2011/04/27 by J. E. G. Peek, Carl Heiles, Kathryn M. G. Peek +2 · 67 citations
Physics and Astronomy · #Absorption (acoustics) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Bubble #Emissivity #Galaxy #Interstellar cloud #Interstellar medium #Local Bubble #Meteorology #Molecular cloud #Optics #Physics #Stars #Stellar, planetary, and galactic studies #Thermal #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/735/2/129
published in The Astrophysical Journal 735(2), 129 (IOP Publishing) · 13 pages, 12 figures. Accepted for publication in the Astrophysical Journal. Vector figure version available at http://www.astro.columbia.edu/~jpeek/
arxiv created 2011/04/27 · openalex publication_date 2011/06/24 · arxiv updated 2015/05/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a multi-wavelength study of the local Leo cold cloud (LLCC), a very nearby, very cold cloud in the interstellar medium (ISM). Through stellar absorption studies we find that the LLCC is between 11.3 pc and 24.3 pc away, making it the closest known cold neutral medium cloud and well within the boundaries of the local cavity. Observations of the cloud in the 21 cm H i line reveal that the LLCC is very cold, with temperatures ranging from 15 K to 30 K, and is best fit with a model composed of two colliding components. The cloud has associated 100 μm thermal dust emission, pointing to a somewhat low dust-to-gas ratio of 48 × 10 −22 MJy sr −1 cm 2 . We find that the LLCC is too far away to be generated by the collision among the nearby complex of local interstellar clouds but that the small relative velocities indicate that the LLCC is somehow related to these clouds. We use the LLCC to conduct a shadowing experiment in 1/4 keV X-rays, allowing us to differentiate between different possible origins for the observed soft X-ray background (SXRB). We find that a local hot bubble model alone cannot account for the low-latitude SXRB, but that isotropic emission from solar wind charge exchange (SWCX) does reproduce our data. In a combined local hot bubble and SWCX scenario, we rule out emission from a local hot bubble with an 1/4 keV emissivity greater than 1.1 Snowdens pc −1 at 3σ, four times lower than previous estimates. This result dramatically changes our perspective on our local ISM.