Regulating Star Formation in Nearby Dusty Galaxies: Low Photoelectric Efficiencies in the Most Compact Systems

McKinney, Jed; Armus, L.; Pope, Alexandra; Díaz-Santos, T.; Charmandaris, V.; Inami, Hanae; Song, Young-Soo; Evans, A. S.

doi:10.3847/1538-4357/abd6f2

Cited by 14 publications

(10 citation statements)

References 101 publications

(195 reference statements)

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“…Therefore, we made the reasonable assumption that the emission of the various PAH features are co-spatial and can be traced by the IRAC 8 𝜇m band. Following the methodology presented in McKinney et al (2021) we projected the Spitzer/IRS aperture and those used for deriving the PAH𝜆3.3 𝜇m feature emission onto the IRAC 8 𝜇m images. To estimate the aperture matching correction we used the ratio between the two apertures.…”

Section: Literature Datamentioning

confidence: 99%

Polycyclic aromatic hydrocarbons in Seyfert and star-forming galaxies

García-Bernete

Rigopoulou

Alonso‐Herrero

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Polycyclic Aromatic Hydrocarbons (PAHs) are carbon-based molecules resulting from the union of aromatic rings and related species, which are likely responsible for strong infrared emission features. In this work, using a sample of 50 Seyfert galaxies (DL < 100 Mpc) we compare the circumnuclear (inner kpc) PAH emission of AGN to that of a control sample of star-forming galaxies (22 luminous infrared galaxies and 30 H ii galaxies), and investigate the differences between central and extended PAH emission. Using Spitzer/InfraRed Spectrograph spectral data of Seyfert and star-forming galaxies and newly developed PAH diagnostic model grids, derived from theoretical spectra, we compare the predicted and observed PAH ratios. We find that star-forming galaxies and AGN-dominated systems are located in different regions of the PAH diagnostic diagrams. This suggests that not only are the size and charge of the PAH molecules different, but also the nature and hardness of the radiation field that excite them. We find tentative evidence that PAH ratios in AGN-dominated systems are consistent with emission from larger PAH molecules (Nc > 300–400) as well as neutral species. By subtracting the spectrum of the central source from the total, we compare the PAH emission in the central versus extended region of a small sample of AGN. In contrast to the findings for the central regions of AGN-dominated systems, the PAH ratios measured in the extended regions of both type 1 and type 2 Seyfert galaxies can be explained assuming similar PAH molecular size distribution and ionized fractions of molecules to those seen in central regions of star-forming galaxies (100 < Nc < 300).

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Section: Literature Datamentioning

confidence: 99%

Polycyclic aromatic hydrocarbons in Seyfert and star-forming galaxies

García-Bernete

Rigopoulou

Alonso‐Herrero

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Similarly, low-redshift LIRGs also show small IR sizes 1-3 kpc (Lutz et al 2016;Bellocchi et al 2022); however, these are commonly confined to merger nuclei, whereas high-z targets can show kinematic evidence for disks with high SFR surface densities (Hodge et al 2016;Calistro Rivera et al 2018;Pantoni et al 2021;Xiao et al 2022). The ISM conditions found within such high-z, dusty star-forming disks seem to resemble those within the cores of local LIRGs (Spilker et al 2016;McKinney et al 2020McKinney et al , 2021aRybak et al 2022).…”

Section: Introductionmentioning

confidence: 97%

“…In general, the optical/near-IR extent of galaxies gets progressively smaller toward higher redshifts at fixed star formation rate (SFR) and stellar mass (Buitrago et al 2008;Conselice 2014;van der Wel et al 2014;Shibuya et al 2015;Mowla et al 2019), and smaller star-forming galaxies tend to support larger SFR surface densities (Lutz et al 2016;Fujimoto et al 2017). The sizes of galaxies also correlate with the conditions of the interstellar medium (ISM; Díaz-Santos et al 2017;McKinney et al 2020McKinney et al , 2021aPuglisi et al 2021), which may drive changes in the underlying mode of star formation. Indeed, the scaling relationship between SFR surface densities and molecular gas surface densities is sensitive to the physics of stellar mass assembly in galaxies (e.g., Schmidt 1959;Kennicutt 1998), and departures from canonical surface density scaling laws have been attributed to changes in the star formation efficiency (Elbaz et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The IR Compactness of Dusty Galaxies Sets Star Formation and Dust Properties at z ∼ 0–2

