A Simple Model for the Absorption of Starlight by Dust in Galaxies

By S. Charlot, S. M. Fall. 2000

1,225 citations recorded by the source corpus.

We present a new model for computing the effects of dust on the integrated spectral properties of galaxies, based on an idealized description of the main features of the interstellar medium (ISM). The model includes the ionization of H II regions in the interiors of the dense clouds in which stars form and the influence of the finite lifetime of these clouds on the absorption of radiation. We compute the production of emission lines and the absorption of continuum radiation in the H II regions and the subsequent transfer of line and continuum radiation in the surrounding H I regions and the ambient ISM. This enables us to interpret simultaneously all the observations of an ultraviolet-selected sample of nearby starburst galaxies, including the ratio of far-infrared to ultraviolet luminosities, the ratio of Hα to Hβ luminosities, the Hα equivalent width, and the ultraviolet spectral slope. We show that the finite lifetime of stellar birth clouds is a key ingredient for resolving an apparent discrepancy between the attenuation of line and continuum photons in starburst galaxies. In addition, we find that an effective absorption curve proportional to λ-0.7 reproduces the observed relation between the ratio of far-infrared to ultraviolet luminosities and the ultraviolet spectral slope. We interpret this relation most simply as a sequence in the overall dust content of the galaxies. The shallow wavelength dependence of the effective absorption curve is compatible with the steepness of known extinction curves if the dust has a patchy distribution. In particular, we find that a random distribution of discrete clouds with optical depths similar to those in the Milky Way provides a consistent interpretation of all the observations. A noteworthy outcome of our detailed analysis is that the observed mean relations for starburst galaxies can be closely approximated by the following simple recipe: use an effective absorption curve proportional to λ-0.7 to attenuate the line and continuum radiation from each stellar generation, and lower the normalization of the curve, typically by a factor of 3 after 107 yr, to account for the dispersal of the birth clouds. This recipe or our full model for absorption can be incorporated easily into any population synthesis model.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/cd09aa9da897ec8e397c65d16d6420e4be9291fd

