Accelerating Star Formation in Clusters and Associations

Palla, F.; Stahler, Steven W.

doi:10.1086/309312

Cited by 249 publications

(268 citation statements)

References 111 publications

(115 reference statements)

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“…This means that the mass of star-forming dense gas increases A49, page 6 of 7 with the mass of the molecular cloud, and the star formation should accelerate over many million years. This conjecture may provide a clue to the star formation histories found by Palla & Stahler (2000) in seven individual molecular clouds such as Taurus-Auriga and ρ Ophiuchi. 8.…”

Section: Discussionmentioning

confidence: 74%

The formation and destruction of molecular clouds and galactic star formation

Inutsuka

Inoue

Iwasaki

et al. 2015

A&A

216

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We describe an overall picture of galactic-scale star formation. Recent high-resolution magneto-hydrodynamical simulations of twofluid dynamics with cooling, heating, and thermal conduction have shown that the formation of molecular clouds requires multiple episodes of supersonic compression. This finding enables us to create a scenario in which molecular clouds form in interacting shells or bubbles on a galactic scale. First, we estimated the ensemble-averaged growth rate of molecular clouds on a timescale longer than a million years. Next, we performed radiation hydrodynamics simulations to evaluate the destruction rate of magnetized molecular clouds by the stellar far-ultraviolet radiation. We also investigated the resulting star formation efficiency within a cloud, which amounts to a low value (a few percent) if we adopt the power-law exponent ∼− 2.5 for the mass distribution of stars in the cloud. We finally describe the time evolution of the mass function of molecular clouds on a long timescale (>1 Myr) and discuss the steady state exponent of the power-law slope in various environments.

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Section: Discussionmentioning

confidence: 74%

The formation and destruction of molecular clouds and galactic star formation

Inutsuka

Inoue

Iwasaki

et al. 2015

A&A

216

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“…In young embedded clusters like the ONC, wide spreads in colour−magnitude diagrams (CMD) have been observed, which have previously been interpreted as age spreads of up to 10 Myr in association members (Palla & Stahler 2000). However, other authors have suggested that the observed CMD spreads are due to a mixture of photometric errors, variability in pre-MS stars (Herbst et al 1994), binarity (Preibisch & Zinnecker 1999), episodic accretion phases (Baraffe et al 2009), or a spread in line-of-sight distances or extinctions.…”

Section: Methodsmentioning

confidence: 99%

Formation and dissolution of leaky clusters

Pfalzner

2011

A&A

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Context. Massive Galactic clusters (>1000 M ) exhibit a clear correlation between cluster density, size, and age and can be sorted into two categories, i.e. starburst and leaky clusters. The reason for having two types of massive clusters is still an open question; however, the answer is probably connected to the different formation histories of the two types. Aims. In this study we concentrate on leaky clusters and investigate possible formation scenarios and the gas expulsion phase. Methods. We use the existing observational data and numerical results of embedded cluster properties. Results. Assuming that a clear correlation between cluster density, size, and age exists, it is shown that the density-radius development over time for embedded clusters can be approximated by ρ ≈ 100 * r −1.3 M pc −3 . The consequences for the star formation process in leaky clusters are discussed and found to favour an inside-out star formation scenario with an initially low, but later accelerated, star formation rate. It is shown how the leaky clusters form in a unique, sequential manner and how rapid gas expulsion is responsible for the 80−90% mass loss over the next 20 Myr.

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“…While the conclusion of Luhman (2007) that the star formation rate in Cha I has declined for several Myr already questions the scenario of Palla & Stahler (2000) in which star formation is a threshold phenomenon and accelerates as a result of cloud contraction (see Sect. 1), our findings raise new questions about the end of star formation.…”

Section: The End Of Star Formation In Cha I?mentioning

confidence: 99%

“…Based on the H-R diagram of the young stellar population known at that time (47 members with known spectral type), Palla & Stahler (2000) conclude that star formation in Cha I began within the last 7 Myr and that its rate steadily increased until recently. They find similar results in several other clouds and draw the general conclusion that star formation in nearby associations and clusters started slowly some 10 Myr ago and accelerated until the present epoch.…”

Section: Introductionmentioning

confidence: 97%

The end of star formation in Chamaeleon I?

Беллоче

Schüller

Parise

et al. 2011

A&A

144

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Context. Chamaeleon I is the most active region in terms of star formation in the Chamaeleon molecular cloud complex. Although it is one of the nearest low-mass star forming regions, its population of prestellar and protostellar cores is not known and a controversy exists concerning its history of star formation. Aims. Our goal is to search for prestellar and protostellar cores and characterize the earliest stages of star formation in this cloud. Methods. We used the bolometer array LABOCA at the APEX telescope to map the cloud in dust continuum emission at 870 μm with a high sensitivity. This deep, unbiased survey was performed based on an extinction map derived from 2MASS data. The 870 μm map is compared with the extinction map and C 18 O observations, and decomposed with a multiresolution algorithm. The extracted sources are analysed by carefully taking into account the spatial filtering inherent in the data reduction process. A search for associations with young stellar objects is performed using Spitzer data and the SIMBAD database. Results. Most of the detected 870 μm emission is distributed in five filaments. We identify 59 starless cores, one candidate first hydrostatic core, and 21 sources associated with more evolved young stellar objects. The estimated 90% completeness limit of our survey is 0.22 M for the starless cores. The latter are only found above a visual extinction threshold of 5 mag. They are less dense than those detected in other nearby molecular clouds by a factor of a few on average, maybe because of the better sensitivity of our survey. The core mass distribution is consistent with the IMF at the high-mass end but is overpopulated at the low-mass end. In addition, at most 17% of the cores have a mass larger than the critical Bonnor-Ebert mass. Both results suggest that a large fraction of the starless cores may not be prestellar in nature. Based on the census of prestellar cores, Class 0 protostars, and more evolved young stellar objects, we conclude that the star formation rate has decreased with time in this cloud. Conclusions. The low fraction of candidate prestellar cores among the population of starless cores, the small number of Class 0 protostars, the high global star formation efficiency, the decrease of the star formation rate with time, and the low mass per unit length of the detected filaments all suggest that we may be witnessing the end of the star formation process in Chamaeleon I.

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Accelerating Star Formation in Clusters and Associations

Cited by 249 publications

References 111 publications

The formation and destruction of molecular clouds and galactic star formation

The formation and destruction of molecular clouds and galactic star formation

Formation and dissolution of leaky clusters

The end of star formation in Chamaeleon I?

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