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  • 1
    Online Resource
    Online Resource
    Giant molecular cloud catalogues for PHANGS-ALMA: methods and initial results
    Oxford University Press (OUP) ; 2021
    In:  Monthly Notices of the Royal Astronomical Society Vol. 502, No. 1 ( 2021-02-02), p. 1218-1245
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 502, No. 1 ( 2021-02-02), p. 1218-1245
    Abstract: We present improved methods for segmenting CO emission from galaxies into individual molecular clouds, providing an update to the cprops algorithms presented by Rosolowsky  & Leroy. The new code enables both homogenization of the noise and spatial resolution among data, which allows for rigorous comparative analysis. The code also models the completeness of the data via false source injection and includes an updated segmentation approach to better deal with blended emission. These improved algorithms are implemented in a publicly available Python package, pycprops. We apply these methods to 10 of the nearest galaxies in the PHANGS-ALMA survey, cataloguing CO emission at a common 90 pc resolution and a matched noise level. We measure the properties of 4986 individual clouds identified in these targets. We investigate the scaling relations among cloud properties and the cloud mass distributions in each galaxy. The physical properties of clouds vary among galaxies, both as a function of galactocentric radius and as a function of dynamical environment. Overall, the clouds in our target galaxies are well-described by approximate energy equipartition, although clouds in stellar bars and galaxy centres show elevated line widths and virial parameters. The mass distribution of clouds in spiral arms has a typical mass scale that is 2.5× larger than interarm clouds and spiral arms clouds show slightly lower median virial parameters compared to interarm clouds (1.2 versus 1.4).
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stab085
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 207232-4
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 2
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    A Model for the Onset of Self-gravitation and Star Formation in Molecular Gas Governed by Galactic Forces. I. Cloud-scale Gas Motions
    American Astronomical Society ; 2018
    In:  The Astrophysical Journal Vol. 854, No. 2 ( 2018-02-20), p. 100-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 854, No. 2 ( 2018-02-20), p. 100-
    Abstract: Modern extragalactic molecular gas surveys now reach the scales of star-forming giant molecular clouds (GMCs; 20–50 pc). Systematic variations in GMC properties with galaxy environment imply that clouds are not universally self-gravitating objects, decoupled from their surroundings. Here we re-examine the coupling of clouds to their environment and develop a model for 3D gas motions generated by forces arising with the galaxy gravitational potential defined by the background disk of stars and dark matter. We show that these motions can resemble or even exceed the motions needed to support gas against its own self-gravity throughout typical galactic disks. The importance of the galactic potential in spiral arms and galactic centers suggests that the response to self-gravity does not always dominate the motions of gas at GMC scales, with implications for observed gas kinematics, virial equilibrium, and cloud morphology. We describe how a uniform treatment of gas motions in the plane and in the vertical direction synthesizes the two main mechanisms proposed to regulate star formation: vertical pressure equilibrium and shear/Coriolis forces as parameterized by Toomre Q  ≈ 1. As the modeled motions are coherent and continually driven by the external potential, they represent support for the gas that is distinct from that conventionally attributed to turbulence, which decays rapidly and thus requires maintenance, e.g., via feedback from star formation. Thus, our model suggests that the galaxy itself can impose an important limit on star formation, as we explore in a second paper in this series.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/aaa290
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2018
    detail.hit.zdb_id: 2960-9
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 3
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    PHANGS CO Kinematics: Disk Orientations and Rotation Curves at 150 pc Resolution
    American Astronomical Society ; 2020
    In:  The Astrophysical Journal Vol. 897, No. 2 ( 2020-07-01), p. 122-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 897, No. 2 ( 2020-07-01), p. 122-
