MAMBO Mapping Of Spitzer c2d Small Clouds And Cores

By Jens Kauffmann, F. Bertoldi, T. Bourke, N. Evans II, C. T. M. F. Radioastronomie, Bonn, Heidelberg · Germany, Initiative in Innovative Computing at Harvard University, H. C. F. Astrophysics, Argelander Institut fuer Astronomie and 3 more. 2008

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Aims. To study the structure of nearby (<500 pc) dense starless and star-forming cores with the particular goal to identify and understand evolutionary trends in core properties, and to explore the nature of Very Low Luminosity Objects (<0.1 L ⊙ ; VeLLOs). Methods. Using the MAMBO bolometer array, we create maps unusually sensitive to faint (few mJy per beam) extended (≈5') thermal dust continuum emission at 1.2 mm wavelength. Complementary information on embedded stars is obtained from Spitzer, IRAS, and 2MASS. Results. Our maps are very rich in structure, and we characterize extended emission features ("subcores") and compact intensity peaks in our data separately to pay attention to this complexity. We derive, e.g., sizes, masses, and aspect ratios for the subcores, as well as column densities and related properties for the peaks. Combination with archival infrared data then enables the derivation of bolometric luminosities and temperatures, as well as envelope masses, for the young embedded stars. Conclusions. Starless and star-forming cores occupy the same parameter space in many core properties; a picture of dense core evolution in which any dense core begins to actively form stars once it exceeds some fixed limit in, e.g., mass, density, or both, is inconsistent with our data. A concept of necessary conditions for star formation appears to provide a better description: dense cores fulfilling certain conditions can form stars, but they do not need to, respectively have not done so yet. Comparison of various evolutionary indicators for young stellar objects in our sample (e.g., bolometric temperatures) reveals inconsistencies between some of them, possibly suggesting a revision of some of these indicators. Finally, we challenge the notion that VeLLOs form in cores not expected to actively form stars, and we present a first systematic study revealing evidence for structural differences between starless and candidate VeLLO cores.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

