The Physical Conditions for Massive Star Formation: Dust Continuum Maps and Modeling

By K. E. Mueller, Y. Shirley, N. Evans II, H. Jacobson. 2002

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Fifty-one dense cores associated with water masers were mapped at 350 μm. These cores are very luminous, 103 < Lbol/L☉ < 106, indicative of the formation of massive stars. Dust continuum contour maps, radial intensity profiles, and photometry are presented for these sources. The submillimeter dust emission peak is, on average, nearly coincident with the water maser position. The spectral energy distributions and normalized radial profiles of dust continuum emission were modeled for 31 sources using a one-dimensional dust radiative transfer code, assuming a power-law density distribution in the envelope, n = nf(r/rf)-p. The best-fit density power-law exponent, p, ranged from 0.75 to 2.5 with ⟨p⟩ = 1.8 ± 0.4, similar to the mean value found recently by Beuther and coworkers in a large sample of massive star-forming regions. The mean value of p is also comparable to that found in regions forming only low-mass stars, but ⟨nf⟩ is over 2 orders of magnitude greater for the massive cores. The mean p is incompatible with a logatropic sphere (p = 1), but other star formation models cannot be ruled out. Different mass estimates are compared and mean masses of gas and dust are reported within a half-power radius determined from the dust emission, ⟨log M(< rdec)⟩ = 2.0 ± 0.6, and within a radius where the total density exceeds 104 cm-3, ⟨log M(< rn)⟩ = 2.5 ± 0.6. Evolutionary indicators commonly used for low-mass star formation, such as Tbol and Lbol/Lsmm, may have some utility for regions forming massive stars. Additionally, for comparison with extragalactic star formation studies, the luminosity-to-dust mass ratio is calculated for these sources, ⟨Lbol/MD⟩ = 1.4 × 104 L☉/M☉, with a method most parallel to that used in studies of distant galaxies. This ratio is similar to that seen in high-redshift starburst galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a4aeb4e6c757bce4aa71414adf7bfb50b4ef40c7

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THE PROPERTIES OF MASSIVE, DENSE CLUMPS: MAPPING SURVEYS OF HCN AND CS (2010, methodology): “Detailed models of individual dense clumps do support density gradients with power laws providing good fits (n(r) ∝ r−p with 〈p〉 = 1.8) (Mueller et al. 2002).”
The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X (2007, background): “In this way, studies by e.g., Molinari et al. (2000) and Sridharan et al. (2002) have identified massive young stellar objects harboring highluminosity infrared protostars (see also Mueller et al. 2002; Faúndez et al. 2004).”
ATLASGAL — towards a complete sample of massive star forming clumps ⋆ (2014, background): “…in column and surface densities have been reported by Butler & Tan (2012) from a comparison of starless cores to the sample of more evolved luminous MYSOs and H II regions studied by Mueller et al. (2002), and by Giannetti et al. (2013) from a comparison of pre-stellar and protostellar clumps.”
Slow Star Formation in Dense Gas: Evidence and Implications (2006, background): “Galactic Far-Infrared Observations Several authors (e.g., Plume et al. 1997; Mueller et al. 2002; Shirley et al. 2003; Wu et al. 2005) use infrared luminosities to estimate the star formation rates within individual cluster-forming gas clumps in the Milky Way.”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “The properties of the Plume et al. (1992) sample have been studied in a series of papers (Plume et al. 1997; Mueller et al. 2002; Shirley et al. 2003), with the most recent summary in Wu et al. (2010a).”
Equilibrium Star Cluster Formation (2006, background): “The expected variation is σ ∝ r1−kρ/2, and observations show kρ ≃ 1.5 (Mueller et al. 2002).”
THE LONG-TERM EVOLUTION OF THE GALACTIC DISK TRACED BY DISSOLVING STAR CLUSTERS (2010, background): “Observations of gas-dominated cluster-forming regions show column densities of ∼ 0.1 − 3 g cm−2 (Plume et al. 1997; Mueller et al. 2002; Shirley et al. 2003; Faúndez et al. 2004; Fontani et al. 2005); the data are summarized in Figure 1 of Fall et al. (2010).”
THE BOLOCAM GALACTIC PLANE SURVEY: SURVEY DESCRIPTION AND DATA REDUCTION (2010, background): “While clumps forming massive clusters may be even denser than cores forming low mass stars (Mueller et al. 2002), in general, clumps are larger and have a lower mean density (McKee & Ostriker 2007).”
Triggered massive-star formation on the borders of Galactic H II regions I. A search for "collect and collapse" candidates (2004, unknown): “Nearby is a dense molecular core which has been observed in the CS and HCN lines (Plume et al. 1992, 1997; Pirogov 1999), and mapped at 350 µm (Mueller et al. 2002).”
Connecting Dense Gas Tracers of Star Formation in our Galaxy to High-z Star Formation (2005, background): “The sample mapped in HCN J = 1− 0 is mostly a subset of a larger sample of Galactic massive dense cores that have been mapped in CS and dust emission (Shirley et al. 2003; Mueller et al. 2002).”
A CS J = 5 → 4 Mapping Survey Toward High-Mass Star-forming Cores Associated with Water Masers (2003, methodology): “Mueller et al. (2002) found a median density over 1.4× 107 cm−3 at the fiducial radius of 1000 AU, and a median temperature of 260 K, leading to a thermal pressure of 4× 109 Kcm−3.”
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).”
Fragmentation and mass segregation in the massive dense cores of Cygnus X (2009, background): “…in the vicinity of luminous IRAS or maser sources in the whole galactic plane (Molinari et al. 1996, Plume et al. 1997, Beuther et al. 2002b, Mueller et al. 2002, Faúndez et al. 2004), and more recently inside the dark filaments seen in the infrared surveys of the Galactic plane, the…”
THE INTERPLAY OF MAGNETIC FIELDS, FRAGMENTATION, AND IONIZATION FEEDBACK IN HIGH-MASS STAR FORMATION (2010, background): “For a field of 10 µG, this corresponds to a column density of 5× 10−2 g cm−2, well below the 0.1-1 g cm−2 characteristic of massive star forming regions (e.g. Mueller et al. 2002; McKee & Tan 2003; Krumholz & McKee 2008).”
Inverse dynamical population synthesis: Constraining the initial conditions of young stellar clusters by studying their binary populations (2012, background): “6 shows that the constraints compare well with masses and densities of molecular clumps that have just begun to form stars Mueller et al. (2002); Shirley et al. (2003); Fontani et al. (2005).”
SIMBA survey of southern high-mass star forming regions. I. Physical parameters of the 1.2-mm/IRAS sources (2004, background): “The dust temperatures of the sources in our sample (〈Td〉 = 32±5 K) are similar to those derived in other large scale surveys (Mueller et al. (2002), 〈Td〉 = 29± 9 K; Sridharan et al. (2002), 〈Td〉 = 45 ± 11) as well as in more limited surveys ( Molinari et al. (2000), 〈Td〉 = 32 ± 5 K, Hunter (1997),…”
Testing grain-surface chemistry in massive hot-core regions (2007, methodology): “Some of our sources have previously been modeled in more detail (e.g., van der Tak et al. 2000; Mueller et al. 2002; Hatchell & van der Tak 2003); these models show some differences, e.g., in the slope of the density distribution from source to source and even for the same source depending on…”