    Abstract: We present kinematic orientations and high-resolution (150 pc) rotation curves for 67 main-sequence star-forming galaxies surveyed in CO (2–1) emission by PHANGS–ALMA. Our measurements are based on the application of a new fitting method tailored to CO velocity fields. Our approach identifies an optimal global orientation as a way to reduce the impact of nonaxisymmetric (bar and spiral) features and the uneven spatial sampling characteristic of CO emission in the inner regions of nearby galaxies. The method performs especially well when applied to the large number of independent lines of sight contained in the PHANGS CO velocity fields mapped at 1″ resolution. The high-resolution rotation curves fitted to these data are sensitive probes of mass distribution in the inner regions of these galaxies. We use the inner slope as well as the amplitude of our fitted rotation curves to demonstrate that CO is a reliable global dynamical mass tracer. From the consistency between photometric orientations from the literature and kinematic orientations determined with our method, we infer that the shapes of stellar disks in the mass range of log( ) = 9.0–10.9 probed by our sample are very close to circular and have uniform thickness.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/ab9953
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2020
    detail.hit.zdb_id: 2960-9
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 4
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    PHANGS–ALMA: Arcsecond CO(2–1) Imaging of Nearby Star-forming Galaxies
    American Astronomical Society ; 2021
    In:  The Astrophysical Journal Supplement Series Vol. 257, No. 2 ( 2021-12-01), p. 43-
    Details
    In: The Astrophysical Journal Supplement Series, American Astronomical Society, Vol. 257, No. 2 ( 2021-12-01), p. 43-
    Abstract: We present PHANGS–ALMA, the first survey to map CO J = 2 → 1 line emission at ∼1″ ∼100 pc spatial resolution from a representative sample of 90 nearby ( d ≲ 20 Mpc) galaxies that lie on or near the z = 0 “main sequence” of star-forming galaxies. CO line emission traces the bulk distribution of molecular gas, which is the cold, star-forming phase of the interstellar medium. At the resolution achieved by PHANGS–ALMA, each beam reaches the size of a typical individual giant molecular cloud, so that these data can be used to measure the demographics, life cycle, and physical state of molecular clouds across the population of galaxies where the majority of stars form at z = 0. This paper describes the scientific motivation and background for the survey, sample selection, global properties of the targets, Atacama Large Millimeter/submillimeter Array (ALMA) observations, and characteristics of the delivered data and derived data products. As the ALMA sample serves as the parent sample for parallel surveys with MUSE on the Very Large Telescope, the Hubble Space Telescope, AstroSat, the Very Large Array, and other facilities, we include a detailed discussion of the sample selection. We detail the estimation of galaxy mass, size, star formation rate, CO luminosity, and other properties, compare estimates using different systems and provide best-estimate integrated measurements for each target. We also report the design and execution of the ALMA observations, which combine a Cycle 5 Large Program, a series of smaller programs, and archival observations. Finally, we present the first 1″ resolution atlas of CO emission from nearby galaxies and describe the properties and contents of the first PHANGS–ALMA public data release.
    Type of Medium: Online Resource
    ISSN: 0067-0049 , 1538-4365
    URL: Article
    DOI: 10.3847/1538-4365/ac17f3
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2021
    detail.hit.zdb_id: 2961-0
    detail.hit.zdb_id: 2006860-8
    SSG: 16,12
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  • 5
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    When Gas Dynamics Decouples from Galactic Rotation: Characterizing ISM Circulation in Disk Galaxies
    American Astronomical Society ; 2020
    In:  The Astrophysical Journal Vol. 892, No. 2 ( 2020-04-01), p. 94-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 892, No. 2 ( 2020-04-01), p. 94-
    Abstract: In galactic disks, galactic rotation sets the bulk motion of gas, and its energy and momentum can be transferred toward small scales. Additionally, in the interstellar medium, random and noncircular motions arise from stellar feedback, cloud–cloud interactions, and instabilities, among other processes. Our aim is to comprehend to what extent small-scale gas dynamics is decoupled from galactic rotation. We study the relative contributions of galactic rotation and local noncircular motions to the circulation of gas, Γ, a macroscopic measure of local rotation, defined as the line integral of the velocity field around a closed path. We measure the circulation distribution as a function of spatial scale in a set of simulated disk galaxies and model the velocity field as the sum of galactic rotation and a Gaussian random field. The random field is parameterized by a broken power law in Fourier space, with a break at the scale . We define the spatial scale at which galactic rotation and noncircular motions contribute equally to Γ. For our simulated galaxies, the gas dynamics at the scale of molecular clouds is usually dominated by noncircular motions, but in the center of galactic disks galactic rotation is still relevant. Our model shows that the transfer of rotation from large scales breaks at the scale , and this transition is necessary to reproduce the circulation distribution. We find that , and therefore the structure of the gas velocity field, is set by the local conditions of gravitational stability and stellar feedback.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/ab7a95
