Metallicity Effects on Mid-Infrared Colors and the 8 μm PAH Emission in Galaxies

By C. Engelbracht, K. Gordon, G. Rieke, M. Werner, D. Dale, W. Latter. 2005

286 citations recorded by the source corpus.

We examine colors from 3.6 to 24 μm as a function of metallicity (O/H) for a sample of 34 galaxies. The galaxies range over 2 orders of magnitude in metallicity. They display an abrupt shift in the 8 μm-to-24 μm color for metallicities between one-third and one-fifth of the solar value. The mean 8-to-24 μm flux density ratio below and above 12 + log (O/H) = 8.2 is 0.08 ± 0.04 and 0.70 ± 0.53, respectively. We use mid-IR colors and spectroscopy to demonstrate that the shift is primarily due to a decrease in the 8 μm flux density, as opposed to an increase in the 24 μm flux density. This result is most simply interpreted as being due to a weakening at low metallicity of the mid-IR emission bands usually attributed to PAHs (polycyclic aromatic hydrocarbons) relative to the small-grain dust emission. However, existing empirical spectral energy distribution models cannot account for the observed short-wavelength (below 8 μm) colors of the low-metallicity galaxies merely by reducing the strength of the PAH features; some other emission source (e.g., hot dust) is required.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/75a36e021c71cdce6559488613eb0fd5873abfe4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. C. Conroy
2. L. Hernquist
3. P. Hopkins
4. P. V. van Dokkum
5. R. Dav'e
6. R. Somerville
7. M. Franx
8. F. Walter

