Constraining the link between the 2175{\AA} dust absorption feature and PAHs in Nearby Star-Forming Galaxies using Swift/UVOT and JWST/MIRI

A. J. Battisti; D. Calzetti; Elisabete da Cunha; E. Wisnioski; H.-J. Park; I. Shivaei; J. Mathew; M. Decleir

REVIEW 3 major objections 4 minor 1 cited by

Constraining the link between the 2175{\AA} dust absorption feature and PAHs in Nearby Star-Forming Galaxies using Swift/UVOT and JWST/MIRI

T0 review · 3 major / 4 minor · reviewed 2026-08-11 · deepseek-v4-flash

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Pith's one-line read This paper tests whether the 2175 Å dust absorption bump and PAH abundance are linked within galaxies, measuring both in resolved regions of 15 nearby star-forming galaxies and controlling for the radiation field.

desk verdict First multi-galaxy resolved test of the 2175A bump-PAH link with JWST/MIRI, but the partial-correlation test is only as good as the RPAH proxy, and that proxy has a known dust-heating degeneracy. read the letter →

arxiv 2412.03690 v1 pith:SRWS6FHT submitted 2024-12-04 astro-ph.GA

A. J. Battisti , I. Shivaei , H.-J. Park , M. Decleir , D. Calzetti , J. Mathew , E. Wisnioski , Elisabete da Cunha This is my paper · ORCID

classification astro-ph.GA

keywords 2175Åbumppolycyclicaromatichydrocarbonsdustattenuationstar-forminggalaxiesSwift/UVOTJWST/MIRISFRsurfacedensitypartialcorrelation

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper asks whether the 2175 Å ultraviolet absorption bump and the polycyclic aromatic hydrocarbons (PAHs) that emit in the mid-infrared are the same dust component. It compares, region by region in 15 nearby star-forming galaxies, a bump-strength measure from Swift/UVOT with a PAH-abundance proxy from JWST/MIRI, finding a moderate raw positive correlation ($\rho \approx 0.3$–$0.5$). The central result is that this correlation largely vanishes when star-formation surface density is held fixed, with a partial Spearman coefficient of $\rho_{AB|C}=0.02$; the paper interprets this as evidence that both quantities decline together because ionizing radiation destroys small grains, not because PAHs cause the bump. Getting the bump–PAH link right matters for dust attenuation corrections and photometric redshifts in distant galaxies.

What carries the argument

The load-bearing machinery is two photometric indices and one statistical test. The bump strength $k_{\mathrm{bump}}=A_{\mathrm{bump}}/E(B-V)_{\mathrm{gas}}$ is formed from three Swift/UVOT filters, with the UVM2 filter sampling the 2175 Å feature and the two wide filters defining the UV continuum; the PAH abundance proxy $R_{\mathrm{PAH}}=(F770W+F1130W)/F2100W$ uses JWST/MIRI filters on the 7.7 and 11.3 µm PAH features over a warm-dust continuum baseline. The statistical test is the partial Spearman correlation of Eq. (13), which asks whether the bump–PAH correlation survives after controlling for $\Sigma_{\mathrm{SFR}}$; it does not, giving $\rho_{AB|C}=0.02$. The machinery also includes a comparison of the $\Sigma_{\mathrm{SFR}}$ dependence of mid-infrared luminosity ratios, which shows that the $R_{\mathrm{PAH}}$ trend can be produced by dust heating as well as by PAH destruction.

What would settle it

Measure the 7.7 and 11.3 µm PAH features spectroscopically in these 15 galaxies, fit the underlying dust continuum, and redo the partial-correlation test with the resulting dust-independent PAH abundance; if that abundance still correlates with $k_{\mathrm{bump}}$ at fixed $\Sigma_{\mathrm{SFR}}$, the paper's conclusion is overturned.