McKinney,

Pope,

Kirkpatrick

et al. 2023

ApJ

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The surface densities of gas, dust, and stars provide a window into the physics of star formation that, until the advent of high-resolution far-IR/submillimeter observations, has been historically difficult to assess among dusty galaxies. To study the link between IR surface densities and dust properties, we leverage the Atacama Large Millimetre/Submillimetre Array archive to measure the extent of cold dust emission in 15 z ∼ 2 IR-selected galaxies selected on the basis of having available mid-IR spectroscopy from Spitzer. We use the mid-IR spectra to constrain the relative balance between dust heating from star formation and active galactic nuclei (AGNs), and to measure emission from polycylic aromatic hydrocarbons (PAHs), small dust grains that play a key role in the photoelectric heating of gas. In general, we find that dust-obscured star formation at high IR surface densities exhibits similar properties at low and high redshift, namely, local luminous IR galaxies (LIRGs) have comparable PAH luminosity to total dust mass ratios as high-z galaxies, and star formation at z ∼ 0–2 is more efficient at high IR surface densities despite the fact that our sample of high-z galaxies is closer to the main sequence than local LIRGs. High star formation efficiencies are coincident with a decline in the PAH-to-IR luminosity ratio reminiscent of the deficit observed in far-IR fine-structure lines. Changes in the gas and dust conditions arising from high star formation surface densities might help drive the star formation efficiency up. This could help explain the high efficiencies needed to reconcile star formation and gas volume densities in dusty galaxies at cosmic noon.

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“…For example, higher fractions of ionized PAHs could lead to a decrease in the photoelectric heating efficiency, as highly charged grains will have higher ionization potentials (Tielens 2008b). This has been observed in variations in the relative strength of far-infrared cooling lines compared to total infrared luminosity as a function of PAH feature ratios, suggesting the properties of the PAHs influence the balance of ISM heating and cooling (Croxall et al 2012;McKinney et al 2021;Sutter & Fadda 2022). As both a source and sink for free electrons, PAHs also play a large role in setting the ionization balance (Bakes & Tielens 1994;Li 2020).…”

Section: Introductionmentioning

confidence: 99%

PHANGS–JWST First Results: Measuring Polycyclic Aromatic Hydrocarbon Properties across the Multiphase Interstellar Medium

Chastenet

Sutter

Sandström

et al. 2023

ApJL

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Ratios of polycyclic aromatic hydrocarbon (PAH) vibrational bands are a promising tool for measuring the properties of the PAH population and their effect on star formation. The photometric bands of the MIRI and NIRCam instruments on JWST provide the opportunity to measure PAH emission features across entire galaxy disks at unprecedented resolution and sensitivity. Here we present the first results of this analysis in a sample of three nearby galaxies: NGC 628, NGC 1365, and NGC 7496. Based on the variations observed in the 3.3, 7.7, and 11.3 μm features, we infer changes to the average PAH size and ionization state across the different galaxy environments. High values of F335MPAH/F1130W and low values of F1130W/F770W are measured in H ii regions in all three galaxies. This suggests that these regions are populated by hotter PAHs, and/or that the PAH ionization fraction is larger. We see additional evidence of heating and/or changes in PAH size in regions with higher molecular gas content as well as increased ionization in regions with higher Hα intensity.

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Regulating Star Formation in Nearby Dusty Galaxies: Low Photoelectric Efficiencies in the Most Compact Systems

Cited by 14 publications

References 101 publications

Polycyclic aromatic hydrocarbons in Seyfert and star-forming galaxies

Polycyclic aromatic hydrocarbons in Seyfert and star-forming galaxies

The IR Compactness of Dusty Galaxies Sets Star Formation and Dust Properties at z ∼ 0–2

PHANGS–JWST First Results: Measuring Polycyclic Aromatic Hydrocarbon Properties across the Multiphase Interstellar Medium

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