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

By N. Evans II, J. Rawlings, Y. Shirley, L. Mundy. 2000

476 citations recorded by the source corpus.

We have modeled the emission from dust in preprotostellar cores, including a self-consistent calculation of the temperature distribution for each input density distribution. Model density distributions include Bonnor-Ebert spheres and power laws. The Bonnor-Ebert spheres fit the data well for all three cores that we have modeled. The dust temperatures decline to very low values (Td ~ 7 K) in the centers of these cores, strongly affecting the dust emission. Compared to earlier models that assume constant dust temperatures, our models indicate higher central densities and smaller regions of relatively constant density. Indeed, for L1544, a power-law density distribution, similar to that of a singular, isothermal sphere, cannot be ruled out. For the three sources modeled herein, there seems to be a sequence of increasing central condensation, from L1512 to L1689B to L1544. The two denser cores, L1689B and L1544, have spectroscopic evidence for contraction, suggesting an evolutionary sequence for preprotostellar cores.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/178e9c21925213f8a52428ee38b7968a0576914b

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In Astronomy and Astrophysics

1. N. Evans II
2. Ralf Klessen
3. Mark R. Krumholz
4. P. Myers
5. P. Caselli
6. E. Bergin
7. S. Andrews
8. E. Dishoeck

In Atmospheric Science

1. P. Caselli
2. E. Dishoeck
3. M. Tafalla
4. N. Evans II
5. E. Bergin
6. E. Herbst
7. Ralf Klessen
8. Cecilia Ceccarelli

Citations in the corpus

• The degree of CO depletion in pre-stellar cores ? (2002, methodology): “The dust temperature was taken to be 7.5K in all cores at their centre, as suggested by the recent works of Zucconi et al. (2001) and Evans et al. (2001).”
• Fragmentation and mass segregation in the massive dense cores of Cygnus X (2009, background): “With an average size of 0.13 pc, and an average density of 1.9 × 105 cm−3, these MDCs have sizes only slightly larger than low-mass dense cores in nearby molecular clouds (Ward-Thompson et al. 1994, Bacmann et al. 2000, Evans et al. 2001, Ward-Thompson et al. 2007).”
• Our astrochemical heritage (2012, background): “…goes from a few times 103 cm−3 toward the outer edges, where they merge with the surrounding molecular cloud, to about 107 cm−3 within the central 1,000 AU (e.g., Evans et al. 2001; Keto and Caselli 2010), where the gas and dust temperature drops to 6–7 K (Crapsi et al. 2007; Pagani et al. 2007).”
• On the Evolutionary Status of Class I Stars and Herbig-Haro Energy Sources in Taurus-Auriga (2004, background): “The low luminosities of class I stars in Taurus consequently lead to very low substellar masses (e.g., Haro 6–33 = IRAS 04385+ 2550; Young et al. 2003 estimate M ¼ 0:01 M ).”
• PROPERTIES OF THE YOUNGEST PROTOSTARS IN PERSEUS, SERPENS, AND OPHIUCHUS (2008, background): “We assume a dust temperature of TD = 15 K for protostellar envelopes, consistent with average isothermal dust temperatures found from radiative transfer models of a sample of Class 0 and Class I protostars (Shirley et al. 2002; Young et al. 2003).”
• On the internal structure of starless cores II. A molecular survey of L1498 and L1517B (2006, methodology): “A different set of abundance determinations in starless cores has been recently provided by the Texas group using a technique similar to ours: density estimates using continuum (SCUBA) data followed by Monte Carlo modeling of the line emission (Evans et al. 2001; Lee et al. 2003).”
• Physical structure and CO abundance of low-mass protostellar envelopes (2002, methodology): “Two sources, L1157 and CB244 only had usable data at 850 µm (see also Shirley et al., 2000), so supplementary data for these two sources were obtained in October 2001 at 450 µm (see Sect.”
• Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A Grid of 200,000 YSO Model SEDs (2006, background): “…(though see Allen et al. (2003) for a discussion of magnetic braking), and observations of radial intensity profiles are consistent with free-fall collapse (Chandler & Richer 2000; van der Tak et al. 2000; Beuther et al. 2002; Mueller et al. 2002; Young et al. 2003; Hatchell & van der Tak 2003).”
• Cold Dark Clouds: The Initial Conditions for Star Formation (2007, background): “…density contrast between the core center and its edge often exceeds the maximum value of ≈ 14 allowed for stable BE spheres (Bacmann et al. 2000; Evans et al. 2001), and it seems unlikely that such an unstable configuration can be realized in nature if thermal pressure is the only balancing…”
• EVOLUTIONARY SIGNATURES IN THE FORMATION OF LOW-MASS PROTOSTARS. II. TOWARD RECONCILING MODELS AND OBSERVATIONS (2005, methodology): “…of Ossenkopf & Henning (1994) appropriate for thin ice mantles after 105 yr of coagulation at a gas density of 106 cm−3 (OH5 dust), which several recent studies have shown to be appropriate for cold, dense cores (e.g., Evans et al. 2001; Shirley et al. 2002; Young et al. 2003; Shirley et al. 2005).”
• Comparing Star Formation on Large Scales in the c2d Legacy Clouds: Bolocam 1.1 mm Dust Continuum Surveys of Serpens, Perseus, and Ophiuchus (2007, background): “Assuming TD = 10 K is a reasonable compromise to cover both prestellar and protostellar sources, based on the results of more detailed radiative transfer models (Evans et al. 2001; Shirley et al. 2002, see also discussion in Paper I).”
• Observing the gas temperature drop in the high-density nucleus of L 1544 (2007, background): “The main results of this work are: 1) The gas temperature drops to ∼5.5 K at the core density peak, in agreement with theoretical model predictions (Zucconi et al. 2001; Evans et al. 2001; Galli et al. 2002) and with the continuum modelling of Doty et al. (2005).”
• The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation (2004, background): “…gas would be very difficult to observe; various efforts to model the observations have suggested central temperatures between 6 K and 10 K for the densest observed prestellar cores, whose peak densities may approach 10−17 g cm−3 (e.g., Zucconi et al. 2001; Evans et al. 2001; Tafalla et al. 2004).”
• The initial conditions of isolated star formation — VI. SCUBA mapping of pre-stellar cores (2005, background): “Evans et al. (2001) also do not treat the chopping in two dimensions, as we do.”
• Does IRAS 16293–2422 have a hot core? Chemical inventory and abundance changes in its protostellar environment (2002, background): “Assuming β = 0.4 (cf., Doty & Leung 1994; Shirley et al. 2000; see also Fig.”
• A “Starless” Core that Isn't: Detection of a Source in the L1014 Dense Core with the Spitzer Space Telescope (2004, methodology): “Both a shallow power-law (n(r) ∝ r−1.0) and a Bonnor-Ebert (BE) sphere were found to provide good fits to the observed 850 µm brightness profile, in agreement with results from other “starless” cores (e.g., Evans et al. 2001).”