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Extended reading notes

Core claim

The paper's central claim is that the apparent correlation between the intrinsic 2175 Å bump strength $k_{\mathrm{bump}}=A_{\mathrm{bump}}/E(B-V)_{\mathrm{gas}}$ and the PAH proxy $R_{\mathrm{PAH}}=(F770W+F1130W)/F2100W$ is largely an artefact of both quantities responding to the ionizing radiation field. In the five galaxies with the most reliable bump measurements, the raw Spearman correlation is only $\rho \approx 0.3$–$0.5$, with large intrinsic scatter, while $k_{\mathrm{bump}}$ and $R_{\mathrm{PAH}}$ each correlate more strongly with $\Sigma_{\mathrm{SFR}}$ and sSFR ($\rho \approx -0.6$). A partial-correlation calculation holding $\Sigma_{\mathrm{SFR}}$ fixed gives $\rho_{AB|C}=0.02$, and subdividing regions into $\Sigma_{\mathrm{SFR}}$ quartiles leaves $\rho \lesssim 0.3$; the paper therefore concludes that the data disfavour a direct physical link between the bump carrier and PAHs. The same qualitative conclusion holds when the bump is normalised by stellar reddening from SED fitting instead of gas reddening.

Load-bearing premise

The analysis assumes the photometric ratio $R_{\mathrm{PAH}}=(F770W+F1130W)/F2100W$ tracks PAH abundance rather than being lowered by dust heating in high star-formation regions; if dust heating drives its trend, the partial-correlation result that disfavours a direct PAH link is biased.

Editorial extensions

If this is right

If correct, the moderate bump–PAH correlation seen in galaxy spectra should not be read as evidence that PAHs are the 2175 Å carrier without first controlling for the radiation field.
Dust corrections in strongly star-forming regions should not assume a fixed bump strength, since the bump weakens with increasing $\Sigma_{\mathrm{SFR}}$ and sSFR.
The $R_{\mathrm{PAH}}$ anti-correlation with $\Sigma_{\mathrm{SFR}}$ is ambiguous: it can flag PAH destruction by UV photons or simply hotter dust raising the F2100W baseline, so mid-IR spectroscopy is needed to separate the two.
The paper's prescriptions for $k_{\mathrm{bump}}$ and $R_{\mathrm{PAH}}$ as functions of $\Sigma_{\mathrm{SFR}}$ and sSFR apply to local massive, metal-rich galaxies, but the $k_{\mathrm{bump}}$ values should be treated as lower limits because the Swift/UVOT filters underestimate the bump.
Within the narrow metallicity range $8.40<12+\log(\mathrm{O/H})<8.65$, no significant metallicity trends are found for either quantity.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

Inference: a decisive follow-up is mid-IR spectroscopy that isolates the PAH features from the dust continuum; if a spectroscopically measured PAH abundance still correlates with $k_{\mathrm{bump}}$ at fixed $\Sigma_{\mathrm{SFR}}$, the null result would be overturned.
Inference: the same partial-correlation strategy could be applied to unresolved high-redshift galaxies using sSFR as the control, where the bump–sSFR relation from earlier spectroscopic work should line up with the local relation after accounting for main-sequence evolution.
Inference: the preliminary inclination trend suggests line-of-sight diffuse dust adds 2175 Å absorption without corresponding PAH emission, so face-on galaxies should show stronger bump–PAH correlations than edge-on ones in a larger sample.
Inference: if broad-band UV filters underestimate bump strengths by factors of roughly three to four, photometric surveys may need calibration corrections before their bump measurements can be used as quantitative dust tracers.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

The genuinely new thing here is the dataset combination: Swift/UVOT three-filter bump estimates plus JWST/MIRI PAH photometry across 15 resolved galaxies, with MUSE for reddening and SFR. That is a real step past Decleir's single galaxy and Shivaei's integrated z~2 work. The paper is careful about its own limitations, and that alone makes it a useful addition to the 2175A debate.

What it does well: the photometric reduction is described in enough detail to reproduce, the selection cuts are explicit, the appendix showing that the UVOT bump is a linear but attenuated version of the true bump (slopes 0.26-0.30 for two Drude widths) is the right way to handle a known systematic, and the authors check their main result twice—once normalizing by gas reddening, once with stellar reddening from MAGPHYS. The quartile analysis in Figure 11 is a sensible visual complement to the partial correlation. The dust-heating degeneracy in RPAH is acknowledged in the text and not hidden.

