PHANGS–JWST First Results: Mapping the 3.3 μm Polycyclic Aromatic Hydrocarbon Vibrational Band in Nearby Galaxies with NIRCam Medium Bands

Sandström, Karin; Chastenet, Jérémy; Sutter, Jessica; Leroy, Adam K.; Egorov, Oleg V.; Williams, Thomas G.; Bolatto, Alberto D.; Boquien, M.; Cao, Yixian; Dale, Daniel A.; Lee, Janice; Rosolowsky, Erik; Schinnerer, E.; Barnes, Ashley; Belfiore, Francesco; Bigiel, Frank; Chevance, Mélanie; Grasha, Kathryn; Groves, Brent; Hassani, Hamid; Hughes, Annie; Klessen, Ralf S.; Kruijssen, J. M. Diederik; Larson, Kirsten L.; Liu, Daizhong; Lopez, Laura A.; Meidt, Sharon E.; Murphy, E. J.; Sormani, Mattia C.; Thilker, David A.; Watkins, Elizabeth J.

doi:10.3847/2041-8213/acb0cf

Cited by 20 publications

(28 citation statements)

References 40 publications

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“…Misclassification could also occur when there is significant PAH (or ISM) emission in the bands we are using as "continuum" bands: F1000W, F300W, and F360W. For example, Lai et al (2020) noted that the 3.47 μm PAH band may contribute to the F360W light, which is also seen in the PHANGS-JWST sample (Sandstrom et al 2023b). Leroy et al (2023) showed evidence that F1000W may have a significant contribution from the wings of the PAH features in adjacent bands.…”

Section: Spectral Energy Distributionsmentioning

confidence: 99%

PHANGS–JWST First Results: The 21 μm Compact Source Population

Hassani

Rosolowsky

Leroy

et al. 2023

ApJL

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We use PHANGS–James Webb Space Telescope (JWST) data to identify and classify 1271 compact 21 μm sources in four nearby galaxies using MIRI F2100W data. We identify sources using a dendrogram-based algorithm, and we measure the background-subtracted flux densities for JWST bands from 2 to 21 μm. Using the spectral energy distribution (SED) in JWST and HST bands plus ALMA and MUSE/VLT observations, we classify the sources by eye. Then we use this classification to define regions in color–color space and so establish a quantitative framework for classifying sources. We identify 1085 sources as belonging to the ISM of the target galaxies with the remainder being dusty stars or background galaxies. These 21 μm sources are strongly spatially associated with H ii regions (>92% of sources), while 74% of the sources are coincident with a stellar association defined in the HST data. Using SED fitting, we find that the stellar masses of the 21 μm sources span a range of 102–104 M ⊙ with mass-weighted ages down to 2 Myr. There is a tight correlation between attenuation-corrected Hα and 21 μm luminosity for L ν,F2100W > 1019 W Hz−1. Young embedded source candidates selected at 21 μm are found below this threshold and have M ⋆ < 103 M ⊙.

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Section: Spectral Energy Distributionsmentioning

confidence: 99%

PHANGS–JWST First Results: The 21 μm Compact Source Population

Hassani

Rosolowsky

Leroy

et al. 2023

ApJL

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“…We find that all 12 show strong PAH emission at 3.3 μm and fall in a region of the F335M versus F330M − F335M CMD that clearly separates from the vast majority of detections. To first order, the PAH emission at 3.3 μm appears to correlate with other dust emission (Sandstrom et al 2023a(Sandstrom et al , 2023bDale et al 2023;Chastenet et al 2023aChastenet et al , 2023b and so should represent a sensitive, high-resolution tracer of dust-reprocessed UV light from young stars. Based on this, we develop criteria to select a larger sample of candidates.…”

