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Observations of ionised carbon at 158 micron ([CII]) from luminous star-forming galaxies at z~0 show that their ratios of [CII] to far infrared (FIR) luminosity are systematically lower than those of more modestly star-forming galaxies. In…

星系天体物理 · 物理学 2017-02-22 Desika Narayanan , Mark Krumholz

We investigate the star formation activity in the molecular complex associated with the Galactic HII region Sh2-90, using radio-continuum maps obtained at 1280 MHz and 610 MHz, Herschel Hi-GAL observations at 70 -- 500 microns, and deep…

太阳与恒星天体物理 · 物理学 2015-06-19 M. R. Samal , A. Zavagno , L. Deharveng , S. Molinari , D. K. Ojha , D. Paradis , J. Tigé , A. K. Pandey , D. Russeil

The physical basis for the belief that the abundant old dwarf galaxies seen in present-day galaxy clusters formed before reionization of the universe is very compelling, because (1) the observed faint end slope of the galaxy luminosity…

天体物理学 · 物理学 2007-05-23 Renyue Cen

(Abridged) The formation of molecular clouds (MCs) from the diffuse interstellar gas appears to be a necessary step for star formation, as young stars invariably occur within them. However, the mechanisms controlling the formation of MCs…

天体物理学 · 物理学 2007-11-26 P. Hennebelle , M. -M. Mac Low , E. Vazquez-Semadeni

Young HII regions are an important site to study O star formation based on distributions of ionized and molecular gas. We revealed that two molecular clouds at $\sim 48$ km s$^{-1}$ and $\sim 53$ km s$^{-1}$ are associated with the HII…

We use Smoothed Particle Hydrodynamics to simulate the formation of a massive (10^6Msun) stellar cluster system formed from the gravitational collapse of a turbulent molecular cloud. We investigate the hierarchical clustering properties of…

太阳与恒星天体物理 · 物理学 2015-05-27 James E. Dale , Ian Bonnell

To investigate the process of star formation triggered by the expansion of an HII region, we present a multi-wavelength analysis of the Galactic HII region RCW 120 and its surroundings. The collect and collapse model predicts that the layer…

The process of atomic-to-molecular (HI-to-H$_2$) gas conversion is fundamental for molecular-cloud formation and star formation. 21 cm observations of the star-forming region W43 revealed extremely high HI column densities, of 120-180…

星系天体物理 · 物理学 2017-02-01 Shmuel Bialy , Simon Bihr , Henrik Beuther , Thomas Henning , Amiel Sternberg

We present a new set of analytic models for the expansion of HII regions powered by UV photoionisation from massive stars and compare them to a new suite of radiative magnetohydrodynamic simulations of turbulent, self-gravitating molecular…

星系天体物理 · 物理学 2016-06-08 Sam Geen , Patrick Hennebelle , Pascal Tremblin , Joakim Rosdahl

(Abridged) We present the results of three-dimensional radiation-hydrodynamics simulations of the formation and evolution of early HII/HeIII regions around the first stars. Cooling (by H2 and HD) and recollapse of the gas in the relic HII…

天体物理学 · 物理学 2008-11-26 Naoki Yoshida , S. Peng Oh , Tetsu Kitayama , Lars Hernquist

We have analyzed new CO($J$ = 1-0) data in the region of a reflection nebula NGC 2023 with a particular focus on the detailed kinematical properties of the molecular gas. The results show that there are two velocity components which…

星系天体物理 · 物理学 2021-07-07 R. Yamada , R. Enokiya , H. Sano , S. Fujita , M. Kohno , D. Tsutsumi , A. Nishimura , K. Tachihara , Y. Fukui

We present semi-analytic dynamical models for giant molecular clouds evolving under the influence of HII regions launched by newborn star clusters. In contrast to previous work, we neither assume that clouds are in virial or energetic…

天体物理学 · 物理学 2008-11-26 Mark R. Krumholz , Christopher D. Matzner , Christopher F. McKee

We are studying the impact of HII regions on star formation in their associated molecular clouds. In this paper we present JCMT RxA molecular line observations of S175 and environs. This is the first within a sample of ten HII regions and…

太阳与恒星天体物理 · 物理学 2015-05-13 Mohaddesseh Azimlu , Michel Fich , Carolyn McCoey

The star-forming ability of a molecular cloud depends on the fraction of gas it can cycle into the dense-phase. Consequently, one of the crucial questions in reconciling star-formation in clouds is to understand the factors that control…

星系天体物理 · 物理学 2017-12-20 S. Anathpindika , A. Burkert , R. Kuiper

Diffuse interstellar clouds show large abundances of H_3^+ which can be maintained only by a high ionization rate of H_2. Cosmic rays are the dominant ionization mechanism in this environment, so the large ionization rate implies a high…

高能天体物理现象 · 物理学 2011-02-11 Nick Indriolo , Brian D. Fields , Benjamin J. McCall

We discuss recent results on the ionizing fluxes of O stars obtained from our "combined stellar structure and atmosphere models" (CoStar) accounting for stellar winds, non-LTE effects and line blanketing. The implications on the ionization…

天体物理学 · 物理学 2008-02-03 Daniel Schaerer

{It has recently been proposed that giant molecular complexes form at the sites where streams of diffuse warm atomic gas collide at transonic velocities.} {We study the global statistics of molecular clouds formed by large scale colliding…

天体物理学 · 物理学 2009-11-13 P. Hennebelle , R. Banerjee , E. Vazquez-Semadeni , R. Klessen , E. Audit

The origin of rovibrational H_2 emission in the central galaxies of cooling flow clusters is poorly understood. Here we address this issue using data from our near-infrared spectroscopic survey of 32 of the most line luminous such systems,…

天体物理学 · 物理学 2009-09-17 R. J. Wilman , A. C. Edge , R. M. Johnstone , A. C. Fabian , S. W. Allen , C. S. Crawford

We investigate the turbulence driving mode of ionizing radiation from massive stars on the surrounding interstellar medium (ISM). We run hydrodynamical simulations of a turbulent cloud impinged by a plane-parallel ionization front. We find…

星系天体物理 · 物理学 2020-03-11 Shyam H. Menon , Christoph Federrath , Rolf Kuiper

Molecular outflows contributing to the matter cycle of star forming galaxies are now observed in small and large systems at low and high redshift. Their physical origin is still unclear. In most theoretical studies only warm ionised/neutral…

星系天体物理 · 物理学 2021-05-28 Philipp Girichidis , Thorsten Naab , Stefanie Walch , Thomas Berlok