New Protostellar Collapse Candidates: An HCO<sup>+</sup>Survey of the Class 0 Sources

Gregersen, E. M.; Evans, Neal J.; Zhou, Shudong; Choi, Minho

doi:10.1086/304297

Cited by 166 publications

(194 citation statements)

References 72 publications

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“…Therefore, we use the expression "infall" signature with quotation marks in the rest of the article to remind the reader that the signature may not trace proper infall motions but only contraction motions when gravity does not (yet) dominate the dynamical evolution of these layers. The opposite signature, i.e., with the red peak emission of the self-absorbed transition stronger than the blue peak, has also been seen in other surveys of dense cores in the past (e.g., Gregersen et al 1997;Mardones et al 1997;Gregersen & Evans 2000. The red-skewed profiles are generally not very well understood.…”

Section: Contraction Motionsmentioning

confidence: 78%

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

Tsitali

Беллоче

Garrod

et al. 2015

A&A

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Context. The Chamaeleon dark molecular clouds are excellent nearby targets for low-mass star formation studies. Even though they belong to the same cloud complex, Cha I and II are actively forming stars while Cha III shows no sign of ongoing star formation. Aims. We aim to determine the driving factors that have led to the very different levels of star formation activity in Cha I and III and examine the dynamical state and possible evolution of the starless cores within them. Methods. Observations were performed in various molecular transitions with the APEX and Mopra telescopes. We examine the kinematics of the starless cores in the clouds through a virial analysis, a search for contraction motions, and velocity gradients. The chemical differences in the two clouds are explored through their fractional molecular abundances, derived from a non-LTE analysis, and comparison to predictions of chemical models.Results. Five cores are gravitationally bound in Cha I and one in Cha III. The so-called infall signature indicating contraction motions is seen toward 8-17 cores in Cha I and 2-5 cores in Cha III, which leads to a range of 13-28% of the cores in Cha I and 10-25% of the cores in Cha III that are contracting and may become prestellar. There is no significant difference in the turbulence level in the two clouds. Future dynamical interactions between the cores will not be dynamically significant in either Cha I or III, but the subregion Cha I North may experience collisions between cores within ∼0.7 Myr. Turbulence dissipation in the cores of both clouds is seen in the high-density tracers N 2 H + 1-0 and HC 3 N 10-9 which have lower non-thermal velocity dispersions compared to C 17 O 2-1, C 18 O 2-1, and C 34 S 2-1. Evidence of depletion in the Cha I core interiors is seen in the abundance distributions of the latter three molecules. The median fractional abundance of C 18 O is lower in Cha III than Cha I by a factor of ∼2. The median abundances of most molecules (except methanol) in the Cha III cores lie at the lower end of the values found in the Cha I cores. A difference in chemistry is thus seen. Chemical models suitable for the Cha I and III cores are used to constrain the effectiveness of the HC 3 N to N 2 H + abundance ratio as an evolutionary indicator. Both contraction and static chemical models indicate that this ratio is a good evolutionary indicator in the prestellar phase for both gravitationally bound and unbound cores. In the framework of these models, we find that the cores in Cha III and the southern part of Cha I are in a similar evolutionary stage and are less chemically evolved than the central region of Cha I. Conclusions. The measured HC 3 N/N 2 H + abundance ratio and the evidence for contraction motions seen towards the Cha III starless cores suggest that Cha III is younger than Cha I Centre and that some of its cores may form stars in the future if contraction does not cease. The cores in Cha I South may on the other hand be transient structures.

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Section: Contraction Motionsmentioning

confidence: 78%

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

Tsitali

Беллоче

Garrod

et al. 2015

A&A

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“…The turbulent line width of this sample is highly supersonic. Our regions are at least 4 times more turbulent than regions involved in lower mass star formation (see Mardones et al 1997;Gregersen et al 1997). Based on comparison of power-law models using dust emission, Mueller et al (2002b) found that these cores were also about 100 times denser on average than the low-mass sample.…”

Section: Line Width-size Relationshipmentioning

confidence: 88%

A CS J = 5 → 4 Mapping Survey Toward High‐Mass Star‐forming Cores Associated with Water Masers

