Article
Astronomy & Astrophysics
David J. Whitworth, Rowan J. Smith, Ralf S. Klessen, Mordecai-Mark Mac Low, Simon C. O. Glover, Robin Tress, Ruediger Pakmor, Juan D. Soler
Summary: Many studies have shown that magnetic fields can suppress star formation in molecular clouds and Milky Way like galaxies. However, most of these studies have focused on fully developed fields at saturation level, and there is little understanding of how weak initial primordial fields affect star formation in low metallicity environments. In this paper, the impact of a weak initial field on low metallicity dwarf galaxies is investigated. High-resolution AREPO simulations are performed, and the results show that the magnetic field has little impact on the global star formation rate (SFR), contrary to some previous studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
David J. Whitworth, Rowan J. Smith, Robin Tress, Scott T. Kay, Simon C. O. Glover, Mattia C. Sormani, Ralf S. Klessen
Summary: This paper investigates the impact of metallicity and ultraviolet (UV) field strength on star formation and the molecular gas Kennicutt-Schmidt (KS) relation within a galaxy. By conducting simulations of isolated dwarf galaxies, the authors find that reducing metallicity and UV field has minimal effect on star formation but moderately steepens the KS relation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Glen H. Hunter, Paul C. Clark, Simon C. O. Glover, Ralf S. Klessen
Summary: In this study, the impact of collision speed, magnetic field inclination, and resolution on the star formation rate (SFR) in cloud-cloud collisions is investigated. A factor of 2-3 increase in the SFR is found compared to no collision simulations, with high collisional velocities, parallel magnetic field and collision axis orientation, and lower resolution leading to earlier star formation. The alignment of velocity and magnetic field is consistent in low-density environments but becomes more perpendicular as density increases, indicating the compression of the magnetic field by collapsing gas.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Gerwyn H. Jones, Paul C. Clark, Simon C. O. Glover, Alvaro Hacar
Summary: HCN J = 1-0 emission is commonly used as a dense gas tracer, but recent observations suggest it can also trace more diffuse gas in molecular clouds. In this study, we investigate the relationship between gas density and HCN emission using simulations of cloud-cloud collisions. We find that HCN emission traces gas with a lower mean density than previously thought, and in some cases, HCN emission is observed even when gas density is below the typical critical density. We also derive conversion factors for HCN luminosity-to-mass, providing valuable information for future studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Paul C. Clark, Anthony P. Whitworth
Summary: The model proposed explains the evolution of a star cluster's SMF involving turbulent fragmentation and competitive accretion, where low-mass seed proto-systems grow into high-mass stars through accretion. The overall shape of the SMF remains consistent even with varying mass supply rates, with the high-mass tail extending as long as gas supply lasts.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
D. Colombo, A. Duarte-Cabral, A. R. Pettitt, J. S. Urquhart, F. Wyrowski, T. Csengeri, K. R. Neralwar, F. Schuller, K. M. Menten, L. Anderson, P. Barnes, H. Beuther, L. Bronfman, D. Eden, A. Ginsburg, T. Henning, C. Konig, M-Y Lee, M. Mattern, S. Medina, S. E. Ragan, A. J. Rigby, A. Sanchez-Monge, A. Traficante, A. Y. Yang, M. Wienen
Summary: This study investigates the imprint of spiral arms on the distribution and properties of molecular gas in the Milky Way. The results show that there is no significant difference in the emission of molecular gas between the spiral arms and inter-arm regions in terms of mass and luminosity. However, the molecular mass in the spiral arms is 1.5 times higher than that of the inter-arm medium. Additionally, the cloud mass surface densities and aspect ratio in the spiral arms show significant differences compared to the inter-arm medium, while other observed differences appear to be driven by a distance bias.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Robin G. Tress, Mattia C. Sormani, Rowan J. Smith, Simon C. O. Glover, Ralf S. Klessen, Mordecai-Mark Mac Low, Paul Clark, Ana Duarte-Cabral