Now the soft spots. The central claim—that the bump-PAH correlation vanishes after controlling for Sigma_SFR (partial rho = 0.02)—rests entirely on RPAH = (F770W+F1130W)/F2100W being a faithful PAH abundance proxy. The stress-test concern is legitimate: F2100W is warm-dust continuum, and Calzetti's own relations show that 21/24 micron emission rises super-linearly with Sigma_SFR. So RPAH declines with Sigma_SFR even at fixed PAH abundance, and the partial correlation is subtracting a dust-temperature signal from RPAH. The authors know this and say it (Section 5.1), but they still put the 'disfavouring a direct link' line in the abstract. That is a soft spot in the interpretation, not a fabrication. The combined correlation analysis also rests on five of fifteen galaxies, with NGC 4303 excluded for an offset that is disclosed but not explained. Minor: the kbump underestimate is well handled, but the scale factor is calibrated for only two Drude widths, which is fine for ranking but not for absolute prescriptions.

Bottom line: this is a solid, honest empirical study that will be useful to anyone working on dust attenuation curves, the 2175A feature, or PAH chemistry in galaxies. It deserves peer review and publication, but the strong conclusion should be tempered until mid-IR spectroscopy can break the dust-heating degeneracy. The reader's conditional verdict matches my own reading.

Yes, send it to review. I would not cite it for the central claim, but I would cite it for the resolved UVOT+MIRI method and the calibrated underestimate relations.

Referee Report

3 major / 4 minor

Summary. This paper uses Swift/UVOT three-filter (UVW2, UVM2, UVW1) photometry and JWST/MIRI (F770W, F1130W, F2100W) plus Spitzer/IRAC data to measure, in spatially resolved regions of 15 nearby PHANGS galaxies (with a 'robust' subset of five), the 2175Å bump strength kbump and a photometric PAH abundance proxy RPAH = (F770W + F1130W)/F2100W. The authors find a moderate positive correlation between kbump and RPAH (Spearman rho ~ 0.3-0.5) but also stronger negative correlations of both quantities with SFR surface density and specific SFR (rho ~ -0.6). Using a partial Spearman correlation (Eq. 13), they obtain rho_AB|C = 0.02 when controlling for Sigma_SFR, and rho_AB|C = 0.19 when controlling for sSFR. They interpret this as evidence that the apparent kbump-RPAH correlation is an indirect consequence of both quantities declining with ionizing radiation intensity, 'disfavouring a direct link' between the bump carrier and PAHs. The paper provides fitting prescriptions for kbump and RPAH as functions of Sigma_SFR and sSFR, and includes extensive appendices on the reliability of the UVOT bump measurement and on the choice of reddening normalization. The authors explicitly acknowledge that the RPAH proxy may be influenced by dust heating and that mid-IR spectroscopy is needed to break this degeneracy.

Significance. If the central claim holds, this is a valuable observational constraint on the carrier of the 2175Å bump in external galaxies, using resolved data that connect UV absorption to mid-IR PAH emission for the first time at ~100 pc scales. The paper is careful in its data handling, uses public PHANGS data products, and provides transparent caveats about the limitations of photometric proxies. The appendices (especially Appendix 1, which calibrates the UVOT-derived kbump against simulated intrinsic bumps, and Appendix 2, which checks the reddening normalization) are a strength. However, the headline conclusion rests on the assumption that RPAH faithfully traces PAH abundance, which is undermined by the dust-heating degeneracy that the authors themselves describe, and on a partial correlation coefficient reported without uncertainty. These issues are fixable and do not invalidate the dataset, but they currently limit the strength of the claim that PAHs are not directly linked to the 2175Å carrier.

major comments (3)

