Galactic Region Research Articles

Atomic Carbon in the Central Molecular Zone of the Milky Way: Possible Cosmic-Ray Induced Chemistry or Time-dependent Chemistry Associated with SNR Sagittarius A East

Abstract Atomic carbon (C0), being one of the most abundant atomic/molecular species observed in dense molecular gas, is potentially a good tracer of molecular gas mass in many chemical/physical environments, though the variation in C0 abundance outside the Galactic disk region is not yet fully known. This paper presents a wide-field 500 GHz [C i] map of the Galactic central molecular zone (CMZ) obtained with the ASTE 10 m telescope. Principal component analysis and non-LTE multi-transition analysis have shown that [C i] emission predominantly originates from the low-excitation gas component with a temperature of 20–50 K and density of ∼103 cm−3, whereas C0 abundance is likely suppressed in the high-excitation gas component. The average N(C0)/N(CO) abundance ratio in the CMZ is 0.3–0.4, which is 2–3 times that in the Galactic disk. The N(C0)/N(CO) ratio increases to 0.7 in the innermost 10 pc region and to ∼2 in the circumnuclear disk. We discovered C0-rich regions distributed in a ring shape encircling the supernova remnant (SNR) Sgr A East, indicating that the C0 enrichment in the central 10 pc region is a consequence of a molecular cloud–SNR interaction. In the 15 atoms/molecules included in principal component analysis, CN is the only other species that increases in the [C i]-bright ring. The origin of the [C i]-bright ring is likely a cosmic-ray-dominated region created by low-energy cosmic-ray particles accelerated by Sgr A East or primitive molecular gas collected by the SNR in which the conversion from C0 to CO has not reached equilibrium.

Studying the interstellar medium to look for relics of triggered star formation among stellar clusters

ABSTRACT Evidence of triggered star formation at large spatial scales involving stellar clusters is scarce. We investigate a Galactic region (l = 130${_{.}^{\circ}}$0, b = 0${_{.}^{\circ}}$35) populated by several open stellar clusters that according to the last Gaia data release, are located at a distance of about 2.9 kpc. By analysing the interstellar medium (ISM) at infrared, centimeter, and millimeter wavelengths towards this group of clusters we discovered a shell of material of about 2° in size at the same distance. We suggest that the shell, mainly observed at 12 μm and in the H i emission at 21 cm, was generated by the action of massive stars belonging to clusters Berkeley 7 and UBC 414, which lie at its centre. Five clusters (MWSC0152, Czernik 6, Czernik 7, Berkeley 6, NGC 663, and NGC 654) lie at the border of this shell. From the comparison between the dynamical time of the discovered H i shell and the analysis of the ages of stellar populations in these clusters, we conclude that the expansion of the shell could have triggered in the past the formation of stars in some of them. We point out that in order to find physical evidence supporting a genetic connection between stellar clusters, it is necessary not only to study the individual clusters and their stellar populations, but also to investigate their surrounding ISM at a large spatial scale.

ALMA View of the ρ Ophiuchi A PDR with a 360 au Beam: The [C i] Emission Originates from the Plane-parallel PDR and Extended Gas

Abstract We present the results of data analysis of the [C i] (3 P 1–3 P 0) emission from the ρ Ophiuchi A photon-dominated region (PDR) obtained in the ALMA ACA standalone mode with a spatial resolution of 2.″6 (360 au). The [C i] emission shows filamentary structures with a width of ∼1000 au, which are adjacent to the shell structure seen in the 4.5 μm map. We found that the 4.5 μm emission, C0, and CO are distributed in this order from the excitation star (S1) in a complementary pattern. These results indicate that [C i] is emitted from a thin layer in the PDR generated by the excitation star, as predicted in the plane-parallel PDR model. In addition, extended [C i] emission was also detected, which shows nearly uniform integrated intensity over the entire field of view (1.′6 × 1.′6). The line profile of the extended component is different from that of the above shell component. The column density ratio of C0 to CO in the extended component was ∼2, which is significantly higher than those of Galactic massive star-forming regions (0.1–0.2). These results suggest that [C i] is emitted also from the extended gas with a density of cm−3, which is not greatly affected by the excitation star.

