THE EFFECT OF LINE-OF-SIGHT TEMPERATURE VARIATION AND NOISE ON DUST CONTINUUM OBSERVATIONS
By R. Shetty, Jens Kauffmann, S. Schnee, A. Goodman, Barbara Ercolano. 2009
161 citations recorded by the source corpus.
We investigate the effect of line-of-sight temperature variations and noise on two commonly used methods to determine dust properties from dust-continuum observations of dense cores. One method employs a direct fit to a modified blackbody spectral energy distribution (SED); the other involves a comparison of flux ratios to an analytical prediction. Fitting fluxes near the SED peak produces inaccurate temperature and dust spectral index estimates due to the line-of-sight temperature (and density) variations. Longer wavelength fluxes in the Rayleigh–Jeans part of the spectrum (≳ 600 μm for typical cores) may more accurately recover the spectral index, but both methods are very sensitive to noise. The temperature estimate approaches the density-weighted temperature, or “column temperature,” of the source as short wavelength fluxes are excluded. An inverse temperature–spectral index correlation naturally results from SED fitting, due to the inaccurate isothermal assumption, as well as noise uncertainties. We show that above some “threshold” temperature, the temperatures estimated through the flux ratio method can be highly inaccurate. In general, observations with widely separated wavelengths, and including shorter wavelengths, result in higher threshold temperatures; such observations thus allow for more accurate temperature estimates of sources with temperatures less than the threshold temperature. When only three fluxes are available, a constrained fit, where the spectral index is fixed, produces less scatter in the temperature estimate when compared to the estimate from the flux ratio method.
Subfields: Astronomy and Astrophysics, Atmospheric Science
View Paper: https://www.semanticscholar.org/paper/e62fa3a2f4940f7be1914f77e55fd86c578f2155
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Citations in the corpus
- Probing the dust properties of galaxies up to submillimetre wavelengths. II. Dust-to-gas mass ratio trends with metallicity and the submm excess in dwarf galaxies (2011, background): “Shetty et al. (2009), however, express caution in the inverse temperature – β interpretation, showing that flux uncertainties, especially in the Rayleigh-Jeans regime, can affect the results for the SED fits as far as temperature and emissivity are concerned.”
- Physical Processes in the Interstellar Medium (2014, methodology): “However, these studies generally fit the spectral energy distribution (SED) with the χ2 linear regression method, which is known to produce an artificial anti-correlation from uncorrelated data in some cases simply due to the presence of noise in the observations (Shetty et al., 2009a,b).”
- Cluster-formation in the Rosette molecular cloud at the junctions of filaments (2012, unknown): “Shetty et al. (2009), for example, showed that this can even produce an anti-correlation ofβ and T which was claimed to be observed by other authors.”
- WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS (2010, background): “Note also that the fitted dust temperature and β are degenerate, and the fitted values can depend sensitively on both noise in the data and temperature variations along the line of sight (Shetty et al. 2009a, 2009b).”
- Herschel-Planck dust optical-depth and column-density maps - I. Method description and results for Orion (2014, unknown): “(1) will not be a simple average of the dust temperatures along the line of sight, but will be biased high (Shetty et al. 2009); as a consequence, the optical depth will be underestimated (Malinen et al. 2011).”
- The dust scaling relations of the Herschel Reference Survey (2012, background): “…galaxies is currently available forλ <200 µm (see Boselli et al. 2010b), making an accurate SED fitting of only the three SPIRE flux densities unfeasible in the case of d- tailed dust models and perhaps not ideal even in the case of a sin- gle modified black-body emission (Shetty et al. 2009a,b).”
- The global dust SED: tracing the nature and evolution of dust with DustEM (2010, background): “The determination of dust temperatures and the dust spectral emissivity index,β (Qabs ∼ νβ), from far-IR to submm data is degenerate and sensitive to the errors or multiple dust temperatures (Dupac et al. 2003; Shetty et al. 2009a,b).”
- ANDROMEDA'S DUST (2013, background): “T correlations can arise from both observational noise and lineof-sight temperature variations (Shetty et al. 2009a, 2009b; Kelly et al. 2012).”
- Planck 2013 results. XI. All-sky model of thermal dust emission (2013, background): “It has been shown by many authors (Blain et al. 2003; Schnee et al. 2007; Shetty et al. 2009b; Kelly et al. 2012; Juvela & Ysard 2012a,b; Ysard et al. 2012) that, in general, the values of Tobs and βobs recovered from an MBB fit cannot be related simply to the mass-weighted average along the line…”
- Dusty Star Forming Galaxies at High Redshift (2014, background): “…temperature dependence, with laboratory experiments suggesting an anti-correlation (Lisenfeld et al., 2000; Dupac et al., 2003; Paradis et al., 2009; Shetty et al., 2009a,b; Veneziani et al., 2010; Bracco et al., 2011; Tabatabaei et al., 2014), although that has little impact on the implied SED…”
- A Herschel view of the far-infrared properties of submillimetre galaxies (2012, background): “The increase ofβ when excluding short-wavelength measurements from the fits agrees with the conclusions of Shetty et al. (2009) studying galactic dense cores : constrai ts on β are highly sensitive to the wavelength coverage used in the fits as well as to the noise properties of the observations.”