Determining dust temperatures and masses in the Herschel era: The importance of observations longward of 200 micron
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Gordon, K. D.
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Determining dust temperatures and masses in the Herschel era: The importance of observations longward of 200 micron
Author
- Gordon, K. D.;
- Galliano, F.;
- Hony, S.;
- Bernard, J. P.;
- Bolatto, Alberto;
- Bot, Caroline;
- Engelbracht, C.;
- Hughes, A.;
- Israel, F. P.;
- Kemper, F.;
- Kim, S.;
- Li, A.;
- Madden, S. C.;
- Matsuura, M.;
- Meixner, M.;
- Misselt, K.;
- Okumura, K.;
- Panuzzo, P.;
- Rubio López, Mónica;
- Reach, W. T.;
- Roman Duval, Julia;
- Sauvage, M.;
- Skibba, R.;
- Tielens, A. G. G. M.;
Abstract
The properties of the dust grains (e.g., temperature and mass) can be derived from fitting far-IR SEDs (≥100 μm). Only with SPIRE on
Herschel has it been possible to get high spatial resolution at 200 to 500 μm that is beyond the peak (∼160 μm) of dust emission in most galaxies.
Aims. We investigate the differences in the fitted dust temperatures and masses determined using only <200 μm data and then also including
>200 μm data (new SPIRE observations) to determine how important having >200 μm data is for deriving these dust properties.
Methods. We fit the 100 to 350 μm observations of the Large Magellanic Cloud (LMC) point-by-point with a model that consists of a single
temperature and fixed emissivity law. The data used are existing observations at 100 and 160 μm (from IRAS and Spitzer) and new SPIRE
observations of 1/4 of the LMC observed for the HERITAGE key project as part of the Herschel science demonstration phase.
Results. The dust temperatures and masses computed using only 100 and 160 μm data can differ by up to 10% and 36%, respectively, from
those that also include the SPIRE 250 & 350 μm data. We find that an emissivity law proportional to λ−1.5 minimizes the 100–350 μm fractional
residuals. We find that the emission at 500 μm is ∼10% higher than expected from extrapolating the fits made at shorter wavelengths. We find the
fractional 500 μm excess is weakly anti-correlated with MIPS 24 μm flux and the total gas surface density. This argues against a flux calibration
error as the origin of the 500 μm excess. Our results do not allow us to distinguish between a systematic variation in the wavelength dependent
emissivity law or a population of very cold dust only detectable at λ ≥ 500 μm for the origin of the 500 μm excess.
General note
Artículo de publicación ISI
Patrocinador
We acknowledge financial support from the NASA
Herschel Science Center, J.P.L. contracts # 1381522 & 1381650. M.R. is supported
by FONDECYT No1080335 and FONDAP No15010003.
Quote Item
A&A 518, L89 (2010) DOI: 10.1051/0004-6361/201014541
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