skip to main content


Title: The origin of the dust extinction curve in milky way-like galaxies
ABSTRACT We develop a cosmological model for the evolution of dust grains in galaxies with a distribution of sizes in order to understand the origin of the Milky Way dust extinction curve. Our model considers the formation of active dust in evolved stars, growth by accretion and coagulation, and destruction processes via shattering, sputtering, and astration in the ISM of galaxies over cosmic time. Our main results follow. Galaxies in our cosmological model with masses comparable to the Milky Way’s at z ∼ 0 exhibit a diverse range of extinction laws, though with slopes and bump strengths comparable to the range observed in the Galaxy. The progenitors of the Milky Way have steeper slopes, and only flatten to slopes comparable to the Galaxy at z ∼ 1. This owes to increased grain growth rates at late times/in high-metallicity environments driving up the ratio of large to small grains, with a secondary dependence on the graphite-to-silicate ratio evolution. The UV bump strengths depend primarily on the graphite-to-silicate ratio, and remain broadly constant in MW-like galaxies between z = 3 and z = 0, though show slight variability. Our models span comparable regions of bump-slope space as sightlines in the Galaxy do, though there is a lack of clear relationship between the model slopes and bump strengths owing to variations among galaxies in the graphite-to-silicate ratio. Our model provides a novel framework to study the origins and variations of dust extinction curves in galaxies over cosmic time.  more » « less
Award ID(s):
1909153
NSF-PAR ID:
10347530
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
507
Issue:
1
ISSN:
0035-8711
Page Range / eLocation ID:
548 to 559
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. null (Ed.)
    Understanding the properties of dust attenuation curves in galaxies and the physical mechanisms that shape them are among the fundamental questions of extragalactic astrophysics, with great practical significance for deriving the physical properties of galaxies. Attenuation curves result from a combination of dust grain properties, dust content, and the spatial arrangement of dust and different populations of stars. In this review, we assess the state of the field, paying particular attention to extinction curves as the building blocks of attenuation laws. We introduce a quantitative framework to characterize extinction and attenuation curves, present a theoretical foundation for interpreting empirical results, overview an array of observational methods, and review observational results at low and high redshifts. Our main conclusions include the following: ▪  Attenuation curves exhibit a wide range of UV-through-optical slopes, from curves with shallow (Milky Way–like) slopes to those exceeding the slope of the Small Magellanic Cloud extinction curve. ▪  The slopes of the curves correlate strongly with the effective optical opacities, in the sense that galaxies with lower dust column density (lower visual attenuation) tend to have steeper slopes, whereas the galaxies with higher dust column density have shallower (grayer) slopes. ▪  Galaxies exhibit a range of 2175-Å UV bump strengths, including no bump, but, on average, are suppressed compared with the average Milky Way extinction curve. ▪  Theoretical studies indicate that both the correlation between the slope and the dust column as well as variations in bump strength may result from geometric and radiative transfer effects. 
    more » « less
  2. ABSTRACT We present predictions for the evolution of the galaxy dust-to-gas ratio (DGR) and dust-to-metal ratio (DTM) from z = 0 → 6, using a model for the production, growth, and destruction of dust grains implemented into the simba cosmological hydrodynamic galaxy formation simulation. In our model, dust forms in stellar ejecta, grows by the accretion of metals, and is destroyed by thermal sputtering and supernovae. Our simulation reproduces the observed dust mass function at z = 0, but modestly underpredicts the mass function by ∼×3 at z ∼ 1–2. The z = 0 DGR versus metallicity relationship shows a tight positive correlation for star-forming galaxies, while it is uncorrelated for quenched systems. There is little evolution in the DGR–metallicity relationship between z = 0 and 6. We use machine learning techniques to search for the galaxy physical properties that best correlate with the DGR and DTM. We find that the DGR is primarily correlated with the gas-phase metallicity, though correlations with the depletion time-scale, stellar mass, and gas fraction are non-negligible. We provide a crude fitting relationship for DGR and DTM versus the gas-phase metallicity, along with a public code package that estimates the DGR and DTM given a set of galaxy physical properties. 
    more » « less
  3. ABSTRACT