Summary: This study investigates the reactions of giant molecular clouds to different environmental conditions in galaxies, revealing that galaxy interactions or isolation have limited effects on cloud masses and sizes, but can promote the formation of counter-rotating clouds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
S. Anathpindika, J. Di Francesco
Summary: This study explores the formation of prestellar cores and reveals that cores formed under different pressures exhibit distinct shapes, as well as the relationship between velocity gradient variations and filament evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. Braine, Y. Sun, Y. Shimajiri, F. F. S. van der Tak, M. Fang, Ph. Andre, H. Chen, Y. Gao
Summary: In this study, maps and spectra of the HCN(1-0) and HCO+(1-0) lines in the extreme outer Galaxy were obtained using the Delingha telescope. The aim was to investigate the structure of molecular clouds in subsolar metallicity regions and their relation with star formation. The results showed that the HCN emission is optically thin and the HCO+ emission is stronger, indicating a low-density solution for the dense gas. The correlation between star formation and dense gas was found to be poor.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Ryan J. Farber, Max Gronke
Summary: Recent observations suggest that galaxies may have a molecular component in their circumgalactic medium. However, the structure and dynamics of the molecular circumgalactic medium are still poorly understood. This study uses simulations to explore the process of fragmentation and shattering of molecular clouds, finding that larger clouds can shatter into tiny droplets, and cold clouds can undergo a process of splintering. These findings have implications for understanding the molecular phase of the circumgalactic medium in observations and cosmological simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ryan J. Farber, Max Gronke
Summary: Recent progress has been made in understanding gas phases in the circumgalactic medium and galactic wind, particularly in relation to the origin and survival of the cold molecular phase, as well as the role of dust in the acceleration process.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
F. Fontani, A. Schmiedeke, A. Sanchez-Monge, L. Colzi, D. Elia, V. M. Rivilla, M. T. Beltran, L. Bizzocchi, P. Caselli, L. Magrini, D. Romano
Summary: The study reveals that the chemical properties of the outer star-forming regions of the Galaxy are similar to those of the inner and local regions. Methanol (CH3OH) is detected in the observed targets, and its emission is associated with an extended envelope, indicating that it mainly comes from a cold and quiescent region. The relative abundance of CH3OH shows good correlations with that of H2CO, but not with HCO. These findings have significant implications for understanding the organic and possibly pre-biotic chemistry in the outermost star-forming regions of the Galaxy.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Jaeyeon Kim, Melanie Chevance, J. M. Diederik Kruijssen, Andreas Schruba, Karin Sandstrom, Ashley T. Barnes, Frank Bigiel, Guillermo A. Blanc, Yixian Cao, Daniel A. Dale, Christopher M. Faesi, Simon C. O. Glover, Kathryn Grasha, Brent Groves, Cinthya Herrera, Ralf S. Klessen, Kathryn Kreckel, Janice C. Lee, Adam K. Leroy, Jerome Pety, Miguel Querejeta, Eva Schinnerer, Jiayi Sun, Antonio Usero, Jacob L. Ward, Thomas G. Williams
Summary: Feedback from massive stars is crucial in molecular cloud evolution. The embedded phase of massive star formation lasts 2-7 million years, with the region heavily obscured in the first half and partially exposed in the second half. After the cloud disperses, ongoing star formation is no longer traced by 24 emission, but can be detected through ambient CO-dark gas emissions for 2-9 million years. Future JWST observations will enable routine measurements across nearby galaxies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
F. D. Priestley, P. C. Clark, S. C. O. Glover, S. E. Ragan, O. Feher, L. R. Prole, R. S. Klessen
