Signatures of Star Cluster Formation by Cold Collapse

Kuznetsova, Aleksandra; Hartmann, L.; Ballesteros-Paredes, Javier

doi:10.1088/0004-637x/815/1/27

Cited by 45 publications

(59 citation statements)

References 46 publications

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“…Closely packed in the PPV space in regions like L1641-N or V380, compact associations of these APOGEE strings would appear as stellar groups with larger velocity dispersion. Conversely, and apparent in dense clusters like the ONC, two-body relaxation processes could have rapidly erased these characteristic kinematic signatures, as has been suggested by recent simulations (e.g., Kuznetsova et al 2015).…”

Section: Discussion: Fibers Chains Of Cores and The Formation Of Stmentioning

confidence: 68%

APOGEE strings: A fossil record of the gas kinematic structure

Hacar

Alves

Forbrich

et al. 2016

A&A

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We compare APOGEE radial velocities (RVs) of young stars in the Orion A cloud with CO line gas emission and find a correlation between the two at large scales in agreement with previous studies. However, at smaller scales we find evidence for the presence of a substructure in the stellar velocity field. Using a friends-of-friends approach we identify 37 stellar groups with almost identical RVs. These groups are not randomly distributed, but form elongated chains or strings of stars with five or more members with low velocity dispersion across lengths of 1−1.5 pc. The similarity between the kinematic properties of the APOGEE strings and the internal velocity field of the chains of dense cores and fibers recently identified in the dense interstellar medium is striking and suggests that for most of the Orion A cloud, young stars keep memory of the parental gas substructure where they originated.

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Section: Discussion: Fibers Chains Of Cores and The Formation Of Stmentioning

confidence: 68%

APOGEE strings: A fossil record of the gas kinematic structure

Hacar

Alves

Forbrich

et al. 2016

A&A

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“…Recently, Kuznetsova et al (2015) have shown that mass segregation is accelerated even during the star formation process if the gas from which stars form is subvirial.…”

Section: Discussionmentioning

confidence: 99%

No preferential spatial distribution for massive stars expected from their formation

Parker

Dale

2017

Monthly Notices of the Royal Astronomical Society

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We analyse N-body and Smoothed Particle Hydrodynamic (SPH) simulations of young star-forming regions to search for differences in the spatial distributions of massive stars compared to lower-mass stars. The competitive accretion theory of massive star formation posits that the most massive stars should sit in deeper potential wells than lower-mass stars. This may be observable in the relative surface density or spatial concentration of the most massive stars compared to other, lower-mass stars. Massive stars in cool-collapse N-body models do end up in significantly deeper potentials, and are mass segregated. However, in models of warm (expanding) star-forming regions, whilst the massive stars do come to be in deeper potentials than average stars, they are not mass segregated. In the purely hydrodynamical SPH simulations, the massive stars do come to reside in deeper potentials, which is due to their runaway growth. However, when photoionisation and stellar winds are implemented in the simulations, these feedback mechanisms regulate the mass of the stars and disrupt the inflow of gas into the clouds' potential wells. This generally makes the potential wells shallower than in the control runs, and prevents the massive stars from occupying deeper potentials. This in turn results in the most massive stars having a very similar spatial concentration and surface density distribution to lower-mass stars. Whilst massive stars do form via competitive accretion in our simulations, this rarely translates to a different spatial distribution and so any lack of primordial mass segregation in an observed star-forming region does not preclude competitive accretion as a viable formation mechanism for massive stars.

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“…These filaments then must have subsequently disappeared, being replaced by the filament that we can currently see, which is one of the most prolific in the nearby universe. In addition, simulations carried out by Kuznetsova et al (2015) show that the sink particles (representing protostars) do not cluster in phase space like the real ISF protostars (see their Figs. 1, 2, and 6 and our Fig.…”

Section: Violent Acceleration: Magnetic Fields Vs Cold Collapsementioning

confidence: 99%

Slingshot mechanism in Orion: Kinematic evidence for ejection of protostars by filaments

Stutz

Gould

2016

A&A

135

260

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By comparing three constituents of Orion A (gas, protostars, and pre-main-sequence stars), both morphologically and kinematically, we derive the following conclusions. The gas surface density near the integral-shaped filament (ISF) is very well represented by a power law, Σ(b) = 37 M pc −2 (b/pc) −5/8 , for the entire range to which we are sensitive, 0.05 pc < b < 8.5 pc, of projected separation from the filament ridge. Essentially all Class 0 and Class I protostars lie superposed on the ISF or on identifiable filament ridges farther south, while almost all pre-main-sequence (Class II) stars do not. Combined with the fact that protostars are moving < ∼ 1 km s −1 relative to the filaments, while stars are moving several times faster, this implies that protostellar accretion is terminated by a slingshot-like "ejection" from the filaments. The ISF is the third in a series of identifiable star bursts that are progressively moving south, with separations of several Myr in time and 2-3 pc in space. This, combined with the observed undulations in the filament (both spatial and velocity), suggest that repeated propagation of transverse waves through the filament is progressively digesting the material that formerly connected Orion A and B into stars in discrete episodes. We construct a simple, circularly symmetric gas density profile ρ(r) = 17 M pc −3 (r/pc) −13/8 consistent with the two-dimensional data. The model implies that the observed magnetic fields in this region are subcritical on spatial scales of the observed undulations, suggesting that the transverse waves propagating through the filament are magnetically induced. Because the magnetic fields are supercritical on scales of the filament as a whole (as traced by the power law), the system as a whole is relatively stable and long lived. Protostellar "ejection" (i.e., the slingshot) occurs because the gas accelerates away from the protostars, not the other way around. The model also implies that the ISF is kinematically young, which is consistent with several other lines of evidence. In contrast to the ISF, the southern filament (L1641) has a broken power law, which matches the ISF profile for 2.5 pc < b < 8.5 pc, but is shallower closer in. L1641 is kinematically older than the ISF.

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Signatures of Star Cluster Formation by Cold Collapse

Cited by 45 publications

References 46 publications

APOGEE strings: A fossil record of the gas kinematic structure

APOGEE strings: A fossil record of the gas kinematic structure

No preferential spatial distribution for massive stars expected from their formation

Slingshot mechanism in Orion: Kinematic evidence for ejection of protostars by filaments

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