PHANGS–JWST First Results: Duration of the Early Phase of Massive Star Formation in NGC 628

Kim, Jaeyeon; Chevance, Mélanie; Kruijssen, J. M. Diederik; Barnes, Ashley; Bigiel, Frank; Blanc, Guillermo A.; Boquien, M.; Cao, Yixian; Congiu, Enrico; Dale, Daniel A.; Egorov, Oleg V.; Faesi, Christopher M.; Glover, Simon C. O.; Grasha, Kathryn; Groves, Brent; Hassani, Hamid; Hughes, Annie; Klessen, Ralf S.; Kreckel, Kathryn; Larson, Kirsten L.; Lee, Janice; Leroy, Adam K.; Liu, Daizhong; Longmore, Steven N.; Meidt, Sharon E.; Pan, Hsi-An; Pety, J.; Rosolowsky, Erik; Tosaki, Tomoka; Sandström, Karin; Schinnerer, E.; Smith, Rowan J.; Usero, A.; Watkins, Elizabeth J.; Williams, Thomas G.

doi:10.3847/2041-8213/aca90a

Cited by 17 publications

(19 citation statements)

References 75 publications

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“…Stellar feedback could also push the gas and form structures in the interarm regions. However, the feedback-driven models so far explained only less-massive structures (∼10 6 M e ; Smith et al 2020;Treß et al 2021;Kim et al 2023). Even for the small masses, these models include spiral arm potentials and assemble the gas primarily by the potentials.…”

Section: Gas Assembly and Molecular Structuresmentioning

confidence: 99%

Diverse Molecular Structures across the Whole Star-forming Disk of M83: High-fidelity Imaging at 40 pc Resolution

Koda

Hirota

Egusa

et al. 2023

ApJ

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We present Atacama Large Millimeter/submillimeter Array (ALMA) imaging of molecular gas across the full star-forming disk of the barred spiral galaxy M83 in CO(J = 1–0). We jointly deconvolve the data from ALMA’s 12 m, 7 m, and Total Power arrays using the MIRIAD package. The data have a mass sensitivity and resolution of 104 M ⊙ (3σ) and 40 pc—sufficient to detect and resolve a typical molecular cloud in the Milky Way with a mass and diameter of 4 × 105 M ⊙ and 40 pc, respectively. The full disk coverage shows that the characteristics of molecular gas change radially from the center to outer disk, with the locally measured brightness temperature, velocity dispersion, and integrated intensity (surface density) decreasing outward. The molecular gas distribution shows coherent large-scale structures in the inner part, including the central concentration, offset ridges along the bar, and prominent molecular spiral arms. However, while the arms are still present in the outer disk, they appear less spatially coherent, and even flocculent. Massive filamentary gas concentrations are abundant even in the interarm regions. Building up these structures in the interarm regions would require a very long time (≳100 Myr). Instead, they must have formed within stellar spiral arms and been released into the interarm regions. For such structures to survive through the dynamical processes, the lifetimes of these structures and their constituent molecules and molecular clouds must be long (≳100 Myr). These interarm structures host little or no star formation traced by Hα. The new map also shows extended CO emission, which likely represents an ensemble of unresolved molecular clouds.

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Section: Gas Assembly and Molecular Structuresmentioning

confidence: 99%

Diverse Molecular Structures across the Whole Star-forming Disk of M83: High-fidelity Imaging at 40 pc Resolution

Koda

Hirota

Egusa

et al. 2023

ApJ

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“…Therefore MIR observations allow us to identify new, young embedded clusters obscured at optical wavelengths (Rodriguez et al 2023), large-scale filamentary structures containing dense, cold gas expected to host future star formation (Thilker et al 2023), and hot dust emission shining in the presence of UV radiation emitted by OB stars (Leroy et al 2023). Piecing these results together provides the observations needed to trace recent star formation histories within these galaxies (Kim et al 2023). In this letter we provide a crucial piece needed to understand the star formation picture-connecting together small-and large-scale feedback processes-by cataloging the feedback-driven bubbles in NGC 628 using Physics at High Angular resolution in Nearby GalaxieS (PHANGS)-JWST.…”