Summary: The study finds that molecular species commonly assumed to trace the dense, star-forming component of molecular clouds actually exist in material transiently enhanced in density. Only N2H+ exists in detectable quantities above a certain volume density, and N2H+ emission can be used to predict star formation in molecular clouds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Kong You Liow, Steven Rieder, Clare L. Dobbs, Sarah E. Jaffa
Summary: Modelling star formation is challenging, but a grouped star formation method has been introduced and tested in simulations of various physical scales and resolutions, showing its robustness.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Lorenz Zwick, Lucio Mayer, Lionel Haemmerle, Ralf S. Klessen
Summary: We study the conditions in supermassive discs formed by the merger of gas-rich, metal-enriched galaxies at redshift z similar to 10. The study reveals that these discs naturally form hydrostatic cores which go through a rapidly accreting supermassive star phase, before collapsing into massive black holes via the general relativistic instability. The growth and collapse of the cores occur within a short time period, producing transient signals in various forms. Based on these findings, it is argued that the merger-driven scenario provides a robust pathway for the rapid formation of supermassive black holes at z > 6.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Da Eun Kang, Ralf S. Klessen, Victor F. Ksoll, Lynton Ardizzone, Ullrich Koethe, Simon C. O. Glover
Summary: This paper presents a new method using a conditional invertible neural network (cINN) to accurately predict the physical properties of star-forming regions by analyzing degenerate observations. The new network, named Noise-Net, takes into account observational uncertainties during training and outperforms the previous version of the cINN, even under large uncertainties.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
David J. Whitworth, Rowan J. Smith, Ralf S. Klessen, Mordecai-Mark Mac Low, Simon C. O. Glover, Robin Tress, Ruediger Pakmor, Juan D. Soler
Summary: Many studies have shown that magnetic fields can suppress star formation in molecular clouds and Milky Way like galaxies. However, most of these studies have focused on fully developed fields at saturation level, and there is little understanding of how weak initial primordial fields affect star formation in low metallicity environments. In this paper, the impact of a weak initial field on low metallicity dwarf galaxies is investigated. High-resolution AREPO simulations are performed, and the results show that the magnetic field has little impact on the global star formation rate (SFR), contrary to some previous studies.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Lukas Eisert, Annalisa Pillepich, Dylan Nelson, Ralf S. Klessen, Marc Huertas-Company, Vicente Rodriguez-Gomez
Summary: By using machine learning techniques, we can infer the unobservable stellar assembly and merger history of central galaxies from their observable properties. This is a crucial first step towards empirical studies of galaxy evolution enriched by cosmological simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Alexander P. Ji, Joshua D. Simon, Ian U. Roederer, Ekaterina Magg, Anna Frebel, Christian I. Johnson, Ralf S. Klessen, Mattis Magg, Gabriele Cescutti, Mario Mateo, Maria Bergemann, John I. Bailey
Summary: The ultrafaint dwarf galaxy Renticulum II experienced a rare and prolific r-process event, providing a unique opportunity to study metal mixing in a relic first galaxy. The study found that approximately 72-82% of the stars in Reticulum II were r-process enhanced, indicating bursty star formation in this ultrafaint dwarf galaxy.
ASTRONOMICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Jonas Haldemann, Victor Ksoll, Daniel Walter, Yann Alibert, Ralf S. Klessen, Willy Benz, Ullrich Koethe, Lynton Ardizzone, Carsten Rother
Summary: Researchers propose using conditional invertible neural networks to calculate the posterior probability of planetary structure parameters, which can speed up the inference process for characterizing exoplanets. By training the neural network on a large database of internal structure models, they show that cINNs can infer the composition of an exoplanet much faster than the commonly used MCMC method. However, computing a large database is still required for training the network.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Sean C. Lewis, Stephen L. W. McMillan, Mordecai-Mark Mac Low, Claude Cournoyer-Cloutier, Brooke Polak, Martijn J. C. Wilhelm, Aaron Tran, Alison Sills, Simon Portegies Zwart, Ralf S. Klessen, Joshua E. Wall
