Infrared emission from protostars

Adams, Fred C.; Shu, Frank H.

doi:10.1086/163483

Cited by 112 publications

(51 citation statements)

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“…They are less than the 0.05-0.1 km s À1 inward speed reported from some starless cores (e.g., Lee et al 1999). Such observed motions may represent an initial condition for collapse, as discussed by Fatuzzo et al (2004, hereafter FAM04) and as predicted by the ambipolar diffusion model of Adams & Shu (2007). On the other hand these same motions are also expected to arise during the early stages of collapse of a centrally condensed core initially at rest (Myers 2005;Kandori et al 2005).…”

Section: Introductionmentioning

confidence: 64%

“…It is well understood how self-gravity can concentrate gas in the presence of magnetic fields, turbulence, rotation, and thermal pressure, leading to protostar formation and accretion (McKee & Ostriker 2007;Adams & Shu 2007;Ballesteros-Paredes et al 2007). Yet such descriptions of the star formation process are incomplete unless they also explain how protostar accretion decreases with time to yield a well-defined protostar mass.…”

Section: Star Formation Modelsmentioning

confidence: 99%

“…in spherical symmetry (Adams & Shu 1985), with the protostar radius R Ã taken to be 3 R (Stahler 1988). Then equations (29) and (31) yield…”

Section: Accretion Luminositymentioning

confidence: 99%

“…It is expected that they condense as self-gravity and thermal physics become more important than the effects of turbulence and magnetic fields (Larson 2003). It is not settled whether this condensation is controlled more by the physics of turbulent flows (Mac Low & Klessen 2004), ambipolar diffusion (Adams & Shu 2007), or magnetohydrodynamic (MHD) waves (Van Loo et al 2006). Since cores are well studied by observations, it is not essential to model their formation in order to describe their structure.…”

Section: Introductionmentioning

confidence: 99%

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Protostar Mass due to Infall and Dispersal

Myers

2008

Astrophysical Journal

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The mass of a protostar is calculated from the infall and dispersal of an isothermal sphere in a uniform background. For high contrast between peak and background densities and for short dispersal time t d , the accretion is ''self-limiting''; gas beyond the core is dispersed before it accretes, and the protostar mass approaches a time-independent value of low mass. For lower density contrast and longer dispersal time, the accretion ''runs away''; gas accretes from beyond the core, and the protostar mass approaches massive star values. The final protostar mass is approximately the initial gas mass whose free-fall time equals t d . This mass matches the peak of the IMF for gas temperature 10 K, peak and background densities 10 6 and 10 3 cm À3 , respectively, and t d comparable to the core free-fall time t core . The accretion luminosity exceeds 1 L for 0.1 Myr, as in the ''Class 0'' phase. For t d /t core ¼ 0:4 0:8 and temperature 7-50 K, selflimiting protostar masses are 0.08-5 M . These protostar and core masses have ratio 0:4 AE 0:2, as expected if the core mass distribution and the initial mass function have the same shape.

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Section: Introductionmentioning

confidence: 64%

Section: Star Formation Modelsmentioning

confidence: 99%

“…in spherical symmetry (Adams & Shu 1985), with the protostar radius R Ã taken to be 3 R (Stahler 1988). Then equations (29) and (31) yield…”

Section: Accretion Luminositymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Protostar Mass due to Infall and Dispersal

Myers

2008

Astrophysical Journal

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“…9a). This suggests that the sphere of thermal influence of R CrA (see Adams & Shu 1985) stretches out to radii greater than 10 000 AU. To study if this is plausible, radiative transfer modelling was employed.…”

Section: Discussionmentioning

confidence: 96%

Probing the effects of external irradiation on low-mass protostars through unbiased line surveys

Lindberg

Jørgensen

Watanabe

et al. 2015

A&A

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Context. The envelopes of molecular gas around embedded low-mass protostars show different chemistries, which can be used to trace their formation history and physical conditions. The excitation conditions of some molecular species can also be used to trace these physical conditions, making it possible to constrain for instance sources of heating and excitation. Aims. We study the range of influence of an intermediate-mass Herbig Be protostar. We also study the effect of feedback from the environment on the chemical and physical properties of embedded protostars. Methods. We followed up on an earlier line survey of the Class 0/I source R CrA IRS7B in the 0.8 mm window with an unbiased line survey of the same source in the 1.3 mm window using the Atacama Pathfinder Experiment (APEX) telescope. We also studied the excitation of the key species H 2 CO, CH 3 OH, and c-C 3 H 2 in a complete sample of the 18 embedded protostars in the Corona Australis star-forming region. Radiative transfer models were employed to establish abundances of the molecular species. Results. We detect line emission from 20 molecular species (32 including isotopologues) in the two surveys. The most complex species detected are CH 3 OH, CH 3 CCH, CH 3 CHO, and CH 3 CN (the latter two are only tentatively detected). CH 3 CN and several other complex organic molecules are significantly under-abundant in comparison with what is found towards hot corino protostars. The H 2 CO rotational temperatures of the sources in the region decrease with the distance to the Herbig Be star R CrA, whereas the c-C 3 H 2 temperatures remain constant across the star-forming region. Conclusions. The high H 2 CO temperatures observed towards objects close to R CrA suggest that this star has a sphere of influence of several 10 000 AU in which it increases the temperature of the molecular gas to 30-50 K through irradiation. The chemistry in the IRS7B envelope differs significantly from many other embedded protostars, which could be an effect of the external irradiation from R CrA.

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