[Section 5.1, Eq. (13)] The partial correlation rho_AB|C = 0.02 is interpreted as 'disfavouring a direct link' between the 2175Å bump and PAHs. This interpretation presupposes that RPAH is a faithful PAH abundance proxy. However, RPAH uses F2100W (warm-dust continuum) in the denominator, and the authors themselves state in Section 5.1 that the RPAH-Sigma_SFR trend 'can be also explained with dust heating, rather than PAH destruction' (see also Eq. 14 and Figure 13). If dust heating drives part of the RPAH-Sigma_SFR anti-correlation, then residualising both kbump and RPAH on Sigma_SFR removes a dust-temperature signal from RPAH, and the near-zero partial correlation is not evidence against a direct bump-PAH link. The paper should either provide a PAH index that is robust against dust-heating variations (e.g., a PAH-feature-to-total-IR ratio, or a version of RPAH using a cooler continuum band) or explicitly re-frame the conclusion as conditional on the PAH proxy being unaffected by dust heating. A concrete test would be to repeat the partial-correlation analysis using a PAH measure that does not divide by F2100W or another warm-dust continuum.
[Section 5.1, Eq. (13)] The partial correlation coefficient is reported as a point estimate (0.02) without any measure of uncertainty. The underlying Spearman coefficients in Table 3 are based on a finite sample of five galaxies (with a few hundred to a few thousand regions per galaxy, but the combined fit gives equal weight per region), and the sampling uncertainty on rho_AB|C could be substantial. A bootstrap or jackknife confidence interval, or at least a p-value, is needed to support the claim that the partial correlation is consistent with zero and significantly smaller than the uncontrolled kbump-RPAH correlation of ~0.3-0.5. Without this, the strength of the conclusion 'disfavouring a direct link' is not quantified.
[Appendix 1, Figure 15] The mapping between the UVOT-derived kbump and the intrinsic bump strength is shown to be linear with slope 0.30 (FWHM=470Å) and 0.26 (FWHM=274Å), but the Drude FWHM is not measured per region. If the true FWHM of the 2175Å feature varies region-to-region, or correlates with Sigma_SFR or other environmental properties, the scaling factor is not constant and the rank order of kbump_obs may not preserve the rank order of the intrinsic bump strength. Because the central claim uses Spearman (rank) correlations, the authors should demonstrate via simulation that plausible FWHM variations (e.g., a distribution of FWHM values drawn from the range in Figure 14, possibly correlated with Sigma_SFR) do not change the sign or significance of the partial correlation in Eq. (13). The current Appendix 1 tests only two discrete FWHM values and shows that the mapping is insensitive to E(B-V) variation, which is not sufficient to rule out FWHM-induced bias in the correlations.

minor comments (4)

[Abstract] The abstract's statement that the results are 'disfavouring a direct link' is stronger than the body's more cautious phrasing, where the authors note that the RPAH trend 'can be also explained with dust heating, rather than PAH destruction.' Consider softening the abstract to match the caveats in Section 5.1.
[Section 3.3, Eq. (7)] The stellar continuum subtraction for RPAH assumes a single blackbody temperature T_eff = 5000 K. The median fraction of emission removed is ~5.6% in F770W and ~1-2% in the other bands; this is not negligible for F770W and could introduce scatter in RPAH if the true stellar population varies. The authors could propagate this assumption as a systematic uncertainty or test the sensitivity with T_eff = 4000-6000 K.
[Table 3] The table would be more informative if it reported the number of regions used in the combined five-galaxy fits and the p-values (or significance levels) of the Spearman correlation coefficients, allowing readers to assess the statistical weight behind the partial correlation value in Eq. (13).
[Section 3.1 and Appendix 1] The statement in Section 3.1 that 'the correlations observed and presented in this work should be robust' relies on the linear mapping in Appendix 1, but the FWHM dependence of the scaling factor is not discussed there. A brief sentence noting this limitation (and referring to Appendix 1) would help readers interpret the robustness claim.

Circularity Check

0 steps flagged · score 1.0 of 10

No significant circularity: kbump, RPAH, and Sigma_SFR are independently measured, the partial-correlation test is not a fitted prediction, and the acknowledged dust-heating degeneracy is a stated caveat rather than a circular step.

