Grain Growth and Density Distribution of the Youngest Protostellar Systems

Kwon, Woojin; Looney, Leslie W.; Mundy, Lee G.; Chiang, Hsin Fang; Kemball, A. J.

doi:10.1088/0004-637x/696/1/841

Cited by 133 publications

(148 citation statements)

References 44 publications

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“…Such steep density profiles have been obtained previously toward more nearby protostars (Looney et al 2003;Chiang et al 2008Chiang et al , 2012Kwon et al 2009). The sources with flat visibility amplitudes appear similar to NGC 1333 IRAS 4B, a source with very flat visibility amplitudes out to ∼80 kλ (Looney et al 2003;Chiang et al 2008); this is equivalent to flat visibility amplitudes out to ∼150 kλ at the distance to Orion.…”

Section: Envelope Density Profilessupporting

confidence: 82%

CHARACTERIZING THE YOUNGESTHERSCHEL-DETECTED PROTOSTARS. I. ENVELOPE STRUCTURE REVEALED BY CARMA DUST CONTINUUM OBSERVATIONS

Tobin

Stutz

Megeath

et al. 2015

ApJ

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We present Combined Array for Research in Millimeter-wave Astronomy 2.9 mm dust continuum emission observations of a sample of 14 Herschel-detected Class 0 protostars in the Orion A and B molecular clouds, drawn from the PACS Bright Red Sources (PBRS) sample. These objects are characterized by very red 24-70 μm colors and prominent submillimeter emission, suggesting that they are very young Class 0 protostars embedded in dense envelopes. We detect all of the PBRS in 2.9 mm continuum emission and emission from four protostars and one starless core in the fields toward the PBRS; we also report one new PBRS source. The ratio of 2.9 mm luminosity to bolometric luminosity is higher by a factor of ∼5 on average, compared to other well-studied protostars in the Perseus and Ophiuchus clouds. The 2.9 mm visibility amplitudes for 6 of the 14 PBRS are very flat as a function of uv distance, with more than 50% of the source emission arising from radii <1500 AU. These flat visibility amplitudes are most consistent with spherically symmetric envelope density profiles with ρ ∝ R −2.5 . Alternatively, there could be a massive unresolved structure like a disk or a high-density inner envelope departing from a smooth power law. The large amount of mass on scales <1500 AU (implying high average central densities) leads us to suggest that that the PBRS with flat visibility amplitude profiles are the youngest PBRS and may be undergoing a brief phase of high mass infall/accretion and are possibly among the youngest Class 0 protostars. The PBRS with more rapidly declining visibility amplitudes still have large envelope masses, but could be slightly more evolved.

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Section: Envelope Density Profilessupporting

confidence: 82%

CHARACTERIZING THE YOUNGESTHERSCHEL-DETECTED PROTOSTARS. I. ENVELOPE STRUCTURE REVEALED BY CARMA DUST CONTINUUM OBSERVATIONS

Tobin

Stutz

Megeath

et al. 2015

ApJ

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“…For OH5 dust, β = 1.75 over all submillimeter and millimeter wavelengths, implying that the emission should have a spectral index of 3.75. However, numerous recent observational studies of protostars have found α < 3.75 over a variety of spatial scales (e.g., Kwon et al 2009;Melis et al 2011;Shirley et al 2011;AMI Consortium et al 2012;Tobin et al 2013). In an extreme example, Tobin et al (2013) measured α = 2 between 3.4 and 0.87 mm over baselines ranging from 10 -500 kλ, implying a flat dust opacity law (β = 0).…”

Section: Dust Opacity Lawmentioning

confidence: 99%

On the reliability of protostellar disc mass measurements and the existence of fragmenting discs