Cosmic rays and non-thermal emission in simulated galaxies − I. Electron and proton spectra compared to Voyager-1 data

ABSTRACT Current-day cosmic ray (CR) propagation studies use static Milky Way models and fit parametrized source distributions to data. Instead, we use three-dimensional magnetohydrodynamic (MHD) simulations of isolated galaxies with the moving-mesh code arepo that self-consistently accounts for hydrodynamic effects of CR protons. In post-processing, we calculate their steady-state spectra, taking into account all relevant loss processes. We show that this steady-state assumption is well justified in the disc and generally for regions that emit non-thermal radio and gamma rays. Additionally, we model the spectra of primary electrons, accelerated by supernova remnants, and secondary electrons and positrons produced in hadronic CR proton interactions with the gas. We find that proton spectra above 10 GeV only weakly depend on galactic radius, while they acquire a radial dependence at lower energies due to Coulomb interactions. Radiative losses steepen the spectra of primary CR electrons in the central galactic regions, while diffusive losses dominate in the outskirts. Secondary electrons exhibit a steeper spectrum than primaries because they originate from the transported steeper CR proton spectra. Consistent with Voyager-1 and AMS-02 data, our models (i) show a turnover of proton spectra below GeV energies due to Coulomb interactions so that electrons start to dominate the total particle spectra and (ii) match the shape of the positron fraction up to 10 GeV. We conclude that our steady-state CR modelling in MHD CR galaxy simulations is sufficiently realistic to capture the dominant transport effects shaping their spectra, arguing for a full MHD treatment to accurately model CR transport in the future.

VINTERGATAN III: how to reset the metallicity of the Milky Way

ABSTRACT Using the cosmological zoom simulation VINTERGATAN, we present a new scenario for the onset of star formation at the metal-poor end of the low-[α/Fe] sequence in a Milky Way-like galaxy. In this scenario, the galaxy is fuelled by two distinct gas flows. One is enriched by outflows from massive galaxies, but not the other. While the former feeds the inner galactic region, the latter fuels an outer gas disc, inclined with respect to the main galactic plane, and with a significantly poorer chemical content. The first passage of the last major merger galaxy triggers tidal compression in the outer disc, which increases the gas density and eventually leads to star formation, at a metallicity 0.75 dex lower than the inner galaxy. This forms the first stars of the low-[α/Fe] sequence. These in situ stars have halo-like kinematics, similar to what is observed in the Milky Way, due to the inclination of the outer disc that eventually aligns with the inner one via gravitational torques. We show that this tilting disc scenario is likely to be common in Milky Way-like galaxies. This process implies that the low-[α/Fe] sequence is populated in situ, simultaneously from two formation channels, in the inner and the outer galaxy, with distinct metallicities. This contrasts with purely sequential scenarios for the assembly of the Milky Way disc and could be tested observationally.

Topological defects inspired static spherically symmetric solution

One of the interesting characteristics of topological defects is the deficit solid angle in the hypersurfaces t = constant. The area of a sphere of radius R in this space is not 4πR2. In the work, we try to find the spacetime geometry of the outside of a spherically symmetric distribution of matter (within a galaxy that can be a galactic halo, etc) where the spacetime geometry is characterized by deficit solid angle in the hypersurfaces t = constant. We obtain a solution of Einstein’s field equations for the outside of spherically symmetric matter distribution in the galactic region. The solution describes a black hole. The several features of the solution are discussed.

The Planck Submillimeter Properties of Galactic High-mass Star-forming Regions: Dust Temperatures, Luminosities, Masses, and Star Formation Efficiency

Abstract Massive star formation occurs in the interior of giant molecular clouds and proceeds through many stages. In this work, we focus on massive young stellar objects (MYSOs) and ultracompact H ii regions (UCH ii), where the former are enshrouded in dense envelopes of dust and gas, the latter of which has begun dispersing. By selecting a complete sample of MYSOs and UCH ii from the Red MSX Source (RMS) survey database, we combine Planck and IRAS data and build their spectral energy distributions. With these, we estimate the physical properties (dust temperatures, mass, luminosity) of the sample. Because the RMS database provides unique solar distances, it also allows the instantaneous star formation efficiency (SFE) to be investigated as a function of Galactocentric radius. We find that the SFE increases between 2 and 4.5 kpc, where it reaches a peak, likely in correspondence with the accumulation of molecular material at the end of the Galactic bar. It then stays approximately constant up to 9 kpc, after which it linearly declines, in agreement with predictions from extragalactic studies. This behavior suggests the presence of a significant amount of undetected molecular gas at R G > 8 kpc. Finally, we present diagnostic colors that can be used to identify sites of massive star formation.

