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Title: The galactic census of high- and medium-mass protostars. II. Luminosities and evolutionary states of a complete sample of dense gas clumps

The Census of High- and Medium-mass Protostars (CHaMP) is the first large-scale (280° < l < 300°, –4° < b < 2°), unbiased, subparsec resolution survey of Galactic molecular clumps and their embedded stars. Barnes et al. presented the source catalog of ∼300 clumps based on HCO{sup +}(1-0) emission, used to estimate masses M. Here we use archival midinfrared-to-millimeter continuum data to construct spectral energy distributions. Fitting two-temperature gray-body models, we derive bolometric luminosities, L. We find that the clumps have 10 ≲ L/L {sub ☉} ≲ 10{sup 6.5} and 0.1 ≲ L/M/[L {sub ☉}/M {sub ☉}] ≲ 10{sup 3}, consistent with a clump population spanning a range of instantaneous star-formation efficiencies from 0 to ∼50%. We thus expect L/M to be a useful, strongly varying indicator of clump evolution during the star cluster formation process. We find correlations of the ratio of warm-to-cold component fluxes and of cold component temperature with L/M. We also find a near-linear relation between L/M and Spitzer-IRAC specific intensity (surface brightness); thus, this relation may also be useful as a star-formation efficiency indicator. The lower bound of the clump L/M distribution suggests that the star-formation efficiency per free-fall time is ε{sub ff} < 0.2.more » We do not find strong correlations of L/M with mass surface density, velocity dispersion, or virial parameter. We find a linear relation between L and L{sub HCO{sup +}(1--0)}, although with large scatter for any given individual clump. Fitting together with extragalactic systems, the linear relation still holds, extending over 10 orders of magnitude in luminosity. The complete nature of the CHaMP survey over a several kiloparsec-scale region allows us to derive a measurement at an intermediate scale, bridging those of individual clumps and whole galaxies.« less
Authors:
; ;  [1]
  1. Department of Astronomy, University of Florida, FL 32611 (United States)
Publication Date:
OSTI Identifier:
22348499
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BOLOMETERS; BRIGHTNESS; CATALOGS; CORRELATIONS; DENSITY; DISPERSIONS; DISTRIBUTION; DUSTS; EFFICIENCY; EMISSION; ENERGY SPECTRA; EVOLUTION; GALAXIES; GALAXY NUCLEI; LUMINOSITY; MASS; PROTOSTARS; RESOLUTION; STAR CLUSTERS; STARS