The Effect of Noise in Dust Emission Maps on the Derivation of Column Density, Temperature, and Emissivity Spectral Index

Schnee, Scott; Kauffmann, Jens; Goodman, Alyssa A.; Bertoldi, F.

doi:10.1086/511054

Cited by 28 publications

(55 citation statements)

References 30 publications

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“…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 T obs and β obs recovered from an MBB fit cannot be related simply to the mass-weighted average along the line of sight of the dust temperature and spectral index. Even for dust with a spectral index constant in frequency (i.e., β does not depend on ν), the distribution of grain sizes and the variations of U along the line of sight could introduce a broadening of the SED relative to the case of a single dust size and single U.…”

Section: Dust Emission Observed By Planckmentioning

confidence: 99%

Planck2013 results. XI. All-sky model of thermal dust emission

Abergel¹,

Ade²,

Aghanim³

et al. 2014

A&A

605

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This paper presents an all-sky model of dust emission from the Planck 353, 545, and 857 GHz, and IRAS 100 µm data. Using a modified blackbody fit to the data we present all-sky maps of the dust optical depth, temperature, and spectral index over the 353-3000 GHz range. This model is a good representation of the IRAS and Planck data at 5 between 353 and 3000 GHz (850 and 100 µm). It shows variations of the order of 30% compared with the widely-used model of Finkbeiner, Davis, and Schlegel. The Planck data allow us to estimate the dust temperature uniformly over the whole sky, down to an angular resolution of 5 , providing an improved estimate of the dust optical depth compared to previous all-sky dust model, especially in high-contrast molecular regions where the dust temperature varies strongly at small scales in response to dust evolution, extinction, and/or local production of heating photons. An increase of the dust opacity at 353 GHz, τ 353 /N H , from the diffuse to the denser interstellar medium (ISM) is reported. It is associated with a decrease in the observed dust temperature, T obs , that could be due at least in part to the increased dust opacity. We also report an excess of dust emission at H  column densities lower than 10 20 cm −2 that could be the signature of dust in the warm ionized medium. In the diffuse ISM at high Galactic latitude, we report an anticorrelation between τ 353 /N H and T obs while the dust specific luminosity, i.e., the total dust emission integrated over frequency (the radiance) per hydrogen atom, stays about constant, confirming one of the Planck Early Results obtained on selected fields. This effect is compatible with the view that, in the diffuse ISM, T obs responds to spatial variations of the dust opacity, due to variations of dust properties, in addition to (small) variations of the radiation field strength. The implication is that in the diffuse high-latitude ISM τ 353 is not as reliable a tracer of dust column density as we conclude it is in molecular clouds where the correlation of τ 353 with dust extinction estimated using colour excess measurements on stars is strong. To estimate Galactic E(B − V) in extragalactic fields at high latitude we develop a new method based on the thermal dust radiance, instead of the dust optical depth, calibrated to E(B− V) using reddening measurements of quasars deduced from Sloan Digital Sky Survey data.

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Section: Dust Emission Observed By Planckmentioning

confidence: 99%

Planck2013 results. XI. All-sky model of thermal dust emission

Abergel¹,

Ade²,

Aghanim³

et al. 2014

A&A

605

View full text Add to dashboard Cite

show abstract

“…Such temperatures even prevail in dense cores residing in molecular clouds forming stellar clusters (i.e., in Perseus; Rosolowsky et al 2007). Finally, Schnee et al (2007b) recently mapped the dust temperature distribution in TMC-1C using data partially also included in the present work. They derived dust temperatures of 13 to 5 K, similar to gas temperatures recently derived for L1544 (Crapsi et al 2007).…”