Infrared photometry and CaT spectroscopy of globular cluster M 28 (NGC 6626)

Context. Recent studies show that the inner Galactic regions host genuine bulge globular clusters, but also halo intruders, complex remnants of primordial building blocks, and objects likely accreted during major merging events. Aims. In this study we focus on the properties of M 28, a very old and massive cluster currently located in the Galactic bulge. Methods. We analysed wide-field infrared photometry collected by the VVV survey, VVV proper motions, and intermediate-resolution spectra in the calcium triplet range for 113 targets in the cluster area. Results. Our results in general confirm previous estimates of the cluster properties available in the literature. We find no evidence of differences in metallicity between cluster stars, setting an upper limit of Δ[Fe/H] < 0.08 dex to any internal inhomogeneity. We confirm that M 28 is one of the oldest objects in the Galactic bulge (13–14 Gyr). From this result and the literature data, we find evidence of a weak age–metallicity relation among bulge globular clusters that suggests formation and chemical enrichment. In addition, wide-field density maps show that M 28 is tidally stressed and that it is losing mass into the general bulge field. Conclusions. Our study indicates that M 28 is a genuine bulge globular cluster, but its very old age and its mass loss suggest that this cluster could be the remnant of a larger structure, possibly a primeval bulge building block.

WALOP-South: a four-camera one-shot imaging polarimeter for PASIPHAE survey. Paper I—optical design

The WALOP-South instrument will be mounted on the 1 m SAAO telescope in South Africa as part of the PASIPHAE program to carry out a linear imaging polarization survey of the Galactic polar regions in the optical band. Designed to achieve polarimetric sensitivity of $0.05~\%$ across a $35\times35$ arcminute field of view, it will be capable of measuring the Stokes parameters I, q and u in a single exposure in the SDSS-r broadband and narrowband filters between $0.5~{\mu}m - 0.7~{\mu}m$. For each measurement, four images of the full field corresponding to linear polarization angles of 0 deg, 45 deg, 90 deg and 135 deg in the instrument coordinate system will be created on four detectors from which the Stokes parameters can be found using differential photometry. In designing the optical system, major challenges included correcting for the dispersion introduced by large split angle Wollaston Prisms used as analysers as well as other aberrations from the entire field to obtain imaging quality PSF at the detector. We present the optical design of the WALOP-South instrument which overcomes these challenges and delivers near seeing limited PSFs for the entire field of view.

APOGEE DR16: A multi-zone chemical evolution model for the Galactic disc based on MCMC methods

Context.The analysis of the latest release of the Apache Point Observatory Galactic Evolution Experiment project (APOGEE DR16) data suggests the existence of a clear distinction between two sequences of disc stars at different Galactocentric distances in the [α/Fe] versus [Fe/H] abundance ratio space: the so-called high-αsequence, classically associated with an old population of stars in the thick disc with high average [α/Fe], and the low-αsequence, which mostly comprises relatively young stars in the thin disc with low average [α/Fe].Aims.We aim to constrain a multi-zone two-infall chemical evolution model designed for regions at different Galactocentric distances using measured chemical abundances from the APOGEE DR16 sample.Methods.We performed a Bayesian analysis based on a Markov chain Monte Carlo method to fit our multi-zone two-infall chemical evolution model to the APOGEE DR16 data.Results.An inside-out formation of the Galaxy disc naturally emerges from the best fit of our two-infall chemical-evolution model to APOGEE-DR16: Inner Galactic regions are assembled on shorter timescales compared to the external ones. In the outer disc (with radiiR > 6 kpc), the chemical dilution due to a late accretion event of gas with a primordial chemical composition is the main driver of the [Mg/Fe] versus [Fe/H] abundance pattern in the low-αsequence. In the inner disc, in the framework of the two-infall model, we confirm the presence of an enriched gas infall in the low-αphase as suggested by chemo-dynamical models. Our Bayesian analysis of the recent APOGEE DR16 data suggests a significant delay time, ranging from ∼3.0 to 4.7 Gyr, between the first and second gas infall events for all the analysed Galactocentric regions. The best fit model reproduces several observational constraints such as: (i) the present-day stellar and gas surface density profiles; (ii) the present-day abundance gradients; (iii) the star formation rate profile; and (iv) the solar abundance values.Conclusions.Our results propose a clear interpretation of the [Mg/Fe] versus [Fe/H] relations along the Galactic discs. The signatures of a delayed gas-rich merger which gives rise to a hiatus in the star formation history of the Galaxy are impressed in the [Mg/Fe] versus [Fe/H] relation, determining how the low-αstars are distributed in the abundance space at different Galactocentric distances, which is in agreement with the finding of recent chemo-dynamical simulations.