THE BOLOCAM GALACTIC PLANE SURVEY: SURVEY DESCRIPTION AND DATA REDUCTION (2010, methodology): “A detailed description of the MAMBO data reduction is given in Kauffmann et al. (2008).”
DIRECT OBSERVATION OF A SHARP TRANSITION TO COHERENCE IN DENSE CORES (2010, methodology): “Dust continuum observations using SCUBA (Hatchell et al. 2005; Kirk et al. 2006), MAMBO (Motte et al. 1998; Kauffmann et al. 2008) and SHARC II (Li et al. 2007) have angular resolution of 15′′, 11′′ and 9′′, respectively, which are high enough to enable the study of the transition to coherence.”
A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey (2015, methodology): “The H2 column density (NH2 ) was then calculated from Σ = μH2 mHNH2 , adopting a mean molecular weight per hydrogen molecule μH2 = 2.8 (e.g., Kauffmann et al. 2008).”
The simultaneous formation of massive stars and stellar clusters (2009, methodology): “We take the standard value of 0.01 for the dust-to-gas ratio (Kauffmann et al. 2008) and a value of 0.1 m2 kg−1 for the dust opacity (Ossenkopf & Henning 1994).”
The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers (2015, unknown): “…dust νij Ajk = gi gj Aij Ajk τdustνij exp(hνij/kTdust) − 1 = gi gj Aij Ajk µmHNH2κνjknph(Tdust, νij) , (16) where µ = 2.8 is the mean mass per H2 molecule (see Kauffmann et al. 2008), NH2 is the H2 column density (cm−2), and κνjk is dust opacity (cm 2/gram of gas) at the frequency of the j →…”
THE EFFECT OF LINE-OF-SIGHT TEMPERATURE VARIATION AND NOISE ON DUST CONTINUUM OBSERVATIONS (2009, methodology): “Ground and space based observations by SCUBA, MAMBO, Bolocam, 2MASS, IRAS, ISO and Spitzer have detected dust emission from many environments, and they have provided much information about starless cores (e.g. Ward-Thompson et al. 2002; Schnee et al. 2007; Kauffmann et al. 2008).”
The ATLASGAL survey: a catalog of dust condensations in the Galactic plane (2013, background): “…is derived from: N(H2) = Fν R Bν(Td)Ω κν µH2 mH (1) whereFν is the peak flux density,Ω is the beam solid angle, µH2 is the mean molecular weight of the interstellar medium with respect to hydrogen molecules, which is equal to 2.8 (Kauffmann et al. 2008)4, andmH is the mass of an hydrogen atom.”
Star Formation in the Milky Way and Nearby Galaxies (2012, background): “The total gas surface density, with He, is Σgas = Σmol + µΣHI, where µ is the mean molecular weight per H atom; µ = 1.41 for MW abundances (Kauffmann et al. 2008), though a value of 1.36 is commonly used.”
HOW MANY INFRARED DARK CLOUDS CAN FORM MASSIVE STARS AND CLUSTERS? (2010, background): “Mueller et al. (2002) list masses for a sphere, not an aperture, and so the mass (taken for the smaller of their radii) has to be scaled up by a factor of order π/2 ≈ 1.57 (Kauffmann et al. 2008, Eq.”
THE PROPERTIES OF MASSIVE, DENSE CLUMPS: MAPPING SURVEYS OF HCN AND CS (2010, methodology): “We calculated the mean volume density (n ≡ n(H2)+n(He)+ ... = ρ/µmH , with µ = 2.37 (Kauffmann et al. 2008) within the FWHM size of the clumps for each transition, according the the following equation: ntransition = Mvir(Rtransition) 4 3πµmHR 3 transition ≈ 4.08 (Mvir/M⊙) (Rtransition/1pc)3 (6) The…”
Characterizing precursors to stellar clusters with Herschel (2011, unknown): “…blackbody expression in the form S ν = 2 hν3 c2(e hν kT − 1) (1 − e−τν) (1) where τν = µH2 mHκνN(H2) (2) where µH2 is the mean molecular weight for which we adopt a value of µH2 = 2.8 (Kauffmann et al. 2008), mH is the mass of hydrogen, N(H2) is the column density, and κν is the dust opacity.”
A COLD COMPLEX CHEMISTRY TOWARD THE LOW-MASS PROTOSTAR B1-b: EVIDENCE FOR COMPLEX MOLECULE PRODUCTION IN ICES (2010, background): “The origin of the CH3OH gas The CH3OH average abundance toward the quiescent CH3OH ‘core’ is ∼ 2× 10 −9 with respect to NH2 , assuming a SCUBA dust intensity conversion factor of NH2/S beam ν of 1.3×1020 cm−2 (mJy beam−1)−1 (Kauffmann et al. 2008).”
Water in star-forming regions with Herschel (WISH). II. Evolution of 557 GHz 110-101 emission in low-mass protostars (2012, methodology): “Assuming spherical infall symmetry, the mass infall rates can be estimated through Ṁinf = 4πR2inf μmH ninf inf where μ is the mean molecular weight (2.8 amu; Kauffmann et al. 2008) and ninf the density at the infall radius.”
Ammonia from cold high-mass clumps discovered in the inner Galactic disk by the ATLASGAL survey (2012, unknown): “We estimated the H2 column density per the relation (Kauffmann et al. 2008) N(H2) = 2.03 × 1016S 40′′870 μmλ3 ( exp ( 1.44 × 104 Tdλ ) − 1 ) κ(λ)θ2 Z Z , (11) where S 40 ′′ 870 μm is the 870 μm flux density in Jy integrated within 40′′, λ the wavelength in μm and Td the dust temperature with Td =…”
LOW VIRIAL PARAMETERS IN MOLECULAR CLOUDS: IMPLICATIONS FOR HIGH-MASS STAR FORMATION AND MAGNETIC FIELDS (2013, methodology): “These masses are calculated from the observed flux following the formalism from Kauffmann et al. (2008), M = 0.12M⊙ ( e1.”
Identifying the Low-Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores (2007, methodology): “…Young et al. (2006a); (7) Motte & André (2001); (8) Bourke et al. (2006); (9) M. Dunham et al. (2008), in preparation; (10) Kirk et al. (2005); (11) Kauffmann et al. (2008); (12) Young et al. (2003); (13) Lehtinen et al. (2005); (14) K. Brede et al. (2008), in preparation; (15) Henning et al.…”
THE STAR FORMATION RATE AND GAS SURFACE DENSITY RELATION IN THE MILKY WAY: IMPLICATIONS FOR EXTRAGALACTIC STUDIES (2010, result): “We use this factor of two instead of the mean molecular weight of H2 (µH2=2.8, derived from cosmic abundances of 71% hydrogen, 27% helium, and 2% metals, e.g., Kauffmann et al. (2008)) to be consistent with the extragalactic studies of Kennicutt (1998b) and Bigiel et al. (2008).”