full rationale

The paper's derivation chain is not circular. The three central quantities are built from independent data: kbump from Swift/UVOT photometry normalized by MUSE Balmer-decrement reddening (Section 3.1), RPAH from JWST/MIRI PAH-filter fluxes with an IRAC-based stellar-continuum subtraction (Section 3.3), and Sigma_SFR from extinction-corrected MUSE H-alpha (Section 3.4). The partial-correlation coefficient in Eq. 13 is a standard statistic applied to measured Spearman ranks from Table 3, not a fitted parameter relabeled as a prediction, and the 'prescriptions' in Section 4 are fits to the data, not claimed predictions. The RPAH proxy is adopted from external PHANGS-JWST work (Chastenet et al. 2023; Sutter et al. 2024), not from the authors' own prior results; self-citations such as Calzetti et al. (2024) and Battisti et al. (2020) are used as empirical calibrations or robustness checks and are not load-bearing for the main conclusion. The paper explicitly acknowledges in Section 5.1 and Section 6 that the F2100W-based RPAH trend with Sigma_SFR and sSFR can be explained by dust heating rather than PAH destruction, and that resolving this requires mid-IR spectroscopy; this is an honest unverified premise, not a definitional reduction. Appendix 1 is a calibration of the UVOT bump estimator, and Appendix 2 repeats the analysis with independently derived AV,star from MAGPHYS, finding qualitatively the same results, which further demonstrates that the central correlation results are not forced by construction. No specific equation reduces the conclusion to an input, so circularity is minimal.

Assumptions & free parameters 3 free parameters · 5 assumptions · 0 invented entities

The central claim rests on three independently measured observables (UVOT bump proxy, MUSE Balmer reddening, MIRI PAH proxy) plus adopted calibrations. The main adopted values, T_eff = 5000 K, M/L = 0.6, and a fixed MW extinction curve for the Balmer decrement, set the zero points and scales of RPAH, Mstar, and E(B-V)_gas but would not change Spearman correlations if they act as constant rescalings. The non-trivial assumptions are the physical interpretations: that E(B-V)_gas tracks stellar reddening, that RPAH is not dominated by dust heating, and that the three-filter bump is monotonically related to the intrinsic bump. No new entities are introduced.

free parameters (3)

Assumed stellar effective temperature T_eff for continuum subtraction in RPAH = 5000 K
Used in Eq. 8 to estimate the stellar flux contribution to F770W/F1130W/F2100W; changing T_eff shifts RPAH zero point, though the median stellar fraction removed is small (5.6% at F770W).
Stellar mass-to-light ratio M/L at 3.6 um = 0.6
Adopted from Querejeta et al. (2015) to convert IRAC P5 stellar maps to stellar mass; enters sSFR, one of the two control variables used in the main partial-correlation test.
k(H-beta) - k(H-alpha) = 1.160 from assumed MW extinction curve = 1.160
Sets the E(B-V)_gas scale via the Balmer decrement (Eq. 6); a different extinction curve changes kbump amplitudes but would not change Spearman correlations if it is a constant rescale.

assumptions (5)

domain assumption Case B recombination with Te = 10^4 K gives F(H-alpha)/F(H-beta) = 2.86 for unreddened gas.
Used in Eq. 6 to convert the observed Balmer ratio into E(B-V)_gas; standard for H II regions but not exact for all regions.
domain assumption E(B-V)_gas tracks E(B-V)_star with a roughly constant offset/slope (~0.5) across the resolved regions.
Justifies normalizing the stellar-continuum-defined bump by gas reddening; the paper checks with MAGPHYS AV,star in Appendix 2 and finds consistent trends, but the assumption enters the definition of kbump in Eq. 5.
domain assumption The ratio RPAH = (F770W + F1130W)/F2100W traces PAH abundance independently of dust heating.
This is the load-bearing assumption behind the partial-correlation interpretation; the paper itself notes in Section 5.1 that dust heating can also lower RPAH at high Sigma_SFR, so the proxy is degenerate.
domain assumption The UVOT three-filter estimate of the bump is monotonically (approximately linearly) related to the true bump strength.
Appendix 1 models show kbump,obs ~ 0.26-0.30 kbump,int over a grid of E(B-V) and two Drude FWHM values; this supports correlation preservation but not absolute amplitudes.
standard math Spearman-based partial correlation formula (Kendall 1942) is valid; assumes monotonic relations.
Used in Eq. 13 to compute rho_AB|C = 0.02; the paper notes the monotonicity assumption.