Multiple HC3N line observations towards 19 Galactic massive star-forming regions

Abstract We performed observations of the HC3N (24–23, 17–16, 11–10, 8–7) lines towards a sample consisting of 19 Galactic massive star-forming regions with the Arizona Radio Observatory 12 m and Caltech Submillimeter Observatory 10.4 m telescopes. HC3N (24–23, 17–16, 11–10, 8–7) lines were detected in sources except for W 44, where only HC3N (17–16, 11–10) were detected. Twelve of the nineteen sources showed probable line wing features. The excitation temperatures were estimated from the line ratio of HC3N (24–23) to HC3N (17–16) for 18 sources and are in the range 23– 57 K. The line widths of higher-J transitions are larger than lower-J ones for most sources. This indicates that the inner dense warm regions have more violent turbulence or other motions (such as rotation) than outer regions in these sources. A possible cutoff tendency was found around LIR ∼ 106 L⊙ in the relation between LIR and full width at half maximum line widths.

Charged perfect fluid dark matter model: Known mass density function approach

The concept of dark matter has been imported to explain the observed velocity profile of the spiral galaxies, the flat rotational velocity. Taking the flatness of rotation curves as an input and assuming that the galactic halo is filled with charged perfect fluid having known mass density function, we obtain a space time metric in the galactic halo region. The acquired solution indicates to a (nearly) flat universe, consistent with the present day cosmological observations. Various other aspects of the solution such as attractive gravity in the halo region, stability of the circular orbit, etc., are also analyzed.

The RR Lyrae projected density distribution from the Galactic centre to the halo

The projected density distribution of type ab RR Lyrae (RRab) stars was characterised from the innermost regions of the Milky Way to the halo, with the aim of placing constraints on the Galaxy’s evolution. The compiled sample (NRRab = 64 850) stems from fundamental mode RR Lyrae variables identified by the VVV, OGLE, and Gaia surveys. The distribution is well fitted by three power laws over three radial intervals. In the innermost region (R < 2.2°) the distribution follows ΣRRab[1] ∝ R−0.94 ± 0.051, while in the external region the distribution adheres to ΣRRab[2] ∝ R−1.50 ± 0.019 for 2.2° < R < 8.0° and ΣRRab[3] ∝ R−2.43 ± 0.043 for 8.0° < R < 30.0°. Conversely, the cumulative distribution of red clump (RC) giants exhibits a more concentrated distribution in the mean, but in the central R < 2.2° the RRab population is more peaked, whereas globular clusters (GCs) follow a density power law (ΣGCs ∝ R−1.59 ± 0.060 for R < 30.0°) similar to that of RRab stars, especially when considering a more metal-poor subsample ([Fe/H] < −1.1 dex). The main conclusion emerging from the analysis is that the RRab distribution favours the star cluster infall and merger scenario for creating an important fraction (> 18%) of the central Galactic region. The radii containing half of the populations (half populations radii) are RH RRab = 6.8° (0.99 kpc), RH RC = 4.2° (0.61 kpc), and RH GCs = 11.9° (1.75 kpc) for the RRab stars, RC giants, and GCs, respectively. Finally, merely ∼1% of the stars have been actually discovered in the innermost region (R < 35 pc) out of the expected (based on our considerations) total number of RRab therein: N ∼ 1562. That deficit will be substantially ameliorated with future space missions like the Nancy Grace Roman Space Telescope (formerly WFIRST).

