Fourier-space combination of Planck and Herschel images
<i>Context. <i/><i>Herschel<i/> has revolutionized our ability to measure column densities (<i>N<i/><sub>H<sub/>) and temperatures (<i>T<i/>) of molecular clouds thanks to its far infrared multiwavelength coverage. However, the lack of a we...
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| Main Authors: | , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
07 August 2017
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| In: |
Astronomy and astrophysics
Year: 2017, Volume: 604 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201628891 |
| Online Access: | Verlag, kostenfrei, Volltext: http://dx.doi.org/10.1051/0004-6361/201628891 Verlag, kostenfrei, Volltext: https://www.aanda.org/articles/aa/abs/2017/08/aa28891-16/aa28891-16.html 
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| Author Notes: | J. Abreu-Vicente, A. Stutz, Th Henning, E. Keto, J. Ballesteros-Paredes, and T. Robitaille |
| Summary: | <i>Context. <i/><i>Herschel<i/> has revolutionized our ability to measure column densities (<i>N<i/><sub>H<sub/>) and temperatures (<i>T<i/>) of molecular clouds thanks to its far infrared multiwavelength coverage. However, the lack of a well defined background intensity level in the <i>Herschel<i/> data limits the accuracy of the <i>N<i/><sub>H<sub/> and <i>T<i/> maps. <i>Aims. <i/>We aim to provide a method that corrects the missing <i>Herschel<i/> background intensity levels using the <i>Planck <i/>model for foreground Galactic thermal dust emission. For the <i>Herschel<i/>/PACS data, both the constant-offset as well as the spatial dependence of the missing background must be addressed. For the <i>Herschel<i/>/SPIRE data, the constant-offset correction has already been applied to the archival data so we are primarily concerned with the spatial dependence, which is most important at 250 <i>μ<i/>m.<i>Methods. <i/>We present a Fourier method that combines the publicly available <i>Planck <i/>model on large angular scales with the <i>Herschel<i/> images on smaller angular scales.<i>Results. <i/>We have applied our method to two regions spanning a range of Galactic environments: Perseus and the Galactic plane region around <i>l<i/> = 11deg (HiGal-11). We post-processed the combined dust continuum emission images to generate column density and temperature maps. We compared these to previously adopted constant-offset corrections. We find significant differences (≳20%) over significant (~15%) areas of the maps, at low column densities (<i>N<i/><sub>H<sub/> ≲ 10<sup>22<sup/> cm<sup>-2<sup/>) and relatively high temperatures (<i>T<i/> ≳ 20 K). We have also applied our method to synthetic observations of a simulated molecular cloud to validate our method.<i>Conclusions. <i/>Our method successfully corrects the <i>Herschel<i/> images, including both the constant-offset intensity level and the scale-dependent background variations measured by <i>Planck<i/>. Our method improves the previous constant-offset corrections, which did not account for variations in the background emission levels. |
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| Item Description: | Gesehen am 26.09.2018 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201628891 |