The mass function of dense molecular cores and the origin of the IMF

By Joao F. Alves, Marco Lombardi, C. Lada. 2006

407 citations recorded by the source corpus.

Context. Stars form in the cold dense cores of interstellar molecular clouds and the detailed knowledge of the spectrum of masses of such cores is clearly a key for the understanding of the origin of the IMF. To date, observations have presented somewhat contradictory evidence relating to this issue. Aims. In this paper we propose to derive the mass function of a complete sample of dense molecular cores in a single cloud employing a robust method that uses uses extinction of background starlight to measure core masses and enables the reliable extension of such measurements to lower masses than previously possible. Methods. We use a map of near-infrared extinction in the nearby Pipe dark cloud to identify the population of dense cores in the cloud and measure their masses. Results. We identify 159 dense cores and construct the mass function for this population. We present the first robust evidence for a departure from a single power-law form in the mass function of a population of cores and find that this mass function is surprisingly similar in shape to the stellar IMF but scaled to a higher mass by a factor of about 3. This suggests that the distribution of stellar birth masses (IMF) is the direct product of the dense core mass function and a uniform star formation efficiency of 30%±10%, and that the stellar IMF may already be fixed during or before the earliest stages of core evolution. These results are consistent with previous dust continuum studies which suggested that the IMF directly originates from the core mass function. The typical density of ∼10 4 cm −3 measured for the dense cores in this cloud suggests that the mass scale that characterizes the dense core mass function may be the result of a simple process of thermal (Jeans) fragmentation.

Subfields: Astronomy and Astrophysics, Instrumentation, Organic Chemistry

View Paper: https://www.semanticscholar.org/paper/8c847a37b1c89bc7fd085aa29971b854a0984ab0

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Citations in the corpus

Structural Analysis of Molecular Clouds: Dendrograms (2008, background): “Indeed, studies have argued for the close relationship between the dense cores and the newlyformed stars based on the similarities of their mass functios (Motte et al. 1998; Testi & Sargent 1998; Alves et al. 2007; Enoch et al. 2006).”
Molecular Clouds in the Milky Way (2015, background): “…of protostellar cores that follow a log-normal function with a peak at a characteristic mass of ∼0.6 − 1 M (Motte et al. 1998, Testi & Sargent 1998, Alves et al. 2007, André et al. 2010, Könyves et al. 2010) yet are similar in shape to the stellar initial mass function (Salpeter 1955, Miller…”
Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region (2013, background): “Core formation, in addition, seems to play a key role in determining the mass of the final star, since the distribution of masses among starless cores in a cloud mimics the initial distribution of stellar masses (Motte et al. 1998; Alves et al. 2007).”
PROPERTIES OF THE YOUNGEST PROTOSTARS IN PERSEUS, SERPENS, AND OPHIUCHUS (2008, methodology): “…stellar mass to initial core mass for the M98 model shown (feff = Mcore/Mstar = 0.3/1.8 = 0.17) is smaller than the values (feff = 0.3 ± 0.1) found by Alves et al. (2007) and Enoch et al. (2008) by comparing the shape of the core mass distribution to the initial mass function (feff = 0.3 ± 0.1 and…”
STAR FORMATION ACTIVITY OF CORES WITHIN INFRARED DARK CLOUDS (2009, background): “If we assume that each quiescent core will form only one star with a 30% star formation efficiency (e.g., Alves et al. 2007; Enoch et al. 2008), then the lower mass limit for a core which can produce a high-mass (M 8 M ) star is ∼25 M .”
THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, background): “The observed displacement of the characteristic mass in the IMF (e.g., Kroupa 2001; Chabrier 2003) with respect to the CMF (e.g., Johnstone et al. 2000) has been taken to argue that might be around 0.3–0.5 (Alves et al. 2007; André et al. 2010); see however Ward et al. (2012).”
EVOLUTIONARY SIGNATURES IN THE FORMATION OF LOW-MASS PROTOSTARS. II. TOWARD RECONCILING MODELS AND OBSERVATIONS (2005, methodology): “If we instead use the three-component power-law IMF found by Kroupa (2002) and assume a 30% star-formation efficiency in dense gas (Alves et al. 2007; see also §4.4) to scale from the IMF to the CMF, we obtain N1/N3 = 2.3 and N1/N0.”
Hipparcos distance estimates of the Ophiuchus and the Lupus cloud complexes (2008, background): “…an error by a factor two on the distance of a cloud translates into an error by a factor four in the mass, and has a thus a huge impact on the estimate of the density, size, stability, and star formation efficiency of their cloud cores (see Alves et al. 2007 for further discussions on this point).”
A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from the Herschel Gould Belt survey (2015, methodology): “…versions of this CMF) is based on a core sample ∼2– 9 times larger than the CMFs derived from earlier ground-based studies (e.g., Motte et al. 1998; Johnstone et al. 2000; Stanke et al. 2006; Alves et al. 2007; Enoch et al. 2008) and that its shape is therefore much more robustly defined.”
The Mass Distribution and Lifetime of Prestellar Cores in Perseus, Serpens, and Ophiuchus (2008, background): “Our conclusion that the core-to-star efficiency is at least 25% is consistent with the value found by Alves et al. (2007) for the Pipe Nebula (30%), and with predicted efficiencies of 25% − 75% from recent analytic models of bipolar protostellar outflows (Matzner & McKee 2000).”
The Stellar IMF, Core Mass Function, & The Last-Crossing Distribution (2012, background): “However, the calculation here suggests that such corrections should be order unity, and arguments from observations and models of outflows similarly suggest a modest core ∼ 0.5 (Matzner & McKee 2000; Stanke et al. 2006; Alves et al. 2007; Enoch et al. c© 0000 RAS, MNRAS 000, 000–000 2008).”
The Aquila prestellar core population revealed by Herschel (2010, background): “…and Orion B have uncovered ’complete’ (but small) samples of prestellar cores whose associated core mass functions (CMF) resemble the stellar IMF (e.g., Motte et al. 1998; Johnstone et al. 2000; Enoch et al. 2006; Nutter & Ward-Thompson 2007; – see also Alves et al. 2007 and André et al. 2007).”
THE FORMATION OF LOW-MASS BINARY STAR SYSTEMS VIA TURBULENT FRAGMENTATION (2010, background): “Observations of starless cores indicate that the core mass function shape is similar to the stellar IMF but is shifted to higher masses by a factor of three (Alves et al. 2007; Enoch et al. 2008).”
Cooling, Gravity, and Geometry: Flow-driven Massive Core Formation (2007, background): “Alves et al. (2007) quote a core mass distribution for the Pipe nebula close to the Salpeter IMF, however, as they point out, the cores that they are using for analysis are probably the direct progenitors of stars – a stage we cannot hope to reach with the models presented here.”
Can Supermassive Black Holes Form in Metal-enriched High-Redshift Protogalaxies? (2008, background): “It is important to stress that, even assuming a star formation efficiency of order unity (which seems likely when the density exceeds k104 cm 3; Alves et al. 2007), the stellar IMF will be strongly affected by gravitational interactions, collisions, and mergers.”
Analytical Theory for the Initial Mass Function: CO Clumps and Prestellar Cores (2008, background): “…of prestellar condensations, as identified in dust continuum surveys, show that the CMF peaks at a mass about 3 times larger than the observational IMF, even though this peak determination still suffers from large uncertainties (Motte et al. 1998; Alves et al. 2007, André et al. 2007, 2008).”