A disk-dominated and clumpy circumgalactic medium of the Milky Way seen in X-ray emission

Kaaret, Philip; Koutroumpa, Dimitra; Küntz, K. D.; Jahoda, K.; Bluem, J.; Gulick, Hannah; Hodges-Kluck, Edmund; LaRocca, Daniel M.; Ringuette, Rebecca; Zajczyk, A.

doi:10.1038/s41550-020-01215-w

Cited by 68 publications

(98 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If the component were to be associated with the halo, the path length through the cool NPS X-ray emitting plasma would likely be different than for the hot NPS component and would impact our physical interpretation of the results. We compared the NPS cool component to measurements for the halo from HaloSat fields in the southern Galactic hemisphere and found the EM values of the NPS cool component to be consistently larger by a factor of 5-10 ( Kaaret et al 2020). The EM of the cool component in the NPS fields is also much higher than the EM seen in adjacent HaloSat fields, which suggests that the cool component is not primarily associated with the Galactic halo.…”

Section: The Halo As the Cool Componentmentioning

confidence: 88%

An Analysis of the North Polar Spur Using HaloSat

LaRocca

Kaaret

Küntz

et al. 2020

ApJ

Self Cite

View full text Add to dashboard Cite

We present HaloSat X-ray observations of the entirety of the bright X-ray emitting feature known as the North Polar Spur (NPS). The large field of view of HaloSat enabled coverage of the entire bright NPS in only 14 fields, which were each observed for ≈30,000 s. We find that the NPS fields are distinct in both brightness and spectral shape from the surrounding halo fields. We fit the NPS as two thermal components in ionization equilibrium with temperatures » kT keV 0.087 cool and » kT keV 0.28 hot . We note a temperature gradient in the NPS hot component with an inner arc temperature warmer than the outer arc. The emission measures we find for the cool component of the NPS is a factor of 3-5 greater than that of the hot component, which suggests that the bulk of the NPS material is in the ≈0.1 keV component. We evaluate distance estimates of 0.4 and 8.0 kpc for the NPS. Our findings suggest a preference for a distant NPS with an energy of ≈ 6×10 54 erg, an age of ≈ 10 Myr, and pressures consistent with a 10μG magnetic field associated with the Fermi bubbles. The electron density ≈10×10 −3 cm −3 is consistent with estimates for the shock region surrounding a Galactic-scale event.Unified Astronomy Thesaurus concepts: X-ray astronomy (1810); Interstellar medium (847); Diffuse x-ray background (384); Superbubbles (1656)

show abstract

Section: The Halo As the Cool Componentmentioning

confidence: 88%

An Analysis of the North Polar Spur Using HaloSat

LaRocca

Kaaret

Küntz

et al. 2020

ApJ

Self Cite

View full text Add to dashboard Cite

show abstract

“…This limits the path length both through the heliosphere and through the X-ray bright parts of the magnetosphere. This provides a significant decrease in SWCX contamination, particularly relative to spacecraft such as XMM-Newton which use a fixed solar array and therefore require observation at angles roughly perpendicular to the Sun [6].…”

Section: Mission and Operations Designmentioning

confidence: 99%

“…There have also been several solar X-ray missions based on CubeSats [4,5]; they are not included in this chapter. HaloSat performed an all-sky survey of oxygen line emission in the soft Xray band to attempt to better understand the distribution of hot plasma in the Milky Way halo [6]. PolarLight is a collimated X-ray polarimeter observing the brightest X-ray sources in the sky in order to diagnose their magnetic field or accretion geometry [3].…”

