SiO2–SiO2 and Cu–Cu interface. Additionally, energy-dispersive X-ray spectrometry (EDS) analyses show no signs of oxides and potassium contaminations at the bonding interfaces.

PHANGS–JWST First Results: A Global and Moderately Resolved View of Mid-infrared and CO Line Emission from Galaxies at the Start of the JWST Era

We explore the relationship between mid-infrared (mid-IR) and CO rotational line emission from massive star-forming galaxies, which is one of the tightest scalings in the local universe. We assemble a large set of unresolved and moderately (∼1 kpc) spatially resolved measurements of CO (1–0) and CO (2–1) intensity, I CO, and mid-IR intensity, I MIR, at 8, 12, 22, and 24 μm. The I CO versus I MIR relationship is reasonably described by a power law with slopes 0.7–1.2 and normalization I CO ∼ 1 K km s−1 at I MIR ∼ 1 MJy sr−1. Both the slopes and intercepts vary systematically with choice of line and band. The comparison between the relations measured for CO (1–0) and CO (2–1) allow us to infer that , in good agreement with other work. The 8 μm and 12 μm bands, with strong polycyclic aromatic hydrocarbon (PAH) features, show steeper CO versus mid-IR slopes than the 22 and 24 μm, consistent with PAH emission arising not just from CO-bright gas but also from atomic or CO-dark gas. The CO-to-mid-IR ratio correlates with global galaxy stellar mass (M ⋆) and anticorrelates with star formation rate/M ⋆. At ∼1 kpc resolution, the first four PHANGS–JWST targets show CO-to-mid-IR relationships that are quantitatively similar to our larger literature sample, including showing the steep CO-to-mid-IR slopes for the JWST PAH-tracing bands, although we caution that these initial data have a small sample size and span a limited range of intensities.

Improving Star Cluster Age Estimates in PHANGS-HST Galaxies and the Impact on Cluster Demographics in NGC 628

ABSTRACT A long-standing problem when deriving the physical properties of stellar populations is the degeneracy between age, reddening, and metallicity. When a single metallicity is used for all the star clusters in a galaxy, this degeneracy can result in ‘catastrophic’ errors for old globular clusters. Typically, approximately 10–20 per cent of all clusters detected in spiral galaxies can have ages that are incorrect by a factor of 10 or more. In this paper, we present a pilot study for four galaxies (NGC 628, NGC 1433, NGC 1365, and NGC 3351) from the PHANGS-HST survey. We describe methods to correct the age-dating for old globular clusters, by first identifying candidates using their colours, and then reassigning ages and reddening based on a lower metallicity solution. We find that young ‘Interlopers’ can be identified from their Hα flux. CO (2-1) intensity or the presence of dust can also be used, but our tests show that they do not work as well. Improvements in the success fraction are possible at the ≈15 per cent level (reducing the fraction of catastrophic age-estimates from between 13 and 21 per cent, to between 3 and 8 per cent). A large fraction of the incorrectly age-dated globular clusters are systematically given ages around 100 Myr, polluting the younger populations as well. Incorrectly age-dated globular clusters significantly impact the observed cluster age distribution in NGC 628, which affects the physical interpretation of cluster disruption in this galaxy. For NGC 1365, we also demonstrate how to fix a second major age-dating problem, where very dusty young clusters with E(B − V) > 1.5 mag are assigned old, globular-cluster like ages. Finally, we note the discovery of a dense population of ≈300 Myr clusters around the central region of NGC 1365 and discuss how this results naturally from the dynamics in a barred galaxy.

COMAP Early Science. VII. Prospects for CO Intensity Mapping at Reionization

We introduce COMAP-EoR, the next generation of the Carbon Monoxide Mapping Array Project aimed at extending CO intensity mapping to the Epoch of Reionization. COMAP-EoR supplements the existing 30 GHz COMAP Pathfinder with two additional 30 GHz instruments and a new 16 GHz receiver. This combination of frequencies will be able to simultaneously map CO(1–0) and CO(2–1) at reionization redshifts (z ∼ 5–8) in addition to providing a significant boost to the z ∼ 3 sensitivity of the Pathfinder. We examine a set of existing models of the EoR CO signal, and find power spectra spanning several orders of magnitude, highlighting our extreme ignorance about this period of cosmic history and the value of the COMAP-EoR measurement. We carry out the most detailed forecast to date of an intensity mapping cross correlation, and find that five out of the six models we consider yield signal to noise ratios (S/Ns) ≳ 20 for COMAP-EoR, with the brightest reaching a S/N above 400. We show that, for these models, COMAP-EoR can make a detailed measurement of the cosmic molecular gas history from z ∼ 2–8, as well as probe the population of faint, star-forming galaxies predicted by these models to be undetectable by traditional surveys. We show that, for the single model that does not predict numerous faint emitters, a COMAP-EoR-type measurement is required to rule out their existence. We briefly explore prospects for a third-generation Expanded Reionization Array (COMAP-ERA) capable of detecting the faintest models and characterizing the brightest signals in extreme detail.