Summary: The feedback from massive stars is crucial for the formation of star clusters. Whether a very massive star is born early or late in the cluster formation process significantly affects the cluster's formation and assembly. In a controlled experiment, we used the Torch software suite to model the effects of early-forming massive stars on star cluster formation from initially identical giant molecular clouds. The early-forming massive stars disrupt the gas structure, leading to a decrease in star formation rate and total mass of stars formed.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Yu-Hsuan Teng, Karin M. Sandstrom, Jiayi Sun, Munan Gong, Alberto D. Bolatto, I-Da Chiang, Adam K. Leroy, Antonio Usero, Simon C. O. Glover, Ralf S. Klessen, Daizhong Liu, Miguel Querejeta, Eva Schinnerer, Frank Bigiel, Yixian Cao, Melanie Chevance, Cosima Eibensteiner, Kathryn Grasha, Frank P. Israel, Eric J. Murphy, Lukas Neumann, Hsi-An Pan, Francesca Pinna, Mattia C. Sormani, J. D. Smith, Fabian Walter, Thomas G. Williams
Summary: The CO-to-H-2 conversion factor (alpha CO) is crucial for measuring molecular gas properties. Previous studies have found lower alpha CO in the centers of some barred galaxies. Through observations of NGC 3627 and NGC 4321, we discovered variations in molecular gas density, temperature, optical depth, and velocity dispersion, which are key drivers of alpha CO. The central regions of these galaxies show significant enhancements in temperature and density. Our findings suggest a correlation between alpha CO and low-J CO optical depths, as well as an anti-correlation with temperature.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Elizabeth J. Watkins, Ashley T. Barnes, Kiana Henny, Hwihyun Kim, Kathryn Kreckel, Sharon E. Meidt, Ralf S. Klessen, Simon C. O. Glover, Thomas G. Williams, Benjamin W. Keller, Adam K. Leroy, Erik Rosolowsky, Janice C. Lee, Gagandeep S. Anand, Francesco Belfiore, Frank Bigiel, Guillermo A. Blanc, Mederic Boquien, Yixian Cao, Rupali Chandar, Ness Mayker Chen, Melanie Chevance, Enrico Congiu, Daniel A. Dale, Sinan Deger, Oleg V. Egorov, Eric Emsellem, Christopher M. Faesi, Kathryn Grasha, Brent Groves, Hamid Hassani, Jonathan D. Henshaw, Cinthya Herrera, Annie Hughes, Sarah Jeffreson, Maria J. Jimenez-Donaire, Eric W. Koch, J. M. Diederik Kruijssen, Kirsten L. Larson, Daizhong Liu, Laura A. Lopez, Ismael Pessa, Jerome Pety, Miguel Querejeta, Toshiki Saito, Karin Sandstrom, Fabian Scheuermann, Eva Schinnerer, Mattia C. Sormani, Sophia K. Stuber, David A. Thilker, Antonio Usero, Bradley C. Whitmore
Summary: The first JWST observations of nearby galaxies have revealed a diverse population of bubbles that can be used to study the interaction between stellar feedback and the interstellar medium. The catalog of bubbles in NGC 628, identified through PHANGS-JWST observations, provides insights into the characteristics and distribution of these bubbles. The analysis suggests that bubble mergers are common and that feedback processes play a significant role in regulating the global star formation rate.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Sharon E. Meidt, Erik Rosolowsky, Jiayi Sun, Eric W. Koch, Ralf S. Klessen, Adam K. Leroy, Eva Schinnerer, Ashley. T. Barnes, Simon C. O. Glover, Janice C. Lee, Arjen van der Wel, Elizabeth J. Watkins, Thomas G. Williams, F. Bigiel, Mederic Boquien, Guillermo A. Blanc, Yixian Cao, Melanie Chevance, Daniel A. Dale, Oleg V. Egorov, Eric Emsellem, Kathryn Grasha, Jonathan D. Henshaw, J. M. Diederik Kruijssen, Kirsten L. Larson, Daizhong Liu, Eric J. Murphy, Jerome Pety, Miguel Querejeta, Toshiki Saito, Karin M. Sandstrom, Rowan J. Smith, Mattia C. Sormani, David A. Thilker