Section: A5 Dust Temperature and Opacitymentioning

confidence: 99%

MAMBO mapping of Spitzer c2d small clouds and cores

Kauffmann

Bertoldi

Bourke

et al. 2008

A&A

Self Cite

632

677

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Aims. To study the structure of nearby (<500 pc) dense starless and star-forming cores with the particular goal to identify and understand evolutionary trends in core properties, and to explore the nature of Very Low Luminosity Objects (≤0.1 L ; VeLLOs). Methods. Using the MAMBO bolometer array, we create maps unusually sensitive to faint (few mJy per beam) extended (≈5 ) thermal dust continuum emission at 1.2 mm wavelength. Complementary information on embedded stars is obtained from Spitzer, IRAS, and 2MASS. Results. Our maps are very rich in structure, and we characterize extended emission features ("subcores") and compact intensity peaks in our data separately to pay attention to this complexity. We derive, e.g., sizes, masses, and aspect ratios for the subcores, as well as column densities and related properties for the peaks. Combination with archival infrared data then enables the derivation of bolometric luminosities and temperatures, as well as envelope masses, for the young embedded stars. Conclusions. Starless and star-forming cores occupy the same parameter space in many core properties; a picture of dense core evolution in which any dense core begins to actively form stars once it exceeds some fixed limit in, e.g., mass, density, or both, is inconsistent with our data. A concept of necessary conditions for star formation appears to provide a better description: dense cores fulfilling certain conditions can form stars, but they do not need to, respectively have not done so yet. Comparison of various evolutionary indicators for young stellar objects in our sample (e.g., bolometric temperatures) reveals inconsistencies between some of them, possibly suggesting a revision of some of these indicators. Finally, we challenge the notion that VeLLOs form in cores not expected to actively form stars, and we present a first systematic study revealing evidence for structural differences between starless and candidate VeLLO cores.

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“…As a result, spectral energy distributions (SEDs) of starless cores have been constructed using flux densities obtained from a small number (3-5) of continuum maps (e.g. Kirk, Ward-Thompson & André 2005Schnee et al 2007). These maps are obtained using facility instruments on different telescopes having different beam sizes, each sensitive to structure on a different scale.…”

Section: Introductionmentioning

confidence: 99%

Far-infrared/submillimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by theHerschelSPIRE instrument – I. Central positions

Makiwa

Naylor

Wiel

et al. 2016

Mon. Not. R. Astron. Soc.

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Dust grains play a key role in the physics of star-forming regions, even though they constitute only ∼1 % of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature (T d ), emissivity spectral index (β) and column density requires broadband continuum observations at far-infrared wavelengths. We present Herschel-SPIRE Fourier Transform Spectrometer (FTS) measurements of three starless cores: L1521E, L1521F and L1689B, covering wavelengths between 194 and 671 µm. This paper is the first to use our recently updated SPIRE-FTS intensity calibration, yielding a direct match with SPIRE photometer measurements of extended sources. In addition, we carefully assess the validity of calibration schemes depending on source extent and on the strength of background emission. The broadband far-infrared spectra for all three sources peak near 250 µm. Our observations therefore provide much tighter constraints on the spectral energy distribution (SED) shape than measurements that do not probe the SED peak. The spectra are fitted using modified blackbody functions, allowing both T d and β to vary as free parameters. This yields T d of 9.8±0.2 K, 15.6±0.5 K and 10.9±0.2 K and corresponding β of 2.6∓0.9, 0.8∓0.1 and 2.4∓0.8 for L1521E, L1521F and L1689B respectively. The derived core masses are 1.0±0.1, 0.10±0.01 and 0.49±0.05 M , respectively. The core mass/Jeans mass ratios for L1521E and L1689B exceed unity indicating that they are unstable to gravitational collapse, and thus prestellar cores. By comparison, the elevated temperature and gravitational stability of L1521F support previous arguments that this source is more evolved and likely a protostar.

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The Effect of Noise in Dust Emission Maps on the Derivation of Column Density, Temperature, and Emissivity Spectral Index

Cited by 28 publications

References 30 publications

Planck2013 results. XI. All-sky model of thermal dust emission

Planck2013 results. XI. All-sky model of thermal dust emission

MAMBO mapping of Spitzer c2d small clouds and cores

Far-infrared/submillimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by theHerschelSPIRE instrument – I. Central positions

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