Section: Discussionmentioning

confidence: 98%

“…In Figure 2, we show color-magnitude diagrams (CMDs) based on F335M and F300M photometry; the former captures flux from the PAH 3.3 μm feature, while the latter primarily probes the stellar and dust continuum (Lee et al 2023;Sandstrom et al 2023aSandstrom et al , 2023bChastenet et al 2023aChastenet et al , 2023b. Panel (a) in Figure 2 shows the 12 visually identified prototype embedded clusters (yellow stars) together with the sample of F335M sources detected using Photutils find_peaks (black dots).…”

Section: Selection Criteria For Embedded Cluster Candidatesmentioning

confidence: 99%

PHANGS–JWST First Results: Dust-embedded Star Clusters in NGC 7496 Selected via 3.3 μm PAH Emission

Rodríguez

Lee

Whitmore

et al. 2023

ApJL

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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 μm 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 μm, and stellar masses (estimated to be between ∼104 and 105 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.

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“…We experimented with simple row-by-row median subtraction but found that it was often unfeasible to calculate a robust background median in the small range covered by each amplifier due to the presence of widespread diffuse emission in most of our images. Moreover, we found that though this median subtraction produced visually better individual images, it yielded poor results when multiple images were combined to estimate 3.3 μm PAH maps (Sandstrom et al 2023a). In those cases, the 1/f noise-driven stripes reappeared and were severe in the star-subtracted PAH images.…”

Section: Principal Component Analysis Destripingmentioning

confidence: 98%

“…Finally, the PHANGS-JWST first results show how PAH features can be sensitive diagnostics of ISM conditions through changing flux ratios. Using empirical methods, Sandstrom et al (2023a) demonstrated how to isolate PAH features from the stellar continuum using JWST bands, which can be developed into a full set of PAH-only maps of the galaxies. Chastenet et al (2023aChastenet et al ( , 2023b used JWST data to find variation in PAH properties in the broader ISM, with Egorov et al (2023) and Dale et al (2023) exploring H II regions and star clusters, respectively.…”

Section: Data Productsmentioning

confidence: 99%

The PHANGS–JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular Resolution in Nearby GalaxieS

Lee

Sandström

Leroy

et al. 2023

ApJL

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The PHANGS collaboration has been building a reference data set for the multiscale, multiphase study of star formation and the interstellar medium (ISM) in nearby galaxies. With the successful launch and commissioning of JWST, we can now obtain high-resolution infrared imaging to probe the youngest stellar populations and dust emission on the scales of star clusters and molecular clouds (∼5–50 pc). In Cycle 1, PHANGS is conducting an eight-band imaging survey from 2 to 21 μm of 19 nearby spiral galaxies. Optical integral field spectroscopy, CO(2–1) mapping, and UV-optical imaging for all 19 galaxies have been obtained through large programs with ALMA, VLT-MUSE, and Hubble. PHANGS–JWST enables a full inventory of star formation, accurate measurement of the mass and age of star clusters, identification of the youngest embedded stellar populations, and characterization of the physical state of small dust grains. When combined with Hubble catalogs of ∼10,000 star clusters, MUSE spectroscopic mapping of ∼20,000 H ii regions, and ∼12,000 ALMA-identified molecular clouds, it becomes possible to measure the timescales and efficiencies of the earliest phases of star formation and feedback, build an empirical model of the dependence of small dust grain properties on local ISM conditions, and test our understanding of how dust-reprocessed starlight traces star formation activity, all across a diversity of galactic environments. Here we describe the PHANGS–JWST Treasury survey, present the remarkable imaging obtained in the first few months of science operations, and provide context for the initial results presented in the first series of PHANGS–JWST publications.

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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

Cited by 20 publications

References 40 publications

PHANGS–JWST First Results: The 21 μm Compact Source Population

PHANGS–JWST First Results: The 21 μm Compact Source Population

PHANGS–JWST First Results: Dust-embedded Star Clusters in NGC 7496 Selected via 3.3 μm PAH Emission

The PHANGS–JWST Treasury Survey: Star Formation, Feedback, and Dust Physics at High Angular Resolution in Nearby GalaxieS

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