Dunham

Vorobyov²,

Arce³

2014

Monthly Notices of the Royal Astronomical Society

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We couple non-magnetic, hydrodynamical simulations of collapsing protostellar cores with radiative transfer evolutionary models to generate synthetic observations. We then use these synthetic observations to investigate the extent to which a simple method for measuring protostellar disc masses used in the literature recovers the intrinsic masses of the discs formed in the simulations. We evaluate the effects of contamination from the surrounding core, partially resolving out the disc, optical depth, fixed assumed dust temperatures, inclination, and the dust opacity law. We show that the combination of these effects can lead to disc mass underestimates by up to factors of 2-3 at millimeter wavelengths and up to an order of magnitude or larger at submillimeter wavelengths. The optically thin portions of protostellar discs are generally cooler in the Class I stage than the Class 0 stage since Class I discs are typically larger and more optically thick, and thus more shielded. The observed disc mass distribution closely resembles the intrinsic distribution if this effect is taken into account, especially at millimeter wavelengths where optical depth effects are minimized. Approximately 50%-70% of protostellar discs observed to date with this method are consistent with the masses of the gravitationally unstable discs formed in the simulations, suggesting that at least some protostellar discs are likely sufficiently massive to fragment. We emphasize key future work needed to confirm these results, including assembling larger, less biased samples, and using molecular line observations to distinguish between rotationally supported, Keplerian discs and magnetically supported pseudodiscs.

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“…However, it is also possible that higher values of β are actually caused by the growth of icy mantles on dust grains (e.g., Schnee et al 2010a, and references therein), but this seems to contradict the chemical features discussed earlier. Conversely, observational results of small values of β are often interpreted to be indicative of grain growth (e.g., Testi et al 2003;Draine 2006;Kwon et al 2009). For example, Kwon et al (2009) found that for their sample of Class 0 sources β 1, implying larger grain sizes due to gas accretion and/or coagulation.…”

Section: Dust Propertiesmentioning

confidence: 99%

SABOCA 350-μm and LABOCA 870-μm dust continuum imaging of IRAS 05399-0121: mapping the dust properties of a pre- and protostellar core system

Miettinen

Offner

2013

A&A

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Context. Thermal emission from dust provides a valuable tool for determining important physical properties of the dense structures within molecular clouds. Aims. We attempt to map the distributions of dust temperature and H 2 column density of IRAS 05399-0121/SMM 1, which is a dense double-core system in Orion B9. We also search for substructures within the cores through high-resolution submillimetre imaging. Methods. The source was mapped with APEX/SABOCA at 350 μm. We combined these data with our previous LABOCA 870-μm data. The spatial resolution of the new SABOCA image, ∼3400 AU, is about 2.6 times better than provided by LABOCA, and is therefore well-suited to our purposes. We also make use of the Spitzer infrared observations to characterise the star-formation activity in the source. Results. The filamentary source remains a double-core system on the 3400 AU scale probed here, and the projected separation between IRAS 05399 and SMM 1 is 0.14 pc. The temperature map reveals warm spots towards IRAS 05399 and the southeastern tip of the source. Both IRAS 05399 and SMM 1 stand out as peaks in the column density map. A simple analysis suggests that the density profile has the form ∼r −(2.3 +2.2 −0.9 ) , as determined at the position of SMM 1. The broadband spectral energy distribution of IRAS 05399 suggests that it is near the Stage 0/I borderline. A visual inspection of the Spitzer/IRAC images provides hints of a quadrupolar-like jet morphology around IRAS 05399, supporting the possibility that it is a binary system. Conclusions. The source splitting into two subcores along the long axis can be explained by cylindrical Jeans-type fragmentation, but the steepness of the density profile is shallower than what is expected for an isothermal cylinder. The difference between the evolutionary stages of IRAS 05399 (protostellar) and SMM 1 (starless) suggests that the former has experienced a phase of rapid mass accretion, supported by the very long outflow it drives. The protostellar jet from IRAS 05399 might have influenced the nearby core SMM 1. In particular, the temperature map features are likely to be imprints of protostellar or shock heating, while external heating could be provided by the nearby high-mass star-forming region NGC 2024.

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Grain Growth and Density Distribution of the Youngest Protostellar Systems

Cited by 133 publications

References 44 publications

CHARACTERIZING THE YOUNGESTHERSCHEL-DETECTED PROTOSTARS. I. ENVELOPE STRUCTURE REVEALED BY CARMA DUST CONTINUUM OBSERVATIONS

CHARACTERIZING THE YOUNGESTHERSCHEL-DETECTED PROTOSTARS. I. ENVELOPE STRUCTURE REVEALED BY CARMA DUST CONTINUUM OBSERVATIONS

On the reliability of protostellar disc mass measurements and the existence of fragmenting discs

SABOCA 350-μm and LABOCA 870-μm dust continuum imaging of IRAS 05399-0121: mapping the dust properties of a pre- and protostellar core system

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