Summary: JWST/Mid-Infrared Instrument imaging reveals a rich network of gas structures in the nearby galaxies IC 5332, NGC 628, NGC 1365, and NGC 7496, consisting of interconnected filaments, shells, and voids. The study investigates whether this multiscale structure is a result of gravitational instability. FilFinder is used to detect filamentary features and determine their characteristics, which are compared to estimates of key lengths from molecular gas observations. The analysis shows that Jeans-scale structures are pervasive, and future work is needed to understand their impact on star formation and stellar feedback.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Astronomy & Astrophysics
Shuo Kong, Volker Ossenkopf-Okada, Hector G. Arce, Ralf S. Klessen, Duo Xu
Summary: In this paper, a pilot parameter exploration for the collision-induced magnetic reconnection (CMR) mechanism that forms filamentary molecular clouds is conducted. The authors utilized Athena++ to simulate CMR in the context of resistive magnetohydrodynamics (MHD) and considered the effect of seven physical conditions on the formation of CMR. The exploration results reveal straight and curved CMR filaments with rich substructures that are highly variable in space and time, reflecting the chaotic nature of magnetic reconnection in CMR. The exploration provides useful initial insights into the CMR mechanism.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2023)
Article
Astronomy & Astrophysics
Fabian Scheuermann, Kathryn Kreckel, Ashley T. Barnes, Francesco Belfiore, Brent Groves, Stephen Hannon, Janice C. Lee, Rebecca Minsley, Erik Rosolowsky, Frank Bigiel, Guillermo A. Blanc, Mederic Boquien, Daniel A. Dale, Sinan Deger, Oleg Egorov, Eric Emsellem, Simon C. O. Glover, Kathryn Grasha, Hamid Hassani, Sarah M. R. Jeffreson, Ralf S. Klessen, J. M. Diederik Kruijssen, Kirsten L. Larson, Adam K. Leroy, Laura A. Lopez, Hsi-An Pan, Patricia Sanchez-Blazquez, Francesco Santoro, Eva Schinnerer, David A. Thilker, Bradley C. Whitmore, Elizabeth J. Watkins, Thomas G. Williams
Summary: Connecting the gas in H II regions to the underlying ionizing radiation source helps us understand stellar feedback and the evolution of H II regions. Using PHANGS-MUSE, we detect and measure physical properties of nearly 24,000 H II regions across 19 galaxies. By analyzing associations with ionizing sources, we find correlations between association ages and various properties, suggesting an evolutionary sequence. We also observe correlations with local metallicity variations, indicating preferential star formation in metal-rich areas.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Muzammil Mushtaq, Daniel Ceverino, Ralf S. Klessen, Stefan Reissl, Prajwal Hassan Puttasiddappa
Summary: This study investigates the behavior of dust in galaxies during cosmic dawn using simulations and radiative transfer code. The results show that the distribution of dust and the attenuation curves are related to the mass of galaxies. Additionally, the relation between the slopes in the far-ultraviolet and the infrared excess is explored, indicating variations with different redshifts.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Maya A. Petkova, J. M. Diederik Kruijssen, Jonathan D. Henshaw, Steven N. Longmore, Simon C. O. Glover, Mattia C. Sormani, Lucia Armillotta, Ashley T. Barnes, Ralf S. Klessen, Francisco Nogueras-Lara, Robin G. Tress, Jairo Armijos-Abendano, Laura Colzi, Christoph Federrath, Pablo Garcia, Adam Ginsburg, Christian Henkel, Sergio Martin, Denise Riquelme, Victor M. Rivilla
Summary: In this study, the authors investigated the influence of the Galactic gravitational potential on the turbulence in the Central Molecular Zone (CMZ) clouds of our Galaxy. They found that the Galactic shear, in combination with the cloud's gravitational collapse, significantly affects the kinematic properties and turbulence of the CMZ clouds, leading to a suppression in the star formation rate (SFR).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
F. D. Priestley, P. C. Clark, S. C. O. Glover, S. E. Ragan, O. Feher, L. R. Prole, R. S. Klessen
Summary: The study finds that molecular species commonly assumed to trace the dense, star-forming component of molecular clouds actually exist in material transiently enhanced in density. Only N2H+ exists in detectable quantities above a certain volume density, and N2H+ emission can be used to predict star formation in molecular clouds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)