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2020
    detail.hit.zdb_id: 2960-9
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 6
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    Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-forming Galaxies
    American Astronomical Society ; 2020
    In:  The Astrophysical Journal Vol. 892, No. 2 ( 2020-04-01), p. 148-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 892, No. 2 ( 2020-04-01), p. 148-
    Abstract: We compare the observed turbulent pressure in molecular gas, P turb , to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, P DE . To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multiwavelength data that trace the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that P turb correlates with—but almost always exceeds—the estimated P DE on kiloparsec scales. This indicates that the molecular gas is overpressurized relative to the large-scale environment. We show that this overpressurization can be explained by the clumpy nature of molecular gas; a revised estimate of P DE on cloud scales, which accounts for molecular gas self-gravity, external gravity, and ambient pressure, agrees well with the observed P turb in galaxy disks. We also find that molecular gas with cloud-scale in our sample is more likely to be self-gravitating, whereas gas at lower pressure it appears more influenced by ambient pressure and/or external gravity. Furthermore, we show that the ratio between P turb and the observed SFR surface density, , is compatible with stellar feedback-driven momentum injection in most cases, while a subset of the regions may show evidence of turbulence driven by additional sources. The correlation between and kpc-scale P DE in galaxy disks is consistent with the expectation from self-regulated star formation models. Finally, we confirm the empirical correlation between molecular-to-atomic gas ratio and kpc-scale P DE reported in previous works.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/ab781c
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2020
    detail.hit.zdb_id: 2960-9
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 7
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    Online Resource
    MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES
    American Astronomical Society ; 2013
    In:  The Astronomical Journal Vol. 146, No. 2 ( 2013-06-17), p. 19-
    Details
    In: The Astronomical Journal, American Astronomical Society, Vol. 146, No. 2 ( 2013-06-17), p. 19-
    Type of Medium: Online Resource
    ISSN: 0004-6256 , 1538-3881
    URL: Article
    DOI: 10.1088/0004-6256/146/2/19
    RVK:
    US 1090
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2013
    detail.hit.zdb_id: 127191-X
    detail.hit.zdb_id: 2003104-X
    SSG: 16,12
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  • 8
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    Online Resource
    PHANGS–MUSE: The H II region luminosity function of local star-forming galaxies
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 658 ( 2022-02), p. A188-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 658 ( 2022-02), p. A188-
    Abstract: We use an unprecedented sample of about 23 000 H  II regions detected at an average physical resolution of 67 pc in the PHANGS–MUSE sample to study the extragalactic H  II region H α luminosity function (LF). Our observations probe the star-forming disk of 19 nearby spiral galaxies with low inclination and located close to the star formation main sequence at z  = 0. The mean LF slope, α , in our sample is =1.73 with a σ of 0.15. We find that α decreases with the galaxy’s star formation rate surface density, Σ SFR , and argue that this is driven by an enhanced clustering of young stars at high gas surface densities. Looking at the H  II regions within single galaxies, we find that no significant variations occur between the LF of the inner and outer part of the star-forming disk, whereas the LF in the spiral arm areas is shallower than in the inter-arm areas for six out of the 13 galaxies with clearly visible spiral arms. We attribute these variations to the spiral arms increasing the molecular clouds’ arm–inter-arm mass contrast and find suggestive evidence that they are more evident for galaxies with stronger spiral arms. Furthermore, we find systematic variations in α between samples of H  II regions with a high and low ionization parameter, q , and argue that they are driven by the aging of H  II regions.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202141907
