Article
Astronomy & Astrophysics
Ameneh Mousavi, Kaijun Liu, Sina Sadeghzadeh
Summary: The scattering of pickup ion ring-beam distributions in the outer heliosheath plays a crucial role in the spatial retention scenario of the ENA ribbon observed by IBEX. Particle-in-cell simulations were carried out to study the high-frequency waves excited by pickup ions and their effect on the pickup ion scattering. The results confirmed the excitation of parallel-propagating, right-hand polarized high-frequency waves as predicted by earlier linear analysis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Ameneh Mousavi, Kaijun Liu, Sina Sadeghzadeh
Summary: One-dimensional hybrid simulations are used to study plasma instabilities driven by pickup ions in the outer heliosheath, confirming predicted unstable modes and showing how pickup ions are scattered by excited waves. The maximum growth rate of the instability occurs at a pickup angle of 82 degrees, while the highest saturation level of the magnetic field fluctuation is observed at a 45 degrees pickup angle. The study goes beyond previous research focused on ring-like distributions at around 90 degrees pickup angle, providing insights into the scattering of pickup ions at small pickup angles.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Ameneh Mousavi, Kaijun Liu, Sina Sadeghzadeh
Summary: This study investigates the instabilities driven by a ring-beam velocity distribution of the pickup ions in the outer heliosheath, revealing the significant impact of different pickup angles on the instability modes and the existence of unstable modes in different ranges.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Pooja Chahal, T. J. Dhilip Kumar
Summary: Computations are performed to obtain cross-sections and excitation rates of the PO+ species in interstellar molecular clouds. A new potential energy surface (PES) is constructed using ab initio methods and trained using neural networks to compute the rotational (de-)excitation cross-sections. The thermally averaged rate coefficients for rotational transitions are found, with the odd transitions favored.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
T. K. Chan, Dusan Keres, Alexander B. Gurvich, Philip F. Hopkins, Cameron Trapp, Suoqing Ji, Claude-Andre Faucher-Giguere
Summary: This study investigates the impact of CRs on the gas dynamics in late-type galaxies, revealing that CRs can influence gas flow and properties, accelerating warm gas and reducing the scale height of hot gas, making the disc-halo interface the most dominant warm-hot phase.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Rodriguez-Gonzalez, P. R. Rivera-Ortiz, A. Castellanos-Ramirez, A. C. Raga, L. Hernandez-Martinez, J. Canto, L. A. Zapata, F. Robles-Valdez
Summary: We conducted gasdynamic simulations to model the CO streamers observed in Orion BN/KL, considering various factors such as ejection velocities, interstellar medium density, and CO content. By calculating CO emissivity and creating CO maps and line profiles, we found that the clumps need to travel within a dense cloud core before entering a lower-density environment in order to reproduce the observed images and line profiles of the streamers.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Traficante, B. M. Jones, A. Avison, G. A. Fuller, M. Benedettini, D. Elia, S. Molinari, N. Peretto, S. Pezzuto, T. Pillai, K. L. J. Rygl, E. Schisano, R. J. Smith
Summary: The mechanism of the formation of the most massive stars is still not completely understood. The SQUALO project, an ALMA survey, was introduced to investigate the properties of 13 massive clumps in different evolutionary stages. The results obtained from the survey show evidence of fragmentation and correlation between the physical properties of the fragments and their parent clumps.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
F. G. Ramon-Fox, I. A. Bonnell
Summary: Star formation occurs on the smallest scales within molecular clouds, likely initiated by large-scale flows driven by galactic dynamics. Local shocks induced by arms and the increase in kinetic energy are crucial elements in forming molecular clouds and driving star formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
S. Heigl, E. Hoemann, A. Burkert
Summary: Simulations show that the growth of core in star-forming filaments is influenced by a mechanism that slows down the growth of end cores. This mechanism involves the formation of a density gradient outside the cores, which reduces the gravitational acceleration, thereby preventing the end cores from dominating over other core formation modes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Bik, G. Ostlin, M. Hayes, J. Melinder, V Menacho
