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Embedded Clusters in Molecular Clouds

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ReviewThe objections and verdict, as JSON Paper breakdownThe authors' claims, conditions and measurements, as JSON Signed receiptProof this review has not been altered
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Charles J. Lada, Elizabeth A. Lada

Astrophysics · Submitted 27 Jan 2003 · 202 references

Pith's verdict: The catalog and the embedded cluster mass function are the durable contributions; the birthrate ratio and the 4-7% survival figure are quoted more precisely than the age normalization behind them can support.

T0 · AI review

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  4. T3 Formal statement The claims written out in a formal math language a computer can read.
  5. T4 Proof Those claims proved, and the proof checked by computer.

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arXiv IDastro-ph/0301540 (version 1)
Pith IDVKQ5SOSY, Pith's permanent record of this paper and its review
CitationCharles J. Lada, Elizabeth A. Lada. "Embedded Clusters in Molecular Clouds." arXiv:astro-ph/0301540 (2003). https://pith.science/paper/VKQ5SOSY
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The paper

The paper claims

Embedded clusters form far faster than open clusters survive, so most newborn star clusters dissolve with their birth clouds.

The reading

The authors set out to show that the dust-shrouded clusters found in infrared surveys of molecular clouds are the birth form of most stars, and that the great majority of these protoclusters do not survive to become ordinary open clusters. They compile a catalog of 76 embedded clusters within about 2 kpc, estimate their masses from a common initial mass function, and compare the cluster birthrate with the birthrate of visible open clusters. The comparison implies that embedded clusters form 5 to 16 times faster than open clusters, so fewer than about 4 to 7 percent survive gas expulsion to reach Pleiades age. The same catalog indicates that about 90 percent of stars forming in embedded clusters are in rich systems of more than 100 members and more than 50 solar masses, making clustered birth the dominant mode of star formation in molecular clouds.

What carries the argument

The argument rests on a literature-compiled catalog of 76 embedded clusters within about 2 kpc, each required to have at least 35 members and evidence of gas or dust association. Cluster masses are inferred by matching observed infrared source counts to synthetic clusters built from the Trapezium initial mass function and its K-band luminosity function, with ages bracketed by the Trapezium and IC 348. The resulting embedded cluster mass distribution function, the product of cluster mass and the number per logarithmic mass bin, is flat between 50 and 1000 solar masses and drops below 50 solar masses. Comparing the number of embedded clusters with the open cluster catalog, after adjusting for fading, turns the catalog into a birthrate and survival-fraction argument.

Extended reading notes

Core claim

The central claim is that the embedded cluster birthrate within roughly 2 kpc is 2 to 4 clusters per million years per square kiloparsec, versus 0.25 to 0.45 for open clusters, and because the embedded catalog is incomplete this is a lower bound. Read together with the observed age distribution, the excess implies a high infant mortality rate: fewer than 4 to 7 percent of embedded clusters survive emergence from their molecular clouds as bound clusters of Pleiades age. The paper also argues that the embedded cluster mass distribution is flat from about 50 to 1000 solar masses, corresponding to a mass spectrum $dN/dM$ proportional to $M^{-2}$, and that more than 90 percent of clustered stars form in systems above 50 solar masses and 100 members.

Load-bearing premise

The birthrate conversion assumes that the catalog's embedded clusters have a mean age of 1 to 2 million years; if their true mean age is closer to 4 million years, the birthrate excess shrinks by a factor of 2 to 4 and the derived survival fraction rises well above 4 to 7 percent.

