Earliest Stages of Protocluster Formation: Substructure and Kinematics of Starless Cores in Orion

Lee, Katherine I.; Looney, Leslie W.; Schnee, Scott; Li, Zhi-Yun

doi:10.1088/0004-637x/772/2/100

Cited by 24 publications

(23 citation statements)

References 73 publications

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“…The Galactic rotation curve doesn't allow for velocities red of ∼60 km s −1 , and almost none of the molecular gas exceeds ∼70 km s The UCH  region G49.27-0.34, which was considered a candidate extended green object (EGO) and subsequently rejected for lack of H 2 emission (De Buizer & Vacca 2010;Lee et al 2013), exhibits a second velocity component at ∼68 km s −1 , slightly but clearly redshifted of the rest of the IRDC. The dust component contains a gas mass ∼2 × 10 3 M based on the BGPS flux and using the assumptions outlined in Aguirre et al (2011), suggesting that the high velocity could be due to infall or virialized gas within a deep potential.…”

Section: B2 the W51 B Filamentmentioning

confidence: 99%

The dense gas mass fraction in the W51 cloud and its protoclusters

Ginsburg

Bally

Battersby

et al. 2015

A&A

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Context. The density structure of molecular clouds determines how they will evolve. Aims. We map the velocity-resolved density structure of the most vigorously star-forming molecular cloud in the Galactic disk, the W51 giant molecular cloud. Methods. We present new 2 cm and 6 cm maps of H 2 CO, radio recombination lines, and the radio continuum in the W51 star forming complex acquired with Arecibo and the Green Bank Telescope at ∼50 resolution. We use H 2 CO absorption to determine the relative line-of-sight positions of molecular and ionized gas. We measure gas densities using the H 2 CO densitometer, including continuous measurements of the dense gas mass fraction (DGMF) over the range 10 4 cm −3 < n(H 2 ) < 10 6 cm −3 -this is the first time a dense gas mass fraction has been measured over a range of densities with a single data set.Results. The DGMF in W51 A is high, f > ∼ 70% above n > 10 4 cm −3 , while it is low, f < 20%, in W51 B. We did not detect any H 2 CO emission throughout the W51 GMC; all gas dense enough to emit under normal conditions is in front of bright continuum sources and therefore is seen in absorption instead. Conclusions.(1) The dense gas fraction in the W51 A and B clouds shows that W51 A will continue to form stars vigorously, while star formation has mostly ended in W51 B. The lack of dense, star-forming gas around W51 C indicates that collect-and-collapse is not acting or is inefficient in W51. (2) Ongoing high-mass star formation is correlated with n > ∼ 1×10 5 cm −3 gas. Gas with n > 10 4 cm −3 is weakly correlated with low and moderate mass star formation, but does not strongly correlate with high-mass star formation. (3) The nondetection of H 2 CO emission implies that the emission detected in other galaxies, e.g. Arp 220, comes from high-density gas that is not directly affiliated with already-formed massive stars. Either the non-star-forming ISM of these galaxies is very dense, implying the star formation density threshold is higher, or H  regions have their emission suppressed.

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Section: B2 the W51 B Filamentmentioning

confidence: 99%

The dense gas mass fraction in the W51 cloud and its protoclusters

Ginsburg

Bally

Battersby

et al. 2015

A&A

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“…To investigate the region-to-region variation of the environments and evolutionary phases of star formation, we compared the number density of the 1.1 mm dust cores, protostars, and pre-main sequence stars in OMC-1, OMC-2/3, OMC-4, DLSF, the bending structure, and the southern part in the 1.1 mm dust continuum map. The OMC-1 region is known to be a highmass star-forming region (Furuya & Shinnaga 2009;Bally et al 2011;Lee et al 2013). The OMC-2/3 region is known to be an intermediate-mass star-forming region (Takahashi et al 2006(Takahashi et al , 2008(Takahashi et al , 2009Takahashi & Ho 2012;Takahashi et al 2013;Shimajiri et al 2008Shimajiri et al , 2009.…”