Section: Introductionmentioning

confidence: 99%

The HaloSat and PolarLight CubeSat Missions for X-ray Astrophysics

Feng¹,

Kaaret²

2022

Preprint

View full text Add to dashboard Cite

Astronomical observations in the X-ray band are subject to atmospheric attenuation and have to be performed in the space. CubeSats offer a cost effective means for space-based X-ray astrophysics but allow only limited mass and volume. In this article, we describe two successful CubeSat-based missions, HaloSat and PolarLight, both sensitive in the keV energy range. HaloSat was a 6U CubeSat equipped with silicon drift detectors. It conducted an all-sky survey of oxygen line emission and revealed the clumpy nature of the circumgalactic medium surrounding the Milky Way. PolarLight is a dedicated X-ray polarimeter performing photoelectron tracking using a gas pixel detector in a 1U payload. It observed the brightest X-ray objects and helped constrain their magnetic field or accretion geometry. Onorbit operation of both missions for multiple years demonstrates the capability of CubeSats as an effective astronomical platforms. The rapid time scales for development and construction of the missions makes them particularly attractive for student training.

show abstract

“…The instrumental background for each DPU was modelled by a power law normalized by the 3 − 7 keV flux (pegpwrlw) folded through a diagonal response matrix. The pegpwrlw photon index was modelled separately for each DPU as a linear function of hard band rate determined from high latitude data (Methods section of Kaaret et al (2020)), and the normalization was left as a free parameter. The instrumental background parameters for each observation are given in Table 2, and the process for modelling the HaloSat instrumental background is documented at the HEASARC 2 .…”

Section: Instrumental Backgroundmentioning

confidence: 99%

“…The HaloSat CubeSat is an all-sky survey that observed in the 0.4 − 7 keV energy range from 2018 October to 2021 January. HaloSat was designed primarily to study diffuse ∼0.6 keV emission expected in the diffuse halo of the Milky Way galaxy (Kaaret et al (2019); Kaaret et al (2020)). Due to the large field of view (FoV; ∼100 deg 2 ), HaloSat has a large grasp 1 and good sensitivity to diffuse emission.…”

mentioning

confidence: 99%

A Search for the 3.5 keV Line from the Milky Way’s Dark Matter Halo with HaloSat

Silich

Jahoda

Angelini

et al. 2021

ApJ

Self Cite

View full text Add to dashboard Cite

Previous detections of an X-ray emission line near 3.5 keV in galaxy clusters and other dark matterdominated objects have been interpreted as observational evidence for the decay of sterile neutrino dark matter. Motivated by this, we report on a search for a 3.5 keV emission line from the Milky Way's galactic dark matter halo with HaloSat. As a single pixel, collimated instrument, HaloSat observations are impervious to potential systematic effects due to grazing incidence reflection and CCD pixelization, and thus may offer a check on possible instrumental systematic errors in previous analyses. We report non-detections of a ∼3.5 keV emission line in four HaloSat observations near the Galactic Center. In the context of the sterile neutrino decay interpretation of the putative line feature, we provide 90% confidence level upper limits on the 3.5 keV line flux and 7.1 keV sterile neutrino mixing angle: F ≤ 0.077 ph cm −2 s −1 sr −1 and sin 2 (2θ) ≤ 4.25 × 10 −11 . The HaloSat mixing angle upper limit was calculated using a modern parameterization of the Milky Way's dark matter distribution, and in order to compare with previous limits, we also report the limit calculated using a common historical model. The HaloSat mixing angle upper limit places constraints on a number of previous mixing angle estimates derived from observations of the Milky Way's dark matter halo and galaxy clusters, and excludes several previous detections of the line. The upper limits cannot, however, entirely rule out the sterile neutrino decay interpretation of the 3.5 keV line feature.

show abstract

A disk-dominated and clumpy circumgalactic medium of the Milky Way seen in X-ray emission

Cited by 68 publications

References 44 publications

An Analysis of the North Polar Spur Using HaloSat

An Analysis of the North Polar Spur Using HaloSat

The HaloSat and PolarLight CubeSat Missions for X-ray Astrophysics

A Search for the 3.5 keV Line from the Milky Way’s Dark Matter Halo with HaloSat

Contact Info

Product

Resources

About