On the Origin of the North Celestial Pole Loop

Abstract

The North Celestial Pole Loop (NCPL) provides a unique laboratory for studying the early-stage precursors of star formation. Uncovering its origin is key to understanding the dynamical mechanisms that control the evolution of its contents. In this study, we explore the 3D geometry and the dynamics of the NCPL using high-resolution dust extinction data and H i data, respectively. We find that material toward Polaris and Ursa Major is distributed along a plane similarly oriented to the Radcliffe wave. The Spider projected in between appears disconnected in 3D, a discontinuity in the loop shape. We find that the elongated cavity that forms the inner part of the NCPL is a protrusion of the Local Bubble (LB) likely filled with warm (possibly hot) gas that passes through and goes beyond the location of the dense clouds. An idealized model of the cavity as a prolate spheroid oriented toward the observer, reminiscent of the cylindrical model proposed by Meyerdierks et al., encompasses the protrusion and fits into arcs of warm H i gas expanding laterally to it. As first argued by Meyerdierks et al., the nonspherical geometry of the cavity and the lack of OB stars interior to it disfavor an origin caused by a single point-like source of energy or multiple supernovae. Rather, the formation of the protrusion could be related to the propagation of warm gas from the LB into a pre-existing nonuniform medium in the lower halo, the topology of which was likely shaped by past star formation activity along the Local Arm.

Joint Modelling of Dust Scattering and Thermal Emission: The Spider Complex

“…However, compared to the scattered light from a distinctive isolated cloud (IFN) that is also optically thin, as we have studied, the DGL is conceptually quite different and is traditionally modeled with Galactic distributions of dust and stars that are described by smooth functions of height above the Galactic disk. Recent descriptions of the Local Bubble in the solar neighborhood (Lallement et al 2019;Leike et al 2020;Pelgrims et al 2020;Zucker et al 2022;Marchal & Martin 2023) indicate that a more sophisticated treatment of the DGL in the high-latitude sky will be required. Still, the DGL is some averaged response to the anisotropies discussed over a considerable part of the high-latitude sky.…”

“…The Spider field is centered on ℓ ∼ 135°, b ∼ 40°and is at a distance of about 320 pc (Zucker et al 2020;Marchal & Martin 2023), thus at a height z = 205 pc above the Galactic plane. It is outside the Local Bubble (Zucker et al 2021) but appears to be related to a extended protrusion (Marchal & Martin 2023). For broader context, the Spider field is at the top of the arch of the North Celestial Pole Loop (NCPL, Martin et al 2015;Blagrave et al 2017;Taank et al 2022;Marchal & Martin 2023).…”

“…The Spider complex (Spider for short) was chosen for this work because a large fraction of the cloud is optically thin and it has been mapped in submillimeter thermal dust emission using the Herschel Space Observatory 9 (hereafter Herschel). The Spider field is centered on ℓ ∼ 135°, b ∼ 40°and is at a distance of about 320 pc (Zucker et al 2020;Marchal & Martin 2023), thus at a height z = 205 pc above the Galactic plane. It is outside the Local Bubble (Zucker et al 2021) but appears to be related to a extended protrusion (Marchal & Martin 2023).…”

“…It is outside the Local Bubble (Zucker et al 2021) but appears to be related to a extended protrusion (Marchal & Martin 2023). For broader context, the Spider field is at the top of the arch of the North Celestial Pole Loop (NCPL, Martin et al 2015;Blagrave et al 2017;Taank et al 2022;Marchal & Martin 2023). Areas in the NCPL have been the target of many IFN images, such as one by R. B. Andrea 10 that includes what we call the Spider.…”

A Recipe for Unbiased Background Modeling in Deep Wide-field Astronomical Images

“…The "Spider" field is a region of (mostly) optically thin Galactic cirrus centering at (l, b) ∼ (135°, 40°), with a distance of ∼320 pc (Zucker et al 2020;Marchal & Martin 2023). Dragonfly observations of the full Spider field were taken in 2021.…”