<i>Herschel-Planck</i>dust optical-depth and column-density maps

Lombardi, Marco; Bouy, H.; Alves, J.; Lada, Charles J.

doi:10.1051/0004-6361/201323293

Cited by 197 publications

(394 citation statements)

References 63 publications

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“…In order to study the extended morphology of these structures, we first identify a ridgeline of peak gas surface density, using the dust column density map of Stutz & Kainulainen (2015) as a function of Declination δ, α ridge (δ). We obtain comparable column density maps to those reported by Polychroni et al (2013) in L1641, Ripple et al (2013) from CO measurements, and Lombardi et al (2014) using a combination of near-infrared extinction and Herschel emission. We then define (x, y) positions by…”

Section: Power-law Morphology Of the Integral-shaped Filamentsupporting

confidence: 72%

“…Such structures are readily produced in simulations of turbulent gas with and without magnetic fields (Padoan 1995;Mac Low & Klessen 2004;Federrath 2016;Smith et al 2014Smith et al , 2016Kirk et al 2015;Chen & Ostriker 2015). The fact that plausible representations of filaments can be produced even without magnetic fileds makes turbulence a leading candidate for the formation of molecular clouds.…”

Section: Molecular Cloud Formationmentioning

confidence: 99%

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

Stutz

Gould

2016

A&A

130

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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Section: Power-law Morphology Of the Integral-shaped Filamentsupporting

confidence: 72%

Section: Molecular Cloud Formationmentioning

confidence: 99%

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

Stutz

Gould

2016

A&A

130

260

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“…Figure 4 shows an LNPL N-pdf having the same width as the LN N-pdf in Figure 1, with a PL of slope −1.31 as in NGC 3603 (Schneider et al 2014b), which joins near the peak of the N-pdf as in Orion B (Lombardi et al 2014). This N-pdf is chosen because its shallow slope and joining point near its peak yield a characteristic filament with high central concentration.…”

Section: Lnpl Column Density Profilementioning

confidence: 97%

“…The structural properties of nearby star-forming molecular clouds have received increased attention recently, as parsecscale maps of dust column density have become available, based mainly on star-count near-infrared extinction (Lada et al 1994;Alves et al 1998;Lombardi et al 2014), and on far-infrared emission observed with the Herschel Space Observatory (André & Saraceno 2005;Pilbratt et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Characteristic Structure of Star-Forming Clouds

Myers

2015

ApJ

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This paper presents a new method to diagnose the star-forming potential of a molecular cloud region from the probability density function of its column density (N-pdf). This method provides expressions for the column density and mass profiles of a symmetric filament having the same N-pdf as a filamentary region. The central concentration of this characteristic filament can distinguish regions and can quantify their fertility for star formation. Profiles are calculated for N-pdfs which are pure lognormal, pure power law, or a combination. In relation to models of singular polytropic cylinders, characteristic filaments can be unbound, bound, or collapsing depending on their central concentration. Such filamentary models of the dynamical state of N-pdf gas are more relevant to star-forming regions than are spherical collapse models. The star formation fertility of a bound or collapsing filament is quantified by its mean mass accretion rate when in radial free fall. For a given mass per length, the fertility increases with the filament mean column density and with its initial concentration. In selected regions the fertility of their characteristic filaments increases with the level of star formation.

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“…These estimates were derived with β = 1.8 and would become ∼20% higher (depending on the details of the fitting) if a value of β = 2.0 were used. More recently, Lombardi et al (2014) derived ratios A(K)/τ(850 μm) of 2640 mag and 3460 mag for the Orion A and B molecular clouds, respectively. The 850 μm optical depth was derived from Herschel observations rescaled using a comparison with Planck measurements, and the NIR extinction was calculated with the method NICEST (Lombardi 2009).…”

Section: Comparison With Other Studiesmentioning

confidence: 99%

Galactic cold cores

Juvela

Ristorcelli

Marshall

et al. 2015

A&A

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Context. The project Galactic Cold Cores has carried out Herschel photometric observations of interstellar clouds where the Planck satellite survey has located cold and compact clumps. The sources represent different stages of cloud evolution from starless clumps to protostellar cores and are located in different Galactic environments. Aims. We examine this sample of 116 Herschel fields to estimate the submillimetre dust opacity and to search for variations that might be attributed to the evolutionary stage of the sources or to environmental factors, including the location within the Galaxy. Methods. The submillimetre dust opacity was derived from Herschel data, and near-infrared observations of the reddening of background stars are converted into near-infrared optical depth. We investigated the systematic errors affecting these parameters and used modelling to correct for the expected biases. The ratio of 250 μm and J band opacities is correlated with the Galactic location and the star formation activity. We searched for local variations in the ratio τ(250 μm)/τ(J) using the correlation plots and opacity ratio maps. Results. We find a median ratio of τ(250 μm)/τ(J) = (1.6 ± 0.2) × 10 −3 , which is more than three times the mean value reported for the diffuse medium. Assuming an opacity spectral index β = 1.8 instead of β = 2.0, the value would be lower by ∼30%. No significant systematic variation is detected with Galactocentric distance or with Galactic height. Examination of the τ(250 μm)/τ(J) maps reveals six fields with clear indications of a local increase of submillimetre opacity of up to τ(250 μm)/τ(J) ∼ 4 × 10 −3 towards the densest clumps. These are all nearby fields with spatially resolved clumps of high column density. Conclusions. We interpret the increase in the far-infrared opacity as a sign of grain growth in the densest and coldest regions of interstellar clouds.

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Herschel-Planckdust optical-depth and column-density maps

Cited by 197 publications

References 63 publications

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

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

Characteristic Structure of Star-Forming Clouds

Galactic cold cores

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