    Observations indicate dust populations vary between galaxies and within them, suggesting a complex life cycle and evolutionary history. Here we investigate the evolution of galactic dust populations across cosmic time using a suite of cosmological zoom-in simulations from the Feedback in Realistic Environments project, spanning $M_{\rm vir}=10^{9-12}{M}_{\odot };\, M_{*}=10^{6-11}\, {M}_{\odot }$. Our simulations incorporate a dust evolution model that accounts for the dominant sources of dust production, growth, and destruction and follows the evolution of specific dust species. All galactic dust populations in our suite exhibit similar evolutionary histories, with gas–dust accretion being the dominant producer of dust mass for all but the most metal-poor galaxies. Similar to previous works, we find the onset of efficient gas–dust accretion occurs above a ‘critical’ metallicity threshold (Zcrit). Due to this threshold, our simulations reproduce observed trends between galactic D/Z and metallicity and element depletion trends in the interstellar medium. However, we find Zcrit varies between dust species due to differences in key element abundances, dust physical properties, and life cycle processes resulting in $Z_{\rm crit}\sim 0.05{\rm Z}_{\odot },\, 0.2{\rm Z}_{\odot },\, 0.5{\rm Z}_{\odot }$ for metallic iron, silicates, and carbonaceous dust, respectively. These variations could explain the lack of small carbonaceous grains observed in the Magellanic Clouds. We also find a delay between the onset of gas–dust accretion and when a dust population reaches equilibrium, which we call the equilibrium time-scale (τequil). The relation between τequil and the metal enrichment time-scale of a galaxy, determined by its recent evolutionary history, can contribute to the scatter in the observed relation between galactic D/Z and metallicity.

     
    more » « less
  4. null (Ed.)
    ABSTRACT The relation between infrared excess (IRX) and UV spectral slope (βUV) is an empirical probe of dust properties of galaxies. The shape, scatter, and redshift evolution of this relation are not well understood, however, leading to uncertainties in estimating the dust content and star formation rates (SFRs) of galaxies at high redshift. In this study, we explore the nature and properties of the IRX–βUV relation with a sample of z = 2–6 galaxies ($M_*\approx 10^9\!-\!10^{12}\, \mathrm{M}_\odot$) extracted from high-resolution cosmological simulations (MassiveFIRE) of the Feedback in Realistic Environments (FIRE) project. The galaxies in our sample show an IRX–βUV relation that is in good agreement with the observed relation in nearby galaxies. IRX is tightly coupled to the UV optical depth, and is mainly determined by the dust-to-star geometry instead of total dust mass, while βUV is set both by stellar properties, UV optical depth, and the dust extinction law. Overall, much of the scatter in the IRX–βUV relation of our sample is found to be driven by variations of the intrinsic UV spectral slope. We further assess how the IRX–βUV relation depends on viewing direction, dust-to-metal ratio, birth-cloud structures, and the dust extinction law and we present a simple model that encapsulates most of the found dependencies. Consequently, we argue that the reported ‘deficit’ of the infrared/sub-millimetre bright objects at z ≳ 5 does not necessarily imply a non-standard dust extinction law at those epochs. 
    more » « less
  5. ABSTRACT

    We report discoveries of 165 new quasar Ca ii absorbers from the Sloan Digital Sky Survey (SDSS) Data Releases 7 and 12. Our ca ii rest-frame equivalent width distribution supports the weak and strong subpopulations, split at ${W}^{\lambda 3934}_{0}=0.7$ Å. Comparison of both populations’ dust depletion shows clear consistency for weak absorber association with halo-type gas in the Milky Way (MW), while strong absorbers have environments consistent with halo and disc-type gas. We probed our high-redshift Ca ii absorbers for 2175 Å dust bumps, discovering 12 2175 Å dust absorbers (2DAs). This clearly shows that some Ca ii absorbers follow the Large Magellanic Cloud (LMC) extinction law rather than the Small Magellanic Cloud extinction law. About 33 per cent of our strong Ca ii absorbers exhibit the 2175 Å dust bump, while only 6 per cent of weak Ca ii absorbers show this bump. 2DA detection further supports the theory that strong Ca ii absorbers are associated with disc components and are dustier than the weak population. Comparing average Ca ii absorber dust depletion patterns to that of Damped Ly α absorbers (DLAs), Mg ii absorbers, and 2DAs shows that Ca ii absorbers generally have environments with more dust than DLAs and Mg ii absorbers, but less dust than 2DAs. Comparing 2175 Å dust bump strengths from different samples and also the MW and LMC, the bump strength appears to grow stronger as the redshift decreases, indicating dust growth and the global chemical enrichment of galaxies in the Universe over time.

     
    more » « less