Tracing the Mass during Low‐Mass Star Formation. II. Modeling the Submillimeter Emission from Preprotostellar Cores

Evans, Neal J.; Rawlings, J. M. C.; Shirley, Yancy L.; Mundy, Lee G.

doi:10.1086/321639

Cited by 344 publications

(557 citation statements)

References 44 publications

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“…In non-embedded cores, the dust temperature drops from around 17 K at the edge of the core to 7 K at the centre of the core, as previous studies have already indicated (Zucconi et al 2001;Evans et al 2001;Stamatellos & Whitworth 2003a). We also find that the dust temperature inside cores with disk-like asymmetry is θ dependent (see Fig.…”

Section: Results: Core Temperatures Seds and Imagessupporting

confidence: 78%

“…Previous continuum radiative transfer modelling of prestellar cores has examined non-embedded BE spheres (Evans et al 2001;Young et al 2003) and embedded BE spheres (Stamatellos & Whitworth 2003a), using 1D (sphericallysymmetric) codes. Zucconi et al (2001) have used an approximate, semi-analytic method to model non-embedded, magnetically flattened prestellar cores, in 2D.…”

Section: Introductionmentioning

confidence: 99%

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Radiative transfer models of non-spherical prestellar cores

Stamatellos

Whitworth

André

et al. 2004

A&A

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Abstract. We present 2D Monte Carlo radiative transfer simulations of prestellar cores. We consider two types of asymmetry: disk-like asymmetry, in which the core is denser towards the equatorial plane than towards the poles; and axial asymmetry, in which the core is denser towards the south pole than the north pole. In both cases the degree of asymmetry is characterized by the ratio e between the maximum optical depth from the centre of the core to its surface and the minimum optical depth from the centre of the core to its surface. We limit our treatment here to mild asymmetries with e = 1.5 and 2.5 . We consider both cores which are exposed directly to the interstellar radiation field and cores which are embedded inside molecular clouds. The SED of a core is essentially independent of the viewing angle, as long as the core is optically thin. However, the isophotal maps depend strongly on the viewing angle. Maps at wavelengths longer than the peak of the SED (e.g. 850 µm) essentially trace the column-density. This is because at long wavelengths the emissivity is only weakly dependent on temperature, and the range of temperature in a core is small (typically T max /T min < ∼ 2). Thus, for instance, cores with disk-like asymmetry appear elongated when mapped at 850 µm from close to the equatorial plane. However, at wavelengths near the peak of the SED (e.g. 200 µm), the emissivity is more strongly dependent on the temperature, and therefore, at particular viewing angles, there are characteristic features which reflect a more complicated convolution of the density and temperature fields within the core. These characteristic features are on scales 1/5 to 1/3 of the overall core size, and so high resolution observations are needed to observe them. They are also weaker if the core is embedded in a molecular cloud (because the range of temperature within the core is then smaller), and so high sensitivity is needed to detect them. Herschel, to be launched in 2007, will in principle provide the necessary resolution and sensitivity at 170 to 250 µm.

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Section: Results: Core Temperatures Seds and Imagessupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Radiative transfer models of non-spherical prestellar cores

Stamatellos

Whitworth

André

et al. 2004

A&A

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“…In particular, we show that the pinching of the magnetic field expected in dense, self-gravitating molecular cloud cores naturally produces a decrease of the polarization degree toward the centre of the core, for a large range of viewing angles. In addition, we find that this geometrical depolarization effect is further enhanced by a dust temperature gradient increasing outward, as expected in externally heated starless cores (Evans et al 2001;Zucconi et al 2001;Stamatellos & Whitworth 2003;Gonçalves et al 2004, hereafter GGW). However, while these effects can contribute substantially to the observed depolarization, the measured p−I relations are sometimes steeper than our predictions.…”

Section: L1544supporting

confidence: 83%

Polarized dust emission of magnetized molecular cloud cores

Gonçalves

Galli²,

Walmsley³

2005

A&A

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Abstract. We compute polarization maps for molecular cloud cores modeled as magnetized singular isothermal toroids, under the assumption that the emitting dust grains are aspherical and aligned with the large-scale magnetic field. We show that, depending on the inclination of the toroid with the line-of-sight, the bending of the magnetic field lines resulting from the need to counteract the inward pull of gravity naturally produces a depolarization effect toward the centre of the map. We compute the decrease of polarization degree with increasing intensity for different viewing angles and frequencies, and we show that an outward increasing temperature gradient, as expected in starless cores heated by the external radiation field, enhances the decrease of polarization. We compare our results with recent observations, and we conclude that this geometrical effect, together with other mechanisms of depolarization, may significantly contribute to the decrease of polarization degrees with intensity observed in the majority of molecular cloud cores. Finally, we consider the dependence of the polarization degree on the dust temperature gradient predicted for externally heated clouds, and we briefly comment on the limits of the Chandrasekhar-Fermi formula to estimate the magnetic field strength in molecular cloud cores.

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“…Such a correlation might be expected based on a model in which the dust is heated by the interstellar radiation field (ISRF). Large column densities then provide more shielding, resulting in cooler dust (Evans et al 2001;Stamatellos et al 2007;Roy et al 2014). But could this correlation be an artifact, induced by a degeneracy between mass and temperature in the SED measurement model?…”

Section: Estimates Of Core Masses and Temperaturesmentioning

confidence: 99%

A census of dense cores in the Taurus L1495 cloud from theHerschelGould Belt Survey

Marsh

Kirk

André

et al. 2016

Mon. Not. R. Astron. Soc.

123

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We present a catalogue of dense cores in a ∼ 4 • × 2 • field of the Taurus star-forming region, inclusive of the L1495 cloud, derived from Herschel SPIRE and PACS observations in the 70 µm, 160 µm, 250 µm, 350 µm, and 500 µm continuum bands. Estimates of mean dust temperature and total mass are derived using modified blackbody fits to the spectral energy distributions. We detect 525 starless cores of which ∼ 10-20% are gravitationally bound and therefore presumably prestellar. Our census of unbound objects is ∼ 85% complete for M > 0.015 M ⊙ in low density regions (A V < ∼ 5 mag), while the bound (prestellar) subset is ∼ 85% complete for M > 0.1 M ⊙ overall. The prestellar core mass function (CMF) is consistent with lognormal form, resembling the stellar system initial mass function, as has been reported previously. All of the inferred prestellar cores lie on filamentary structures whose column densities exceed the expected threshold for filamentary collapse, in agreement with previous reports. Unlike the prestellar CMF, the unbound starless CMF is not lognormal, but instead is consistent with a power-law form below 0.3 M ⊙ and shows no evidence for a lowmass turnover. It resembles previously reported mass distributions for CO clumps at low masses (M < ∼ 0.3 M ⊙ ). The volume density PDF, however, is accurately lognormal except at high densities. It is consistent with the effects of self-gravity on magnetized supersonic turbulence. The only significant deviation from lognormality is a high-density tail which can be attributed unambiguously to prestellar cores.

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Tracing the Mass during Low‐Mass Star Formation. II. Modeling the Submillimeter Emission from Preprotostellar Cores

Cited by 344 publications

References 44 publications

Radiative transfer models of non-spherical prestellar cores

Radiative transfer models of non-spherical prestellar cores

Polarized dust emission of magnetized molecular cloud cores

A census of dense cores in the Taurus L1495 cloud from theHerschelGould Belt Survey

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