Editorial extensions

If this is right

  • Most stars in giant molecular clouds, roughly 70 to 90 percent by the paper's cited surveys, form in embedded clusters rather than as isolated stars.
  • The field star population should therefore be dominated by stars that were born in clusters and later released when the clusters dissolved.
  • Only the most massive embedded clusters, above roughly 500 solar masses, are plausible progenitors of long-lived Pleiades-like open clusters.
  • The embedded cluster mass spectrum matches the dense core mass spectrum and the open cluster mass spectrum, suggesting a common star formation efficiency across cluster-forming cores.
  • Disk fractions near 80 to 85 percent in the youngest clusters and near zero by 5 to 6 million years set a short window for planet formation.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If most field stars are former cluster members, searches for chemical or dynamical relics of cluster birth in the field population become a direct test of the infant-mortality picture.
  • The survival percentage is more fragile than the qualitative mortality claim because it depends on the assumed mean age; a targeted age survey could move the number without changing the main conclusion.
  • The paper's own comparison between embedded and open cluster mass functions sits awkwardly with scenarios in which emerging clusters lose half or more of their stars, so resolved halos of unbound young stars around emerging clusters would be a useful check.
  • The high disk fraction measured for brown dwarfs in the Trapezium suggests planet-forming disks may not be restricted to stars, an extension the paper notes but does not fully test.
Original abstract

Stellar clusters are born embedded within giant molecular clouds (GMCs) and during their formation and early evolution are often only visible at infrared wavelengths, being heavily obscured by dust. Over the last 15 years advances in infrared detection capabilities have enabled the first systematic studies of embedded clusters in galactic molecular clouds. In this article we review the current state of empirical knowledge concerning these extremely young protocluster systems. From a survey of the literature we compile the first extensive catalog of galactic embedded cluster properties. We use the catalog to construct the mass function and estimate the birthrate for embedded clusters within roughly 2 Kpc of the Sun. We find that the embedded cluster birthrate exceeds that of visible open clusters by an order of magnitude or more indicating a high infant mortality rate for protocluster systems. Less than 4-7% of embedded clusters survive emergence from molecular clouds to become bound clusters of Pleiades age. The vast majority (90%) of stars that form in embedded clusters form in rich clusters of 100 or more members with masses in excess of 50 solar masses. We review the role of embedded clusters in investigating the nature of the IMF which, in one nearby example, has been measured over the entire range of stellar and substellar mass, from OB stars to subsellar objects near the deuterium burning limit. We also review the role embedded clusters play in the investigation of circumstellar disk evolution and the important constraints they provide for understanding the origin of planetary systems. Finally, we discuss current ideas concerning the origin and dynamical evolution of embedded clusters and the implications for the formation of bound open clusters.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 8,263 input tokens.

What the abstract itself states, as probabilities: claims first 0.85 · states limitation 0.23 · human participants 0.01 · controlled comparison 0.31 · randomized assignment 0.01 · states quantitative result 0.98 · compares with prior results 0.70 · mentions code or data availability 0.05.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