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Citations in the corpus

Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs (2018, methodology): “…addition to absorption and scattering out of the line of sight, the scattering into the line of sight and the effects of dust/star distribution and viewing orientation (the “geometry”; see review by Calzetti 2001, also Charlot & Fall 2000; Conroy et al. 2010; Conroy 2013; Chevallard et al. 2013).”
Simulations of Galaxy Formation in a Λ Cold Dark Matter Universe. II. The Fine Structure of Simulated Galactic Disks (2002, background): “…are neglected, except for a 5We express the present value of Hubble’s constant as H(z = 0) = H0 = 100 h km s−1 Mpc−1 temporary wavelength-dependent dimming introduced to take into account the gradual dispersal of the dust clouds that obscure the formation sites of young stars (Charlot & Fall 2000).”
Stellar population synthesis at the resolution of 2003 (2003, background): “To account for the attenuation of starlight by dust, the simple but realistic prescription of Charlot & Fall (2000) is particularly well suited to population synthesis studies.”
Constraining the galaxy–halo connection over the last 13.3 Gyr: star formation histories, galaxy mergers and structural properties (2017, methodology): “Based on the analysis carried out in Pérez-González et al. (2008), these authors found that a Charlot & Fall (2000) dust attenuation model gives, on average, galaxy stellar masses that are 0.1 dex larger compared to a Calzetti et al. (2000) law.”
STELLAR MASSES AND STAR FORMATION RATES FOR 1 M GALAXIES FROM SDSS+WISE (2015, methodology): “In Brinchmann et al. (2004) the adopted slope for the attenuation curve is -0.7, following Charlot & Fall (2000).”
DUST-CORRECTED STAR FORMATION RATES OF GALAXIES. II. COMBINATIONS OF ULTRAVIOLET AND INFRARED TRACERS (2011, methodology): “…within ±1σ uncertainty, and the main contributors to the different relations are the star formation history and the dust attenuation curve that includes the effect of the dust/star distribution, as suggested by other authors (e.g., Charlot & Fall 2000; Kong et al. 2004; Burgarella et al. 2005).”
The optical morphologies of galaxies in the IllustrisTNG simulation: a comparison to Pan-STARRS observations (2018, methodology): “Optionally, a simple Charlot & Fall (2000) model can be implemented at this stage in order to estimate the effects of an unresolved dust distribution (e.g. Torrey et al. 2015; Trayford et al. 2015; Nelson et al. 2018).”
Star formation history and dust content of galaxies drawn from ultraviolet surveys (2003, neutral): “Using thismodel, Charlot & Fall (2000) show that the tight IRX-UV relation forstarburst galaxies can be understood most simply as a sequence inth overall dust content.”
Size evolution of normal and compact galaxies in the EAGLE simulation (2015, methodology): “Galaxy colours from the simulation are produced by using the stellar population synthesis models of Bruzual & Charlot (2003) and applying the dust model of Charlot & Fall (2000).”
Empirical determination of the shape of dust attenuation curves in star-forming galaxies (2011, background): “Wild et al. (2011) compared mid-IR and optical emission line strengths to show that a two component model (Charlot & Fall 2000), with diffuse dust accounting for a fraction (µ) of the optical depth at 5500̊A, and denser birth-cloud dust accounting for the remainder, is consistent with the…”
Introducing the Illustris Project: the evolution of galaxy populations across cosmic time (2014, methodology): “1 6(b), we further add the effects of dust extinction using the simple model of Charlot & Fall (2000), which prescribes an optical depth for dust extinction as a simple function of wavelength for any given stellar population age.”
The ages and metallicities of galaxies in the local universe (2005, methodology): “The z-band attenuation Az is inferred from the difference between the emission-line corrected fibre r − i colour7 of the galaxy and the r − i colour of the redshifted (dust-free) model, assuming a single power law (∝ λ−0.7) attenuation curve (Charlot & Fall 2000).”
DUST-CORRECTED STAR FORMATION RATES OF GALAXIES. I. COMBINATIONS OF Hα AND INFRARED TRACERS (2009, methodology): “(2) Equations (1) and (2) represent simple approximations to a much more complicated dust radiative transfer process in galaxies (e.g., Witt & Gordon 2000; Charlot & Fall 2000), but their physical motivation can be readily understood as follows.”
GALAXY STELLAR MASS ASSEMBLY BETWEEN 0.2 < z < 2 FROM THE S-COSMOS SURVEY (2009, methodology): “We computed the stellar masses using both the Calzetti et al. (2000) and the Charlot & Fall (2000) extinction laws (the latter is included in BC03).”
Spectroscopic detection of C iv λ1548 in a galaxy at z = 7.045: implications for the ionizing spectra of reionization-era galaxies (2015, methodology): “We also include attenuation of line and continuum photons by dust in the neutral ISM, using the 2-component model of Charlot & Fall (2000), as implemented by da Cunha et al. (2008, their equations 1– 4).”
Optical Star Formation Rate Indicators (2005, positive): “Alternatively, Charlot & Fall (2000) advocate a power-law attenuation curve, k(k) / k 0:7, based on a multiwavelength analysis of nearby starburst galaxies and simple radiation transfer arguments.”
Inferring the star formation histories of massive quiescent galaxies with bagpipes: evidence for multiple quenching mechanisms (2017, methodology): “For the Charlot & Fall (2000) model we define k(λ) RV = (λ/5500Å)−n (5) where n is the slope of the attenuation law.”
NEW CONSTRAINTS ON THE EVOLUTION OF THE STELLAR-TO-DARK MATTER CONNECTION: A COMBINED ANALYSIS OF GALAXY–GALAXY LENSING, CLUSTERING, AND STELLAR MASS FUNCTIONS FROM z = 0.2 to z = 1 (2011, methodology): “The assumed dust model is Charlot & Fall (2000).”
CONFIRMATION OF A STAR FORMATION BIAS IN TYPE Ia SUPERNOVA DISTANCES AND ITS EFFECT ON THE MEASUREMENT OF THE HUBBLE CONSTANT (2014, background): “Dust is associated with star formation (e.g., Charlot & Fall 2000; Simones et al. 2014; Verley et al. 2010) and so can have a strong impact on the observed UV light around the SN location.”