Cosmological direct-collapse black hole formation sites hostile for their growth

ABSTRACT The direct collapse (DC) is a promising mechanism that provides massive seed black holes (BHs) with ∼105 M⊙ in the early universe. To study a long-term accretion growth of a direct-collapse black hole (DCBH), we perform cosmological radiation-hydrodynamics simulations, extending our previous work where we investigated its formation stage. With a high spatial resolution down below the Bondi radius, we show that the accretion rate on to the BH is far below the Eddington value. Such slow mass growth is partly because of the strong radiative feedback from the accreting BH to the surrounding dense gas. Even after it falls into the first galaxy, the accretion rate is substantially suppressed due to the supernova feedback associated with the intense star formation. Moreover, the BH has a large velocity of ∼100 km s−1 relative to the gas, which further reduces the accretion rate. This large relative velocity stems from the fact that the DCBHs form in metal-free environments typically at ∼1 kpc from the galaxy. The BH accelerates as it approaches the galactic centre due to the gravity. The relative velocity never damps and the BH wanders around the outer galactic region. An analytic estimate predicts that the DCBH formation within ∼100 pc around the galactic centre is necessary to decelerate the BH with dynamical friction before z = 7. Since metal enrichment with Z ∼ 10−5−10−3 Z⊙ is expected there, the formation of DCBHs in the metal-enriched environments is preferable for the subsequent rapid growth.

Searching for intergalactic star forming regions in Stephan’s Quintet with SITELLE

Based on SITELLE spectroscopy data, we studied the ionised gas emission for the 175 Hα emission regions in the Stephan’s Quintet (SQ). In this paper we perform a detailed analysis of the star formation rate (SFR), oxygen abundance, and nitrogen-to-oxygen abundance ratio (N/O) of the SQ regions, with the intention of exploring the provenance and evolution of this complex structure. According to the BPT diagram, we found 91 HII, 17 composite, and 7 active galactic nucleus-like regions in SQ. Several regions are compatible with fast shocks models without a precursor for solar metallicity and low density (n = 0.1 cm−3), with velocities in the range of 175–300 km s−1. We derived the total SFR in SQ (log(SFR/M⊙ yr−1 = 0.496)). Twenty-eight percent of the total SFR in SQ comes from starburst A, while 9% is in starburst B, and 45% comes from the regions with a radial velocity lower than 6160 km s−1. For this reason, we assume that the material prior to the collision with the new intruder does not show a high SFR, and therefore SQ was apparently quenched. When considering the integrated SFR for the whole SQ and the new intruder, we found that both zones have a SFR consistent with those obtained in the SDSS star-forming galaxies. At least two chemically different gas components cohabit in SQ where, on average, the regions with high radial velocities (v > 6160 km s−1) have lower values of oxygen abundance and N/O than those with low radial velocities (v ≤ 6160 km s−1). The values found for the line ratios considered in this study, as well as in the oxygen abundance and N/O for the southern debris region and the northernmost tidal tail, are compatible with regions belonging to the outer part of the galaxies. We highlight the presence of inner-outer variation for metallicity and some emission line ratios along the new intruder strands and the young tidal tail south strand. Finally, the SQ Hα regions are outside the galaxies because the interactions have dispersed the gas to the peripheral zones.

Multi-wavelength study of Galactic star-forming regions with near-infrared instruments on 2 - 4 meter class Indian telescopes.

We present a brief description of the activities of the infrared astronomy group of Tata Institute of Fundamental Research with special emphasis on the near-infrared instrumentation for star formation studies using 2 - 4-meter class Indian ground-based telescopes.

Hunting Gravitational Wave Black Holes with Microlensing

Abstract Gravitational microlensing is a powerful tool to search for a population of invisible black holes (BHs) in the Milky Way (MW), including isolated BHs and binary BHs at wide orbits that are complementary to gravitational wave observations. By monitoring highly populated regions of source stars like the MW bulge region, one can pursue microlensing events due to these BHs. We find that if BHs have a Salpeter-like mass function extended beyond 30M ⊙ and a similar velocity and spatial structure to stars in the Galactic bulge and disk regions, the BH population is a dominant source of microlensing events at long timescales of the microlensing light curve ≳100 days. This is due to a boosted sensitivity of the microlensing event rate to lens mass, given as M 2, for such long-timescale events. A monitoring observation of 2 × 1010 stars in the bulge region over 10 yr with the Rubin Observatory Legacy Survey of Space and Time (LSST) would enable one to find about 6 × 105 BH microlensing events. We evaluate the efficiency of potential LSST cadences for characterizing the light curves of BH microlensing and find that nearly all events of long timescales can be detected.