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Cite this review

Pith. "Pith review of Constraining the link between the 2175{\AA} dust absorption feature and PAHs in Nearby Star-Forming Galaxies using Swift/UVOT and JWST/MIRI." pith.science (2026). https://pith.science/paper/SRWS6FHT

@misc{pith2026241203690,
  author       = {Pith},
  title        = {Pith review of: Constraining the link between the 2175\AA dust absorption feature and PAHs in Nearby Star-Forming Galaxies using Swift/UVOT and JWST/MIRI},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/SRWS6FHT}},
  note         = {Machine review of arXiv:2412.03690}
}

read the original abstract

The 2175{\AA} bump is a prominent absorption feature at ultraviolet (UV) wavelengths in dust extinction and attenuation curves. Understanding the relative strength of this feature is important for accurate dust corrections at both low- and high-redshift. This feature is postulated to arise from polycyclic aromatic hydrocarbon (PAH) dust grains; however, the carrier has not been definitively established. We present results on the correlation between the 2175{\AA} feature and PAH abundances in a spatially-resolved manner for 15 local galaxies in the PHANGS-JWST survey that have NUV and mid-IR imaging data from Swift/UVOT and JWST/MIRI, respectively. We find a moderate positive correlation between the 2175{\AA} feature strength and PAH abundance, albeit with large intrinsic scatter. However, most of this trend can be attributed to a stronger negative correlation of both quantities with SFR surface density and specific-SFR (proxies of ionising radiation). The latter trends are consistent with previous findings that both the 2175{\AA} carrier and PAHs are small grains that are easily destroyed by UV photons, although the proxy for PAH abundance could also be influenced by dust heating. When controlling for SFR surface density, we find weaker correlations between the 2175{\AA} feature and PAH abundances, disfavouring a direct link. However, analyses based on spectroscopic measurements of the 2175{\AA} feature and PAH features are required to verify our findings. No significant trends with gas-phase metallicity are found for the 2175{\AA} feature and PAHs, however the metallicity range of our sample is limited. We provide prescriptions for the strength of the 2175{\AA} feature and PAHs in local massive (metal-rich) galaxies with SFR surface density and specific-SFR, however the former should be used with caution since bump strengths measured from Swift/UVOT are expected to be underestimated.

Figures

Figures reproduced from arXiv: 2412.03690 by the authors.

**Figure 1.** Gallery of data used in our study. For each galaxy we show a 10′×10′ postage stamp of the Swift/UVOT RGB composite, JWST/MIRI RGB composite, VLT/MUSE Hα, and Spitzer/IRAC 3.6 µm (dust-corrected), and the area of mutual overlap (limited by MIRI and MUSE data). All images are log-scale. Our main analysis is restricted to the region of overlap between the datasets. (figure continues on the next page) [PITH_FULL_IMAGE:… view at source ↗

**Figure 1.** (continued figure) [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗

**Figure 1.** (continued figure) [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗

Figures from the paper (19 more)

**Figure 2.** Figure 2: The data processing workflow to enable consistent photometric and spectroscopic comparison. ((a) ⇒ (b)) We start with a fully-reduced and calibrated image or line map at its native resolution and convolve it with a 2.5′′ Gaussian kernel (Swift/UVOT PSF), which is the l…

**Figure 3.** Figure 3: Example of derived property maps for NGC 4321. From left to right, the 2175Å strength Abump, ionised gas reddening E(B – V)gas, PAH abundance RPAH, log(SFR), log(M⋆), BPT classifications, and gas-phase metallicity (using Scal). The methods used to derive each property …

**Figure 4.** Figure 4: Example of how the 2175Å feature strength, Abump, is derived for each region based on the Swift data (black squares). We fit the UV continuum slope, βSwift (black line), from the two off-feature Swift filters (UVW2 and UVW1) and determine the expected flux density at U…

**Figure 5.** Figure 5: Derived property maps for regions that satisfy the selection cuts described in Section 3.9. Each property (i.e., column) uses the same colour-scale range, covering 2.5%-97.5% of the full distribution (see brackets at top). From left to right: the intrinsic 2175Å streng…