Section: Cross Identification Between the 11 MM Dust Cores And The Ca...mentioning

confidence: 99%

Catalog of Dense Cores in the Orion a Giant Molecular Cloud

Shimajiri

Kitamura

Nakamura

et al. 2015

ApJS

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We present Orion A giant molecular cloud core catalogs, which are based on 1.1 mm map with an angular resolution of 36 ′′ (∼ 0.07 pc) and C 18 O (J=1-0) data with an angular resolution of 26.4 ′′ (∼ 0.05 pc). We have cataloged 619 dust cores in the 1.1 mm map using the Clumpfind method. The ranges of the radius, mass, and density of these cores are estimated to be 0.01 -0.20 pc, 0.6 -1.2 × 10 2 M ⊙ , and 0.3 × 10 4 -9.2 × 10 6 cm −3 , respectively. We have identified 235 cores from the C 18 O data. The ranges of the radius, velocity width, LTE mass, and density are 0.13 -0.34 pc, 0.31 -1.31 km s −1 , 1.0 -61.8 M ⊙ , and (0.8 -17.5) × 10 3 cm −3 , respectively. From the comparison of the spatial distributions between the dust and C 18 O cores, four types of spatial relations were revealed:(1) the peak positions of the dust and C 18 O cores agree with each other (32.4% of the C 18 O cores), (2) two or more C 18 O cores are distributed around the peak position of one dust core (10.8% of the C 18 O cores), (3) 56.8% of the C 18 O cores are not associated with any dust cores, and (4) 69.3% of the dust cores are not associated with any C 18 O cores. The data sets and analysis are public.1 The data sets and annotation files for M IRIAD and KARM A of Tables 2 and 4 are available at the NRO star-formation project web site via http://th.nao.ac.jp/MEMBER/nakamrfm/sflegacy/data.html . 2 James Clerk Maxwell Telescope 2.2. The C 18 O (J=1-0) emission line 2.2.1. Core identification in the C 18 O mapThe overall distribution of the C 18 O emission and the velocity structure are described by Shimajiri et al. (2014). To identify cores from the C 18 O (J=1-0) data, we applied the Clumpfind algorithm (Williams et al. 1994) to the C 18 O (J=1-0) cube data with an angular resolution of 26 ′′ .4 and a velocity channel width of 0.104 km s −1 . Here, note that we applied the Gaussian gridding convolution function (GCF) with 22 ′′ .5 FWHM size to the original C 18 O data, resulting in the effective angular resolution of 26 ′′ .4, and did no smoothing in

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“…The search for compact substructure within starless cores with interferometers has typically targeted sources with signs of being near protostellar collapse (e.g., Kirk et al 2009;Chen & Arce 2010;Pineda et al 2011Pineda et al , 2015Bourke et al 2012;Nakamura et al 2012;Lee et al 2013;Friesen et al 2014;Kainulainen et al 2016). Many of these studies focused on isolated Bok globules rather than on starless cores within larger-scale clouds, and all but two of those have small samples of one or two sources.…”

Section: Introductionmentioning

confidence: 99%

“…Many of these studies focused on isolated Bok globules rather than on starless cores within larger-scale clouds, and all but two of those have small samples of one or two sources. The two exceptions are Lee et al (2013), who surveyed eight cores but only detected compact substructure in molecular line emission and not continuum emission, and Kainulainen et al (2016), discussed in more detail in Section 5.2. Larger continuum surveys of many starless cores in the same cloud tend to yield a low detection rate.…”

Section: Introductionmentioning

confidence: 99%

ALMA Observations of Starless Core Substructure in Ophiuchus

Kirk¹,

Dunham²,

Francesco³

et al. 2017

ApJ

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Compact substructure is expected to arise in a starless core as mass becomes concentrated in the central region likely to form a protostar. Additionally, multiple peaks may form if fragmentation occurs. We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 observations of 60 starless and protostellar cores in the Ophiuchus molecular cloud. We detect eight compact substructures which are 15 >  from the nearest Spitzer young stellar object. Only one of these has strong evidence for being truly starless after considering ancillary data, e.g., from Herschel and X-ray telescopes. An additional extended emission structure has tentative evidence for starlessness. The number of our detections is consistent with estimates from a combination of synthetic observations of numerical simulations and analytical arguments. This result suggests that a similar ALMA study in the ChamaeleonI cloud, which detected no compact substructure in starless cores, may be due to the peculiar evolutionary state of cores in that cloud.

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Earliest Stages of Protocluster Formation: Substructure and Kinematics of Starless Cores in Orion

Cited by 24 publications

References 73 publications

The dense gas mass fraction in the W51 cloud and its protoclusters

The dense gas mass fraction in the W51 cloud and its protoclusters

Catalog of Dense Cores in the Orion a Giant Molecular Cloud

ALMA Observations of Starless Core Substructure in Ophiuchus

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