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200 papers

Stars orbiting within 1$\arcsec$ of the supermassive black hole in the Galactic Centre, Sgr A*, are notoriously difficult to detect due to obscuration by gas and dust. We show that some stars orbiting this region may be detectable via…

Astrophysics of Galaxies · Physics 2015-10-28 Idan Ginsburg , Xiawei Wang , Abraham Loeb , Ofer Cohen

The relationship between B-field orientation and density structure in molecular clouds is often assessed using the Histogram of Relative Orientations (HRO). We perform a plane-of-the-sky geometrical analysis of projected B-fields, by…

In most of particle dark matter (DM) models, the DM candidate injects sizable fluxes of high-energy electrons and positrons through its annihilations or decays. Emitted in regions with magnetic field, they in turn give raise to a…

High Energy Physics - Phenomenology · Physics 2011-12-09 Marco Regis

We report results of molecular line observations carried out toward a massive dense core in the Cyg OB 7 molecular cloud. The core has an extraordinarily large mass ($\sim1.1 \times 10^4$ $M_\odot$) and size ($\sim2 \times 5$ pc$^2$), but…

Astrophysics of Galaxies · Physics 2015-06-23 Kazuhito Dobashi , Tomoaki Matsumoto , Tomomi Shimoikura , Hiro Saito , Ko Akisato , Kenjiro Ohashi , Keisuke Nakagomi

We perform numerical magnetohydrodynamic (MHD) simulations of the gravitational collapse and fragmentation of a cylindrical molecular cloud with the help of the FLASH code. The cloud collapses rapidly along its radius without any signs of…

Astrophysics of Galaxies · Physics 2024-05-15 I. M. Sultanov , S. A. Khaibrakhmanov

We discuss the lifetimes and evolution of dense cores formed as turbulent density fluctuations in magnetized, isothermal molecular clouds. We consider numerical simulations in which we measure the cores' magnetic criticality and Jeans…

Astrophysics · Physics 2007-05-23 E. Vazquez-Semadeni , J. Kim , M. Shadmehri , J. Ballesteros-Paredes

Cosmic-rays constitute the main ionising and heating agent in dense, starless, molecular cloud cores. We reexamine the physical quantities necessary to determine the cosmic-ray ionisation rate (especially the cosmic ray spectrum at E < 1…

Astrophysics of Galaxies · Physics 2015-06-16 Marco Padovani , Daniele Galli

Cosmic rays (CRs) are fundamental to the chemistry and physics of star-forming regions, influencing molecular gas ionization, mediating interactions with interstellar magnetic fields, and regulating star formation from the diffuse…

Astrophysics of Galaxies · Physics 2025-02-12 Andrea Bracco , Marco Padovani , Daniele Galli , Stefania Pezzuto , Alexandre Cipriani , Alexander Drabent

Deuterium fractionation in molecular ions, in particular HCO+, has been extensively used to estimate the degree of ionization in molecular clouds. This paper reviews recent work on ionization degree in homogeneous clouds. We will show that…

Astrophysics · Physics 2009-11-07 Paola Caselli

The Universe's magnetogenesis can be investigated with radio observations of cosmic filaments, where the information on the initial magnetic field seeds is expected to be preserved in time. In this work, we update the comparison between…

Cosmology and Nongalactic Astrophysics · Physics 2025-05-27 Ettore Carretti , Franco Vazza

Cosmic rays (CR) play an important role in dense molecular cores, affecting their thermal and dynamical evolution and initiating the chemistry. Several studies have shown that the formation of protostellar discs in collapsing clouds is…

Astrophysics of Galaxies · Physics 2015-06-17 Marco Padovani , Patrick Hennebelle , Daniele Galli

Star formation is inefficient. Recent advances in numerical simulations and theoretical models of molecular clouds show that the combined effects of interstellar turbulence, magnetic fields and stellar feedback can explain the low…

Solar and Stellar Astrophysics · Physics 2020-02-12 Christoph Federrath

We review some of the properties of extensive cosmic ray air showers and describe a simple model of the radio-frequency radiation generated by shower electrons and positrons as they bend in the Earth's magnetic field. We perform simulations…

Astrophysics · Physics 2009-11-07 Denis A. Suprun , Peter W. Gorham , Jonathan L. Rosner

A red giant star is an evolved low- or intermediate-mass star that has exhausted its central hydrogen content, leaving a helium core and a hydrogen-burning shell. Oscillations of stars can be observed as periodic dimmings and brightenings…

Solar and Stellar Astrophysics · Physics 2022-10-26 Gang Li , Sébastien Deheuvels , Jérôme Ballot , François Lignières

Polarization observations at 21cm and 18cm towards the local Taurus molecular cloud complex were made with the Effelsberg 100-m telescope. Highly structured, frequency-dependent polarized emission features were detected. We discuss…

Astrophysics · Physics 2009-11-10 M. Wolleben , W. Reich

In cold molecular clouds submillimetre emission lines are excited by the ambient radiation field. The pumping is dominated by the cosmic microwave background (CMB). It is usual in molecular line radiative transfer modelling to simply assume…

Astrophysics · Physics 2009-11-10 M. P. Redman , J. M. C. Rawlings , J. A. Yates , D. A. Williams

The dynamical state of star-forming molecular clouds cannot be understood without determining the structure and strength of their magnetic fields. Measurements of polarized far-infrared radiation from thermally aligned dust grains are used…

Astrophysics · Physics 2009-11-06 F. Heitsch , E. G. Zweibel , M. -M. Mac Low , P. S. Li , M. L. Norman

We review recent advances in the analytical and numerical modeling of the star formation rate in molecular clouds and discuss the available observational constraints. We focus on molecular clouds as the fundamental star formation sites,…

We present Submillimeter Array (SMA) observations of seven massive molecular clumps which are dark in the far-infrared for wavelengths up to 70 $\mu$m. Our 1.3 mm continuum images reveal 44 dense cores, with gas masses ranging from 1.4 to…

Astrophysics of Galaxies · Physics 2019-12-11 Shanghuo Li , Qizhou Zhang , Thushara Pillai , Ian W. Stephens , Junzhi Wang , Fei Li

Dense cores in massive, parsec-scale molecular clumps are sites that harbor protocluster formation. We present results from observations towards a hub-filament structure of a massive Infrared Dark Cloud (IRDC) G14.225-0.506 using the…

Astrophysics of Galaxies · Physics 2025-03-14 Yanhanle Zhao , Qizhou Zhang , Junhao Liu , Xing Pan , Lingzhen Zeng