Browsing by Author "Draine, B. T."

Now showing 1 - 3 of 3
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    Comprehensive comparison of models for spectral energy distributions from 0.1 μm to 1mm of nearby star-forming galaxies
    (2019) Hunt, L. K.; De Looze, I; Boquien, M.; Nikutta, R.; Rossi, A.; Bianchil, S.; Dale, D. A.; Granato, G. L.; Kennicutt, R. C.; Silva, L.; Ciesla, L.; Relano, M.; Viaene, S.; Brandl, B.; Calzetti, D.; Croxall, K., V; Draine, B. T.; Galametz, M.; Gordon, K. D.; Groves, B. A.; Helou, G.; Herrera-Camus, R.; Hinz, J. L.; Koda, J.; Salim, S.; Sandstrom, K. M.; Smith, J. D.; Wilson, C. D.; Zibetti, S.
    We have fit the far-ultraviolet (FUV) to sub-millimeter (850 mu m) spectral energy distributions (SEDs) of the 61 galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel (KINGFISH). The fitting has been performed using three models: the Code for Investigating GALaxy Evolution (CIGALE), the GRAphite-SILicate approach (GRASIL), and the Multiwavelength Analysis of Galaxy PHYSical properties (MAGPHYS). We have analyzed the results of the three codes in terms of the SED shapes, and by comparing the derived quantities with simple "recipes" for stellar mass (M-star), star-formation rate (SFR), dust mass (M-dust), and monochromatic luminosities. Although the algorithms rely on different assumptions for star-formation history, dust attenuation and dust reprocessing, they all well approximate the observed SEDs and are in generally good agreement for the associated quantities. However, the three codes show very different behavior in the mid-infrared regime: in the 5-10 mu m region dominated by PAH emission, and also between 25 and 70 mu m where there are no observational constraints for the KINGFISH sample. We find that different algorithms give discordant SFR estimates for galaxies with low specific SFR, and that the standard recipes for calculating FUV absorption overestimate the extinction compared to the SED-fitting results. Results also suggest that assuming a "standard" constant stellar mass-to-light ratio overestimates Mstar relative to the SED fitting, and we provide new SED-based formulations for estimating Mstar from WISE W1 (3.4 mu m) luminosities and colors. From a principal component analysis of M-star, SFR, M-dust, and O/H, we reproduce previous scaling relations among Mstar, SFR, and O/H, and find that Mdust can be predicted to within similar to 0.3 dex using only M-star and SFR.
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    Gas, dust, and the CO-to-molecular gas conversion factor in low-metallicity starbursts⋆
    (2023) Hunt, L. K.; Belfiore, F.; Lelli, F.; Draine, B. T.; Marasco, A.; Garcia-Burillo, S.; Venturi, G.; Combes, F.; Weiss, A.; Henkel, C.; Menten, K. M.; Annibali, F.; Casasola, V.; Cignoni, M.; McLeod, A.; Tosi, M.; Beltran, M.; Concas, A.; Cresci, G.; Ginolfi, M.; Kumari, N.; Mannucci, F.
    The factor relating CO emission to molecular hydrogen column density, X-CO, is still subject to uncertainty, in particular at low metallicity. In this paper, to quantify X-CO at two different spatial resolutions, we exploited a dust-based method together with ALMA 12-m and ACA data and H I maps of three nearby metal-poor starbursts, NGC 625, NGC 1705, and NGC 5253. Dust opacity at 250 pc resolution was derived based on dust temperatures estimated by fitting two-temperature modified blackbodies to Herschel PACS data. By using the HI maps, we were then able to estimate dust-to-gas ratios in the regions dominated by atomic gas, and, throughout the galaxy, to infer total gas column densities and H-2 column densities as the difference with HI. Finally, from the ACA CO(1-0) maps, we derived X-CO. We used a similar technique with 40 pc ALMA 12-m data for the three galaxies, but instead derived dust attenuation at 40 pc resolution from reddening maps based on VLT/MUSE data. At 250 pc resolution, we find X-CO  & SIM; 10(22) - 10(23) cm(-2)/K km s(-1), 5-1000 times the Milky Way value, with much larger values than would be expected from a simple metallicity dependence. Instead, at 40 pc resolution, X-CO again shows large variation, but is roughly consistent with a power-law metallicity dependence, given the Z  & SIM; 1/3 Z(& ODOT;) metal abundances of our targets. The large scatter in both estimations could imply additional parameter dependence, which we have investigated by comparing X-CO with the observed velocity-integrated brightness temperatures, I-CO, as predicted by recent simulations. Indeed, larger X-CO is significantly correlated with smaller I-CO, but with slightly different slopes and normalizations than predicted by theory. Such behavior can be attributed to the increasing fraction of CO-faint (or dark) H-2 gas with lower spatial resolution (larger beams). This confirms the idea the X-CO is multivariate, depending not only on metallicity but also on the CO brightness temperature and beam size. Future work is needed to consolidate these empirical results by sampling galaxies with different metal abundances observed at varying spatial resolutions.
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    The State-of-Play of Anomalous Microwave Emission (AME) research
    (2018) Dickinson, Clive; Ali-Haimoud, Y.; Barr, A.; Battistelli, E. S.; Bell, A.; Bernstein, L.; Casassus, S.; Cleary, K.; Draine, B. T.; Genova-Santos, R.; Harper, S. E.; Hensley, B.; Hill-Valler, J.; Thiem Hoang; Israel, F. P.; Jew, L.; Lazaria