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Maps of the Number of H I Clouds along the Line of Sight at High Galactic Latitude

Panopoulou, G. V. and Lenz, D. (2020) Maps of the Number of H I Clouds along the Line of Sight at High Galactic Latitude. Astrophysical Journal, 902 (2). Art. No. 120. ISSN 1538-4357.

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Characterizing the structure of the Galactic interstellar medium (ISM) in three dimensions is of high importance for accurate modeling of dust emission as a foreground to the cosmic microwave background (CMB). At high Galactic latitude, where the total dust content is low, accurate maps of the 3D structure of the ISM are lacking. We develop a method to quantify the complexity of the distribution of dust along the line of sight with the use of H i line emission. The method relies on a Gaussian decomposition of the H i spectra to disentangle the emission from overlapping components in velocity. We use this information to create maps of the number of clouds along the line of sight. We apply the method to (a) the high Galactic latitude sky and (b) the region targeted by the BICEP/Keck experiment. In the north Galactic cap we find on average three clouds per 0.2 square degree pixel, while in the south the number falls to 2.5. The statistics of the number of clouds are affected by intermediate-velocity clouds (IVCs), primarily in the north. IVCs produce detectable features in the dust emission measured by Planck. We investigate the complexity of H i spectra in the BICEP/Keck region and find evidence for the existence of multiple components along the line of sight. The data (doi: 10.7910/DVN/8DA5LH) and software are made publicly available and can be used to inform CMB foreground modeling and 3D dust mapping.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Panopoulou, G. V.0000-0001-7482-5759
Lenz, D.0000-0001-5820-475X
Additional Information:© 2020 The American Astronomical Society. Received 2020 March 31; revised 2020 September 6; accepted 2020 September 8; published 2020 October 20. The authors thank Kostas Tassis and Vincent Pelgrims for comments on the paper. G.V.P. thanks Alberto Krone-Martins, Marc-Antoine Miville-Deschênes, and Brandon Hensley for helpful discussions. We thank Vincent Guillet for suggesting the use of a column-density-weighted number of clouds metric. We thank Mathieu Remazeilles for providing the χ2 map of the dust model from Planck. G.V.P. acknowledges support from the National Science Foundation, under grant No. AST-1611547. Support for this work was provided by NASA through the NASA Hubble Fellowship grant No. HST-HF2-51444.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This work made use of healpy (Zonca et al. 2019) and Astropy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018). Facilities: Effelsberg - Effelsberg Radio Telescope, Parkes - , Planck - . Software: astropy (Astropy Collaboration et al. 2013), healpy (Zonca et al. 2019).
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51444.001-A
Subject Keywords:Interstellar medium ; Neutral hydrogen clouds ; Interstellar atomic gas
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Interstellar medium (847); Neutral hydrogen clouds (1099); Interstellar atomic gas (833)
Record Number:CaltechAUTHORS:20200629-092419826
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Official Citation:G. V. Panopoulou and D. Lenz 2020 ApJ 902 120
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104115
Deposited By: Tony Diaz
Deposited On:29 Jun 2020 17:08
Last Modified:21 Oct 2020 19:30

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