Tiny-scale Structure Discovered toward PSR B1557–50
Liu,Mengting1,2; Kr?o,Marko1; Li,Di1,2,3; Hobbs,George4; Dawson,J. R.4,5; Heiles,Carl6; Jameson,Andrew7,8; Stanimirovi?,Sne?ana9; Johnston,Simon4; Dickey,John M.10
Source PublicationThe Astrophysical Journal Letters
AbstractAbstract Optical depth variations in the Galactic neutral interstellar medium (ISM) with spatial scales from hundreds to thousands of astronomical units have been observed through H i absorption against pulsars and continuum sources, while extremely small structures with spatial scales of tens of astronomical units remain largely unexplored. The nature and formation of such tiny-scale atomic structures (TSAS) need to be better understood. We report a tentative detection of TSAS with a signal-to-noise ratio of 3.2 toward PSR B1557?50 in the second epoch of two Parkes sessions just 0.36 yr apart, which are the closest-spaced spectral observations toward this pulsar. One absorption component showing marginal variations has been identified. Based on the pulsar’s proper motion of 14 mas yr?1 and the component’s kinematic distance of 3.3 kpc, the corresponding characteristic spatial scale is 17 au, which is among the smallest sizes of known TSAS. Assuming a similar line-of-sight (LOS) depth, the tentative TSAS cloud detected here is overdense and overpressured relative to the cold neutral medium (CNM), and can radiatively cool fast enough to be in thermal equilibrium with the ambient environment. We find that turbulence is not sufficient to confine the overpressured TSAS. We explore the LOS elongation that would be required for the tentative TSAS to be at the canonical CNM pressure, and find that it is ~5000—much larger than filaments observed in the ISM. We see some evidence of line width and temperature variations in the CNM components observed at the two epochs, as predicted by models of TSAS-like cloud formation colliding warm neutral medium flows.
KeywordInterstellar medium Interstellar absorption Interstellar clouds Radio pulsars Pulsars H I line emission Distance measure Cold neutral medium Warm neutral medium
WOS IDIOP:2041-8205-911-1-abef6e
PublisherThe American Astronomical Society
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Document Type期刊论文
Corresponding AuthorLiu,Mengting
Affiliation1.National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China;
2.University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China;
3.NAOC-UKZN Computational Astrophysics Centre, University of KwaZulu-Natal, Durban 4000, South Africa
4.CSIRO Astronomy & Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710, Australia
5.Department of Physics and Astronomy and MQ Research Centre in Astronomy, Astrophysics and Astrophotonics, Macquarie University, NSW 2109, Australia
6.Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
7.Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122, Australia
8.Australia Research Council Centre for Excellence for Gravitational Wave Discovery (OzGrav), Australia
9.Department of Astronomy, University of Wisconsin–Madison, Madison, WI 53706, USA
10.School of Maths and Physics, University of Tasmania, Hobart, TAS 7001, Australia
First Author AffilicationNational Astronomical Observatories, Chinese Academy of Sciences
Corresponding Author AffilicationNational Astronomical Observatories, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
Liu,Mengting,Kr?o,Marko,Li,Di,等. Tiny-scale Structure Discovered toward PSR B1557–50[J]. The Astrophysical Journal Letters,2021,911(1).
APA Liu,Mengting.,Kr?o,Marko.,Li,Di.,Hobbs,George.,Dawson,J. R..,...&Dickey,John M..(2021).Tiny-scale Structure Discovered toward PSR B1557–50.The Astrophysical Journal Letters,911(1).
MLA Liu,Mengting,et al."Tiny-scale Structure Discovered toward PSR B1557–50".The Astrophysical Journal Letters 911.1(2021).
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