**Figure 5.** Figure 5: (continued figure) [PITH_FULL_IMAGE:figures/full_fig_p013_5.png]

**Figure 6.** Figure 6: (Left:) Intrinsic 2175Å feature strength, kbump=Abump/E(B – V)gas, vs. PAH abundance, RPAH=(F770W+F1130W)/F2100W, for the 15 galaxies in our sample. The Spearman correlation coefficient for each galaxy is indicated in the upper-right of each panel for cases with a p-va…

**Figure 7.** Figure 7: Similar to [PITH_FULL_IMAGE:figures/full_fig_p015_7.png]

**Figure 8.** Figure 8: Similar to [PITH_FULL_IMAGE:figures/full_fig_p015_8.png]

**Figure 9.** Figure 9: Similar to [PITH_FULL_IMAGE:figures/full_fig_p016_9.png]

**Figure 10.** Figure 10: Similar to [PITH_FULL_IMAGE:figures/full_fig_p016_10.png]

**Figure 11.** Figure 11: Similar to [PITH_FULL_IMAGE:figures/full_fig_p017_11.png]

**Figure 12.** Figure 12: Top: Cartoon visualisation of how changes in the inclination angle of a disk galaxy could affect the correlation strength between kbump and RPAH. kbump is measured via the effect of dust attenuation toward UV-bright young stars that are affected by both birth-cloud du…

**Figure 13.** Figure 13: 2D histogram of the F770W/F2100W surface luminosity ratio as a function of ΣSFR for the six ‘robust’ galaxies (NGC 1365, 1566, 1672, 3627, 4303, and 4321). The best-fit linear slope (orange dashed line) is consistent with the slope using the Calzetti et al. (2007) 8µm…

**Figure 14.** Figure 14 [PITH_FULL_IMAGE:figures/full_fig_p023_14.png]

**Figure 15.** Figure 15: Left: Comparison between UV slopes βIUE, derived using the 10 spectral windows from Calzetti et al. (1994), and βswift (see eq 2). The symbols indicate 6 different values of the intrinsic bump strength kbump,int and are shown for 6 different values of reddening (E(B –…

**Figure 16.** Figure 16: Top panels: Maps of AV,stars, derived from MAGPHYS SED modelling of the photometry of individual regions, and AV,gas, derived from the Balmer decrement using VLT/MUSE IFS data and assuming a MW-extinction curve for the nebular reddening for NGC 1300 (left) and NGC 432…

**Figure 17.** Figure 17: 2D histograms of AV,stars vs AV,gas for all galaxies, which show moderately tight (0.4 ≲ ρ ≲ 0.9), linear correlations. The regions shown are restricted to those satisfying criteria (1)-(3) in Section 3.9 and also AV > 0.1 and σ(AV ) < 0.3 (for both cases). The stella…

**Figure 18.** Figure 18: Similar to [PITH_FULL_IMAGE:figures/full_fig_p026_18.png]

**Figure 19.** Figure 19: Similar to [PITH_FULL_IMAGE:figures/full_fig_p026_19.png]

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Mapping Dust Attenuation at Kiloparsec Scales. III. The 2175\AA\ Bump
astro-ph.GA 2026-07 conditional novelty 6.0 of 10

The 2175Å attenuation bump is strongest at low Σ_Hα/Σ_* (especially non-SF regions) while absolute strength tracks dust column, supporting local radiation-field processing of its carriers.

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Pith tools

Reviewed August 11, 2026 · model on record in the stance chip above.

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, " * write output.state after.block = add.period write newline

ENTRY address archivePrefix author booktitle chapter doi edition editor eprint howpublished institution journal key month note number organization pages publisher school series title type volume year label extra.label sort.label short.list INTEGERS output.state before.all mid.sentence after.sentence after.block FUNCTION init.state.consts #0 'before.all :=...

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write newline

" write newline "" before.all 'output.state := FUNCTION format.doi doi empty "" "doi:" doi * if FUNCTION format.eprint eprint empty "" archivePrefix empty "" archivePrefix ":" * if eprint field.or.null * if FUNCTION format.pid eprint empty format.doi format.eprint if FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = ...

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