High-Mass Proto-Stellar Candidates - II : Density structure from dust continuum and CS emission

By H. Beuther, Peter Schilke, K. Menten, Fr'ed'erique Motte, Sridharan T. K., F. Wyrowski. 2001

397 citations recorded by the source corpus.

We present a detailed 1.2 mm continuum and CS spectral line study of a large sample of 69 massive star forming regions in very early stages of evolution, most of them prior to building up an ultracompact HII region. The continuum data show a zoo of different morphologies and give detailed information on the spatial distributions, the masses, column densities and average densities of the whole sample. Fitting the radial intensity profiles shows that three parameters are needed to describe the spatial distribution of the sources: constant emission from the center out to a few arcsec radius followed by a first power law intensity distribution which steepens further outside into a second power law distribution. The mean inner power law intensity index mi (I~r^(-mi)) is 1.2 corresponding to density indices p (n~r^(-p)) of 1.6. In total the density distribution of our massive star formations sites seem to be not too different from their low-mass counterparts, but we show that setting tight constrains on the density indices is very difficult and subject to many possible errors. The local densities we derive from CS calculations are higher (up to one order of magnitude) than the mean densities we find via the mm-continuum. Such inhomogeneous density distribution reflects most likely the ubiquitous phenomenon of clumping and fragmentation in molecular clouds. Linewidth-mass relations show a departure from virial equilibrium in the stages of strongly collapsing cores.

Subfields: Astronomy and Astrophysics

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Chemistry as a probe of the structures and evolution of massive star-forming regions (2002, background): “…infrared observations of gas and ices) have led to a new and better understanding of the environment around massive YSOs (see e.g., Garay & Lizano 1999; van Dishoeck & Hogerheijde 1999; Hatchell et al. 2000; Send offprint requests to: S. Doty, e-mail: doty@cc.dension.edu Beuther et al. 2002).”
High-Mass Protostellar Candidates. I. The Sample and Initial Results (2001, methodology): “Follow-up interferometric observations with the VLA and the Australian Telescope Compact Array(H2O) have been conducted, and a detailed analysis and(CH3OH)comparison of the data with the other data sets will be published Beuther et al. 2002d. 3.2.3.3.”
Initial highlights of the HOBYS key program, the Herschel imaging survey of OB young stellar objects (2010, background): “Bright IRAS sources embedded within massive envelopes have been recognized as HMPOs containing evolved high-mass protostars (e.g. Beuther et al. 2002).”
The earliest phases of high-mass star formation: a 3 square degree millimeter continuum mapping of Cygnus X (2007, methodology): “As interesting illustrations, the Cygnus X HMPOs called IRAS 20343+4129 and IRAS 20293+3952 (Beuther et al. 2002) are twice as large and 7 times less dense than the dens cores we have identified within them (see CygX-N5, CygX-N6 and CygX-S30 in Table 1).”
Collapse, outflows and fragmentation of massive, turbulent and magnetized prestellar barotropic cores (2011, background): “In the context of massive cores (Beuther et al. 2002a, Motte et al. 2007, Wu et al. 2010, Csengeri et al. 2010), the influence of the magnetic field is not extensively explored yet because only few studies have been performed (e.g. Banerjee & Pudritz 2007) in spite of the measurement which suggest…”
Parallaxes and proper motions of interstellar masers toward the Cygnus X star-forming complex. I. Membership of the Cygnus X region (2011, background): “All phases of star formation and stellar evolution are observed projected across the CygnusX region, including a population of dense, massive, and dusty cores with embedded protoclusters and high-mass protostellar objects (Sridharan et al. 2002; Beuther et al. 2002; Motte etal.”
A study of high velocity molecular outflows with an up-to-date sample (2004, background): “For example, IRAS 05358+3543, detected as one outflow, was separated into at least three outflows by the Plateau de Bure interferometer (Beuther et al. 2002a,c), including one highly collimated outflow.”
Fragmentation and mass segregation in the massive dense cores of Cygnus X (2009, background): “A few nearby HMPOs from the Sridharan et al. (2002) sample were observed with the PdBI (see for instance Beuther et al. 2002a; Leurini et al. 2007), while a sample of not too distant IRDCs is presented in Rathborne et al. (2007).”
From Massive Protostars to a Giant H II Region: Submillimeter Imaging of the Galactic Ministarburst W43 (2002, neutral): “Similar densities, sizes, masses and line widths have already been recorded for protoclusters harboring UCH iis and HMPOs (Hunter et al. 2000; Plume et al. 1999; Beuther et al. 2002).”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “…formation, using tracers requiring higher densities (e.g., Plume et al. 1992; Beuther et al. 2002) or millimeter continuum emission from dust (e.g., Beuther et al. 2002; Mueller et al. 2002) have identified slightly smaller structures (r ∼ 0.5 pc) that are much denser, indeed denser on average…”
THE PROPERTIES OF MASSIVE, DENSE CLUMPS: MAPPING SURVEYS OF HCN AND CS (2010, background): “There have been many detailed studies of individual regions of massive star formation and surveys of likely regions in tracers of dense gas or dust (e.g., Plume et al. 1992, 1997; Zinchenko, Mattila, & Toriseva, 1995; Anglada et al. 1996; Sridharan et al. 2002; Beuther et al. 2002; Wu & Evans 2003).”
CH3OH and H2O masers in high-mass star-forming regions (2002, methodology): “A detailed description of the data reduction and analysis can be found in Beuther et al. (2002b).”
IRAS 05358+3543: Multiple outflows at the earliest stages of massive star formation (2002, methodology): “Assuming optically thin dust emission, masses and column densities presented in Table 3 were calculated at 30 K (for more details on the calculations see Beuther et al. 2002a).”
The simultaneous formation of massive stars and stellar clusters (2009, background): “…et al. 1998; Egan et al. 1998; Carey et al. 2000; Rathborne, Jackson & Simon 2006; Simon et al. 2006) and high-mass protostellar objects (HMPOs) (Beuther et al. 2002; Sridharan et al. 2002; Faúndez et al. 2004; Williams, Fuller & Sridharan 2004) have begun to probe the earliest stages of the…”
Filaments and ridges in Vela C revealed by Herschel: from low-mass to high-mass star-forming sites (2011, background): “Recent work has focused on finding candidate early stage protostars indicative of the earliest stages of high-mass star formation (e.g. Beuther et al. 2002; Hill et al. 2005; Motte et al. 2007; Rathborne et al. 2007).”
OUTFLOW FEEDBACK REGULATED MASSIVE STAR FORMATION IN PARSEC-SCALE CLUSTER-FORMING CLUMPS (2009, background): “Centrally condensed density profiles are also inferred for dense clumps before the onset of massive star formation from dust continuum emission (e.g., Beuther et al. 2002).”
UV-photoprocessing of interstellar ice analogs: New infrared spectroscopic results (2003, background): “For the molecular cloud Cepheus B, the filling factor, the ratio of average over local densities, is FV = 2–4% (Beuther et al. 2000, 2002).”