In Global and Planetary Change

1. C. Steidel
2. Naveen A. Reddy
3. A. Shapley
4. D. Erb
5. M. Pettini
6. M. Franx
7. P. V. van Dokkum
8. H. Netzer

Citations in the corpus

• DUST-CORRECTED STAR FORMATION RATES OF GALAXIES. I. COMBINATIONS OF Hα AND INFRARED TRACERS (2009, background): “…longer wavelength tracers such as the 24 μm emission, with systematic dependences of the emissivity on metal abundance, and local radiation field strength and hardness (e.g., Madden 2000; Peeters et al. 2004; Engelbracht et al. 2005, 2008; Dale et al. 2005; Wu et al. 2006; Smith et al. 2007; C07).”
• ISM properties in low-metallicity environments I. mid-infrared spectra of dwarf galaxies (2005, background): “Recent Spitzer observations also confirm this (Houck et al. 2004; Engelbracht et al. 2005; Wu et al. 2005).”
• DUST OBSCURATION AND METALLICITY AT HIGH REDSHIFT: NEW INFERENCES FROM UV, Hα, AND 8 μm OBSERVATIONS OF z ∼ 2 STAR-FORMING GALAXIES (2010, background): “…from OB stars and hence the global star formation rate in nearby galaxies (e.g., Förster Schreiber et al. 2004; Roussel et al. 2001), albeit with some variation depending on metallicity and ionizing hardness (e.g., Engelbracht et al. 2005; Hogg et al. 2005; Helou et al. 2001; Normand et al. 1995.”
• The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, background): “…intensity, star-formation-rate surface density, and stellar population age (e.g., Normand et al. 1995; Helou et al. 2001; Alonso-Herrero et al. 2004; Engelbracht et al. 2005; Hogg et al. 2005; Madden et al. 2006; Draine et al. 2007; Smith et al. 2007; Galliano et al. 2008; Hunt et al. 2010;…”
• THE SPITZER LOCAL VOLUME LEGACY: SURVEY DESCRIPTION AND INFRARED PHOTOMETRY (2009, background): “…is starved or the relatively fragile PAHs are photo-dissociated in the hard radiation fields typically associated with low-metallicity environments (Engelbracht et al. 2005; Madden et al. 2006; Wu et al. 2006; Jackson et al. 2006; Draine et al. 2007; Sloan et al. 2008; Gordon et al. 2008; Dale et…”
• THE CALIBRATION OF MONOCHROMATIC FAR-INFRARED STAR FORMATION RATE INDICATORS (2010, background): “The separating value in metallicity is chosen after Engelbracht et al. (2005), Jackson et al. (2006), Draine et al. (2007), and Engelbracht et al. (2008), where it is found that galaxies roughly below this metallicity value tend to be underluminous in their PAH emission (as measured in the…”
• The Behavior of the Aromatic Features in M101 H II Regions: Evidence for Dust Processing (2008, methodology): “…of Toledo, Toledo, OH 43603 4 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK gle sources (Werner et al. 2004), among various Galactic sources (van Diedenhoven et al. 2004), and among galaxies (Engelbracht et al. 2005; Madden et al. 2006; Wu et al. 2006).”
• Gas-to-dust mass ratios in local galaxies over a 2 dex metallicity range (2013, background): “This 12 + log(O/H) value of ∼8.1 has already been noted as being special for dwarf galaxies (e.g., for the strength of the PAH features: Engelbracht et al. 2005, 2008; Madden et al. 2006; Draine et al. 2007; Galliano et al. 2008).”
• Stellar Evolutionary Effects on the Abundances of Polycyclic Aromatic Hydrocarbons and Supernova-Condensed Dust in Galaxies (2007, methodology): “…combined ISO samples of starbursts and AGNs (Laurent et al. 2000), spirals (Roussel et al. 2001), ellipticals (Xilouris et al. 2004), dwarf galaxies (Madden et al. 2006), and the low-metallicity sources of the Spitzer sample presented by Engelbracht et al. (2005) which were observed by Spitzer IRS.”
• RADIAL DISTRIBUTION OF STARS, GAS, AND DUST IN SINGS GALAXIES. II. DERIVED DUST PROPERTIES (2009, background): “…the years, a body of observational evidence has been collected showing that PAH emission is weak or even suppressed in low-metallicity systems (see e.g. Boselli et al. 1998; Sturm et al. 2000; Madden 2000; Madden et al. 2006; Hunt et al. 2005; Hogg et al. 2005; D07; Engelbracht et al. 2005, 2008).”
• Star Formation and Extinction in Redshift z~2 Galaxies: Inferences from Spitzer MIPS Observations (2006, background): “Therefore, the metallicity dependence of the IR/MIR ratio found for local galaxies (e.g., Engelbracht et al. 2005) suggests that we may not be able to ascribe the IR/MIR ratio for a galaxy of a given stellar mass at z ¼ 0 to a galaxy at z 2 with the same stellar mass.”
• The Calibration of Mid-Infrared Star Formation Rate Indicators (2007, methodology): “Of these, 13 also have Spitzer imaging as part of the MIPS and IRS GTO observations (Engelbracht et al. 2005).”
• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample (2007, methodology): “21 Note that the oxygen abundances used by Engelbracht et al. (2005) were based on a heterogeneous compilation of measurements from the literature, whereas the abundances in our study have been derived self-consistently and placed on a common abundance scale (for details see J. Moustakas et al.…”
• Deriving Physical Properties from Broadband Photometry with Prospector: Description of the Model and a Demonstration of its Accuracy Using 129 Galaxies in the Local Universe (2016, result): “…this is consistent with previous observations which show the PAH mass fraction is very low for galaxies below a gasphase metallicity of log(O/H) + 12∼8.1, with considerable natural variation above this threshold (Roche et al. 1991; Engelbracht et al. 2005; Hunt et al. 2005; Draine et al. 2007).”
• Dust spectral energy distributions of nearby galaxies: an insight from the Herschel Reference Survey (2014, result): “We also confirm on a larger sample the results of Engelbracht et al. (2005) who found a weakening of the PAH features at low metallicity from 8 to 24 µm flux density ratios, and Smith et al. (2007) who found that the strength of the PAH bands is directly linked to the metallicity from the…”
• Spitzer Survey of the Large Magellanic Cloud: Surveying the Agents of a Galaxy’s Evolution (SAGE). I. Overview and Initial Results (2006, unknown): “…IRAC mapping of the lowermetallicity LMCwill yield high-resolution insight into recent work on the paucity of PAH emission in low-metallicity galaxies (Madden 2000, 2006; Houck et al. 2004; Engelbracht et al. 2005; Galliano et al. 2005; Dale et al. 2005; Wu et al. 2006; O’Halloran et al. 2006).”
• An Ultraviolet-to-Radio Broadband Spectral Atlas of Nearby Galaxies (2006, background): “Low metallicity systems, for example, are known to be deficient in PAH emission (e.g., Dale et al. 2005; Engelbracht et al. 2005; Galliano et al. 2005; Walter et al. 2006).”
• Infrared Spectral Energy Distributions of Nearby Galaxies (2005, background): “Some of the low-metallicity objects lie dramatically below the canonical star-forming galaxy curves, consistent with the Engelbracht et al. (2005) and Galliano et al. (2005) empirical finding that low-metallicity galaxies show relatively low 8.0 m emission.”