Far-infrared spectral energy distribution fitting for galaxies near and far

By C. Casey. 2012

287 citations recorded by the source corpus.

Spectral energy distribution (SED) fitting in the far-infrared (FIR) is greatly limited by a dearth of data and an excess of free parameters – from galaxies’ dust composition, temperature, mass, orientation, opacity, to heating from active galactic nuclei (AGN). This paper presents a simple FIR SED fitting technique joining a modified, single dust temperature greybody, representing the reprocessed starburst emission in the whole galaxy, to a mid-infrared (MIR) power law, which approximates hot-dust emission from AGN heating or clumpy, hot starbursting regions. This FIR SED can be used to measure IR luminosities, dust temperatures and dust masses for both local and high-z galaxies with three to 10+ FIR photometric measurements. While the fitting technique does not model emission from polycyclic aromatic hydrocarbons (PAHs) in the MIR, the impact of PAH features on integrated FIR properties is negligible when compared to the bulk emission at longer wavelengths. This fitting method is compared to IR template SEDs in the literature using photometric data on 65 local luminous and ultraluminous infrared galaxies, (U)LIRGs. Despite relying only on 2–4 free parameters, the coupled greybody/power-law SED fitting described here produces better fits to photometric measurements than best-fitting literature template SEDs (with residuals a factor of ∼2 lower). A mean emissivity index of β = 1.60 ± 0.38 and MIR power-law slope of α = 2.0 ± 0.5 is measured; the former agrees with the widely presumed emissivity index of β = 1.5 and the latter is indicative of an optically thin dust medium with a shallow radial density profile, ≈r−1/2. Adopting characteristic dust temperature as the inverse wavelength where the SED peaks, dust temperatures ∼25–45 K are measured for local (U)LIRGs, ∼5–15 K colder than previous estimates using only simple greybodies. This comparative study highlights the impact of SED fitting assumptions on the measurement of physical properties such as IR luminosity (and thereby IR-based star formation rate), dust temperature and dust mass, for both local and high-redshift galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/67fa326e95258cad55d70d6975d325ca7f2636f8

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In Astronomy and Astrophysics

1. D. M. Alexander
2. D. Narayanan
3. C. Casey
4. L. Hernquist
5. P. Hopkins
6. A. Cooray
7. F. Walter
8. R. Somerville

Citations in the corpus

• Very extended cold gas, star formation and outflows in the halo of a bright QSO at z>6 (2014, methodology): “In this paper we use the IDL SED fitting code developed by Caitlin M. Casey (Casey 2012).”
• CIGALE: a python Code Investigating GALaxy Emission (2018, methodology): “…page 16 of 33 A103, page 17 of 33 gas (Inoue 2011), attenuation by dust (Calzetti et al. 2000; Charlot & Fall 2000) and re-emission of the energy at longer wavelengths (Draine & Li 2007; Casey 2012; Dale et al. 2014), active nuclei (Fritz et al. 2006; Dale et al. 2014), and the IGM (Meiksin 2006).”
• Inferring the star formation histories of massive quiescent galaxies with bagpipes: evidence for multiple quenching mechanisms (2017, background): “This kind of two-component approach has been shown to be successful in modelling observed infrared SEDs (e.g. Casey 2012), and work is ongoing to test our model against observational data at these wavelengths.”
• Planckintermediate results (2016, methodology): “…of a single temperature model for detailed, high signal-to-noise SED shapes (e.g. Dale & Helou 2002; Wiklind 2003), the cold dust component (λ >∼ 100 µm) tends to be well represented using a single effective temperature modified blackbody (Draine & Li 2007; Casey 2012; Clemens et al. 2013).”
• SPECTRAL ENERGY DISTRIBUTIONS OF LOCAL LUMINOUS AND ULTRALUMINOUS INFRARED GALAXIES (2012, methodology): “We compute a new total infrared luminosity, LIR = 8 − 1000µm, by using χ 2 minimization to fit the MIR-FIR-submm portion (14 data points) of the SEDs with different dust models and a modified black body fit (CE,DH,SK,mBB: Chary & Elbaz 2001; Dale & Helou 2002; Siebenmorgen & Krügel 2007; Casey 2012”
• Constraining the properties of AGN host galaxies with spectral energy distribution modelling (2015, methodology): “The energy absorbed by the dust is reemitted in the IR using a choice of different dust templates (Dale & Helou 2002; Dale et al. 2014; Draine & Li 2007; Casey 2012).”
• A TURNOVER IN THE GALAXY MAIN SEQUENCE OF STAR FORMATION AT M* ∼ 1010 M☉ FOR REDSHIFTS z < 1.3 (2015, methodology): “It has been shown that measuring the LIR from fitting the farinfrared data to libraries of SED (e.g. Chary & Elbaz 2001; Dale & Helou 2002) gives roughly the same results as the modified blackbody plus power-law model (Casey 2012; U et al. 2012; Lee et al. 2013).”
• The dust content of galaxies from z = 0 to z = 9 (2016, background): “G A ] 2 7 star-formation rate (SFR; da Cunha et al. 2010; Casey 2012; Santini et al. 2014), and the dust mass function of galaxies (Dunne, Eales & Edmunds 2003; Vlahakis, Dunne & Eales 2005; Dunne et al. 2011; Eales et al. 2009; Clemens et al. 2013).”
• Dusty Star Forming Galaxies at High Redshift (2014, background): “…of DSFGs in the local and high-z Universe; the local samples are collated from the Revised Bright Galaxy Sample (Chapman et al. 2003c, most recently with re-analyzed SEDs in U et al., 2012) and high-z samples are all Herschel-Spire selected (Casey, 2012; Symeonidis et al., 2013; Lee et al., 2013).”
• x-cigale: fitting AGN/galaxy SEDs from X-ray to infrared (2020, unknown): “For simplicity, we adopt the “grey body” model (e.g. Casey 2012), i.e. Lν(λ) ∝ ( 1 − e−(λ0/λ) β ) ( c λ )3 ehc/λkT − 1 , (10) where λ0 is fixed at 200 µm, emissivity (β) and temperature (T) are free parameters set by the user.”
• ISM MASSES AND THE STAR FORMATION LAW AT Z = 1 TO 6: ALMA OBSERVATIONS OF DUST CONTINUUM IN 145 GALAXIES IN THE COSMOS SURVEY FIELD (2015, methodology): “For sources with detections in at least at least two of the five available Herschel bands, LIR is estimated by fitting far-infrared photometry to a cou- pled, modified greybody plus mid-infrared power law, as in Casey (2012).”
• AN ALMA SURVEY OF SUB-MILLIMETER GALAXIES IN THE EXTENDED CHANDRA DEEP FIELD SOUTH: PHYSICAL PROPERTIES DERIVED FROM ULTRAVIOLET-TO-RADIO MODELING (2015, background): “…al. (2005) and Swinbank et al. (2014) are typically lower than our luminosity-averaged temperatures, but this could be simply because of the different temperature definition and/or the way the infrared SEDs are fitted (as discussed in, e.g., Casey 2012; Hayward et al. 2012; Magnelli et al. 2012).”
• Characterization of Scuba-2 450 μm and 850 μm selected galaxies in the COSMOS field (2013, background): “The emissivity index, β = 1.5 is fixed (e.g. Pope et al. 2008; Younger et al. 2009; Chapin et al. 2010), as is the midinfrared powerlaw index, α = 2.0 (e.g. Blain et al. 2003; Casey 2012).”