Summary: This study investigates the kinematics of nearby starburst galaxies selected from SDSS data. The results show a correlation between the rotational velocity and velocity dispersion of the gas and stellar components, and propose a scenario where gravitational instabilities determine the global kinematics of galaxies. The study highlights the importance of understanding the physics and assembly history of galaxies.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
M. Benedettini, A. Traficante, L. Olmi, S. Pezzuto, A. Baldeschi, S. Molinari, D. Elia, E. Schisano, M. Merello, F. Fontani, K. L. J. Rygl, J. Brand, M. T. Beltran, R. Cesaroni, S. J. Liu, L. Testi
Summary: Recent spectroscopic surveys of the Milky Way plane have allowed for the creation of extensive catalogues of molecular clouds, providing insights into their physical properties and behavior across the galaxy. The study found that the mass surface density of molecular clouds remains consistent across the galactocentric radius, primarily influenced by local conditions. Additionally, a comparison between clouds derived from (CO)-C-12 (1-0) and (CO)-C-13 (1-0) data in the surveyed portion of the Galactic plane showed good agreement, likely due to relatively low H-2 column density in that region.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
S. D. Clarke, A. Sanchez-Monge, G. M. Williams, A. D. P. Howard, S. Walch, N. Schneider
Summary: We present an analysis of the outer Galaxy giant molecular filament G214.5-1.8 using Herschel data. The study reveals the unique morphology of G214.5, with a predominance of star formation activity in the Main filament. It resembles a 'Bone' candidate GMF but exhibits colder temperatures, narrower structure, and lower density gas. Its highly asymmetric profile suggests external compression. Co-incidentally, G214.5 is found to be spatially and kinematically associated with an H i superbubble, suggesting a potential interaction explaining its morphology, asymmetry, and paucity of dense gas and star formation activity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. S. N. Kumar, D. Arzoumanian, A. Men'shchikov, P. Palmeirim, M. Matsumura, S. Inutsuka
Summary: This study examines the detailed structure of the Mon R2 star-forming region, focusing on the role of hub-filament systems in massive star formation. The researchers find that lower density filaments converge to form higher density filaments within the hub. The structure of the hub is not a single massive clump as previously believed, but rather a network of short, high-density filaments. The analysis shows that the total mass in the region is distributed between filaments, an extended cloud, and sources. The orientation and mass per unit length of the filaments also vary with distance from the hub center.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Gilberto C. Gomez, Catherine Walsh, Aina Palau
Summary: This study explores how the measurement of dense filament widths using different molecular species can be influenced by gas accretion. The abundance of various molecules is affected differently by the changing environment as a gas parcel falls into the filament. The widths of filaments measured from time-dependent abundances of certain molecules are most sensitive to this effect, while others are less sensitive. The ratios of filament widths for different tracers could be a useful tool for estimating the accretion rate onto the filament.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Sajay Sunny Mathew, Christoph Federrath
Summary: The study demonstrates that various factors in star cluster formation, including protostellar outflows, affect the star formation rate, mass distribution, and initial mass function. The turbulence-based model and observational IMF agree well in the high-mass and low-mass regime, but do not predict any brown dwarfs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
P. Swaczyna, F. Rahmanifard, E. J. Zirnstein, D. J. McComas, J. Heerikhuisen
Summary: The study evaluates the impact of elastic collisions on the primary ISN helium population, finding that these collisions slow down and heat the helium atoms compared to pristine VLISM conditions, resulting in a change in the parameters derived from IBEX observations, such as the Sun's relative speed and temperature.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