Stellar clusters are born embedded within giant molecular clouds (GMCs) and during their formation and early evolution are often only visible at infrared wavelengths, being heavily obscured by dust. Over the last 15 years advances in infrared detection capabilities have enabled the first systematic studies of embedded clusters in galactic molecular clouds. In this article we review the current state of empirical knowledge concerning these extremely young protocluster systems. From a survey of the literature we compile the first extensive catalog of galactic embedded cluster properties. We use the catalog to construct the mass function and estimate the birthrate for embedded clusters within roughly 2 Kpc of the Sun. We find that the embedded cluster birthrate exceeds that of visible open clusters by an order of magnitude or more indicating a high infant mortality rate for protocluster systems. Less than 4-7% of embedded clusters survive emergence from molecular clouds to become bound clusters of Pleiades age. The vast majority (90%) of stars that form in embedded clusters form in rich clusters of 100 or more members with masses in excess of 50 solar masses. We review the role of embedded clusters in investigating the nature of the IMF which, in one nearby example, has been measured over the entire range of stellar and substellar mass, from OB stars to subsellar objects near the deuterium burning limit. We also review the role embedded clusters play in the investigation of circumstellar disk evolution and the important constraints they provide for understanding the origin of planetary systems. Finally, we discuss current ideas concerning the origin and dynamical evolution of embedded clusters and the implications for the formation of bound open clusters.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 Stellar clusters are born embedded within giant molecular clouds (GMCs) and during their formation and early evolution are often only visible at infrared wavelengths, being heavily obscured by dust. background 1.00 0.04 0.02 asserted 0.95
s1 Over the last 15 years advances in infrared detection capabilities have enabled the first systematic studies of embedded clusters in galactic molecular clouds. background 0.98 0.04 0.02 asserted 1.00
s2 In this article we review the current state of empirical knowledge concerning these extremely young protocluster systems. contribution 0.92 0.43 0.02 asserted 0.66
s3 From a survey of the literature we compile the first extensive catalog of galactic embedded cluster properties. contribution 0.90 0.94 0.03 asserted 0.99
s4 We use the catalog to construct the mass function and estimate the birthrate for embedded clusters within roughly 2 Kpc of the Sun. method 0.50 0.95 0.04 asserted 0.90
s5 We find that the embedded cluster birthrate exceeds that of visible open clusters by an order of magnitude or more indicating a high infant mortality rate for protocluster systems. result 0.88 0.95 0.60 asserted 0.84
s6 Less than 4-7% of embedded clusters survive emergence from molecular clouds to become bound clusters of Pleiades age. result 0.99 0.79 0.36 asserted 0.99
s7 The vast majority (90%) of stars that form in embedded clusters form in rich clusters of 100 or more members with masses in excess of 50 solar masses. result 1.00 0.62 0.07 asserted 1.00
s8 We review the role of embedded clusters in investigating the nature of the IMF which, in one nearby example, has been measured over the entire range of stellar and substellar mass, from OB stars to subsellar objects near the deuterium burning limit. contribution 0.64 0.23 0.03 asserted 0.98
s9 We also review the role embedded clusters play in the investigation of circumstellar disk evolution and the important constraints they provide for understanding the origin of planetary systems. contribution 0.77 0.13 0.02 asserted 0.92
s10 Finally, we discuss current ideas concerning the origin and dynamical evolution of embedded clusters and the implications for the formation of bound open clusters. contribution 0.59 0.33 0.04 unclear 0.91

What kind of paper the classifier reports this is: review 0.78 · evidence from literature 0.68.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. — Optical (top) and Infrared (bottom) images of the RC
Figure 2. — The embedded cluster mass distribution function (E
Figure 3. — Observed frequency distribution of ages for open an
Figure 4. — Contour map of the surface density of J-band infrare
Figure 5. — The V, V-I color magnitude diagram for IC 348 compile
Figure 6. — The V, V-I color magnitude diagram for the 5 Myr open c
Figure 7. — Comparison of theoretical predictions for the lumi
Figure 8. — Optical (top) and deep JHK infrared (bottom) images of the Trapezium cluster in Orion obtained with the NASA HST and the ESO VLT, respectively. The infrared observations taken from Muench et al. 2002
Figure 10. — The IMF derived for the Trapezium cluster from Mont
Figure 11. — Comparison of IMFs derived from infrared observat
Figure 12. — Comparison of the observed KLFs (adjusted to the sa
Figure 13. — Model luminosity functions (KLFs) of synthetic cl
Figure 14. — The KLF and derived IMF for IC 348. The left panel sho
Figure 15. — Disk Fraction as a function of cluster age for a samp

Showing 14 of the paper's 15 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:astro-ph/0301540 by the authors.

References
How later papers used it

561 later papers cite it

Evidence: substantial. 561 of the citing papers share no author with it, and 43 of those carry a confident label from Pith's citation classifier.

Pith read 40 of the 769 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Uses its data or values 3 of 19 papers with this label
Compares with it 2 of 11 papers with this label
Cites it as support 2 of 12 papers with this label
How the literature uses it

71 arXiv papers cite this in 100 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 65 sentences without a confident label

Uses its method or tool 1 paper
Uses its data or values 3 papers
Compares with it 2 papers
Cites it as background 28 papers

Discussion

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