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CALIBRATION OF EVOLUTIONARY DIAGNOSTICS IN HIGH-MASS STAR FORMATION

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Zeitschriftentitel: The Astrophysical Journal Letters
Personen und Körperschaften: Molinari, S., Merello, M., Elia, D., Cesaroni, R., Testi, L., Robitaille, T.
In: The Astrophysical Journal Letters, 826, 2016, 1, S. L8
Format: E-Article
Sprache: Unbestimmt
veröffentlicht:
American Astronomical Society
Schlagwörter:
Space and Planetary Science
Astronomy and Astrophysics
Details
Zusammenfassung: <jats:title>ABSTRACT</jats:title> <jats:p>The evolutionary classification of massive clumps that are candidate progenitors of high-mass young stars and clusters relies on a variety of independent diagnostics based on observables from the near-infrared to the radio. A promising evolutionary indicator for massive and dense cluster-progenitor clumps is the <jats:italic>L/M</jats:italic> ratio between the bolometric luminosity and the mass of the clumps. With the aim of providing a quantitative calibration for this indicator, we used SEPIA/APEX to obtain CH<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>H(<jats:italic>J</jats:italic> = 12–11) observations, which is an excellent thermometer molecule probing densities <jats:inline-formula> <jats:tex-math> <?CDATA $\geqslant {10}^{5}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≥</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlaa2222ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> cm<jats:sup>−3</jats:sup>, toward 51 dense clumps with <jats:inline-formula> <jats:tex-math> <?CDATA $M\geqslant 1000$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>M</mml:mi> <mml:mo>≥</mml:mo> <mml:mn>1000</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlaa2222ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA ${}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow /> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlaa2222ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and uniformly spanning −2 ≲ Log(<jats:italic>L/M</jats:italic>) [<jats:italic>L</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA ${}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow /> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlaa2222ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>/<jats:italic>M</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA ${}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow /> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlaa2222ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>] ≲ 2.3. We identify three distinct ranges of <jats:italic>L/M</jats:italic> that can be associated to three distinct phases of star formation in massive clumps. For <jats:italic>L/M</jats:italic> <jats:inline-formula> <jats:tex-math> <?CDATA $\leqslant \;1$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≤</mml:mo> <mml:mspace width="0.25em" /> <mml:mn>1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlaa2222ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> no clump is detected in CH<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>H, suggesting an inner envelope temperature below ∼30K. For 1 ≲ <jats:italic>L/M</jats:italic> ≲ 10 we detect 58% of the clumps with a temperature between ∼30 and ∼35 K independently from the exact value of <jats:italic>L/M</jats:italic>; such clumps are building up luminosity due to the formation of stars, but no star is yet able to significantly heat the inner clump regions. For <jats:italic>L/M</jats:italic> ≳ 10 we detect all the clumps with a gas temperature rising with Log(<jats:italic>L/M</jats:italic>), marking the appearance of a qualitatively different heating source within the clumps; such values are found toward clumps with UCH <jats:sc>ii</jats:sc> counterparts, suggesting that the quantitative difference in <jats:italic>T</jats:italic> versus <jats:italic>L/M</jats:italic> behavior above <jats:italic>L/M</jats:italic> ∼ 10 is due to the first appearance of ZAMS stars in the clumps.</jats:p>
Umfang: L8
ISSN: 2041-8205
2041-8213
DOI: 10.3847/2041-8205/826/1/l8