The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation

Jappsen, Anne‐Katharina; Klessen, Ralf S.; Larson, Richard B.; Li, Y.; Low, Mordecai–Mark Mac

doi:10.1007/978-1-4020-3407-7_69

Cited by 4 publications

(1 citation statement)

References 27 publications

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“…the cloud cooling is driven by hydrogen-deuterium (HD) and atomic hydrogen (H) cooling (Uehara & Inutsuka 2000;Johnson & Bromm 2006). Other processes including turbulent fragmentation (Klessen et al 2005), magnetically-regulated fragmentation (Silk & Langer 2006) and 1 See O'Shea et al (2008) for a discussion on naming conventions. dust cooling at very high densities (Omukai et al 2005) could also explain stars with lower masses <100 M 2 .…”

Section: Introductionmentioning

confidence: 99%

First stars and the extragalactic background light: how recentγ-ray observations constrain the early universe

Kneiske

Mazin

2009

A&A

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Context. The formation of the first stars (Population III; PopIII) marks the end of the dark ages of the universe, a subject of lively scientific debate. Not (yet) accessible to direct observations, this early stage of the universe is mostly studied via theoretical calculations and numerical simulations. An indirect window is provided by integrated present day observables such as the metal abundance or the diffuse extragalactic photon fields. Aims. We aim to derive constraints on the properties of the PopIII and low metallicity Population II (LM PopII) stars utilizing limits on the density of the extragalactic background light (EBL), recently derived from very-high-energy (E > 100 GeV; VHE) observations. Methods. A model calculation for the evolving EBL density produced by PopIII/LM PopII stars is presented. The model utilizes stellar population spectra (SPS) for zero and low metallicity stars and accounts for the changing emission of an aging stellar population. Emission from the dense HII regions surrounding the stars (nebula) is included. The resulting EBL density for different scenarios (metallicity, star formation rate, initial mass function) is compared to the limit on the EBL density. The potential for detecting a cut-off in HE/VHE spectra is discussed. Results. Assuming a maximum contribution from PopIII/LM PopII stars to the EBL density of 5 nW m −2 s −1 at 2 μm, a limit on the star formation rate (SFR) of the first stars of 0.3 to 3 M Mpc −3 yr −1 in the redshift range 7−14 is derived. The limit depends on the assumed shape of the SFR and metallicity. Conclusions. The EBL can be used as a probe to investigate the properties of PopIII/LM PopII stars. Limits on the EBL density derived from VHE observations can provide constraints on the parameters of the these stars, in particular the star formation rate.

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Section: Introductionmentioning

confidence: 99%

First stars and the extragalactic background light: how recentγ-ray observations constrain the early universe

Kneiske

Mazin

2009

A&A

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Magnetic fields at the onset of high-mass star formation

Beuther

Soler

Vlemmings

et al. 2018

A&A

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Context. The importance of magnetic fields at the onset of star formation related to the early fragmentation and collapse processes is largely unexplored today. Aims. We want to understand the magnetic field properties at the earliest evolutionary stages of high-mass star formation. Methods. The Atacama Large Millimeter Array is used at 1.3 mm wavelength in full polarization mode to study the polarized emission and by that the magnetic field morphologies and strengths of the high-mass starless region IRDC 18310-4. Results. The polarized emission is clearly detected in four sub-cores of the region. In general it shows a smooth distribution, also along elongated cores. Estimating the magnetic field strength via the Davis-Chandrasekhar-Fermi method and following a structure function analysis, we find comparably large magnetic field strengths between ∼0.6 and 3.7 mG. Comparing the data to spectral line observations, the turbulent-to-magnetic energy ratio is low, indicating that turbulence does not significantly contribute to the stability of the gas clump. A mass-to-flux ratio around the critical value 1.0 -depending on column density -indicates that the region starts to collapse which is consistent with the previous spectral line analysis of the region. Conclusions. While this high-mass region is collapsing and thus at the verge of star formation, the high magnetic field values and the smooth spatial structure indicate that the magnetic field is important for the fragmentation and collapse process. This single case study can only be the starting point for larger sample studies of magnetic fields at the onset of star formation.

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ALMA reveals the magnetic field evolution in the high-mass star forming complex G9.62+0.19

Dall'Olio

Vlemmings

Persson

et al. 2019

A&A

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Context. The role of magnetic fields during the formation of high-mass stars is not yet fully understood, and the processes related to the early fragmentation and collapse are as yet largely unexplored. The high-mass star forming region G9.62+0.19 is a well known source, presenting several cores at different evolutionary stages. Aims. We seek to investigate the magnetic field properties at the initial stages of massive star formation. We aim to determine the magnetic field morphology and strength in the high-mass star forming region G9.62+0.19 to investigate its relation to the evolutionary sequence of the cores. Methods. We made use of Atacama Large Millimeter Array (ALMA) observations in full polarisation mode at 1 mm wavelength (Band 7) and we analysed the polarised dust emission. We estimated the magnetic field strength via the Davis-Chandrasekhar-Fermi and structure function methods. Results. We resolve several protostellar cores embedded in a bright and dusty filamentary structure. The polarised emission is clearly detected in six regions: two in the northern field and four in the southern field. Moreover the magnetic field is orientated along the filament and appears perpendicular to the direction of the outflows. The polarisation vectors present ordered patterns and the cores showing polarised emission are less fragmented. We suggest an evolutionary sequence of the magnetic field, and the less evolved hot core exhibits a stronger magnetic field than the more evolved hot core. An average magnetic field strength of the order of 11 mG was derived, from which we obtain a low turbulent-to-magnetic energy ratio, indicating that turbulence does not significantly contribute to the stability of the clump. We report a detection of linear polarisation from thermal line emission, probably from methanol or carbon dioxide, and we tentatively compared linear polarisation vectors from our observations with previous linearly polarised OH masers observations. We also compute the spectral index, column density, and mass for some of the cores. Conclusions. The high magnetic field strength and smooth polarised emission indicate that the magnetic field could play an important role in the fragmentation and the collapse process in the star forming region G9.62+019 and that the evolution of the cores can be magnetically regulated. One core shows a very peculiar pattern in the polarisation vectors, which can indicate a compressed magnetic field. On average, the magnetic field derived by the linear polarised emission from dust, thermal lines, and masers is pointing in the same direction and has consistent strength.

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The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation

Cited by 4 publications

References 27 publications

First stars and the extragalactic background light: how recentγ-ray observations constrain the early universe

First stars and the extragalactic background light: how recentγ-ray observations constrain the early universe

Magnetic fields at the onset of high-mass star formation

ALMA reveals the magnetic field evolution in the high-mass star forming complex G9.62+0.19

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