Section: Introductionmentioning

confidence: 97%

PHANGS–JWST First Results: A Statistical View on Bubble Evolution in NGC 628

Watkins¹,

Barnes

Henny

et al. 2023

ApJL

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The first JWST observations of nearby galaxies have unveiled a rich population of bubbles that trace the stellar-feedback mechanisms responsible for their creation. Studying these bubbles therefore allows us to chart the interaction between stellar feedback and the interstellar medium, and the larger galactic flows needed to regulate star formation processes globally. We present the first catalog of bubbles in NGC 628, visually identified using Mid-Infrared Instrument F770W Physics at High Angular resolution in Nearby GalaxieS (PHANGS)–JWST observations, and use them to statistically evaluate bubble characteristics. We classify 1694 structures as bubbles with radii between 6 and 552 pc. Of these, 31% contain at least one smaller bubble at their edge, indicating that previous generations of star formation have a local impact on where new stars form. On large scales, most bubbles lie near a spiral arm, and their radii increase downstream compared to upstream. Furthermore, bubbles are elongated in a similar direction to the spiral-arm ridgeline. These azimuthal trends demonstrate that star formation is intimately connected to the spiral-arm passage. Finally, the bubble size distribution follows a power law of index p = −2.2 ± 0.1, which is slightly shallower than the theoretical value by 1–3.5σ that did not include bubble mergers. The fraction of bubbles identified within the shells of larger bubbles suggests that bubble merging is a common process. Our analysis therefore allows us to quantify the number of star-forming regions that are influenced by an earlier generation, and the role feedback processes have in setting the global star formation rate. With the full PHANGS–JWST sample, we can do this for more galaxies.

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“…More recently, Linden et al (2023) used near-IR imaging data from JWST to infer that about two-thirds of the stellar clusters younger than 4 Myr are missed by standard UV-optical observations in the relatively nearby luminous infrared galaxy VV114. Kim et al (2023) used JWST mid-IR imaging, combined with Hα and CO imaging, of the nearby star-forming galaxy NGC 628 to infer that the embedded phase of star formation lasts about 5 Myr, during the first half of which dust obscuration is so high that the Hα emission is not detectable. In a complementary fashion, Whitmore et al (2023) combined HST optical with JWST near-and mid-IR medium and broadband imaging of the galaxy NGC 1365 to conclude that massive (M∼10 6 M e ) stellar clusters in this galaxy remain completely or partially obscured for about 4 ± 1 Myr.…”

Section: Introductionmentioning

confidence: 99%

“…In a complementary fashion, Whitmore et al (2023) combined HST optical with JWST near-and mid-IR medium and broadband imaging of the galaxy NGC 1365 to conclude that massive (M∼10 6 M e ) stellar clusters in this galaxy remain completely or partially obscured for about 4 ± 1 Myr. However, Linden et al (2023), Kim et al (2023), and Whitmore et al (2023) do not have information on the infrared hydrogen recombination lines, which are key for constraining the ages of young stellar clusters when these are marginally detected or undetected at optical wavelengths. Clearly, more investigations are needed to obtain a census of the fraction of dust-embedded star formation in galaxies and address its implications for the efficacy of pre-SN feedback.…”

Section: Introductionmentioning

confidence: 99%

Dust-buried Compact Sources in the Dwarf Galaxy NGC 4449

Calzetti

Linden

McQuaid

et al. 2023

ApJ

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Multiwavelength images from the Hubble Space Telescope covering the wavelength range 0.27–1.6 μm show that the central area of the nearby dwarf galaxy NGC 4449 contains several tens of compact sources that are emitting in the hydrogen recombination line Paβ (1.2818 μm) but are only marginally detected in Hα (0.6563 μm) and undetected at wavelengths λ ≤ 0.55 μm. An analysis of the spectral energy distributions (SEDs) of these sources indicates that they are likely relatively young stellar clusters heavily attenuated by dust. The selection function used to identify the sources prevents meaningful statistical analyses of their age, mass, and dust extinction distributions. However, these cluster candidates have ages ∼5–6 Myr and A V > 6 mag, according to their SED fits, and are extremely compact, with typical deconvolved radii of 1 pc. The dusty clusters are located at the periphery of the dark clouds within the galaxy and appear to be partially embedded. Density and pressure considerations indicate that the H ii regions surrounding these clusters may be stalled, and that pre-supernova (pre-SN) feedback has not been able to clear the clusters of their natal cocoons. These findings are in potential tension with existing models that regulate star formation with pre-SN feedback, since pre-SN feedback acts on short timescales, ≲4 Myr, for a standard stellar initial mass function. The existence of a population of dusty stellar clusters with ages >4 Myr, if confirmed by future observations, paints a more complex picture for the role of stellar feedback in controlling star formation.

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PHANGS–JWST First Results: Duration of the Early Phase of Massive Star Formation in NGC 628

Cited by 17 publications

References 75 publications

Diverse Molecular Structures across the Whole Star-forming Disk of M83: High-fidelity Imaging at 40 pc Resolution

Diverse Molecular Structures across the Whole Star-forming Disk of M83: High-fidelity Imaging at 40 pc Resolution

PHANGS–JWST First Results: A Statistical View on Bubble Evolution in NGC 628

Dust-buried Compact Sources in the Dwarf Galaxy NGC 4449

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