S. A. Fuselier, A. Galli, J. D. Richardson, D. B. Reisenfeld, E. J. Zirnstein, J. Heerikhuisen, M. A. Dayeh, N. A. Schwadron, D. J. McComas, H. A. Elliott, R. G. Gomez, M. J. Starkey, M. Z. Kornbleuth, M. Opher, K. Dialynas
Summary: This study uses Voyager 2 observations to model and estimate the energetic neutral atom fluxes from the heliosheath, comparing them with observed fluxes from the Interstellar Boundary Explorer (IBEX) to find that around 10% of fluxes at most energies come from the heliosheath. This percentage varies depending on several factors such as termination shock properties, plasma density, bulk plasma flow characteristics, heliopause shape, and turbulent energy diffusion in the heliosheath.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
E. J. Zirnstein, R. Kumar, R. Bandyopadhyay, M. A. Dayeh, J. Heerikhuisen, D. J. McComas
Summary: Through simulations, it has been found that interstellar pickup ions (PUI) accelerated at the heliospheric termination shock experience preferential heating by the motional electric field, but do not develop a power-law tail without the presence of turbulence. Voyager 2 observations suggest a moderate amount of turbulence downstream of the heliospheric termination shock.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
Bishwas L. Shrestha, Eric J. Zirnstein, Jacob Heerikhuisen, Gary P. Zank
Summary: This study estimates the compression ratio of the heliospheric termination shock at multiple directions by comparing observed and simulated ENA fluxes. The results show that the estimated compression ratio is in agreement with observations by Voyager 2, and similar compression ratios are found in directions near the ecliptic plane. The weakest shock compression is identified on the port side of the heliosphere at a particular direction.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2021)
Article
Astronomy & Astrophysics
Daniel B. Reisenfeld, Maciej Bzowski, Herbert O. Funsten, Jacob Heerikhuisen, Paul H. Janzen, Marzena A. Kubiak, David J. McComas, Nathan A. Schwadron, Justyna M. Sokol, Alex Zimorino, Eric J. Zirnstein
Summary: The IBEX mission has shown correlations between variations in ENA flux from the outer heliosphere and the solar cycle, allowing for the creation of a 3D map of the heliosphere. The shortest distance to the heliopause is found to be slightly south of the nose direction at around 110-120 AU, with extensions flaring towards the flanks and poles reaching around 160-180 AU, and the heliosphere is shown to extend at least 350 AU tailward.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2021)
Article
Astronomy & Astrophysics
Federico Fraternale, Nikolai Pogorelov, Jacob Heerikhuisen
Summary: A new model has been developed to study the interaction between the solar wind and the local interstellar medium, focusing on the transport of interstellar neutral helium and the deviations in properties caused by charge exchange processes. It shows that secondary helium atoms born in the outer heliosheath exhibit an average deflection of around 12 degrees in front of the heliopause, with significant temperature anisotropy and velocity distribution function asymmetries observed even for primary helium atoms without charge exchange experience.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Review
Astronomy & Astrophysics
Jens Kleimann, Konstantinos Dialynas, Federico Fraternale, Andre Galli, Jacob Heerikhuisen, Vladislav Izmodenov, Marc Kornbleuth, Merav Opher, Nikolai Pogorelov
Summary: This review summarizes the current research on the global heliosphere, using both analytical and numerical modeling methods, with a focus on the plasma/neutral flow and magnetic field structure, as well as its relation to energetic neutral atoms. The paper also introduces key concepts and discusses early works, and highlights the numerical modeling frameworks and open issues.
SPACE SCIENCE REVIEWS
(2022)
Article
Astronomy & Astrophysics
Eric J. Zirnstein, Bishwas L. Shrestha, David J. McComas, Maher A. Dayeh, Jacob Heerikhuisen, Daniel B. Reisenfeld, Justyna M. Sokol, Pawel Swaczyna
Summary: This study used the 2014 solar wind dynamic pressure increase event to derive the high-resolution distances of the heliospheric termination shock and heliopause from measurements by the Interstellar Boundary Explorer. The analysis revealed significant asymmetries in the heliosphere structure and approximately ten astronomical unit-sized spatial variations in the boundaries, with larger variations on the HTS surface compared to the HP, and a large-scale, southwards-directed obliquity of the surfaces in the meridional plane.