Study on Gas Adsorption Properties (N2, H2, O2, NO, NO2, CO, CO2, SO2, H2S, H2O and NH3) on the O-vacancy-containing Sc2CO2 Monolayer

In this work, we have studied the (N2, H2, O2, NO, NO2, CO, CO2, SO2, H2S, H2O, and NH3) gases adsorption properties on the O-vacancy-containing Sc2CO2 monolayer by first-principles calculations. We have determined the preferred adsorption positions and the structural features of the O-vacancy-containing Sc2CO2 monolayer after adsorption of different gas molecules. The adsorption energy and charge transfer from the monolayer to the gas molecules have been calculated. The calculated results show that H2, N2, NH3, H2S and H2O molecules are physisorbed, while CO2, CO, NO2, NO, O2 and SO2 molecules are chemisorbed in the neighboring area of the O-vacancy of the Sc2CO2 monolayer. The existence of the O-vacancy significantly enhances the CO and CO2 adsorption intensity of the defect Sc2CO2 monolayer compared to the original Sc2CO2 monolayer. Our results show that the O-vacancy-containing Sc2CO2 monolayer can be used for detecting NO gas as a resistive sensor.

An Intensity Mapping Constraint on the CO-galaxy Cross-power Spectrum at Redshift ∼3

Abstract The abundance of cold molecular gas plays a crucial role in models of galaxy evolution. While deep spectroscopic surveys of CO emission lines have been a primary tool for measuring this abundance, the difficulty of these observations has motivated alternative approaches to studying molecular gas content. One technique, line intensity mapping, seeks to constrain the average molecular gas properties of large samples of individually undetectable galaxies through the CO brightness power spectrum. Here we present constraints on the cross-power spectrum between CO intensity maps and optical galaxy catalogs. This cross-measurement allows us to check for systematic problems in CO intensity mapping data, and validate the data analysis used for the auto-power spectrum measurement of the CO Power Spectrum Survey. We place a 2σ upper limit on the band-averaged CO-galaxy cross-power of P × < 540 μK h−3 Mpc3. Our measurement favors a nonzero 〈T CO〉 at around 90% confidence and gives an upper limit on the mean molecular gas density at z ∼ 2.6 of 7.7 × 108 M ⊙ Mpc−3. We forecast the expected cross-power spectrum by applying a number of literature prescriptions for the CO luminosity–halo mass relation to a suite of mock light cones. Under the most optimistic forecasts, the cross-spectrum could be detected with only moderate extensions of the data used here, while more conservative models could be detected with a factor of 10 increase in sensitivity. Ongoing CO intensity mapping experiments will target fields allowing for extensive cross-correlation analysis and should reach the sensitivity required to detect the cross-spectrum signal.

The Kiloparsec-scale Neutral Atomic Carbon Outflow in the Nearby Type 2 Seyfert Galaxy NGC 1068: Evidence for Negative AGN Feedback

Abstract Active galactic nucleus (AGN) feedback is postulated as a key mechanism for regulating star formation within galaxies. Studying the physical properties of the outflowing gas from AGNs is thus crucial for understanding the coevolution of galaxies and supermassive black holes. Here we report 55 pc resolution ALMA neutral atomic carbon [C i] 3 P 1−3 P 0 observations toward the central 1 kpc of the nearby Type 2 Seyfert galaxy NGC 1068, supplemented by 55 pc resolution CO(J = 1−0) observations. We find that [C i] emission within the central kiloparsec is strongly enhanced by a factor of >5 compared to the typical [C i]/CO intensity ratio of ∼0.2 for nearby starburst galaxies (in units of brightness temperature). The most [C i]-enhanced gas (ratio > 1) exhibits a kiloparsec-scale elongated structure centered at the AGN that matches the known biconical ionized gas outflow entraining molecular gas in the disk. A truncated, decelerating bicone model explains well the kinematics of the elongated structure, indicating that the [C i] enhancement is predominantly driven by the interaction between the ISM in the disk and the highly inclined ionized gas outflow (which is likely driven by the radio jet). Our results strongly favor the “CO dissociation scenario” rather than the “in situ C formation” one, which prefers a perfect bicone geometry. We suggest that the high-[C i]/CO intensity ratio gas in NGC 1068 directly traces ISM in the disk that is currently dissociated and entrained by the jet and the outflow, i.e., the “negative” effect of the AGN feedback.

CONCERTO at APEX: Installation and first phase of on-sky commissioning

CONCERTO (CarbON CII line in post-rEionisation and ReionisaTiOn) is a large field-of-view (FoV) spectro-imager that has been installed on the Cassegrain Cabin of Atacama Pathfinder EXperiment (APEX) telescope in April 2021. CONCERTO hosts 2 focal planes and a total number of 4000 Kinetic Inductance Detectors (KID), with an instantaneous FoV of 18.6 arcminutes in the range of 130-310 GHz. The spectral resolution can be easily tuned down to 1 GHz depending on the scientific target. The scientific program of CONCERTO has many objectives, with two main programs focused on mapping the fluctuations of the [CII] line intensity in the reionisation and postreionisation epoch (4.5<z<8.5), and on studying galaxy clusters via the thermal and kinetic Sunyaev-Zel’dovich (SZ) effect. CONCERTO will also measure the dust and molecular gas contents of local and intermediate-redshift galaxies, it will study the Galactic star-forming clouds and finally it will observe the CO intensity fluctuations arising from 0.3<z<2 galaxies. The design of the instrument, installation at APEX and current status of the commissioning phase and science verification will be presented. Also we describe the deployment and first on-sky tests performed between April and June 2021.

Stellar structures, molecular gas, and star formation across the PHANGS sample of nearby galaxies

We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 μm images. At the simplest level, we distinguish five environments: centres, bars, spiral arms, interarm regions, and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, which are publicly released but not explicitly used in this paper. We examine trends with environment in the molecular gas content, star formation rate, and depletion time using PHANGS–ALMA CO(2–1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals clearly dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt–Schmidt relation with a slope compatible with unity within the uncertainties and without significant slope differences among environments. In contrast to what has been suggested by early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle.