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  • 1
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    Online Resource
    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
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 944, No. 2 ( 2023-02-01), p. L10-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 944, No. 2 ( 2023-02-01), p. L10-
    Abstract: 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 μ m. 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 R 21 ∝ I MIR 0.2 , in good agreement with other work. The 8 μ m and 12 μ m bands, with strong polycyclic aromatic hydrocarbon (PAH) features, show steeper CO versus mid-IR slopes than the 22 and 24 μ m, 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.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/acab01
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 2
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    PHANGS–JWST First Results: Mapping the 3.3 μm Polycyclic Aromatic Hydrocarbon Vibrational Band in Nearby Galaxies with NIRCam Medium Bands
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 944, No. 2 ( 2023-02-01), p. L7-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 944, No. 2 ( 2023-02-01), p. L7-
    Abstract: We present maps of the 3.3 μ m polycyclic aromatic hydrocarbon (PAH) emission feature in NGC 628, NGC 1365, and NGC 7496 as observed with the Near-Infrared Camera imager on JWST from the PHANGS–JWST Cycle 1 Treasury project. We create maps that isolate the 3.3 μ m PAH feature in the F335M filter (F335M PAH ) using combinations of the F300M and F360M filters for removal of starlight continuum. This continuum removal is complicated by contamination of the F360M by PAH emission and variations in the stellar spectral energy distribution slopes between 3.0 and 3.6 μ m. We modify the empirical prescription from Lai et al. to remove the starlight continuum in our highly resolved galaxies, which have a range of starlight- and PAH-dominated lines of sight. Analyzing radially binned profiles of the F335M PAH emission, we find that between 5% and 65% of the F335M intensity comes from the 3.3 μ m feature within the inner 0.5 r 25 of our targets. This percentage systematically varies from galaxy to galaxy and shows radial trends within the galaxies related to each galaxy’s distribution of stellar mass, interstellar medium, and star formation. The 3.3 μ m emission is well correlated with the 11.3 μ m PAH feature traced with the MIRI F1130W filter, as is expected, since both features arise from C–H vibrational modes. The average F335M PAH /F1130W ratio agrees with the predictions of recent models by Draine et al. for PAHs with size and charge distributions shifted toward larger grains with normal or higher ionization.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/acb0cf
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 3
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    PHANGS–JWST First Results: Destruction of the PAH Molecules in H ii Regions Probed by JWST and MUSE
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 944, No. 2 ( 2023-02-01), p. L16-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 944, No. 2 ( 2023-02-01), p. L16-
    Abstract: Polycyclic aromatic hydrocarbons (PAHs) play a critical role in the reprocessing of stellar radiation and balancing the heating and cooling processes in the interstellar medium but appear to be destroyed in H ii regions. However, the mechanisms driving their destruction are still not completely understood. Using PHANGS–JWST and PHANGS–MUSE observations, we investigate how the PAH fraction changes in about 1500 H ii regions across four nearby star-forming galaxies (NGC 628, NGC 1365, NGC 7496, and IC 5332). We find a strong anticorrelation between the PAH fraction and the ionization parameter (the ratio between the ionizing photon flux and the hydrogen density) of H ii regions. This relation becomes steeper for more luminous H ii regions. The metallicity of H ii regions has only a minor impact on these results in our galaxy sample. We find that the PAH fraction decreases with the H α equivalent width—a proxy for the age of the H ii regions—although this trend is much weaker than the one identified using the ionization parameter. Our results are consistent with a scenario where hydrogen-ionizing UV radiation is the dominant source of PAH destruction in star-forming regions.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/acac92
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 4
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    C I and CO in nearby spiral galaxies : I. Line ratio and abundance variations at ∼200 pc scales
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 672 ( 2023-04), p. A36-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 672 ( 2023-04), p. A36-
    Abstract: We present new neutral atomic carbon [C  I ] ( 3 P 1  →  3 P 0 ) mapping observations within the inner ∼7 kpc and ∼4 kpc of the disks of NGC 3627 and NGC 4321 at a spatial resolution of 190 pc and 270 pc, respectively, using the Atacama Large Millimeter/Submillimeter Array (ALMA) Atacama Compact Array (ACA). We combine these with the CO(2−1) data from PHANGS-ALMA, and literature [C  I ] and CO data for two other starburst and/or active galactic nucleus (AGN) galaxies (NGC 1808, NGC 7469) with the aim of studying: (a) the spatial distributions of C  I and CO emission; (b) the observed line ratio R C  I /CO = I [ C  I ](1−0 ) / I CO(2−1 ) as a function of various galactic properties; and (c) the abundance ratio of [C  I /CO]. We find excellent spatial correspondence between C  I and CO emission and nearly uniform R C  I /CO ∼ 0.1 across the majority of the star-forming disks of NGC 3627 and NGC 4321. However, R C  I /CO strongly varies from ∼0.05 at the center of NGC 4321 to 〉 0.2 − 0.5 in NGC 1808’s starbursting center and NGC 7469’s center with an X-ray-luminous AGN. Meanwhile, R C  I /CO does not obviously vary with ⟨ U ⟩, which is in line with predictions from photodissociation-dominated region (PDR) models. We also find a mildly decreasing R C  I /CO value with an increasing metallicity over 0.7 − 0.85  Z ⊙ , which is consistent with the literature. Assuming various typical interstellar medium (ISM) conditions representing giant molecular clouds, active star-forming regions, and strong starbursting environments, we calculated the (non)local-thermodynamic-equilibrium radiative transfer and estimated the [C  I /CO] abundance ratio to be ∼0.1 across the disks of NGC 3627 and NGC 4321, similar to previous large-scale findings in Galactic studies. However, this abundance ratio likely experiences a substantial increase, up to ∼1 and ≳1 − 5 in NGC 1808’s starburst and NGC 7469’s strong AGN environments, respectively. This result is in line with the expectations for cosmic-ray dominated region (CRDR) and X-ray dominated region (XDR) chemistry. Finally, we do not find robust evidence for a generally CO-dark-and-C  I -bright gas in the disk areas we probed.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202244564
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 5
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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: 2006860-8
    detail.hit.zdb_id: 2207650-5
    SSG: 16,12
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  • 6
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    The Physical Drivers and Observational Tracers of CO-to-H 2 Conversion Factor Variations in Nearby Barred Galaxy Centers
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Vol. 950, No. 2 ( 2023-06-01), p. 119-
    Details
    In: The Astrophysical Journal, American Astronomical Society, Vol. 950, No. 2 ( 2023-06-01), p. 119-
    Abstract: The CO-to-H 2 conversion factor ( α CO ) is central to measuring the amount and properties of molecular gas. It is known to vary with environmental conditions, and previous studies have revealed lower α CO in the centers of some barred galaxies on kiloparsec scales. To unveil the physical drivers of such variations, we obtained Atacama Large Millimeter/submillimeter Array bands (3), (6), and (7) observations toward the inner ∼2 kpc of NGC 3627 and NGC 4321 tracing 12 CO, 13 CO, and C 18 O lines on ∼100 pc scales. Our multiline modeling and Bayesian likelihood analysis of these data sets reveal variations of molecular gas density, temperature, optical depth, and velocity dispersion, which are among the key drivers of α CO . The central 300 pc nuclei in both galaxies show strong enhancement of temperature T k ≳ 100 K and density n H 2 〉 10 3 cm −3 . Assuming a CO-to-H 2 abundance of 3 × 10 −4 , we derive 4–15 times lower α CO than the Galactic value across our maps, which agrees well with previous kiloparsec-scale measurements. Combining the results with our previous work on NGC 3351, we find a strong correlation of α CO with low- J 12 CO optical depths ( τ CO ), as well as an anticorrelation with T k . The τ CO correlation explains most of the α CO variation in the three galaxy centers, whereas changes in T k influence α CO to second order. Overall, the observed line width and 12 CO/ 13 CO 2–1 line ratio correlate with τ CO variation in these centers, and thus they are useful observational indicators for α CO variation. We also test current simulation-based α CO prescriptions and find a systematic overprediction, which likely originates from the mismatch of gas conditions between our data and the simulations.
    Type of Medium: Online Resource
    ISSN: 0004-637X , 1538-4357
    URL: Article
    DOI: 10.3847/1538-4357/accb86
    RVK:
    UA 1000
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 1473835-1
    SSG: 16,12
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  • 7
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    PHANGS–JWST First Results: Tracing the Diffuse Interstellar Medium with JWST Imaging of Polycyclic Aromatic Hydrocarbon Emission in Nearby Galaxies
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 944, No. 2 ( 2023-02-01), p. L8-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 944, No. 2 ( 2023-02-01), p. L8-
    Abstract: JWST observations of polycyclic aromatic hydrocarbon (PAH) emission provide some of the deepest and highest resolution views of the cold interstellar medium (ISM) in nearby galaxies. If PAHs are well mixed with the atomic and molecular gas and illuminated by the average diffuse interstellar radiation field, PAH emission may provide an approximately linear, high-resolution, high-sensitivity tracer of diffuse gas surface density. We present a pilot study that explores using PAH emission in this way based on Mid-Infrared Instrument observations of IC 5332, NGC 628, NGC 1365, and NGC 7496 from the Physics at High Angular resolution in Nearby GalaxieS-JWST Treasury. Using scaling relationships calibrated in Leroy et al., scaled F1130W provides 10–40 pc resolution and 3 σ sensitivity of Σ gas ∼ 2 M ⊙ pc −2 . We characterize the surface densities of structures seen at 〈 7 M ⊙ pc −2 in our targets, where we expect the gas to be H i -dominated. We highlight the existence of filaments, interarm emission, and holes in the diffuse ISM at these low surface densities. Below ∼10 M ⊙ pc −2 for NGC 628, NGC 1365, and NGC 7496 the gas distribution shows a “Swiss cheese”-like topology due to holes and bubbles pervading the relatively smooth distribution of the diffuse ISM. Comparing to recent galaxy simulations, we observe similar topology for the low-surface-density gas, though with notable variations between simulations with different setups and resolution. Such a comparison of high-resolution, low-surface-density gas with simulations is not possible with existing atomic and molecular gas maps, highlighting the unique power of JWST maps of PAH emission.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/aca972
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 8
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    The PHANGS-MUSE survey : Probing the chemo-dynamical evolution of disc galaxies
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 659 ( 2022-03), p. A191-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 659 ( 2022-03), p. A191-
    Abstract: We present the PHANGS-MUSE survey, a programme that uses the MUSE integral field spectrograph at the ESO VLT to map 19 massive (9.4  〈  log( M ⋆ / M ⊙ ) 〈 11.0) nearby ( D  ≲ 20 Mpc) star-forming disc galaxies. The survey consists of 168 MUSE pointings (1′ by 1′ each) and a total of nearly 15 × 10 6 spectra, covering ∼1.5 × 10 6 independent spectra. PHANGS-MUSE provides the first integral field spectrograph view of star formation across different local environments (including galaxy centres, bars, and spiral arms) in external galaxies at a median resolution of 50 pc, better than the mean inter-cloud distance in the ionised interstellar medium. This ‘cloud-scale’ resolution allows detailed demographics and characterisations of H  II regions and other ionised nebulae. PHANGS-MUSE further delivers a unique view on the associated gas and stellar kinematics and provides constraints on the star-formation history. The PHANGS-MUSE survey is complemented by dedicated ALMA CO(2–1) and multi-band HST observations, therefore allowing us to probe the key stages of the star-formation process from molecular clouds to H  II regions and star clusters. This paper describes the scientific motivation, sample selection, observational strategy, data reduction, and analysis process of the PHANGS-MUSE survey. We present our bespoke automated data-reduction framework, which is built on the reduction recipes provided by ESO but additionally allows for mosaicking and homogenisation of the point spread function. We further present a detailed quality assessment and a brief illustration of the potential scientific applications of the large set of PHANGS-MUSE data products generated by our data analysis framework. The data cubes and analysis data products described in this paper represent the basis for the first PHANGS-MUSE public data release and are available in the ESO archive and via the Canadian Astronomy Data Centre.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202141727
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 9
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    PHANGS–JWST First Results: Dust-embedded Star Clusters in NGC 7496 Selected via 3.3 μm PAH Emission
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 944, No. 2 ( 2023-02-01), p. L26-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 944, No. 2 ( 2023-02-01), p. L26-
    Abstract: The earliest stages of star formation occur enshrouded in dust and are not observable in the optical. Here we leverage the extraordinary new high-resolution infrared imaging from JWST to begin the study of dust-embedded star clusters in nearby galaxies throughout the Local Volume. We present a technique for identifying dust-embedded clusters in NGC 7496 (18.7 Mpc), the first galaxy to be observed by the PHANGS–JWST Cycle 1 Treasury Survey. We select sources that have strong 3.3 μ m PAH emission based on a F300M − F335M color excess and identify 67 candidate embedded clusters. Only eight of these are found in the PHANGS-HST optically selected cluster catalog, and all are young (six have SED fit ages of ∼1 Myr). We find that this sample of embedded cluster candidates may significantly increase the census of young clusters in NGC 7496 from the PHANGS-HST catalog; the number of clusters younger than ∼2 Myr could be increased by a factor of 2. Candidates are preferentially located in dust lanes and are coincident with the peaks in the PHANGS-ALMA CO (2–1) maps. We take a first look at concentration indices, luminosity functions, SEDs spanning from 2700 Å to 21 μ m, and stellar masses (estimated to be between ∼10 4 and 10 5 M ⊙ ). The methods tested here provide a basis for future work to derive accurate constraints on the physical properties of embedded clusters, characterize the completeness of cluster samples, and expand analysis to all 19 galaxies in the PHANGS–JWST sample, which will enable basic unsolved problems in star formation and cluster evolution to be addressed.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/aca653
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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  • 10
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    PHANGS–JWST First Results: Multiwavelength View of Feedback-driven Bubbles (the Phantom Voids) across NGC 628
    American Astronomical Society ; 2023
    In:  The Astrophysical Journal Letters Vol. 944, No. 2 ( 2023-02-01), p. L22-
    Details
    In: The Astrophysical Journal Letters, American Astronomical Society, Vol. 944, No. 2 ( 2023-02-01), p. L22-
    Abstract: We present a high-resolution view of bubbles within the Phantom Galaxy (NGC 628), a nearby (∼10 Mpc), star-forming (∼2 M ⊙ yr −1 ), face-on ( i ∼ 9°) grand-design spiral galaxy. With new data obtained as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS)-JWST treasury program, we perform a detailed case study of two regions of interest, one of which contains the largest and most prominent bubble in the galaxy (the Phantom Void, over 1 kpc in diameter), and the other being a smaller region that may be the precursor to such a large bubble (the Precursor Phantom Void). When comparing to matched-resolution H α observations from the Hubble Space Telescope, we see that the ionized gas is brightest in the shells of both bubbles, and is coincident with the youngest (∼1 Myr) and most massive (∼10 5 M ⊙ ) stellar associations. We also find an older generation (∼20 Myr) of stellar associations is present within the bubble of the Phantom Void. From our kinematic analysis of the H I , H 2 (CO), and H ii gas across the Phantom Void, we infer a high expansion speed of around 15 to 50 km s −1 . The large size and high expansion speed of the Phantom Void suggest that the driving mechanism is sustained stellar feedback due to multiple mechanisms, where early feedback first cleared a bubble (as we observe now in the Precursor Phantom Void), and since then supernovae have been exploding within the cavity and have accelerated the shell. Finally, comparison to simulations shows a striking resemblance to our JWST observations, and suggests that such large-scale, stellar-feedback-driven bubbles should be common within other galaxies.
    Type of Medium: Online Resource
    ISSN: 2041-8205 , 2041-8213
    URL: Article
    DOI: 10.3847/2041-8213/aca7b9
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2207648-7
    detail.hit.zdb_id: 2006858-X
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