Mapping Metallicity Variations across Nearby Galaxy Disks

Kreckel, Kathryn; Ho, I-Ting; Blanc, Guillermo A.; Groves, Brent; Santoro, Francesco; Schinnerer, E.; Bigiel, Frank; Chevance, Mélanie; Congiu, Enrico; Emsellem, Éric; Faesi, Christopher M.; Glover, Simon C. O.; Grasha, Kathryn; Kruijssen, J. M. Diederik; Lang, P.; Leroy, Adam K.; Meidt, Sharon E.; McElroy, Rebecca; Pety, J.; Rosolowsky, Erik; Saito, Toshiki; Sandström, Karin; Sánchez‐Blázquez, P.; Schruba, Andreas

doi:10.3847/1538-4357/ab5115

Cited by 168 publications

(232 citation statements)

References 110 publications

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“…We examine the statistical distribution of gas-phase abundances within the ISM of eight nearby (D < 17 Mpc) galaxies. Each galaxy has hundreds to thousands of H II regions with measured 12 + log(O/H) based on strong-line metallicity prescriptions, as observed by the PHANGS-MUSE survey (Kreckel et al 2019; Emsellem et al, in preparation). After fitting and removing a linear gradient in Paper I, we find rms scatter in residual metallicity of 0.04-0.05 dex.…”

Section: O N C L U S I O N Smentioning

confidence: 99%

Measuring the mixing scale of the ISM within nearby spiral galaxies

Kreckel

Blanc

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The spatial distribution of metals reflects, and can be used to constrain, the processes of chemical enrichment and mixing. Using PHANGS-MUSE optical integral field spectroscopy, we measure the gas phase oxygen abundances (metallicities) across 7138 H ii regions in a sample of eight nearby disc galaxies. In Paper I we measure and report linear radial gradients in the metallicities of each galaxy, and qualitatively searched for azimuthal abundance variations. Here, we examine the two-dimensional variation in abundances once the radial gradient is subtracted, Δ(O/H), in order to quantify the homogeneity of the metal distribution and to measure the mixing scale over which HII region metallicities are correlated. We observe low (0.03–0.05 dex) scatter in Δ(O/H) globally in all galaxies, with significantly lower (0.02–0.03 dex) scatter on small (<600 pc) spatial scales. This is consistent with the measurement uncertainties, and implies the two-dimensional metallicity distribution is highly correlated on scales of ≲ 600” pc. We compute the two point correlation function for metals in the disc in order to quantify the scale lengths associated with the observed homogeneity. This mixing scale is observed to correlate better with the local gas velocity dispersion (of both cold and ionized gas) than with the star formation rate. Selecting only H ii regions with enhanced abundances relative to a linear radial gradient, we do not observe increased homogeneity on small scales. This suggests that the observed homogeneity is driven by the mixing introducing material from large scales rather than by pollution from recent and on-going star formation.

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Section: O N C L U S I O N Smentioning

confidence: 99%

Measuring the mixing scale of the ISM within nearby spiral galaxies

Kreckel

Blanc

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Considering that this only seems to affect sulfur lines, these latter authors suggest that this is due to limitations in stellar atmosphere modeling and/or the atomic data for sulfur. Based on the observation that the discrepancy holds for single H ii regions (from Kreckel et al 2019), Mingozzi et al (2020) exclude the role of diffuse ionized gas as a cause of this issue. However, in our study, we see in Fig.…”