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 626-9
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 9
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    A CO isotopologue Line Atlas within the Whirlpool galaxy Survey (CLAWS)
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 662 ( 2022-6), p. A89-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 662 ( 2022-6), p. A89-
    Abstract: We present the CO isotopologue Line Atlas within the Whirpool galaxy Survey (CLAWS), which is based on an IRAM 30 m large programme that provides a benchmark study of numerous faint CO isotopologues in the millimetre-wavelength regime across the full disc of the nearby grand-design spiral galaxy M 51 (NGC 5194). The survey’s core goal is to use the low- J CO isotopologue lines to constrain CO excitation and chemistry, and therefrom the local physical conditions of the gas. In this survey paper, we describe the CLAWS observing and data reduction strategies. We map the J = 1 → 0 and 2 → 1 transitions of the CO isotopologues 12 CO, 13 CO, C 18 O, and C 17 O, as well as several supplementary lines within the 1 mm and 3 mm window (CN(1-0), CS (2-1), CH 3 OH(2-1), N 2 H + (1–0), and HC 3 N (10–9)) at ~1 kpc resolution. A total observation time of 149 h offers unprecedented sensitivity. We use these data to explore several CO isotopologue line ratios in detail, study their radial (and azimuthal) trends, and investigate whether changes in line ratios stem from changes in interstellar medium properties such as gas temperatures, densities, or chemical abundances. For example, we find negative radial trends for the 13 CO/ 12 CO, C 18 O/ 12 CO, and C 18 O/ 13 CO line ratios in their J = 1 → 0 transitions. We also find variations with the local environment, such as higher 12 CO (2–1)/(1–0) or 13 CO/ 12 CO (1-0) line ratios in interarm regions compared to spiral arm regions. We propose that these aforementioned variations in CO line ratios are most likely due to a variation in the optical depth, though abundance variations due to selective nucleosynthesis on a galaxy-wide scale could also play a role. We also study the CO spectral line energy distribution (SLED) using archival JCMT 12 CO (3–2) data and find a variation in the SLED shape with local environmental parameters, suggesting changes in the optical depth, gas temperatures, or densities.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202142247
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 626-9
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 10
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    A sensitive, high-resolution, wide-field IRAM NOEMA CO(1–0) survey of the very nearby spiral galaxy IC 342
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 680 ( 2023-12), p. A4-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 680 ( 2023-12), p. A4-
    Abstract: We present a new wide-field 10.75 × 10.75 arcmin 2 (≈11 × 11 kpc 2 ), high-resolution ( θ  = 3.6″ ≈ 60 pc) NOEMA CO(1–0) survey of the very nearby ( d  = 3.45 Mpc) spiral galaxy IC 342. The survey spans out to about 1.5 effective radii and covers most of the region where molecular gas dominates the cold interstellar medium. We resolved the CO emission into 〉 600 individual giant molecular clouds and associations. We assessed their properties and found that overall the clouds show approximate virial balance, with typical virial parameters of α vir  = 1 − 2. The typical surface density and line width of molecular gas increase from the inter-arm region to the arm and bar region, and they reach their highest values in the inner kiloparsec of the galaxy (median Σ mol  ≈ 80, 140, 160, and 1100  M ⊙ pc −2 , σ CO  ≈ 6.6, 7.6, 9.7, and 18.4 km s −1 for inter-arm, arm, bar, and center clouds, respectively). Clouds in the central part of the galaxy show an enhanced line width relative to their surface densities and evidence of additional sources of dynamical broadening. All of these results agree well with studies of clouds in more distant galaxies at a similar physical resolution. Leveraging our measurements to estimate the density and gravitational free-fall time at 90 pc resolution, averaged on 1.5 kpc hexagonal apertures, we estimate a typical star formation efficiency per free-fall time of 0.45% with a 16 − 84% variation of 0.33 − 0.71% among such 1.5 kpc regions. We speculate that bar-driven gas inflow could explain the large gas concentration in the central kiloparsec and the buildup of the massive nuclear star cluster. This wide-area CO map of the closest face-on massive spiral galaxy demonstrates the current mapping power of NOEMA and has many potential applications. The data and products are publicly available.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202143023
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 626-9
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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