Shirley

Evans

Young

et al. 2003

ASTROPHYS J SUPPL S

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258

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We have mapped 63 regions forming high-mass stars in CS J ¼ 5 ! 4 using the CSO. The CS peak position was observed in C 34 S J ¼ 5 ! 4 toward 57 cores and in 13 CS J ¼ 5 ! 4 toward the nine brightest cores. The sample is a subset of a sample originally selected toward water masers; the selection on maser sources should favor sources in an early stage of evolution. The cores are located in the first and second Galactic quadrants with an average distance of 5:3 AE 3:7 kpc and were well detected with a median peak signalto-noise ratio in the integrated intensity of 40. The integrated intensity of CS J ¼ 5 ! 4 correlates very well with the dust continuum emission at 350 lm. For 57 sufficiently isolated cores, a well-defined angular size (FWHM) was determined. The core radius (R CS ), aspect ratio [ða=bÞ obs ], virial mass (M vir ), surface density (AE), and the luminosity in the CS J ¼ 5 ! 4 line (LðCS54Þ) are calculated. The distributions of size, virial mass, surface density, and luminosity are all peaked with a few cores skewed toward much larger values than the mean. The median values, l 1/2 , are as follows: l 1/2 ðR CS Þ ¼ 0:32 pc, l 1/2 ðða=bÞ obs Þ ¼ 1:20, l 1/2 ðM vir Þ ¼ 920 M , l 1/2 ðAEÞ ¼ 0:60 g cm À2 , l 1/2 ðLðCS54ÞÞ ¼ 1:9 Â 10 À2 L , and l 1/2 ðL bol =M vir Þ ¼ 165 ðL=MÞ . We find a weak correlation between C 34 S line width and size, consistent with Dv $ R 0:3 . The line widths are much higher than would be predicted by the usual relations between line width and size determined from regions of lower mass. These regions are very turbulent. The derived virial mass agrees within a factor of 2-3 with mass estimates from dust emission at 350 lm after corrections for the density structure are accounted for. The resulting cumulative mass spectrum of cores above 1000 M can be approximated by a power law with a slope of about À0.9, steeper than that of clouds measured with tracers of lower density gas and close to that for the total masses of stars in OB associations. The median turbulent pressures are comparable to those in UCH ii regions, and the pressures at small radii are similar to those in hypercompact H ii regions (P=k $ 10 10 K cm À3 ). The filling factors for dense gas are substantial, and the median abundance of CS is about 10 À9 . The ratio of bolometric luminosity to virial mass is much higher than the value found for molecular clouds as a whole, and the correlation of luminosity with mass is tighter.

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“…Individual outflows in Serpens have been recorded in a wide variety of molecular tracers and different transitions; e.g. CS in Testi et al (2000), Mangum et al (1996), Wolf-Chase et al (1998); H 2 CO in Mangum et al (1996); CH 3 OH in Garay et al (2002) and Testi et al (2000); HCO + in Gregersen et al (1997) and Hogerheijde et al (1999); HCN, SO, and SiO in Hogerheijde et al (1999) and Garay et al (2002); NH 3 in Torrelles et al (1992). Widefield, homogenous outflow mapping of the Serpens Core has so far only been performed at the J = 1 → 0 (Narayanan et al 2002) and J = 2 → 1 (White et al 1995;Davis et al 1999) transitions of carbon monoxide.…”

Section: Introductionmentioning

confidence: 99%

Wide field COJ= 3 → 2 mapping of the Serpens cloud core

Dionatos

Nisini

Codella

et al. 2010

A&A

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Context. Outflows provide indirect means to gain insight into diverse star formation-associated phenomena. At the level of individual protostellar cores, both outflows and the intrinsic core properties can be used to study the mass accretion/ejection process of heavily embedded protostellar sources. Aims. The main objective of the paper is to study the overall outflow distribution and its association with the young population of the Serpens Core cluster. In addition, the paper addresses the correlation of the outflow momentum flux with the bolometric luminosity of their driving sources using this homogeneous dataset for a single star-forming site.Methods. An area comprising 460 × 230 of the Serpens cloud core was mapped in 12 CO J = 3 →2 with the HARP-B heterodyne array at the James Clerk Maxwell Telescope; J = 3 →2 observations are more sensitive tracers of hot outflow gas than lower J CO transitions; combined with the high sensitivity of the HARP-B receptors outflows are sharply outlined, enabling their association with individual protostellar cores. Results. Most of ∼20 observed outflows are found to be associated with known protostellar sources in bipolar or unipolar configurations. All but two outflow/core pairs in our sample tend to have a projected orientation spanning roughly NW-SE. The overall momentum driven by outflows in Serpens lies between 3.2 and 5.1 × 10 −1 M km s −1 , the kinetic energy from 4.3 to 6.7 × 10 43 erg, and momentum flux is between 2.8 and 4.4 × 10 −4 M km s −1 yr −1 . Bolometric luminosities of protostellar cores based on Spitzer photometry are found up to an order of magnitude lower than previous estimations derived with IRAS/ISO data. Conclusions. We confirm the validity of the existing correlations between the momentum flux and bolometric luminosity of Class I sources for the homogenous sample of Serpens, though we suggest that they should be revised by a shift to lower luminosities. All protostars classified as Class 0 sources stand well above the known Class I correlations, indicating a decline in momentum flux between the two classes.

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New Protostellar Collapse Candidates: An HCO⁺Survey of the Class 0 Sources

Cited by 166 publications

References 72 publications

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

A CS J = 5 → 4 Mapping Survey Toward High‐Mass Star‐forming Cores Associated with Water Masers

Wide field COJ= 3 → 2 mapping of the Serpens cloud core

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New Protostellar Collapse Candidates: An HCO+Survey of the Class 0 Sources

Cited by 166 publications

References 72 publications

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

A CS J = 5 → 4 Mapping Survey Toward High‐Mass Star‐forming Cores Associated with Water Masers

Wide field COJ= 3 → 2 mapping of the Serpens cloud core

Contact Info

Product

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New Protostellar Collapse Candidates: An HCO⁺Survey of the Class 0 Sources