Section: Low Ionization Line Diagnostics: Progress and Caveatsmentioning

confidence: 99%

Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies

Ramambason

Schaerer

Stasińska

et al. 2020

A&A

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Context. Finding and elucidating the properties of Lyman-continuum(LyC)-emitting galaxies is an important step in improving our understanding of cosmic reionization. Aims. Although the z ∼ 0.3 − 0.4 LyC emitters found recently show strong optical emission lines, no consistent quantitative photoionization model taking into account the escape of ionizing photons and inhomogenous interstellar medium (ISM) geometry of these galaxies has yet been constructed. Furthermore, it is unclear to what extent these emission lines can be used to distinguish LyC emitters. Methods. To address these questions we construct one- and two-zone photoionization models accounting for the observed LyC escape, which we compare to the observed emission line measurements. The main diagnostics used include lines of [O III], [O II], and [O I] plus sulfur lines ([S II], [S III]) and a nitrogen line ([N II]), which probe regions of different ionization in the ISM. Results. We find that single (one-zone) density-bounded photoionization models cannot reproduce the emission lines of the LyC leakers, as pointed out by earlier studies, because they systematically underpredict the lines of species of low ionization potential, such as [O I] and [S II]. Introducing a two-zone model, with differing ionization parameter and a variable covering fraction and where one of the zones is density-bounded, we show that the observed emission line ratios of the LyC emitters are well reproduced. Furthermore, our model yields LyC escape fractions, which are in fair agreement with the observations and independent measurements. The [O I] λ6300 excess, which is observed in some LyC leakers, can be naturally explained in this model, for example by emission from low-ionization and low-filling-factor gas. LyC emitters with a high escape fraction (fesc ≳ 38%) are deficient both in [O I] λ6300 and in [S II] λλ6716,6731. We also confirm that a [S II] λλ6716,6731 deficiency can be used to select LyC emitter candidates, as suggested earlier. Finally, we find indications for a possible dichotomy in terms of escape mechanisms for LyC photons between galaxies with relatively low (fesc ≲ 10%) and higher escape fractions. Conclusions. We conclude that two-zone photoionization models are sufficient and required to explain the observed emission line properties of z ∼ 0.3 − 0.4 LyC emitters. This is in agreement with UV absorption line studies, which also show the co-existence of regions with high hydrogen column density (i.e., no escape of ionizing photons) and density-bounded or very low column density regions responsible for the observed escape of LyC radiation. These simple but consistent models provide a first step towards the use of optical emission lines and their ratios as quantitative diagnostics of LyC escape from galaxies.

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“…Here, we report on an augmentation of the publicly available SED fitting package CIGALE: Code Investigating GALaxy Emission 1 (Burgarella, Buat & Iglesias-Páramo 2005;Noll et al 2009;Boquien et al 2019) to derive ages, stellar masses, and reddenings for star clusters identified in the Physics at High Angular resolution in Nearby GalaxieS-HST (PHANGS-HST) survey (Lee et al 2021). 2 PHANGS 3 is a panchromatic collaboration comprised of: PHANGS-ALMA, a large CO(2-1) mapping program aimed at covering a representative sample of ∼74 nearby galaxies (Leroy et al, in preparation); PHANGS-MUSE, a Very Large Telescope (VLT) imaging program of ∼20 of the PHANGS galaxies with the MUSE optical integral field unit (IFU) instrument (Emsellem et al, in preparation; see first results in Kreckel et al 2016Kreckel et al , 2019; and PHANGS-HST which aims to chart the connections between molecular clouds and young star clusters/associations throughout a range of galactic environments by imaging the 38 galaxies from the PHANGS sample best suited 4 for study of resolved stellar populations. PHANGS-HST observations, which begun in 2019 April and are scheduled to conclude in mid-2021, are expected to yield NUV-U-B-V-I photometry for tens of thousands of stellar clusters and associations.…”

Section: Introductionmentioning

confidence: 99%

PHANGS–HST: star cluster spectral energy distribution fitting with cigale

Turner

Dale

Lee

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The sensitivity and angular resolution of photometric surveys executed by the Hubble Space Telescope (HST) enable studies of individual star clusters in galaxies out to a few tens of megaparsecs. The fitting of spectral energy distributions (SEDs) of star clusters is essential for measuring their physical properties and studying their evolution. We report on the use of the publicly available Code Investigating GALaxy Emission (cigale) SED fitting package to derive ages, stellar masses, and reddenings for star clusters identified in the Physics at High Angular resolution in Nearby GalaxieS–HST (PHANGS–HST) survey. Using samples of star clusters in the galaxy NGC 3351, we present results of benchmark analyses performed to validate the code and a comparison to SED fitting results from the Legacy Extragalactic Ultraviolet Survey. We consider procedures for the PHANGS–HST SED fitting pipeline, e.g. the choice of single stellar population models, the treatment of nebular emission and dust, and the use of fluxes versus magnitudes for the SED fitting. We report on the properties of clusters in NGC 3351 and find, on average, the clusters residing in the inner star-forming ring of NGC 3351 are young (<10 Myr) and massive (105 M⊙) while clusters in the stellar bulge are significantly older. Cluster mass function fits yield β values around −2, consistent with prior results with a tendency to be shallower at the youngest ages. Finally, we explore a Bayesian analysis with additional physically motivated priors for the distribution of ages and masses and analyse the resulting cluster distributions.

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Mapping Metallicity Variations across Nearby Galaxy Disks

Cited by 168 publications

References 110 publications

Measuring the mixing scale of the ISM within nearby spiral galaxies

Measuring the mixing scale of the ISM within nearby spiral galaxies

Reconciling escape fractions and observed line emission in Lyman-continuum-leaking galaxies

PHANGS–HST: star cluster spectral energy distribution fitting with cigale

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