Article
Astronomy & Astrophysics
P. Swaczyna, F. Rahmanifard, E. J. Zirnstein, J. Heerikhuisen
Summary: It has been found that elastic collisions, in addition to charge exchange collisions, contribute to the filtration of interstellar neutral helium atoms outside the heliopause. A global three-dimensional heliosphere model is used to calculate the transport of these atoms, and it is confirmed that momentum exchange modifies the velocity and temperature of the primary and secondary populations. The study emphasizes the importance of accounting for these processes in future observations of the heliosphere and interstellar neutral atoms.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
E. J. Zirnstein, P. Swaczyna, M. A. Dayeh, J. Heerikhuisen
Summary: In 2009, the IBEX discovered a narrow ribbon of energetic neutral atom emissions across the sky. The ribbon is believed to be formed from the escape of heliospheric ENAs into the interstellar medium. Two opposing models of pitch angle scattering rates were tested, and the analysis favors the spatial retention mechanism as the source of the IBEX ribbon.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
J. S. Rankin, D. J. McComas, E. J. Zirnstein, L. F. Burlaga, J. Heerikhuisen
Summary: The magnetic field observations of the Voyager missions and the IBEX mission have provided insights into the structure of the interstellar magnetic field and raised questions about its global behavior. The discrepancies between the measurements and predictions indicate a need for further investigation.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
P. Swaczyna, M. Bzowski, S. A. Fuselier, A. Galli, J. Heerikhuisen, M. A. Kubiak, D. J. McComas, E. Mobius, F. Rahmanifard, N. A. Schwadron
Summary: The response of the IBEX-Lo instrument to helium atoms is analyzed using the observations in ESA steps 1-4. The ratios of observed count rates are compared to the mean energy of the interstellar neutral helium atoms estimated using the Warsaw Test Particle Model. The obtained relative responses supplement the laboratory calibration and facilitate in-depth quantitative studies of the interstellar neutral helium signal.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Astronomy & Astrophysics
P. Swaczyna, M. Bzowski, J. Heerikhuisen, M. A. Kubiak, F. Rahmanifard, E. J. Zirnstein, S. A. Fuselier, A. Galli, D. J. McComas, E. Mobius, N. A. Schwadron
Summary: In-situ observations of interstellar neutral helium atoms are used to determine the velocity and temperature of the pristine very local interstellar medium (VLISM). The observations are compared with a parameterized model of helium transport in the heliosphere, taking into account filtration processes at the heliospheric boundaries. The derived pristine VLISM parameters provide insights into the interstellar conditions, and a strong correlation between interstellar plasma density and magnetic field strength is demonstrated.
ASTROPHYSICAL JOURNAL
(2023)
Article
Public, Environmental & Occupational Health
Jesse Whitehead, Han Gan, Jacob Heerikhuisen, George Gray, Trevor Richardson, Paul Brown, Ross Lawrenson
Summary: This study aims to investigate the impact of Omicron on Maori, Pacific, and Other ethnicities in the Te Manawa Taki Midland region of New Zealand, as well as the influence of age and vaccination. The study found that the per-capita infection rate was highest among Pacific and Maori populations, and the highest among individuals aged 12-24. Maori, Pacific, over 75-year-olds, and unvaccinated individuals were more likely to be hospitalized, and older individuals had longer hospital stays.
EPIDEMIOLOGY AND INFECTION
(2023)
Article
Astronomy & Astrophysics
E. J. Zirnstein, M. A. Dayeh, J. Heerikhuisen
Summary: The ribbon of enhanced ENA fluxes observed by IBEX is a persistent feature that is likely formed from secondary ENAs outside the heliopause, influenced by various factors including the ISMF draping and SW latitudinal structure. Simulations demonstrate that the ribbon's geometry depends on the pitch-angle scattering rate of ions outside the heliopause, with different models producing results that are in varying degrees of agreement with IBEX observations. The presence of interstellar He has a limited impact on the ribbon, and the results slightly favor the strong-scattering limit for the ribbon's origin.
ASTROPHYSICAL JOURNAL
(2021)