N ii] Fine-structure Emission at 122 and 205 μm in a Galaxy at z = 2.6: A Globally Dense Star-forming Interstellar Medium

Abstract We present new observations with the Atacama Large Millimeter/submillimeter Array of the 122 and 205 μm fine-structure line emission of singly ionized nitrogen in a strongly lensed starburst galaxy at z = 2.6. The 122/205 μm [N ii] line ratio is sensitive to electron density, , in the ionized interstellar medium, and we use this to measure n e ≈ 300 cm−3, averaged across the galaxy. This is over an order of magnitude higher than the Milky Way average, comparable to localized Galactic star-forming regions. Combined with observations of the atomic carbon (C i) and carbon monoxide (CO J = 4–3) in the same system, we reveal the conditions in this intensely star-forming system. The majority of the molecular interstellar medium has been driven to high density, and the resultant conflagration of star formation produces a correspondingly dense ionized phase, presumably colocated with myriad H ii regions that litter the gas-rich disk.

Thermodynamic Constraints on the Non-Baryonic Dark Matter Gas Composing Galactic Halos

To explain rotation curves of spiral galaxies through Newtonian orbital models, massive halos of non-baryonic dark matter (NBDM) are commonly invoked. The postulated properties are that NBDM interacts gravitationally with baryonic matter, yet negligibly interacts with photons. Since halos are large, low-density gaseous bodies, their postulated attributes can be tested against classical thermodynamics and the kinetic theory of gas. Macroscopic models are appropriate because these make few assumptions. NBDM–NBDM collisions must be elastic to avoid the generation of light, but this does not permit halo gas temperature to evolve. If no such collisions exist, then the impossible limit of absolute zero would be attainable since the other available energy source, radiation, does not provide energy to NBDM. The alternative possibility, an undefined temperature, is also inconsistent with basic thermodynamic principles. However, a definable temperature could be attained via collisions with baryons in the intergalactic medium since these deliver kinetic energy to NBDM. In this case, light would be produced since some proportion of baryon collisions are inelastic, thereby rendering the halo detectable. Collisions with baryons are unavoidable, even if NBDM particles are essentially point masses. Note that <0.0001 × the size of a proton is needed to avoid scattering with γ-rays, the shortest wavelength used to study halos. If only elastic collisions exist, NBDM gas would collapse to a tiny, dense volume (zero volume for point masses) during a disturbance—e.g., cosmic rays. NBDM gas should occupy central galactic regions, not halos, since self-gravitating objects are density stratified. In summary, properties of NBDM halos as postulated would result in violations of thermodynamic laws and in a universe unlike that observed.

FEEDBACK: a SOFIA Legacy Program to Study Stellar Feedback in Regions of Massive Star Formation

FEEDBACK is a SOFIA (Stratospheric Observatory for Infrared Astronomy) legacy program dedicated to study the interaction of massive stars with their environment. It performs a survey of 11 galactic high mass star-forming regions in the 158 μm (1.9 THz) line of [C ii] and the 63 μm (4.7 THz) line of [O i]. We employ the 14 pixel Low Frequency Array and 7 pixel High Frequency Array upGREAT heterodyne instrument to spectrally resolve (0.24 MHz) these far-infrared fine structure lines. With a total observing time of 96h, we will cover ∼6700 arcmin2 at 14.″1) angular resolution for the [C ii] line and 6.″3 for the [O i] line. The observations started in spring 2019 (Cycle 7). Our aim is to understand the dynamics in regions dominated by different feedback processes from massive stars such as stellar winds, thermal expansion, and radiation pressure, and to quantify the mechanical energy injection and radiative heating efficiency. This is an important science topic because feedback of massive stars on their environment regulates the physical conditions and sets the emission characteristics in the interstellar medium (ISM), influences the star formation activity through molecular cloud dissolution and compression processes, and drives the evolution of the ISM in galaxies. The [C ii] line provides the kinematics of the gas and is one of the dominant cooling lines of gas for low to moderate densities and UV fields. The [O i] line traces warm and high-density gas, excited in photodissociations regions with a strong UV field or by shocks. The source sample spans a broad range in stellar characteristics from single OB stars, to small groups of O stars, to rich young stellar clusters, to ministarburst complexes. It contains well-known targets such as Aquila, the Cygnus X region, M16, M17, NGC7538, NGC6334, Vela, and W43 as well as a selection of H ii region bubbles, namely RCW49, RCW79, and RCW120. These [C ii] maps, together with the less explored [O i] 63 μm line, provide an outstanding database for the community. They will be made publically available and will trigger further studies and follow-up observations.